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Evolution of glacial lakes from the Northern Patagonia Icefield and terrestrial water storage in a sea-level rise context
... Proglacial lakes have reportedly grown in number and size across different mountain regions such as the Southern Alps of New Zealand, the Himalayas and Patagonian Andes (e.g., Kirkbride, 1993;Sakai and Fujita, 2010;Carrivick and Tweed, 2013;Loriaux and Casassa, 2013;Iribarren Anacona et al., 2014;Nie et al., 2017;Shukla et al., 2018;Shugar et al., 2020;Zhang et al., 2021). Proglacial lake development can alter ice dynamics by several mechanisms such as flotation of the glacier's terminus, formation of a calving front, and increased ice flow (e.g., Robertson et al., 2012;Tsutaki et al., 2013;Tsutaki et al., 2019). ...
... In 2015 a debris flow entered Chileno Lake, located in Chileno Valley ( Figure 1A), triggering a GLOF that drained an estimated volume of 105 × 10 6 m 3 of water over 7 days (Wilson et al., 2019). In April 2018, the failure of a lateral moraine located in Bayo Glacier, drained Triángulo Lake (0.95 km 2 ) (Loriaux and Casassa, 2013). During the GLOF event, water discharge entered the main trunk of Exploradores Glacier and drained supra-and sub-glacially, damaging a gauging station located downstream. ...
... This is a distinct feature of a glacier in this location, given that most NPI glaciers have experienced a net retreat of the termini from their LIA moraines dated 12th-17th century (Aniya et al., 2007). Recent geomorphological changes in Exploradores Glacier include the development of an ice-dammed lake at the eastern margin (Loriaux and Casassa, 2013;Wilson et al., 2018), an increase in debris cover thickness (Glasser et al., 2016) and supraglacial pond enlargement (Aniya et al., 2007). Moreover, current debris cover disruption by formation of supraglacial ponds and lakes have led previous researchers to hypothesize that the first kilometers (from the glacier front) are disintegrating (Aniya et al., 2007). ...
Proglacial lakes are ubiquitous features formed during deglaciarization and are currently increasing in number in Patagonia and elsewhere. Proglacial lakes can affect glacier dynamics, catchment hydrology and have the potential to cause glacial lake outburst floods. Therefore, monitoring the onset and development of proglacial lake formation is relevant to understand glacial processes and anticipate glacier response to climate change. In this study, we integrate geomorphological and ice-dynamic information to assess proglacial lake development in Exploradores Glacier, Chilean Patagonia. We monitor recent spatial and temporal changes in the lower trunk of Exploradores Glacier (10 km 2) to provide a 20-year observation record by combining eight uncrewed aerial vehicles (UAV) surveys between 2019 and 2020, with high-medium resolution satellite imagery (Rapid Eye and Landsat) between 2000 and 2018. We use feature tracking techniques, digital surface elevation model analysis and field data to create a multi-temporal scale (inter-annual and seasonal) and a multi-spatial (cm to km) data set. Our analysis shows that surface velocity overall trend has not changed over the last 20 years and that surface velocity near the terminus is significant (>10 m a −1). Moreover, an exceptional advance over moraine deposits was detected. We also found low downwasting rates (<0.5 m a −1) close to the glacier terminus which are attributed to sufficient ice flux and the insulation effect of the debris-covered surface. However, hundreds of supraglacial ponds were observed and are currently coalescing and expanding by ice-cliff backwasting favoring glacier disintegration. Lastly, it was found that calving losses at the east marginal lake equaled ice-flux input into the lake for the UAV monitored period. This study contributes to a better understanding of glacial lake dynamics during proglacial lake development, and our results may help ice modelling efforts to predict glacier response to future climate scenarios.
... In recent years, numerous glacial lakes expanded or formed as a result of climate variations and related glacier melting (Davies and Glasser, 2012;Dussaillant et al., 2010;Harrison et al., 2006). At the Northern Patagonian Icefield, the total glacial lake area increased by 66 km 2 (65%) from 102 km 2 in 1945 to 168 km 2 in 2011 (Loriaux and Casassa, 2013). Between 1985 and 2011, 65 glacial lakes expanded, and more than 100 new ones formed at the NPI, which resulted in an increase in total glacial lake area by 11.6 km 2 (59%) (Paul and Mölg, 2014). ...
... Compared to the outlines of Alpine glaciers, glacial lake boundaries are levelled and relatively smooth and, hence, easier to edit manually, which-since the lakes can be frozen-is required for most of the glacial lakes in the high elevations of the Andes (Veettil et al., 2017a). The most commonly used automatic method for glacial lake delineation is the normalized difference water index (NDWI=[NIR-SWIR]/[NIR+SWIR]) (Cook et al., 2016;Anacona et al., 2014;UGRH, 2014;Loriaux and Casassa, 2013). Once a glacial lake has been delineated, additional characteristics such as elevation can be calculated with the help of a topographic map or DEM. ...
In this article, we review the current knowledge of the glacial recession and related glacial lake development in the Andes of South America. Since the mid-1980s, hundreds of glacial lakes either expanded or formed, and predictions show that additional hundreds of lakes will form throughout the 21st century. However, studies on glacial lakes in the Andes are still relatively rare. Many glacial lakes pose a potential hazard to local communities, but glacial lake outburst floods (GLOFs) are understudied. We provide an overview on hazards from glacial lakes such as GLOFs and water pollution, and their monitoring approaches. In real-time monitoring, the use of unmanned aerial systems (UASs) and early warning systems (EWSs) is still extremely rare in the Andes, but increasingly authorities plan to install mitigation systems to reduce glacial lake risk and protect local communities. In support, we propose an international remote sensing-based observation initiative following the model of, for example, the Global Land Ice Measurements from Space (GLIMS) one, with the headquarters in one of the Andean nations.
... Another significant portion of the ice mass loss is stored as fresh water in growing (pro)glacial lakes (Tweed and Carrivick, 2015;Wilson et al., 2018). Loriaux and Casassa (2013) calculated that at least 10% of the ice mass loss between 2001 and 2011 is currently stored as fresh water in glacial lakes. Furthermore, the region is increasingly prone to glacial lake outburst floods (GLOFs), which can perturb downstream hydrology and constitute a serious societal threat, as they can destroy downstream agricultural lands, infrastructure, and in extreme cases, cause fatalities (Carey, 2005;Kääb et al., 2005;Casassa et al., 2010;Dussaillant et al., 2010;Anacona et al., 2014;Tweed and Carrivick, 2015;Carrivick and Tweed, 2016;Wilson et al., 2018). ...
... A sudden lowering of the water level was interpreted as GLOF. The volume of the glacial lakes was estimated based on the volumearea scaling model of Loriaux and Casassa (2013). The volume of the lakes was estimated based on the highest possible lake levels and therefore give maximum estimates. ...
Proglacial lakes are effective sediment traps but their impact on the reliability of downstream sediment records to reconstruct glacier variability remains unclear. Here, we investigate the sedimentary signature of the recent recession of Steffen Glacier (Chilean Patagonia, 47°S) in downstream fjord sediments, with a focus on identifying the trapping (decreased downstream sediment yield) and filtering (removal of coarse particles) effectiveness of a growing intermediate proglacial lake. Four sediment cores were collected along a 14 km longitudinal transect in Steffen Fjord and the sediment physical and chemical properties were compared with aerial imagery at high temporal resolution. The 137Cs chronology of the most distal core and sediment trap data suggest that sediment accumulation in the fjord remained relatively stable through time, despite the accelerating glacier recession and the growth of Steffen proglacial lake. This is in contrast with many studies that indicate a decrease in sediment yield during proglacial lake expansion. It implies that the increase in sediment export due to accelerating meltwater production may be balanced by the sediment trapping effect of the growing proglacial lake. The fjord sediments show a slight fining upward accompanied by a marked decrease in flood‐induced grain‐size peaks, most likely due to the increasing filtering and dampening effect of the expanding proglacial lake. Our findings show that the filtering effect of the proglacial lake reached a threshold in 1985, when the lake attained an area of 2.02 km2. The additional 5 km of glacier recession during the following 32 years did not have any significant impact on downstream sedimentation. This study confirms that proglacial lakes act as sediment traps but it indicates that (1) the trapping effect can be outpaced by accelerating glacier recession and (2) the filtering effect becomes stable once the lake attains a certain critical size.
... However, in the case of glaciers terminating in lakes, buoyancy forces [1] are the primary calving factor, promoting formation of tabular icebergs, as observed in proglacial lakes of, e.g., Patagonia [1] and Alaska [3]. While freshwater calving does not contribute to the global sea level rise as strongly as the tidewater calving, it influences dynamics of proglacial lakes, which have potential to store large amounts of meltwater [4] and provide water for agriculture and even hydropower downstream [5]. ...
... Melting of sediment-laden icebergs and influx of meltwater drive large amounts of sediment to the lagoon changing the water's color. The terminal lagoon of San Quintín increased in area between 1947 and 2011 and is the largest of the proglacial lagoons surrounding NPI [4]. In such environment, OBIA promises better classification results than a pixel-based study thanks to its ability to classify objects by analyzing features other than just spectral response in four bands. ...
In the field of iceberg and glacier calving studies, it is important to collect comprehensive datasets of populations of icebergs. Particularly, calving of lake-terminating glaciers has been understudied. The aim of this work is to present an object-based method of iceberg detection and to create an inventory of icebergs located in a proglacial lagoon of San Quintín glacier, Northern Patagonia Icefield, Chile. This dataset is created using high-resolution WorldView-2 imagery and a derived DEM. We use it to briefly discuss the iceberg size distribution and area–volume scaling. Segmentation of the multispectral imagery produced a map of objects, which were classified with use of Random Forest supervised classification algorithm. An intermediate classification product was corrected with a ruleset exploiting contextual information and a watershed algorithm that was used
to divide multiple touching icebergs into separate objects. Common theoretical heavy-tail statistical distributions were tested as descriptors of iceberg area and volume distributions. Power law models were proposed for the area–volume relationship. The proposed method performed well over the open lake detecting correctly icebergs in all size bands except 5–15 m 2 where many icebergs were missed. A section of the lagoon with ice melange was not reliably mapped due to uniformity of the area in the imagery and DEM. The precision of the DEM limited the scaling effort to icebergs taller than 1.7 m and larger than 99 m 2 , despite the inventory containing icebergs as small as 4 m2 . The work demonstrates viability of object-based analysis for lacustrine iceberg detection and shows that the statistical properties of iceberg population at San Quintín glacier match those of populations produced by tidewater glaciers.
... Past events affected areas tens to hundreds of kilometres downstream (Carrivick and Tweed, 2016). Retreating glaciers produced lakes at their fronts in many high mountain regions in recent decades (Frey et al., 2010;Gardelle et al., 2011;Loriaux and Casassa, 2013). Lake systems in High Mountain Asia also often developed on the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). ...
... Lake systems in High Mountain Asia also often developed on the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). Corroborating SREX and AR5 findings, there is high confidence that current global glacier shrinkage caused new lakes to form and existing lakes to grow in most regions, for instance in South America, High mountain Asia and Europe (Loriaux and Casassa, 2013;Paul and Mölg, 2014;Zhang et al., 2015;Buckel et al., 2018). Exceptions occurred and are expected to occur in the future for few lakes where evaporation, runoff and reduced melt water influx in total led to a negative water balance (Sun et al., 2018a). ...
The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high mountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s 5th Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland and Scandinavia, which are included in this chapter.
... In addition to glacier mass losses owed to climate change, the presence of glacial lakes at glacier terminus is known to boost glacier area reduction and glacier thinning through calving (Basnett et al., 2013;Brun et al., 2019). In the Patagonian Andes, proglacial lake expansion has been mostly observed in the large outlet glaciers flowing down the Patagonian Icefields (Harrison et al., 2006;Loriaux and Casassa, 2013), yet the influence of glacier-lake interactions in the shrinkage of smaller glaciers is poorly known. ...
... Using the same dataset from these authors, we conducted a t-test and found that in the glacierized area east of the NPI and SPI, the 2000-2012 thinning rate of lake terminating glaciers (−0.88 m a −1 ) was significantly higher (p < 10 −8 ) than that of land terminating glaciers (−0.27 m a −1 ) at the 95% confidence level. At an even broader scale, also the outlet glaciers of the SPI and NPI have shrank alongside the increase in debris covered-ice and glacial lake area, whereas for the smaller, mostly debris-free glaciers, no relation was found between the proportion of debris-covered ice and annual rates of glacier retreat (Loriaux and Casassa, 2013;Glasser et al., 2016). Moreover, the negative 1981-2000 Río Lácteo and San Lorenzo Sur mass budget might be underestimated to some extent, as proglacial lake depth has not been accounted for due to the lack of bathymetry data (Bolch et al., 2011a). ...
A full understanding of glacier changes in the Patagonian Andes over decadal to century timescales is presently limited by a lack of detailed and appropriate long-term observations. Here, we present geodetic mass and area changes of three valley glaciers from Monte San Lorenzo derived from stereo aerial photos, the Shuttle Radar Topography Mission (SRTM) and satellite imagery (SPOT5 and Pleiades) spanning four periods from 1958 to 2018. Our results indicate that net mass balance was negative throughout the six decades, with a mean mass loss of −1.35 ± 0.08 m w.e. a −1 and a total glacier area loss of 14.2 ± 0.7 km 2 (23 ± 1% or 0.40 ± 0.02% a −1). The period 1981-2000 had the most negative mass budget, with an area-averaged mass loss of 1.67 ± 0.11 m w.e. a −1 and a maximum loss of −2.23 ± 0.07 m w.e. a −1 at San Lorenzo Sur glacier. Over the periods of 2000-2012 and 2012-2018, the mass budget of these three glaciers remained virtually unchanged at −1.37 ± 0.06 and −1.36 ± 0.17 m w.e. a −1 , respectively. To place these results into a broader geographical context, the mass balance of a further 15 glaciers from around the Monte San Lorenzo massif was determined from 2000 onwards. This wider analysis reveals a period of reduced mass loss of −0.13 ± 0.21 m w.e. a −1 from 2012 to 2018 after a period of enhanced mass loss of −0.31 ± 0.16 m w.e. a −1 between 2000 and 2012. We find that increasing air temperatures coupled with diminishing precipitation across the region explains the observed patterns and are the main drivers of the negative mass budget. Furthermore, increased calving and melting into recently formed proglacial lakes has further enhanced mass loss at some lake-terminating glaciers.
... Past events affected areas tens to hundreds of kilometres downstream (Carrivick and Tweed, 2016). Retreating glaciers produced lakes at their fronts in many high-mountain regions margins in recent decades (Frey et al., 2010;Gardelle et al., 2011;Loriaux and Casassa, 2013). Lake systems in High Mountain Asia also often developed at the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). ...
... Lake systems in High Mountain Asia also often developed at the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). Corroborating SREX and AR5 findings, there is high confidence that current global glacier shrinkage caused new lakes to form and existing lakes to grow in most regions, for instance in South America, High-Mountain Asia and Europe (Loriaux and Casassa, 2013;Paul and Mölg, 2014;Zhang et al., 2015;Buckel et al., 2018). Exceptions occurred and are expected to occur in the future for few lakes where evaporation, run-off and reduced meltwater influx in total led to a negative water balance (Sun et al., 2018a). ...
The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high mountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s Fifth Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland, and Scandinavia, which are included in this chapter.
... Past events affected areas tens to hundreds of kilometres downstream (Carrivick and Tweed, 2016). Retreating glaciers produced lakes at their fronts in many high-mountain regions margins in recent decades (Frey et al., 2010;Gardelle et al., 2011;Loriaux and Casassa, 2013). Lake systems in High Mountain Asia also often developed at the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). ...
... Lake systems in High Mountain Asia also often developed at the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012;Narama et al., 2017). Corroborating SREX and AR5 findings, there is high confidence that current global glacier shrinkage caused new lakes to form and existing lakes to grow in most regions, for instance in South America, High-Mountain Asia and Europe (Loriaux and Casassa, 2013;Paul and Mölg, 2014;Zhang et al., 2015;Buckel et al., 2018). Exceptions occurred and are expected to occur in the future for few lakes where evaporation, run-off and reduced meltwater influx in total led to a negative water balance (Sun et al., 2018a). ...
The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of high-mountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s Fifth Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter
... There are, however, few data to evaluate these models, and it is not clear that these models have skills at reproducing subtile details of the spatial variation in ice thickness within glaciers and ice fields. The lack of precise bed elevation and thickness data therefore limits our ability to quantify the potential contribution to sea level by this region, model glacier dynamics in response to climate change, or study the impacts of climate change on freshwater resource management and natural hazards such as lake outburst floods (Loriaux & Casassa, 2013). ...
... Over the next century, NPI and SPI are expected to increase their rapid contribution to sea level (Braithwaite & Raper, 2002;Gardner et al., 2013;Glasser et al., 2011;Levermann et al., 2013), enhanced hazards from glacial lake outburst floods (Anacona et al., 2015;Dussaillant et al., 2009;Loriaux & Casassa, 2013), and issues with freshwater resource management. From our product, the largest potential for sea level change exist for San Rafael and San Quintin in NPI, Jorge Montt, Pio XI, Occidental, O'Higgins, and possibly Upsala in SPI. ...
The Northern and Southern Patagonian Icefields are the largest ice masses in the Southern Hemisphere outside Antarctica, but their ice volume and bed topography are poorly known. Here, we combine airborne gravity data collected in 2012 and 2016, with radar data from the Warm Ice Experiment Sounder and Centro de Estudios Cient´ıficos’s to map bed elevation and ice thickness in great detail. We perform a 3D inversion of the gravity data constrained by radar-derived thickness and fjord bathymetry to infer bed elevation at 500-m spacing, with a precision of about 60 m. We detect deep glacial valleys with ice thickness exceeding 1,400 m and sectors below sea level on the western branch of Glaciar Pio XI, Occidental, between San Rafael and Colonia, and near Fitz Roy. We calculate an ice volume of 4,756±923 km3 for NPI and SPI, or 40 times the volume of glaciers in the European Alps.
... The temporal distribution of the GLOFs reported in the literature is not consistent either and changes due to inconsistency of the research practices during different epochs and the growing research interest in glaciers [11]. Although a number of studies reported global [6] and regional (e.g., [16][17][18]) glacial lake expansion, there is only limited evidence for changes in frequency of GLOFs. By compiling a global GLOF database [11] also challenges the opinion that more GLOFs occur under the warming climate. ...
Glacial lakes are an important and dynamic component of terrestrial meltwater storage, responding to climate change and glacier retreat. Although there is evidence of rapid worldwide growth of glacial lakes, changes in frequency and magnitude of glacier lake outbursts under climatic changes are not yet understood. This study proposes and discusses a method framework for regional-scale mapping of glacial lakes and area change detection using large time-series of optical satellite images and the cloud processing tool Google Earth Engine in a semi-automatic way. The methods are presented for two temporal scales, from the 2-week Landsat revisit period to annual resolution. The proposed methods show how constructing an annual composite of pixel values such as minimum or maximum values can help to overcome typical problems associated with water mapping from optical satellite data such as clouds, or terrain and cloud shadows. For annual-resolution glacial lake mapping, our method set only involves two different band ratios based on multispectral satellite images. The study demonstrates how the proposed method framework can be applied to detect rapid lake area changes and to produce a complete regional-scale glacial lake inventory, using the Greater Caucasus as example.
... Particularly as there is an increasing body of research which highlights the exacerbation of glacier retreat rates where they are in contact with proglacial lakes, through mechanical and thermo-erosional processes (Lliboutry et al. 1977;Kirkbride 1993;Kirkbride and Warren 1997;Warren and Kirkbride 1998;Warren and Kirkbride 2003;Roehl 2006;Komori 2008;Robertson et al. 2012;Trussel et al. 2013;Tsutaki et al. 2013;Wang et al. 2015;Carr et al. 2013;King et al. 2017King et al. , 2018Minowa et al. 2017;Mallalieu et al. 2020;Watson et al. 2020). Proglacial lake distribution and extent has been mapped at the regional scale in the Alps, Greater Himalaya, Peru, Greenland, Norway, and Patagonia through analysis of multispectral satellite imagery (Buchroithner et al. 1982;Huggel et al. 2002;Gardelle et al. 2011;Loriaux and Casassa 2013;Carrivick and Quincey 2014;Hanshaw and Bookhagen 2014;Yao et al. 2018;How et al. 2021;Kumar et al. 2020;Andreassen et al. 2022). Furthermore, Pierre et al. (2019) called for a global proglacial lake inventory as they found that proglacial freshwater may act as a 'globally relevant' sink for atmospheric CO 2 through chemical reactions in turbid meltwater. ...
Proglacial lakes have increased in number and extent in Arctic Sweden since the 1950s/1960s as glaciers have retreated dramatically. Interrogation of Rapid Eye imagery highlights that some lake terminating glaciers had substantial (>100 m) rates of retreat between 2010 and 2018, with one other land terminating glacier also retreating at a similar rate. However, analysis of a regional remote sensing time series suggests that proglacial lake formation in this period across the area has not been uniform. Despite glacier accumulation areas having similar maximum elevations (∼2,000 m) and similar alpine topography, proglacial lakes in the southern area (Sarek) were found to be significantly smaller than proglacial lakes in the northern area (Kebnekaise), which had smaller glaciers within corries and more prominent terminal moraines. Therefore, it cannot be assumed that proglacial lake formation will occur as glaciers retreat in response to elevated air temperature, particularly as only 33% of glaciers had proglacial lakes in their forefield. Thus, whilst it cannot be assumed that proglacial lakes will accommodate water currently held in glaciers, the 108 lakes mapped here present a substantial area (4.767 ± 0.377 km²) of fresh water that has not previously been included in the Global Lakes and Wetlands Database (GLWD). This inventory therefore provides an important dataset that can be used to underpin our understanding of the role of proglacial lakes within the hydrological system in this area of the Arctic.
... One of the consequences of the ongoing shrinkage of Patagonian glaciers (Figures 7-9) is the formation and expansion of lakes in lands recently abandoned by ice. For example, at the NPI, Loriaux and Casassa (2013) detected an increase in glacial lake area of 66 km 2 between 1945 and 2011. At Monte San Lorenzo, south-east of the NPI, Falaschi et al. (2019) measured a three-fold increase in the number of lakes and 5 km 2 of new lake area formed between 1958 and 2018. ...
This chapter addresses the distribution and characteristics of the Patagonian glaciers together with their recent changes and hydrological implications. Recently published national glacier inventories for the Andes between ca. 37 °S and 55 °S indicate that this region contains 24,000 ice masses covering ca. 26,100 km2. This includes the Southern Patagonia Icefield (SPI), the largest ice mass of the Southern Hemisphere outside Antarctica. The region also includes several thousand smaller ice masses, such as mountain glaciers, valley glaciers, rock glaciers, and perennial snowfields, which collectively are crucial water resources to sustain nature contributions to people, socioeconomic activities, and hydropower generation. Recent findings in mass balance and ice dynamics along the Patagonian Andes highlight the processes behind the mass change and differential response of glaciers to climate change. Although most glaciers have experienced considerable thinning and recession in recent decades, they have not responded in the same manner to climate change. Ice-dynamic processes, such as calving, drive mass change of larger Patagonian glaciers. However, ice melt increases, and snowfall depletion have been attributed as the main cause for the shrinkage of the smaller ice masses. It is expected that glacier retreat will continue impacting runoff and glacier-related hazards. Modeling studies suggest strongest impacts due to this recent ice mass loss can be expected, particularly during the dry season. In concordance with the increase in the number and size of proglacial lakes, there has been an increase in the magnitude and frequency of glacial lake outburst floods in the Patagonian Andes.
... Hindered by turbidity, the derivation of reflectance-depth relationships of a lake from satellite sensors has not yet been reliably achieved (Box and Ski, 2007). Consequently, most studies adopted an empirical approach to calculate the volume or depth of a glacial lake (Evans, 1986;O'Connor et al., 2001;Huggel et al., 2002;Yao et al., 2012;Loriaux and Casassa, 2013;Carrivick and Quincey, 2014). In this study, the most widely used relationship proposed by Huggel et al. (2002) was used to estimate the water storage and depth of the Jionglaco. ...
Glacial lake outburst floods (GLOFs) are a serious potential threat to the safety of life and property in downstream areas. In this study, moraine-dammed glacial lakes in the Yi’ong Zangbo River basin were recognized based on Landsat ETM+/TM/OLI images in 2000 and 2019. Also, GLOFs for the Jionglaco, the largest glacial lake in this basin, were simulated using the one-dimensional hydrodynamic model. The results show that the total number and area of moraine-dammed glacial lakes in this basin increased by 10 (10.52%) and 5.49 km2 (48.24%) from 2000 to 2019, respectively, in which the area of the Jionglaco increased by 3.22 km2. The peak discharge at the breach outlet for five scenarios with different combinations of breach width (80 and 120 m), depth (2.5 and 5 m), and flood time (1.5 and 3 h) are 489 , 1,327.43, 444.32, 617.47, and 1,570.61 m3/s. With the addition of baseflow in the river, the peak discharge at bridge site 15,138.93 km from Jionglaco, is 1,040.89, 1,724.00, 1,024.85, 1,162.25, and 1,990.52 m3/s. The combination of baseflow in river and the GLOF discharge results in an increasing peak discharge in the further downstream region. However, the arrival of peak discharge in downstream areas is delayed, which increases the chances of people escaping.
... For the accuracy of the manual glacier/lake delineation process (δA), we assumed an error of ±1-pixel size (n) (Williams and others, 1997). This delineation error was then multiplied by the perimeter length ( pL) of the glacier/lake feature being mapped (Loriaux and Casassa, 2013;Casassa and others, 2014). (1955), Chile-80 (1983) and GEOTEC (1996) aerial imagery, Structure from Motion (SfM) techniques were applied. ...
Glaciers on Earth along other components of the cryosphere are important for the climate system. However, it is widely known that the vast majority of glaciers are retreating and thinning since the early part of the 20th century. Additionally, future projections have highlighted that at the end of the 21st century, glaciers are going to lose a considerable part of their remaining mass. These glacier changes have several implications for physical, biological and human systems, affecting the water availability for downstream communities and contribute to sea level rise. Unlike other regions, where glaciers are less relevant for the overall hydrology, glaciers in South America constitute a critical resource since minimum flow levels in headwaters of the Andean mountains are usually sustained by ice melt, especially during late summer and droughts, when the contribution from the seasonal snow cover is depleted. In the last decades, the number of studies has increased considerable, however, in the Southern Andes and the surrounding sub-Antarctic islands glaciers still are less studied in comparison with their counterparts in the Northern Hemisphere. The few studies on glacier mass balance in this region suggest a risk of water scarcity for many Andean cities which freshwater supply depends on glacial meltwater. Additionally, glaciers on sub-Antarctic islands have not been completely assessed and their contribution to the sea level rise has been roughly estimated. Hence, the monitoring of glaciers is critical to provide baseline information for regional climate change adaptation policies and facilitate potential hazard assessments. Close and long-range remote sensing techniques offer the potential for repeated measurements of glacier variables (e.g. glacier mass balance, area changes). In the last decades, the number of sensors and methods has increased considerably, allowing time series analysis as well as new and more precise measurements of glacier changes. The main goal of this thesis is to investigate and provide a detailed quantification of glacier elevation and mass changes of the Southern Andes with strong focus on the Central Andes of Chile and South Georgia. Six comprehensive studies were performed to provide a better understanding of the development and current status of glaciers in this region. Overall, the glacier changes were estimated by means of various remote sensing techniques. For the Andes as a whole, the first continent-wide glacier elevation and mass balance was conducted for 85% of the total glacierized area of South America. A detailed estimation of mass changes using the bi-static synthetic aperture radar interferometry (Shuttle Radar Topography Mission -SRTM- and TerraSAR-X add-on for Digital Elevation Measurements -TanDEM-X- DEMs) over the years 2000 to 2011/2015 was computed. A total mass loss rate of 19.43 ± 0.60 Gt a-1 (0.054 ± 0.002 mm a-1 sea level rise contribution) from elevation changes above ground, sea or lake level was calculated, with an extra 3.06 ± 1.24 Gt a-1 derived from subaqueous ice mass loss. The results indicated that about 83% of the total mass loss observed in this study was contributed by the Patagonian icefields (Northern and Southern), which can largely be explained by the dynamic adjustments of large glaciers. For the Central Andes of Chile, four studies were conducted where detailed times series of glacier area, mass and runoff changes were performed on individual glaciers and at a region level (Maipo River basin). Glaciers in the central Andes of Chile are a fundamental natural resources since they provide freshwater for ecosystems and for the densely populated Metropolitan Region of Chile. The first study was conducted in the Maipo River basin to obtain time series of basin-wide glacier mass balance estimates. The estimations were obtained using historical topographic maps, SRTM, TanDEM-X, and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results showed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, with more negative values between 2000 and 2013. A mean basin-wide glacier mass balance of −0.12 ± 0.06 m w.e. a-1 , with a total mass loss of 2.43 ± 0.26 Gt between 1955–2013 was calculated. For this region, a 20% reduction in glacier ice volume since 1955 was observed with associated consequences for the meltwater contribution to the local river system. Individual glacier studies were performed for the Echaurren Norte and El Morado glaciers. Echaurren Norte Glacier is a reference glacier for the World Glacier Monitoring Service. An ensemble of different data sets was used to derive a complete time series of elevation, mass and area changes. For El Morado Glacier, a continuous thinning and retreat since the 20th century was found. Overall, highly negative elevation and mass changes rates were observed from 2010 onwards. This coincides with the severe drought in Chile in this period. Moreover, the evolution of a proglacial lake was traced. If drained, the water volume poses an important risk to down-valley infrastructure. The glacier mass balance for the Central Andes of Chile has been observed to be highly correlated with precipitation (ENSO). All these changes have provoked a glacier volume reduction of one-fifth between 1955 and 2016 and decrease in the glacier runoff contribution in the Maipo basin. The thesis closes with the first island-wide glacier elevation and mass change study for South Georgia glaciers, one of the largest sub-Antarctic islands. There, glaciers changes were inferred by bi-static synthetic aperture radar interferometry between 2000 and 2013. Frontal area changes were mapped between 2003 and 2016 to roughly estimate the subaqueous mass loss. Special focus was given to Szielasko Glacier where repeated GNSS measurements were available from 2012 and 2017. The results showed an average glacier mass balance of −1.04 ± 0.09 m w.e. a-1 and a mass loss rate of 2.28 ± 0.19 Gt a-1 (equivalent to 0.006 ± 0.001 mm a-1 sea level rise) in the period 2000-2013. An extra 0.77 ± 0.04 Gt a-1 was estimated for subaqueous mass loss. The concurrent area change rate of the marine and lake-terminating glaciers amounts to −6.58 ± 0.33 km2 a-1 (2003–2016). Overall, the highest thinning and retreat rates were observed for the large outlet glaciers located at the north-east coast. Neumayer Glacier showed the highest thinning rates with the disintegration of some tributaries. Our comparison between InSAR data and GNSS measurements showed good agreement, demonstrating consistency in the glacier elevation change rates from two different methods. Our glacier elevation and mass changes assessment provides a baseline for further comparison and calibration of model projection in a sparsely investigated region. Future field measurements, long-term climate reanalysis, and glacier system modelling including ice-dynamic changes are required to understand and identify the key forcing factors of the glacier retreat and thinning.
... This group of glaciers also has the greatest magnitude of change in their average geodetic mass balance between the two time periods (Table 4). Increased retreat for lake-terminating glaciers in the NPI has been attributed to glacial lake development and expansion in other studies (Loriaux and Casassa, 2013;Glasser, 2016). This result also agrees with Falaschi et al. (2019), who found the highest thinning rates among laketerminating glaciers from 2000-2012 on the eastern flanks of the SPI and in mountain ranges directly east of the icefields. ...
Southern Andean glaciers contribute substantially to global sea-level rise. Unfortunately, mass balance estimates prior to 2000 are limited, hindering our understanding of the evolution of glacier mass changes over time. Elevation changes over 1976/1979 to 2000 derived from historical KH-9 Hexagon imagery and NASADEM provide the basis for geodetic mass balance estimates for subsets of the Northern Patagonian Icefield (NPI) and the Southern Patagonian Icefield (SPI), extending current mass balance observations by ∼20 years. Geodetic mass balances were −0.63 ± 0.03 m w.e. yr−1 for 63% of the NPI and −0.33 ± 0.05 m w.e. yr−1 for 52% of the SPI glacierized areas for this historical period. We also extend previous estimates temporally by 25% using NASADEM and ASTER elevation trends for the period 2000 to 2020, and find geodetic mass balances of −0.86 ± 0.03 m w.e. yr−1 for 100% of the NPI and −1.23 ± 0.04 m w.e. yr−1 for 97% of the SPI glacierized areas. 2000–2020 aggregations for the same areas represented in the 1976/1979 to 2000 estimates are −0.78 ± 0.03 m w.e. yr−1 in the NPI and −0.80 ± 0.04 m w.e. yr−1 on the SPI. The significant difference in SPI geodetic mass balance in the modern period for 100% vs. 52% of the glacierized area suggests subsampling leads to significant biases in regional mass balance estimates. When we compare the same areas in each time period, the results highlight an acceleration of ice loss by a factor of 1.2 on the NPI and 2.4 on the SPI in the 21st century as compared to the 1976/1979 to 2000 period. While lake-terminating glaciers show the most significant increase in mass loss rate from 1976/1979–2000 to 2000–2020, mass balance trends are highly variable within glaciers of all terminus environments, which suggests that individual glacier sensitivity to climate change is dependent on a multitude of morphological and climatological factors.
... Several area-volume empirical relations of glacial lakes were accordingly proposed and applied to derive lake depth by incorporating bathymetrically derived data, which has reduced some amount of fieldwork in inaccessible terrains (Carrivick 180 and Quincey, 2014;Evans, 1986;Huggel et al., 2002;Loriaux and Casassa, 2013;O'connor et al., 2001;Yao et al., 2012b). ...
As the Third Pole of the Earth and the Water Tower of Asia, Tibetan Plateau (TP) nurtures large numbers of glacial lakes, which are sensitive to global climate change. These lakes modulate the freshwater ecosystem in the region, but concurrently pose severe threats to the valley population by means of sudden glacial lake outbursts and consequent floods (GLOFs). Lack of high-resolution multi-temporal inventory of glacial lakes in TP hampers a better understanding and prediction of the future trend and risk of glacial lakes. Here, we created a multi-temporal inventory of glacial lakes in TP using 30 years record of 42833 satellite images (1990-2019), and discussed their characteristics and spatio-temporal evolution over the years. Results showed that their number and area had increased by 3285 and 258.82 km2 in the last 3 decades, respectively. We noticed that different regions of TP exhibited varying change rates in glacial lake size, most regions show a trend of expansion and increase in glacial lakes, while some regions show a trend of decreasing such as the western Pamir and the eastern Hindu Kush. The mapping uncertainty is about 17.5%, lower than other available datasets, thus making our inventory reliable for the spatio-temporal evolution analysis of glacial lakes in TP. Our lake inventory data are freely available at https://doi.org/10.5281/zenodo.5574289 (Dou et al, 2021), it can help to study climate change-glacier-glacial lake-GLOF interactions in the Third Pole and serve input to various hydro-climatic studies.
... This will be caused by the replacement of predictable summer glacier melt by less predictable rainfall events and snowmelt runoff regimes, and these shifts are already visible in the Pyrenees and the Alps (Milner et al., 2017). In the recent decades, retreating glaciers produce lakes at their fronts in many high mountain regions (Gardelle et al., 2011;Loriaux & Casassa, 2013), and lake outbursts are causing floods. Major floods in mountain areas are also generated by rain-on-snow events 24 (Jeong & Sushama, 2018) that are favored by climate change. ...
Mountains and mountain rivers provide a multitude of invaluable goods and services to a profound portion of the planet’s population. As “water towers” of the Earth mountains are sources of the mightiest world rivers and play a pivotal role for global biodiversity, freshwater, and sediment supply. Distinct morphological, climatic, hydrological, hydrochemical, and biological features of mountainous river ecosystems, compared to lowland ones, make them particularly fragile and vulnerable to human interference. Despite a number of remote mountain areas and rivers still remaining intact from direct human pressures, the majority of mountain ecosystems, are being increasingly threatened by adverse local and global changes driven by market economy. To efficiently conserve and sustainably use mountain ecosystems and contribute to the survival of the planet, it is critical to change our standards and life attitudes by realizing and appreciating our immediate connection to the global ecosystem, change attitudes and current consumption patterns, and stimulate the ways our global society functions and interacts with the natural environment.
... One such relationship developed by Huggel et al. (2002) using various types of lakes situated globally has gained significant attention and has been used by many researchers in several studies to estimate lake volume (Huggel et al. 2004;Bolch et al. 2011;Mergili and Schneider 2011;Jain et al. 2012;Byers et al. 2013;Gruber and Mergili 2013;Wilcox et al. 2013;Che et al. 2014). However, this equation had also been modified for specific locations by Loriaux and Casassa (2013) and Yao et al. (2012c). However, there is still a question on applying these empirical relationships confidently across a range of locations and to various types of lakes (Cook and Quincey 2015). ...
Glacial Lake Outburst Floods (GLOFs) in a deglaciating environment, representing significant threat to downstream people and infrastructure, increasing the necessity of prioritization and assessment of potentially critical glacial lakes (PCGLs). In this current study, a comprehensive updated inventory of glacial lakes for the Indus River basin has been prepared, resulting in 5,335 lakes (≥ 0.0025 ± 0.0006 km²), covering a total area of 173.95 ± 10.13 km². Parameters have been derived using satellite data for two purposes, ‘preliminary screening’ and ‘quantitative assessment’. Using 4 parameters, 367 lakes were preliminary screened-in for further analysis, and 6 quantitative parameters were analysed using Equal Weights (EW) and Unequal Weights methods (UEW). These both methods were applied for two scenarios, scenario-1 which considers 73 lakes (≥ 0.1 km²), and scenario-2 which considers all 367 preliminary screened-in lakes (≥ 0.02 km²). UEW outperformed EW analysis and identified 20 and 48 high potential lakes for scenario-1 and scenario-2 respectively, where all 20 lakes of scenario-1 have been found in common with those of scenario-2, with a difference in their rank. But only 10 of them have storage volume ≥10 MCM and has been flagged as high-risk lakes, of which 6 are end-moraine dammed lakes and have been considered as PCGLs, due to their high bursting potential and self-destructive nature. Rest 4 high risk lakes along with remaining 38 lakes with volume <10 MCM, are considered as critical lakes in case of dynamic mode of failure, caused due to mass movement of avalanche, landslide, heavy precipitation, etc.
... In particular, post-Little Ice Age climatic warming has enhanced ice melt, leading to the development of a large number of glacial lakes behind ice dams, lateral and terminal moraines and within over-deepened de-glaciated valley bottoms (Quincey et al., 2007;Wilson et al., 2018). Glacial lakes are important globally and regionally as (1) they represent a considerable water resource (Loriaux and Casassa, 2013), (2) when in contact with or dammed by glaciers, they can have negative impacts on glacier mass balance (e.g. King et al., 2019), and (3) they are the source of glacial lake outburst floods (GLOFs; Richardson and Reynolds, 2000;Carrivick and Tweed, 2016;Harrison et al., 2018) which are considered to be the largest and most extensive glacial hazard in terms of disaster and damage potential (UNEP, 2007). ...
Glacier recession in response to climate warming has resulted in an increase in the size and number of glacial lakes. Glacial lakes are an important focus for research as they impact water resources, glacier mass balance, and some produce catastrophic glacial lake outburst floods (GLOFs). Glaciers in Peru have retreated and thinned in recent decades, prompting the need for monitoring of ice- and water-bodies across the cordilleras. These monitoring efforts have been greatly facilitated by the availability of satellite imagery. However, knowledge gaps remain, particularly in relation to the formation, temporal evolution, and catastrophic drainage of glacial lakes. In this paper we address this gap by producing the most current and detailed glacial lake inventory in Peru and provide a set of reproducible methods that can be applied consistently for different time periods, and for other mountainous regions.
The new lake inventory presented includes a total of 4557 glacial lakes covering a total area of 328.85 km². In addition to detailing lake distribution and extent, the inventory includes other metrics, such as dam type and volume, which are important for GLOF hazard assessments. Analysis of these metrics showed that the majority of glacial lakes are detached from current glaciers (97%) and are classified as either embedded (i.e. bedrock dammed; ~64% of all lakes) or (moraine) dammed (~28% of all lakes) lakes. We also found that lake size varies with dam type; with dammed lakes tending to have larger areas than embedded lakes. The inventory presented provides an unparalleled view of the current state of glacial lakes in Peru and represents an important first step towards (1) improved understanding of glacial lakes and their topographic and morphological characteristics and (2) assessing risk associated with GLOFs.
... hydropower, tourism, outburst hazards; cf. (Bajracharya and Mool 2009;Haeberli et al. 2016;Loriaux and Casassa 2013;Terrier et al. 2011). ...
... Meltwater can be withdrawn for human use or stored in glacial lakes (Haeberli and Linsbauer, 2013). For example, in Patagonia, terrestrial storage in the lakes of the Northern Patagonian Icefield is as high as 10% of its glacier melt contribution to sea level rise (Loriaux and Casassa, 2013). ...
Glacier ice, including ice sheets and ice caps, covers about 10% of the Earth's surface and stores 69% of freshwater. Over the last millennium, glaciers reached their maximum extent during the Little Ice Age but began to retreat at the end of the 19th century. Glacier wastage has been accelerating worldwide since the second half of the 20th century. Currently, glaciers across most of the polar and mountain regions have negative mass balance dominated by surface melt. This global trend is attributed to the continuing climatic warming. Glaciers in the Karakoram-Kunlun-Pamir region are a notable exception. Recent advancements in satellite data acquisition enabled more reliable assessments of mass balance of ice sheets. Increasing loss of ice from the Greenland and West Antarctic ice sheets and their peripheral glaciers has been observed since the 1990s. The combined glacier and ice sheet contribution is now the dominant source of global mean sea level rise. The Greenland ice sheet makes the largest contribution followed by a combined input from glaciers. Both significantly exceed that of Antarctica. Alaska, the Canadian Arctic, and the Southern Andes account for the largest contribution from glaciers. Glacier wastage is expected to continue in the future, and in many mountain regions glaciers may disappear or retreat to high elevations. Large uncertainty surrounds future evolution of ice sheets but there is a possibility that the Greenland ice sheet may decline to the point of no recovery.
... Chilean Patagonia appears to be particularly vulnerable to GLOFs, which is frequently described in the literature as a consequence of the rise in the number of glacial lakes related to the accelerated glacier recession in the southern Andes . Between 1945 and 2011, it is estimated that the glacial lake volume for the NPI has increased by 4.8 km³, with the largest increase after 1987 (Loriaux and Casassa, 2013). During the last decades, Patagonian glacial lakes, excluding the three largest lakes Argentino, Viedma, and San Martin, have more than doubled in volume (Shugar et al., 2020), and their number increased from 2926 to 4202 (43 %) . ...
Glacial Lake Outburst Floods (GLOFs) constitute one of the most notorious and destructive geohazards worldwide. They have occurred throughout recorded history and form a constant threat for local communities near glacierized regions. Although the recent deglaciation resulted in an increase in glacial lakes, both in size and number, worldwide, little is known about the possible relationship between climate variability and GLOF occurrence. Yet, it is generally assumed that GLOF frequency is currently increasing due to global glacier retreat. This is mainly due to a lack of continuous long-term flood records. Current records of GLOF occurrence, which are based on instrumental and historical data, are intrinsically limited to the last centuries. Consequently, the effect of climate change on GLOF occurrence and the likely evolution of GLOFs under future climate change scenarios remains unclear. However, a comprehensive understanding of the link between climate change, glacier variability, and GLOF occurrence is fundamental for future GLOF predictions and to improve flood hazard assessments. As in many other glacierized regions, GLOFs are a well-known phenomenon in the Patagonian Andes. They are particularly pronounced in the Baker region of Chilean Patagonia (47–48 °S), where repeated GLOFs occurred from the abrupt drainage of ice-dammed Cachet 2 Lake between April 2008 and November 2020. During these events, water from Cachet 2 Lake spills into Colonia River, a tributary of Baker River, and increases both river discharge and sediment suspended concentrations. Colonia GLOFs are able to block the regular Baker River flow and result in the inundation of large areas upstream of the Colonia-Baker confluence, such as the Valle Grande floodplain. Downstream, the Baker River triples in discharge and large amounts of sediment are transported, and ultimately deposited, in fjords. The repeated Baker River GLOFs during the 21st century and the location of the Baker River, which drains most of the eastern side of the Northern Patagonian Icefield (NPI) and therefore integrates meltwater from several lake-river systems, makes the Baker region ideally suited to investigate GLOFs and to study the impact of climate change on GLOF occurrence. To examine how GLOFs are recorded in fjord sediments, this study mapped the bathymetry of the head of Martínez Channel, i.e. the fjord in which the Baker River discharges, using multibeam echosounding. Results show that the subaquatic delta of Baker River is deeply incised by sinuous channels. The presence of sediment waves and coarser sediment within these channels suggest recent channel activity by turbidity currents. The latter is confirmed by sediment records collected at the head of the fjord, which reveal the presence of turbidites intercalated within silty background sediments, particularly on the delta plain in front of the main submarine channel. Although the turbidity currents are most likely generated by elevated river discharge and the associated relatively high suspended sediment loads, most turbidites are not related to GLOFs. Instead, they seem to represent other extreme discharge events, such as extreme precipitation or rain-on-snow events. By comparing geochemical and sedimentological results obtained on the sediment cores to the recent GLOF history of Baker River, we show that the recent 21st century Cachet 2 GLOF deposits can be distinguished from background sediments by their finer grain size and lower organic carbon content, reflecting the increased input of glacial sediments during GLOFs. In addition, the results obtained on the fjord sediment cores demonstrate that the 21st century GLOFs from Cachet 2 Lake, which occurred less than one year apart, are not recorded as individual layers but as units richer in sediment of glacial origin. This suggests that it is not possible to reconstruct GLOF frequency nor magnitude solely based on fjord sediments. Although 21 GLOFs from Cachet 2 Lake occurred between 2008 and 2017, the deposits with the clearest GLOF signature represent the initial events, implying that more glacial sediment was released during those first GLOFs, possibly due to lake-bed erosion. Consequently, it appears that sediment availability plays a more important role than flood magnitude in controlling GLOF deposit properties. Although GLOF frequency and magnitude cannot be accurately reconstructed using fjord sediments, high accumulation rates at the head of Martínez Channel highlight the potential of fjord sediment archives to establish pre-historical GLOF records at high temporal resolution. In addition, the bathymetric imagery and the sediment records obtained at the head of Martínez Channel show that site selection and multi-coring are fundamental to reconstruct the Baker River GLOF history, as fjord heads are dynamic sedimentary environments with rapidly migrating channels. Ideal locations to reconstruct GLOFs are found on the delta slope, away from any submarine channel influence. GLOF deposits are best identified close to the river mouth, as background sediments become progressively finer and less organic, thus more similar to GLOF deposits, with increasing distance from the lip of the Baker River delta. Given the unique context of the Baker River system, where a significant portion of the watershed is vegetated and where the fine and organic-poor signature of GLOF deposits clearly contrasts with the slightly coarser and organic background sediments, our results may only be applicable to fjord sediments from temperate regions. Distinguishing GLOF deposits from background sediments would likely be more challenging in high latitude fjords. Sediments deposited in floodplains constitute another faithful recorder of Baker River GLOFs. In the Valle Grande floodplain, which is located immediately upstream of the Colonia-Baker confluence, GLOFs are registered as organic-poor deposits intercalated within organic-rich background sediments. In contrast to marine archives, the sediments of the Valle Grande floodplain have lower accumulation rates, and can therefore be used to determine changes in GLOF occurrence on longer timescales (late Holocene). Based on four radiocarbon-dated sediment cores collected in the Valle Grande floodplain, our results show that high-magnitude GLOFs occurred intermittently in the upper Baker River watershed over the past 2.75 kyr. Two periods of increased flood activity occurred between approximately 2.57 and 2.17 cal kyr BP, and from 0.75 to 0 cal kyr BP. Comparison with independent proxy records of glacier variability reveals that these two periods of increased flood frequency match with Neoglacial advances. These advances seem to result from lower-than-average temperatures and wetter conditions. Based on these results, we suggest that there is a strong, yet indirect, link between climate variability and GLOF occurrence. We hypothesize that, on multi-millennial timescales, high-magnitude GLOFs from eastern NPI glaciers are more frequent at times when glaciers are larger and thicker, as such glaciers most likely form larger and stronger ice dams, which in turn are able to retain larger lakes. Our results therefore suggest that the probability that high-magnitude GLOFs occur decreases as glaciers thin and retreat. Conversely, the frequency of lower magnitude GLOFs tends to increase during glacier recession because of the rapid growth of glacial lakes and formation of new lakes. Although isolated cases of new lakes formed behind large glaciers could still produce large GLOFs locally, the likelihood of large lake drainage and therefore high-magnitude GLOF occurrence decreases. This study supports the use of sediment-based GLOF records in other GLOF-prone regions for proper flood hazard assessment. A broader knowledge of the impact of climate change on GLOF occurrence can help to prevent further development in flood-prone regions and will reduce the vulnerability of communities to floods. Long-term paleoflood records can be of great importance for integrating spatial planning and planned infrastructure projects, such as hydroelectric dams, particularly since electricity demand is increasing with economic growth.
... GLOFs are of particular contemporary interest due to the role of climate change on the magnitude and frequency of events and therefore societal risk (Carrivick and Tweed, 2016). In a global analysis of GLOFs it was found there was a decrease in flood frequency over recent decades (Carrivick and Tweed, 2016), despite remote sensing studies that show an increase in the number and area of glacial lakes in regions such as Greenland (Carrivick and Quincey, 2014), the Himalaya (Dubey and Goyal, 2020) and Patagonia (Loriaux and Casassa, 2013;Wilson et al., 2018). Focusing only on moraine dam failures, Harrison et al. (2018) note a reduction in floods since the 1970s, but also argue that the greatest frequency of events (1930se1960s) reflect a lagged response to warming at the end of the Little Ice Age (LIA). ...
Glacier outburst floods are a major hazard in glacierized catchments. Global analyses have shown reduced frequency of glacier floods over recent decades but there is limited longer-term data on event magnitude and frequency. Here, we present a Holocene palaeoflood record from the Río Baker (Chilean Patagonia), quantifying the discharge and timing of glacier floods over millennial timescales. A catastrophic flood of 110,000 m³/s (0.11 Sv) occurred at 9.6 ± 0.8 ka, during final stages of the Late Glacial Interglacial Transition, followed by five flood-phases coeval or post-dating Holocene neoglacials. Highest flood frequencies occurred at 4.3–4.4 ka, with 26 floods of minimum discharges of 10,000–11,000 m³/s, and 0.6 ka with 10 floods exceeding 4600–5700 m³/s. The largest modern outburst flood recorded surpassed ∼3810 m³/s. Thus glacier flood magnitude declines from the order of 0.1 to 0.01 Sv over the Early to Mid Holocene, and to 0.001 Sv in the instrumental record.
... Despite the widths of uncertainty bands and prediction intervals of these datasets being high (Froehlich, 1995;Wahl, 2004), they represent useful tools for approximating the range of plausible values. Evans, 1986;O'Connor et al., 2001;Huggel et al., 2002;Wang et al., 2012;Fujita et al., 2013;Loriaux and Casassa, 2013;Emmer and Vilimek, 2014;Cook and Quincey, 2015;Kapitsa et al., 2017;Muñoz et al., 2020 Breach time: tb MacDonald and Langridge- Monopolis, 1984;Costa, 1985;Bureau of Reclamation, 1988;Von Thun and Gillette, 1990;Froehlich, 1995;Wahl, 2004 Peak discharge: Qp Kirkpatrick, 1977;Price et al., 1977;Soil Conservation Service, 1981;Bureau of Reclamation, 1982;Hagen, 1982;MacDonald and Langridge-Monopolis, 1984;Singh and Snorrason, 1984;Costa, 1985;Evans, 1986;Froehlich, 1995;Wahl, 2004 3.5 Process chain simulation with r.avaflow 195 We back-calculate part of the complex GLOF process chain, employing the simulation tool r.avaflow (Mergili et al., 2017;Pudasaini and Mergili, 2019;. r.avaflow is a GIS-based open source simulation framework for multi-phase mass flows, which has the capacity to dynamically compute the interaction between landslides and lakes. ...
We analyze and reconstruct a recent Glacial Lake Outburst Flood (GLOF) process chain on 26 June 2020, involving the moraine-dammed proglacial lake Jinwuco (30.356°N, 93.631°E) in eastern Nyainqentanglha, Tibet, China. Satellite images reveal that from 1965 to 2020, the surface area of Jinwuco has expanded by 0.2 km2 (+56%) to 0.56 km2, and subsequently decreased to 0.26 km2 (-54%) after the GLOF. Estimates based on topographic reconstruction and sets of published empirical relationships indicate that the GLOF had a volume of 10 million m3, an average breach time of 0.62 hours, and an average peak discharge of 5,390 m3/s at the dam. Based on pre-and post-event high-resolution satellite scenes, we identified a large progressive debris landslide originating from western lateral moraine, having occurred 5-17 days before the GLOF. This landslide was most likely triggered by extremely heavy, south Asian monsoon-associated rainfall in June. The time lag between the landslide and the GLOF suggests that pre-weakening of the dam due to landslide-induced outflow pushed the system towards a tipping point, that was finally exceeded following subsequent rainfall, snowmelt, a secondary landslide, or calving of ice into the lake. We back-calculate part of the GLOF process chain, using the GIS-based open source numerical simulation tool r.avaflow. Two scenarios are considered, assuming a debris landslide-induced impact wave with overtopping and resulting retrogressive erosion of the moraine dam (Scenario A), and retrogressive erosion due to pre-weakening of the dam without a major impact wave (Scenario B). Both scenarios yield plausible results which are in line with empirically derived ranges of peak discharge and breach time. The breaching process is characterized by a slower onset and a resulting delay in Scenario B, compared to Scenario A. Evidence, however, points towards Scenario B as a more realistic possibility. There were no casualties from this GLOF but it caused severe destruction of infrastructure (e.g. roads and bridges) and property losses in downstream areas. Given the clear role of continued glacial retreat in destabilizing the adjacent lateral moraine slopes, and directly enabling the landslide to deposit into the expanding lake body, the GLOF process chain under Scenario B can be robustly attributable to anthropogenic climate change, while downstream consequences have been enhanced by the development of infrastructure on exposed flood plains. Such process chains could become more frequent under a warmer and wetter future climate, calling for comprehensive and forward-looking risk reduction planning.
... For the accuracy of the manual glacier/lake delineation process (δ A ), we assumed an error of ±1-pixel size (n) (Williams and others, 1997). This delineation error was then multiplied by the perimeter length ( pL) of the glacier/lake feature being mapped (Loriaux and Casassa, 2013;Casassa and others, 2014). ...
Using an ensemble of close- and long-range remote sensing, lake bathymetry and regional
meteorological data, we present a detailed assessment of the geometric changes of El Morado Glacier in the Central Andes of Chile and its adjacent proglacial lake between 1932 and 2019. Overall, the results revealed a period of marked glacier down wasting, with a mean geodetic glacier mass balance of −0.39 ± 0.15 m w.e.a−1 observed for the entire glacier between 1955 and 2015 with an area loss of 40% between 1955 and 2019. We estimate an ice elevation change of −1.00 ± 0.17 m a−1 for the glacier tongue between 1932 and 2019. The increase in the ice thinning rates and area loss during the last decade is coincident with the severe drought in this region (2010–present), which our minimal surface mass-balance model is able to reproduce. As a result of the glacier changes observed, the proglacial lake increased in area substantially between 1955
and 2019, with bathymetry data suggesting a water volume of 3.6 million m3 in 2017. This study highlights the need for further monitoring of glacierised areas in the Central Andes. Such efforts would facilitate a better understanding of the downstream impacts of glacier downwasting.
... One of the consequences of the ongoing shrinkage of Patagonian glaciers (Figures 7-9) is the formation and expansion of lakes in lands recently abandoned by ice. For example, at the NPI, Loriaux and Casassa (2013) detected an increase in glacial lake area of 66 km 2 between 1945 and 2011. At Monte San Lorenzo, south-east of the NPI, Falaschi et al. (2019) measured a three-fold increase in the number of lakes and 5 km 2 of new lake area formed between 1958 and 2018. ...
The Andes Cordillera contains the most diverse cryosphere on Earth, including extensive areas covered by seasonal snow, numerous tropical and extratropical glaciers, and many mountain permafrost landforms. Here, we review some recent advances in the study of the main components of the cryosphere in the Andes, and discuss the changes observed in the seasonal snow and permanent ice masses of this region over the past decades. The open access and increasing availability of remote sensing products has produced a substantial improvement in our understanding of the current state and recent changes of the Andean cryosphere, allowing an unprecedented detail in their identification and monitoring at local and regional scales. Analyses of snow cover maps has allowed the identification of seasonal patterns and long term trends in snow accumulation for most of the Andes, with some sectors in central Chile and central-western Argentina showing a clear decline in snowfall and snow persistence since 2010. This recent shortage of mountain snow has caused an extended, severe drought that is unprecedented in the hydrological and climatological records from this region. Together with data from global glacier inventories, detailed inventories at local/regional scales are now also freely available, providing important new information for glaciological, hydrological, and climatological assessments in different sectors of the Andes. Numerous studies largely based on field measurements and/or remote sensing techniques have documented the recent glacier shrinkage throughout the Andes. This observed ice mass loss has put Andean glaciers among the highest contributors to sea level rise per unit area. Other recent studies have focused on rock glaciers, showing that in extensive semi-arid sectors of the Andes these mountain permafrost features contain large reserves of freshwater and may play a crucial role as future climate becomes warmer and drier in this region. Many relevant issues remain to be investigated, however, including an improved estimation of ice volumes at local scales, and detailed assessments of the hydrological significance of the different components of the cryosphere in Andean river basins. The impacts of future climate changes on the Andean cryosphere also need to be studied in more detail, considering the contrasting climatic scenarios projected for each region. The sustained work of various monitoring programs in the different Andean countries is promising and will provide much needed field observations to validate and improve the analyses made from remote sensors and modeling techniques. In this sense, the development of a well-coordinated network of high-elevation hydro-meteorological stations appears as a much needed priority to complement and improve the many glaciological and hydro-climatological assessments that are being conducted across the Andes.
... Glacier recession is accelerating in Patagonia (Aniya, 1999;Meier et al., 2018;Braun et al., 2019), causing sea level rise (Gardner et al., 2013;Malz et al., 2018), enlarging glacial lakes and increasing flood risk (Loriaux and Casassa, 2013;Wilson et al., 2018), and affecting water availability and hydropower opportunities (Huss and Hock, 2018;Milner et al., 2017). The Southern Andes region had a mass loss of 1,208 Gt from 1961 to 2016, and is the largest contributor to global sea level rise outside of Greenland and Alaska (Zemp et al., 2019). ...
We present PATICE, a GIS database of Patagonian glacial geomorphology and recalibrated chronological data. PATICE includes 58,823 landforms and 1,669 geochronological ages, and extends from 38°S to 55°S in southern South America. We use these data to generate new empirical reconstructions of the Patagonian Ice Sheet (PIS) and subsequent ice masses and ice-dammed palaeolakes at 35 ka, 30 ka, 25 ka, 20 ka, 15 ka, 13 ka (synchronous with the Antarctic Cold Reversal), 10 ka, 5 ka, 0.2 ka and 2011 AD. At 35 ka, the PIS covered of 492.6 x10³ km², had a sea level equivalent of ~1,496 mm, was 350 km wide and 2090 km long, and was grounded on the Pacific continental shelf edge. Outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams. The PIS reached its maximum extent by 33 – 28 ka from 38°S to 48°S, and earlier, around 47 ka from 48°S southwards. Net retreat from maximum positions began by 25 ka, with ice-marginal stabilisation then at 21 – 18 ka, which was then followed by rapid irreversible deglaciation. By 15 ka, the PIS had separated into disparate ice masses, draining into large ice-dammed lakes along the eastern margin, which strongly influenced rates of recession. Glacial readvances or stabilisations occurred at least at 14 – 13 ka, 11 ka, 6 – 5 ka, 2 – 1 ka, and 0.5 – 0.2 ka. We suggest that 20th century glacial recession (% a⁻¹) is occurring faster than at any time documented during the Holocene.
... Glacier shrinking has resulted in the formation and expansion of a large number of glacial lakes on/in front of the glaciers (Ding and Liu, 1992;Komori, 2008;Benn et al., 2012;Sakai, 2012). This tendency has been observed worldwide over the last several decades, e.g., in the Third Pole (Gardelle, et al., 2011;Zhang et al., 2015), central Asia (Wang et al., 2013) and extra-tropical Andes (Loriaux and Casassa, 2013). The evolution of glacial lakes has exacerbated glacier hazards such as glacial lake outburst floods (GLOF). ...
... The latter, in particular, is supposed to play a predominant role, both in affecting basal sliding and the efficiency of direct glacierbed erosion, and in evacuating sediments keeping the bedrock accessible for further erosion (Haeberli et J o u r n a l P r e -p r o o f region (Gardelle et al., 2011;Worni et al., 2013;Zhang et al., 2015;Salerno et al., 2016), Mount Everest (Wessels et al., 2002;Bolch et al., 2008;Tartari et al., 2008;Salerno et al., 2012), the Tibetan Plateau (Zhang et al., 2017), Tien Shan (Bolch et al., 2011) and Bhutan (Komori, 2008). There are also examples in South America, across the Andes (Loriaux and Casassa, 2012;Hanshaw and Bookhagen, 2014;Emmer et al., 2016;Drenkhan et al., 2018). Some studies refer to Iceland (Schomacker, 2010), Alaska (Capps and Clague, 2014) and the Caucasus (Stokes et al., 2007). ...
Aosta Valley (Western Alps, Italy) is the region with the largest glacierized area of Italy. Like other high mountain regions, it has shown a significant glacier retreat starting from the end of the ‘Little Ice Age’ that is expected to continue in the future. As a direct consequence of glacier shrinkage, glacier-bed overdeepenings become exposed, offering suitable geomorphological conditions for glacier lakes formation. In such a densely populated and developed region, opportunities and risks connected to lakes may arise: 1) economic exploitation for hydropower production, tourism and water supply; 2) environmental relevance for high mountain biodiversity and geodiversity; 3) potential risks due to outbursts and consequent floods.
In this study, the locations of potential future glacier lakes over large glacierized areas (183 glaciers covering 163,1 km2) of Aosta Valley were assessed by using the GlabTop2 model.
46 overdeepenings larger than 10,800 m2 were identified, covering an area of 3.1 ± 0.9 km2 and having a volume of 0.06 ± 0.02 km3. The majority of the overdeepenings are located in the Monte Rosa-Cervino massif and a mean depth <10 m characterizes them. Moreover, an estimation of the most recent total ice volume for the Aosta Valley was provided (5.2 ± 1.6 km3 referred to 2008).
Thanks to the validation by the proposed “backward approach” and GPR (Ground Penetrating Radar) data, we can confirm that the location of the overdeepenings is robust while their actual dimensions are subject to considerable uncertainties. Almost all of large lakes (area > 10,000 m2), potentially the most dangerous, are modelled. Finally, we suggest choosing medium pixel size (about 60 m) of the DEM in order to obtain, at least, the location of the largest lakes and to avoid overestimations of ice thickness and thus a great number of false positive overdeepenings.
The results presented here can be useful for understanding how the alpine environment will look in the future and can help the management of water resources and risks related to glacier lakes.
... Due to the absence of bathymetric data for Safed Lake, we employed an area-based scaling relationship to calculate the total volume of the lake. Several empirical relationships are available to roughly estimate the total volume of glacial lakes based on the total surface area [24,[27][28][29][30][31]. The relation given by Huggel et al. [24] is among the most widely used and has been employed in several previous GLOF hazard studies, where no direct bathymetric measurements are available [14,[32][33][34][35][36][37]. ...
Climate change has led to the formation of numerous high-altitude lakes of glacial origin in the Himalaya. Safed Lake is one of the largest glacial lakes, located at an elevation 4882 m a.s.l. in the state of Uttarakhand, central Himalaya, India. A temporal analysis of the lake surface using satellite imagery shows that the lake has grown more than double its size from 0.10 km 2 to 0.23 km 2 over the past 50 years. In this study, we performed a hazard assessment of the lake using 1D and 2D hydrodynamic modeling. We identified the potential glacial lake outburst flood (GLOF) triggering factors and evaluated the impact of a moraine breach event of the lake on the nearest village located 16.2 km downstream of the lake. A series of dynamic simulations were performed for different scenario-models based on varied breach depths, breach widths and time of moraine failure. In a worst-case GLOF scenario where breach depth reached up to 60 m, hydrodynamic routing of the breach hydrograph along the given channel revealed inundation depth up to 5 m and flow velocities up to 3.2 m s −1 at Milam village. Considering the flat geometry of the frontal moraine, hazard assessment of the lake was performed by for different breach incision depths (30 and 15 m). In addition, the study incorporated a series of hydrodynamic routing to understand the sensitivity of GLOF to different model input parameters and terrain conditions. The sensitivity of the initial GLOF hydrograph to breach formation time (T f) was evaluated by considering different hypothetical breach scenarios with a varied time of failure. Increases of 11.5% and 22% in the peak flooding were recorded when the moraine failure time was decreased by 15 and 30 min respectively. The two-dimensional sensitivity revealed flow velocity (m s −1) to be more sensitive to change in Manning's N when compared to the inundation depth (m). Changes of 10.7% and 0.5% in the mean flow velocity (in m s −1) and flow depth (in m) were recorded when dN was 0.01. The flow velocity was more sensitive to the slope and the top-width of the channel when compared to the inundation depths. A regression of flow velocity versus slope gives a correlation coefficient of 0.76. GLOF flow hydraulics are sensitive to changes in terrain elevation, where flow depth and velocity vary in a similar manner.
... From a fluvial geomorphological perspective, these are events that can generate radical changes in the shape of rivers (Ulloa et al., 2015). According to the glacial lake survey done by Loriaux and Casassa (2013), beyond the risk of GLOFs, glacial lakes have an important role as buffer units. As glaciers retreat, lakes formed store important volumes of water which would otherwise contribute to rising sea level. ...
Fluvial systems provide multiple life-supporting functions, but their values are affected by a range of anthropogenic disturbances. Hydromorphology is used as a conceptual framework for assessing the status of fluvial systems and design river restoration strategies but is rarely applied to nearly pristine environments. This paper presents one of the first assessments of river characteristics and changes in the Aysen Region, an area in southern Chilean Patagonia. The analysis of multitemporal satellite images allowed to define key patterns related to river morphology of the Exploradores river network. The Exploradores basin experienced only limited and recent human disturbances, and fluvial changes are related almost only to natural climatic or geomorphological processes. The river experienced moderate reduction of active channel width and braiding index over the past 70 years. The basin represents a suitable site to study fluvial processes and dynamics in nearly reference conditions, and changes due to the likely increase of human activities and disturbances in the near future.
... hydropower, tourism, outburst hazards; cf. (Bajracharya and Mool 2009;Haeberli et al. 2016;Loriaux and Casassa 2013;Terrier et al. 2011). ...
Climate change has enormous impacts on the cryosphere In the Indian Himalayan Region (IHR) which have been increasingly documented over the past years. The effects of cryosphere change on people, ecosystems and economic sectors is less clear but bears important risks. Adaptation to changing conditions and risks is a priority for the region. Here we draw on experiences of Indo-Swiss collaborations in the field of climate change, cryosphere, risks and adaptation in the IHR. First, we provide a synthesis of the climate and cryosphere in the IHR, and related impacts on downstream communities and systems. Second, we analyze the associated risks from a conceptual and adaptation perspective. We then introduce concepts of co-production of knowledge as an approach to an inclusive and sustainable adaptation process which includes the development of future scenarios with a wide range of stakeholders. We visualize this approach using examples of the water resource sector.
Glacial lake outburst floods (GLOFs) are a severe threat to communities in the Himalayas; however, GLOF mitigation strategies have been implemented for only a few lakes, and future changes in hazard are rarely considered. Here, we present a comprehensive assessment of current and future GLOF hazard for Gepang Gath Lake, Western Himalaya, considering rock and/or ice avalanches cascading into the lake. We consider ground surface temperature and topography to define avalanche source zones located in areas of potentially degrading permafrost. GLOF process chains in current and future scenarios, also considering engineered lake lowering of 10 and 30 m, were evaluated. Here, varied avalanche impact waves, erosion patterns, debris flow hydraulics, and GLOF impacts at Sissu village, under 18 different scenarios were assessed. Authors demonstrated that a larger future lake does not necessarily produce larger GLOF events in Sissu, depending, among other factors, on the location from where the triggering avalanche initiates and strikes the lake. For the largest scenarios, 10 m of lowering reduces the high‐intensity zone by 54% and 63% for the current and future scenarios, respectively, but has little effect on the medium‐intensity flood zone. Even with 30 m of lake lowering, the Sissu helipad falls in the high‐intensity zone under all moderate‐to‐large scenarios, with severe implications for evacuations and other emergency response actions. The approach can be extended to other glacial lakes to demonstrate the efficiency of lake lowering as an option for GLOF mitigation and enable a robust GLOF hazard and risk assessment.
Glacial lake outburst floods (GLOFs) is one of the main natural disasters in alpine areas, which can cause extreme destruction to downstream settlements and infrastructures. A moraine-dammed lake named JiwenCo glacial lake (JGL) in the southeastern Qinghai-Tibetan Plateau failed on 26 June 2020, destroying many buildings, roads, bridges, and farmlands along the flow path. We reconstructed the process of this GLOF event by the Hydrological Engineering Center’s River Analysis System (HEC-RAS) and examined the JGL’s evolution (area, length, and volume) before its outburst, based on the measured cross sections and hydrological data, videos, and pictures taken by inhabitants, DEM data, and Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper (ETM+)/Operational Land Imager (OLI) images. The result showed that area, length, and volume of the JGL increased by 0.20 ± 0.07 km ² , 0.66 ± 0.03 km, and 0.03 ± 0.001 km ³ from 1988 to 2020 (before the outburst), respectively. Approximately 0.05 km ³ of water volume was discharged with the dropped water level of 15.63 m after the outburst. The peak flow was 534.4 m ³ /s at breach and increased to 1,408.11 m ³ /s at Zhongyu town. The difference between the simulated and measured peak flows in Zhongyu town was 41.88 m ³ /s (3.53%), showing the high accuracy of the modeling results. For villages along the river-channel, the highest velocity was found in Yiga village (14.23 m/s) and the lowest was in Gongwa village (1.22 m/s). The maximum depth was gradually increased as the river reached downstream, 8.03 m in Yiga village and 50.96 m in Duiba village. The combination of landslide, high temperature, and extremely heavy precipitation resulted in this GLOF disaster. An integrated disaster prevention and mitigation plan needs to be developed for susceptible areas such as Niduzangbo basin that experienced two GLOFs in recent 10 years.
Recent studies indicate that - due to climate change - the Earth is undergoing rapid changes in all cryospheric components, including polar sea ice shrinkage, mountain glacier recession, thawing permafrost, and diminishing snow cover. This book provides a comprehensive summary of all components of the Earth's cryosphere, reviewing their history, physical and chemical characteristics, geographical distributions, and projected future states. This new edition has been completely updated throughout, and provides state-of-the-art data from GlobSnow-2 CRYOSAT, ICESAT, and GRACE. It includes a comprehensive summary of cryospheric changes in land ice, permafrost, freshwater ice, sea ice, and ice sheets. It discusses the models developed to understand cryosphere processes and predict future changes, including those based on remote sensing, field campaigns, and long-term ground observations. Boasting an extensive bibliography, over 120 figures, and end-of-chapter review questions, it is an ideal resource for students and researchers of the cryosphere.
Glacial lake outburst floods (GLOFs) – sudden releases of water retained in glacial lakes – are among the consequences of retreating glaciers. In high mountain regions across the globe, glaciers have receded from their Little Ice Age (LIA) positions, leading to the formation and evolution of different types of glacial lakes. By integrating the analysis of remotely sensed imageries, documentary data sources, field data as well as other data and approaches, this study aims at revealing the relationship between evolution of different generations (and sub-types) of glacial lakes and the occurrence of GLOFs, and characterizing past events for better anticipation of future ones. The primary geographical focus of this work is on the Peruvian Andes with special attention given to the most glacierized part of it – the Cordillera Blanca, certain chapters and section also focus on High Asia (parts of Indian and Nepal Himalaya) and Austrian Alps (Tyrol and Salzburg provinces). This habilitation is designed as a collection of published studies of the author and the core of this work is a set of 23 peer-reviewed lake- and GLOF- oriented papers and one book chapter, published between 2015 and 2021.
Inventories of high mountain lakes prepared in this work provide insights into the characteristics and dynamics of evolution of glacial lakes in different parts of the world. Unlike most of the existing lake inventories, insights into qualitative lake characteristics (e.g. dam type, lake evolution phase) are derived and analyzed. Several thousands of lakes are inventoried in the three study regions (Peruvian Andes, Sikkim Himalaya, Austrian Alps), revealing general patterns suggesting that: (i) moraine-dammed lakes are dominant lake type forming and evolving in earlier stages of the post-LIA glacier retreat; (ii) the formation and evolution of bedrock-dammed lakes and lakes with combined dams dominate in later stages; (iii) relatively narrow elevational band hosts currently forming (proglacial) lakes. As a result of climate change-driven glacier retreat, this ‘active’ band of proglacial lakes evolution is documented to be shifting upwards and in combination with topographical setting control the formation and evolution of new glacial lakes.
This study presents unprecedently detailed GLOF inventory for the Peruvian Andes, which provides novel insights into the GLOF triggering and characterization and in combination with the lake inventory generate apparent utilizations for GLOF hazard identification and assessment efforts. It was shown that most of the high magnitude GLOFs originated from failures of moraine dams of lakes in the proglacial stage of their evolution, highlighting the monitoring priority. Trigger-wise, rapid mass movements into the lake dominated, while other triggers were documented rather marginally. Strikingly, Peruvian Andes are among the few regions of the world where there is an evidence of earthquake triggering of GLOFs – a specific process chain. By combining GLOF inventory with the lake inventory, it is shown that GLOFs occur in temporal clusters (peak frequencies) which are associated with specific stages of glacier retreat, lake formation and evolution (e.g. an increased number of proglacial moraine-dammed lakes) or extreme triggering events (e.g. a strong earthquake). Importantly lagged response of glaciers, lakes and GLOFs to initial forcings are desired to be considered in the anticipation of future GLOFs.
A substantial part of this habilitation focuses on characterization and reconstruction of past GLOF events. Several recent (e.g. the 2020 Lake Salkantaycocha GLOF in Peru; the 2020 Lake Jinwuco GLOF in Tibet) as well as historic lake outbursts (e.g. the 1941 Lake Palcacocha GLOF) are analyzed and modelled in order to: (i) understand drivers and processes involved in GLOF preconditioning, triggering, propagation and attenuation; (ii) derive a set of plausible parameters for the modelling of potential future events. In addition, the evolution of future lakes and potential future GLOFs are modelled at selected study sites in Peruvian Andes and Indian Himalaya, with obvious implications for GLOF hazard and risk management.
Last but not least, observations and findings from study sites in South America, Asia and Europe are put into the context of GLOF research and sustainable development efforts in mountain regions across the globe.
Patagonia is one of the regions of the world with the highest spatial contrast in terms of water availability. The rain shadow effect on the leeward side of the Andes mountain range induces a strong negative gradient of rainfall in a narrow 60 km strip. Therefore, two highly differentiated hydroclimatic-ecological regions can be identified:
1.
The Andean Patagonia, which is a water-producing area, containing glaciers, seasonal snow, valleys with large drainage networks of torrential courses, big lakes, and wetlands, wherein the forest is the dominant vegetation
2.
The Extra Andean Patagonia, which extends to the east of the Andes through the windy and arid/semiarid plateau, wherein water productivity is very low and steppe vegetation dominates
This chapter focuses on the main hydrologic systems of these regions and presents an overview of the state of knowledge regarding the main surface water bodies, river basin features, main water uses, and the conflicts linked to the pressure on water resources by human activities in a context of increasing development and climate change.KeywordsPatagonian riversAndean hydrologyWater usesWater managementPatagonia
Lake volume is a critical parameter in the prediction of potential flood volume and peak discharge in the risk assessment of glacial lake outburst flood (GLOF). As existing volume–area scaling relationships often blur the complexity of lake geometry, we presented a new volume-scaling law specific to moraine-dammed lakes, derived from a large lake bathymetry dataset. The relationship was based on the premise that lake geometry parameters (i.e., area, volume, width/length ratio) scale predictably. We then critically evaluated the performance of the new approach and compared it with 19 existing empirical relationships by examining a database of glacial lake bathymetry obtained without repeated measurements. Overall, the new volume-scaling relationship showed a more robust performance than other published formulas. In addition, an intriguing result was that regional differences were not always controlled by the predictability of lake volumes, that is, there were no regional restrictions on the use of the new method, at least not in the Himalayas. Finally, using the new approach and high-resolution Landsat imagery, our results of sequential mapping of all lakes in the Poiqu basin indicated that the total lake volume has increased by 148% from 1974 to 2020. Compared with other formulas, the lake volume estimation approach proposed in this paper provides an approximate mean value, which provides a key input parameter for flood simulation and a new alternative for estimating lake volume.
Monitoring and inventorying proglacial lakes in the Maritime Antarctica region is essential for understanding the effects of climate change on these environments. This study uses Landsat images to create a map of lakes in ice-free areas of the South Shetlands Islands (SSI) for 1986/89, 2000/03 and 2020, and verification of patterns of change in lake areas and numbers. Normalized water difference index (NDWI) products, image segmentation, field records, and cartographic products from other studies were used to validate the results. Results show a 60% increase in the number of lakes from 1986/89 to 2000/03; and a 55% increase from 2000/03 to 2020. There was a 52% increase in lake areas from 1986/89 to 2000/03; a 79% increase from 2000/03 to 2020; and a 173% increase from 1986 to 2020. From 1986 to 2020, the most significant changes were a decrease in the average elevation and distance from glaciers and an increase in distance from the sea. In 2020, SSI lakes were predominantly coastal and ice-marginal, with an E and S orientations, flat surfaces, and a low declivity.
Rapid changes of glacial lakes are among the most visible indicators of global warming in glacierized areas around the world. The general trend is that the area and number of glacial lakes increase significantly in high mountain areas and polar latitudes. However, there is a lack of knowledge about the current state of glacial lakes in the High Arctic. This study aims to address this issue by providing the first glacial lake inventory from Svalbard, with focus on the genesis and evolution of glacial lakes since the end of the Little Ice Age. We use aerial photographs and topographic data from 1936 to 2012 and satellite imagery from 2013 to 2020. The inventory includes the development of 566 glacial lakes (total area of 145.91 km2) that were in direct contact with glaciers in 2008–2012. From the 1990s to the end of the 2000s, the total glacial lake area increased by nearly a factor of six. A decrease in the number of lakes between 2012 and 2020 is related to two main processes: the drainage of 197 lakes and the merger of smaller reservoirs into larger ones. The changes of glacial lakes show how climate change in the High Arctic affect proglacial geomorphology by enhanced formation of glacial lakes, leading to higher risks associated with glacier lake outburst floods in Svalbard.
Glacial lake outburst floods (GLOFs) are a serious potential threat to the safety of life and property in downstream areas. In this study, moraine-dammed glacial lakes in the Yi’ong Zangbo River basin were recognized based on Landsat ETM+/TM/OLI images in 2000 and 2019. And the GLOFs for the Jionglaco, the largest glacial lake in this basin, was simulated using the one-dimensional hydrodynamic model. The results show that the total number and area of moraine-dammed glacial lakes in this basin increased by 10 (10.52%) and 5.49 km ² (48.24%) from 2000 to 2019, in which the area of the Jionglaco increased by 3.22 km ² . The peak discharge at the breach outlet for five scenarios with different combinations of breach width (80 m and 120 m), depth (2.5 m and 5 m) and flood time (1.5 h and 3 h) are 489 m ³ /s, 1327.43 m ³ /s, 444.32 m ³ /s, 617.47 m ³ /s and 1570.61 m ³ /s. With the addition of baseflow in river, the peak discharge at bridge site 15 138.93 km from Jionglaco are 1040.89 m ³ /s, 1724.00 m ³ /s, 1024.85 m ³ /s, 1162.25 m ³ /s and 1990.52 m ³ /s. The combination of baseflow in river and the GLOFs discharge results in the increasing peak discharge in the further downstream region. However, the arrival of peak discharge in downstream areas is delayed, which increases the chances of people escaping. This study aims to provide some references for the prevention of GLOFs in this region.
We analyze and reconstruct a recent glacial lake outburst
flood (GLOF) process chain on 26 June 2020, involving the moraine-dammed
proglacial lake – Jinwuco (30.356∘ N, 93.631∘ E) in
eastern Nyainqentanglha, Tibet, China. Satellite images reveal that from
1965 to 2020, the surface area of Jinwuco has expanded by 0.2 km2
(+56 %) to 0.56 km2 and subsequently decreased to 0.26 km2
(−54 %) after the GLOF. Estimates based on topographic reconstruction and
sets of published empirical relationships indicate that the GLOF had a
volume of 10 million cubic meters, an average breach time of 0.62 h, and an
average peak discharge of 5602 m3/s at the dam. Based on pre- and
post-event high-resolution satellite scenes, we identified a large debris
landslide originating from western lateral moraine that was most likely
triggered by extremely heavy, south-Asian-monsoon-associated rainfall in
June 2020. We back-calculate part of the GLOF process chain, using the
GIS-based open-source numerical simulation tool r.avaflow. Two scenarios are
considered, assuming a debris-landslide-induced impact wave with overtopping
and resulting retrogressive erosion of the moraine dam (Scenario A), as well as
retrogressive erosion without a major impact wave (Scenario B). Both
scenarios are in line with empirically derived ranges of peak discharge and
breach time. The breaching process is characterized by a slower onset and a
resulting delay in Scenario B compared to Scenario A. Comparison of the
simulation results with field evidence points towards Scenario B, with a peak
discharge of 4600 m3/s. There were no casualties from
this GLOF, but it caused severe destruction of infrastructure (e.g., roads and
bridges) and property losses in downstream areas. Given the clear role of
continued glacial retreat in destabilizing the adjacent lateral moraine
slopes and directly enabling the landslide to deposit into the expanding
lake body, the GLOF process chain can be plausibly linked to anthropogenic
climate change, while downstream consequences have been enhanced by the
development of infrastructure on exposed flood plains. Such process chains
could become more frequent under a warmer and wetter future climate, calling
for comprehensive and forward-looking risk reduction planning.
Rapid growth of proglacial lakes in the current warming climate can pose
significant outburst flood hazards, increase rates of ice mass loss, and alter
the dynamic state of glaciers. We studied the nature and rate of proglacial
lake evolution at Pasterze Glacier (Austria) in the period 1998–2019 using
different remote-sensing (photogrammetry, laser scanning) and fieldwork-based
(global navigation satellite system – GNSS, time-lapse photography, geoelectrical resistivity tomography – ERT, and
bathymetry) data. Glacier thinning below the spillway level and glacier
recession caused flooding of the glacier, initially forming a glacier-lateral
to supraglacial lake with subaerial and subaquatic debris-covered dead-ice
bodies. The observed lake size increase in 1998–2019 followed an exponential
curve (1998 – 1900 m2, 2019 – 304 000 m2). ERT data from 2015
to 2019 revealed widespread existence of massive dead-ice bodies exceeding
25 m in thickness near the lake shore. Several large-scale and rapidly
occurring buoyant calving events were detected in the 48 m deep basin
by time-lapse photography, indicating that buoyant calving is a crucial
process for the fast lake expansion. Estimations of the ice volume losses by
buoyant calving and by subaerial ablation at a 0.35 km2 large
lake-proximal section of the glacier reveal comparable values for both
processes (ca. 1×106 m3) for the period August 2018 to
August 2019. We identified a sequence of processes: glacier recession into a
basin and glacier thinning below the spillway level; glacio-fluvial sedimentation
in the glacial–proglacial transition zone covering dead ice; initial formation
and accelerating enlargement of a glacier-lateral to supraglacial lake by
ablation of glacier ice and debris-covered dead ice forming thermokarst
features; increase in hydrostatic disequilibrium leading to destabilization of
ice at the lake bottom or at the near-shore causing fracturing, tilting,
disintegration, or emergence of new icebergs due to buoyant calving; and
gradual melting of icebergs along with iceberg capsizing events. We conclude
that buoyant calving, previously not reported from the European Alps, might
play an important role at alpine glaciers in the future as many glaciers are
expected to recede into valley or cirque overdeepenings.
Ice marginal lakes are a dynamic component of terrestrial meltwater storage at the margin of the Greenland Ice Sheet. Despite their significance to the sea level budget, local flood hazards and bigeochemical fluxes, there is a lack of Greenland-wide research into ice marginal lakes. Here, a detailed multi-sensor inventory of Greenland’s ice marginal lakes is presented based on three well-established detection methods to form a unified remote sensing approach. The inventory consists of 3347 (±8%) ice marginal lakes (>0.05km2) detected for the year 2017. The greatest proportion of lakes lie around Greenland’s ice caps and mountain glaciers, and the southwest margin of the ice sheet. Through comparison to previous studies, a ∼75% increase in lake frequency is evident over the west margin of the ice sheet since 1985. This suggests it is becoming increasingly important to include ice marginal lakes in future sea level projections, where these lakes will form a dynamic storage of meltwater that can influence outlet glacier dynamics. Comparison to existing global glacial lake inventories demonstrate that up to 56% of ice marginal lakes could be unaccounted for in global estimates of ice marginal lake change, likely due to the reliance on a single lake detection method.
The response of glaciers to atmospheric warming has become a key issue in scientific as well as public and even political discussions about human impacts on the climate system. The predominant tendency of continued worldwide glacier shrinkage indeed constitutes one of the clearest indications in nature of rapid climate change at a global scale. The observed trend of increasingly negative mass balances is consistent with an accelerated trend in global warming and correspondingly enhanced energy flux toward the earth surface. Mountain ranges at lower latitudes have lost large percentages of their glacier areas and volumes since the end of the Little Ice Age. Many of them may become mostly or even completely de-glaciated during the coming decades. Such changes have the potential to profoundly affect environmental conditions far beyond cold mountain chains. Sea-level rise, shifting seasonality in water supply, and local formation of new lakes reflect changes in the water cycle at global, continental, and regional-to-local scales. They are accompanied by rather marked changes in cold-mountain landscape appearance, slope stability, erosion/sedimentation, and hazard conditions. Worldwide monitoring of glaciers today involves process-oriented field measurements, high-resolution geodetic information from space and new terrestrial technologies, but also faces difficult challenges of vanishing glaciers with long-term mass-balance observations. Combining rich observational data with spatio-temporal modeling increasingly helps to prepare integrated analyses of observed phenomena and with anticipating likely future developments as a basis for the planning and realization of climate adaptation strategies. This article examines the monitoring and inventory of glaciers worldwide, observed and forecasted changes, and impacts of deglaciation on geomorphic and water resources systems.
Glacier lake outburst floods (GLOF) at Laguna de los Témpanos, a glacier-dammed side lake of Glaciar Steffen, Hielo Patagónico Norte, were documented for a period between December 1974 and February 2020. With manual interpretation of 150 remote sensing images of aerial surveys, vertical aerial photographs, Landsat MSS, TM, ETM and OLI, ALOS, and ASTER images, 19 GLOFs were captured/inferred by focusing on icebergs and water levels, except two periods in the 1980s and the 1990s for which no image was available. This translates to the occurrence of the GLOF on average once ca. every 14 months. Many GLOFs occurred in late summer to early fall, with a few in late spring: but one GLOF was inferred to have occurred in wintertime. The causes of GLOFs were supposed to be heavy rainfalls, probably accompanied with rapid snow/ice melting by warm air temperatures, judging from the general weather condition over the laguna area. The latest two GLOFs (2016 & 2017) were very large, enough to have completely exposed the lake floor in the middle section. The GLOF of 2017 (Mar. 31) was registered in a hydrograph set up at Lower Río Huemules. After this GLOF, the water level has become stable with a more or less continuous outlet stream along the glacier sidewall and there has been no GLOF to date. So probably the prospect of another GLOF has considerably diminished by now. As Glaciar Steffen receded about 6km during this study period, the glacier has thinned accordingly, to which the water level adjusted with three distinctive relatively stable states while fluctuating frequently.
Glacial lakes are rapidly growing in response to climate change and glacier retreat. The role of these lakes as terrestrial storage for glacial meltwater is currently unknown and not accounted for in global sea level assessments. Here, we map glacier lakes around the world using 254,795 satellite images and use scaling relations to estimate that global glacier lake volume increased by around 48%, to 156.5 km3, between 1990 and 2018. This methodology provides a near-global database and analysis of glacial lake extent, volume and change. Over the study period, lake numbers and total area increased by 53 and 51%, respectively. Median lake size has increased 3%; however, the 95th percentile has increased by around 9%. Currently, glacial lakes hold about 0.43 mm of sea level equivalent. As glaciers continue to retreat and feed glacial lakes, the implications for glacial lake outburst floods and water resources are of considerable societal and ecological importance. Warming is increasing glacial lakes, and scaling relations show a 48% increase in volume for 1990 to 2018. All measures—area, volume, number—increased, providing water storage but also representing a potential hazard with the risk of outburst floods.
Glacial lakesare mostoften locatedin remote placesmaking it difficult to carry outdetailedbathymetric surveys.Consequently, lake depths and volumes for unmeasured lakes are often estimated using empirical relationships developed mainly from small bathymetric datasets. In this study, we use the bathymetry dataset of the Cordillera Blanca, Peru comprising 121 detailed lake bathymetries, the most extensive dataset in the world. We assess the performance of the most commonly applied empirical relationships for lake mean depth and volume estimation, but also investigate relationships between different geometric lake variables. We find that lake volume estimation performs better when derived from lake mean depth, which in turn is estimated from lake width. The findings also reveal the extreme variability of lake geometry, which depends on glacio-geomorphological processes that empirical– statistical relationships cannot adequately represent. Such relationships involve characteristic uncertainty ranges of roughly ±50%. We also estimate potential peak discharges of outburst floods from these lakes by applying empirical relationships from the literature, which results in discharges varying by up to one-order of magnitude. Finally, the results are applied to the 860 lakes without bathymetric measurements from the inventory dataset of the Cordillera Blanca to estimate lake mean depth, volume and possible peak discharge for all unmeasured lakes. Estimations show that ca. 70% (610) of the lakes have a mean depth lower than 10m and very few longer than 40m. Lake volume of unmeasured lakes represent ca. 32% (5.18 × 108 m3) of the total lake volume (1.15 × 109 m3) in the Cordillera Blanca.Approximately, 50% of the lakes havepotential peak discharges > 1000 m3/s in case of lakeoutburst floods, implying a need for additional studies for risk assessment.
Glacier retreat is accompanied by formation of lakes within glacier moraines. The lakes may produce outburst floods which can transform into destructive debris flows. In the Central Caucasus this hazard has not been sufficiently studied, and the location and size of glacial lakes is not shown on the topographical maps. We have combined field and remote sensing research to study glacial lakes and debris flow initiation zones in periglacial areas. Two case studies are presented. Bashkara lakes in the upper Adyl-Su River valley have been subject to detailed monitoring since 1999. In 2005 their total area reached 93,000 m 2, and the total volume exceeded 900,000 m 3. Buildings, bridges and camping sites are in areas endangered by potential debris flows. A second group of 13 glacier lakes was identified in 2005 on the northeastern slopes of Mt. Elbrus. In July 2006 the area of the largest lake reached 89,000 m 2, and its volume was 550,000 m 3. On August 11, 2006 the lake produced an outburst flood releasing about 400,000 m 3 of water which later transformed into a debris flow that entrained up to 350,000 m 3 of solid material. A downstream mineral water resort was damaged. We have identified 71 glacial lakes in the Central Caucasus. These include post-disaster lakes, e.g. in the Genaldon River valley where 13 new lakes formed after a glacier disaster in 2002, which at one point reached 437,000 m 2 in area and 5,000,000 m 3 in volume. In the future we hope to develop detailed recommendations for risk management of glacier and debris flow hazards in the Central Caucasus.
A revised glacier inventory comprising glacier changes between 1986 and 2000 have been compiled for the Southern Patagonia Icefield (SPI) based on Landsat TM and Landsat ETM+ imagery acquired on January 14, 1986 and October 27, 2000, respectively. Elevation data from the Shuttle Radar Topography Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) were used to interpret ice divides. The 1986 ice area of the 48 major SPI glaciers is 11,022 ± 412 km2, which represents 85 % of the total SPI area of 13,003 ± 282 km2. Our results agree in general with Aniya et al. (1996), although there are large differences in the basin limits for a few glaciers. Area loss of 489 ± 377 km2 is obtained for the period 1986–2000 for the whole SPI, of which 68 % corresponds to the 48 major glaciers (333 ± 106 km2). Major (> 5 km2) area loss is detected in 20 glaciers (268 ± 87 km2), which accounts for 80 % of the total area loss of the major glaciers between 1986 and 2000. Smaller (< 5 km2) but significant area losses have occurred within 17 other glaciers, all of which have retreated more than 100 m. While our new results confirm the general retreat of the SPI reported earlier (Aniya et al. 1997; Rignot et al. 2003), we show that 9 glaciers within the latitudes of 49°48′–50°25′S had relatively stable frontal positions between 1986 and 2000, 8 of which were previously retreating over the period 1944/1986. Independent evaluation of ice thickness changes within the SPI (Rignot et al. 2003) show that significant thinning exists for only 2 of the 9 glaciers with stable fronts (excluding Moreno Glacier which we regard as stable). The stable frontal positions of the 13 glaciers might be due to the recent increase of precipitation in the central–south sector of the SPI. Although enhanced precipitation has not yet been detected by observations, it is to be expected based on the intensification of the westerly circulation, as has already been observed in the Southern Hemisphere since the mid-1960s (Marshall, 2003).
A Landsat TM mosaic of the Southern Patagonia Icefield (SPI), South America, was utilized as an image base map to inventory its outlet glaciers. The spI is South America's larg-est ice mass with an area of approximately 13,000 km2. The icefield does not have complete topographic map coverage. With the aid of stereoscopic interpretation of aerial photo-graphs and digital enhancement of the Landsat TM image, glacier divides were located and glacier drainage basins were delineated, giving a total of 48 outlet glaciers. Employing a supervised classification using Landsat TM bands 1, 4, and 5, glacier drainage basins were further divided into accumula-tion and ablation areas, thereby determining the position of the transient snow line (TSL). After comparing with existing data, it was found that the TSL could be taken, for practical purposes, as the equilibrium line (EL). The position of the TSL was then compared with topographic maps, where available, to determine the equilibrium line altitude (ELA). Altogether, 11 parameters relating primarily to glacier morphology were inventoried. Pio XI Glacier (1265 kmz) is found to be the largest outlet glacier in South America, a i d m a y also be its longest. The average accumulation area ratio of 0.75 is larger than those of the Northern Patagonia Icefield and European glaciers. All but two outlet glaciers calve into fjords or pro-glacial lakes.
Glacier lakes are a common phenomenon in high mountain areas. Outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure. In several high mountain ranges around the world, a grave uncertainty about the hazard potential of glacier lakes still exists, especially with respect to the effects of accelerating rates of glacier retreat as a consequence of atmospheric warming. Area-wide detection and modeling of glacier lake hazard potentials is, therefore, a major challenge. In this study, an approach integrating three scale levels allows for the progressive focus on critical glacier lakes. Remote sensing methods for application in glacier lake hazard assessment are presented, and include channel indexing, data fusion, and change detection. Each method matches the requirements of a certain scale level. For estimating potential disaster amplitudes, assessments must be made of maximum discharge and runout distance of outbursts floods and debris flows. Existing empirical relations are evaluated and complementary ones as derived from available data are proposed. Tests with observations from a recent outburst event from a moraine-dammed lake in the Swiss Alps show the basic applicability of the proposed techniques and the usefulness of empirical relations for first hazard assessments. In particular, the observed runout distance of the debris flow resulting from the outburst does not exceed the empirically estimated maximum runout distance. A list of decision criteria and related remote sensing techniques are discussed in conclusion. Such a list is an essential tool for evaluating the hazard potential of a lake. A systematic application of remote sensing based methods for glacier lake hazard assessment is recommended.
Summit Lake, which is impounded by Salmon Glacier, is the largest self-draining, ice-dammed lake in Canada. Until 1961, it contained few icebergs and was stable, overflowing to the north into the Bowser River valley. The first jokulhlaup occurred in December 1961, after a lengthy period of thinning and retreat of Salmon Glacier, when a subglacial tunnel developed in the weakened ice dam, allowing the lake to drain suddenly. This flood and two others in 1965 and 1967 caused major damage to the road system in the Salmon River valley south of the lake. Since 1965, with three exceptions, Summit Lake has drained annually; minor floods along Salmon River in 1966, 1969, and 1973 may record partial drainings of the lake, although other explanations are possible. Jokulhlaups in recent years have been smaller and have occurred earlier in the year than most of the early floods. Rapid water-level fluctuations associated with the annual emptying and refilling of Summit Lake have generated large numbers of icebergs, derived from the Salmon Glacier dam; these icebergs presently choke the surface of the lake. The present jokulhlaup cycle is likely to continue either until the glacier readvances or until it retreats to the point that it no longer forms an effective seal.
Mass balance variations of Glaciar San Rafael, the northernmost tidewater glacier in the Southern Hemisphere, are reconstructed over the period 1950-2005 using NCEP-NCAR reanalysis climate data together with sparse, local historical observations of air temperature, precipitation, accumulation, ablation, thinning, calving, and glacier retreat. The combined observations over the past 50 yr indicate that Glaciar San Rafael has thinned and retreated since 1959, with a total mass loss of ~22 km3 of ice eq. Over that period, except for a short period of cooling from 1998-2003, the climate has become progressively warmer and drier, which has resulted primarily in pervasive thinning of the glacier surface and a decrease in calving rates, with only minor acceleration in retreat of the terminus. A comparison of calving fluxes derived from the mass balance variations and from theoretical calving and sliding laws suggests that calving rates are inversely correlated with retreat rates, and that terminus geometry is more important than balance fluxes to the terminus in driving calving dynamics. For Glaciar San Rafael, regional climate warming has not yet resulted in the significant changes in glacier length seen in other calving glaciers in the region, emphasizing the complex dynamics between climate inputs, topographic constraints and glacier response in calving glacier systems.
Ice elevation changes of the Northern Patagonia Icefield (NPI) were analyzed by comparing three Digital Elevation Models (DEM) corresponding to 1975 (constructed based on topographic maps), the SRTM DEM of 2000 yr and a SPOT 5 DEM of 2005. In addition, the glacier length fluctuations and the surface area evolution between 2001 and 2011 of 25 glaciers of the NPI were studied: the information extracted from the Landsat ETM+ satellite image of 11 March 2001 was compared to the measurements performed based on the Landsat ETM+ satellite image of 19 February 2011. From a global point of view, the majority of the studied glaciers thinned, retreated and lost surface between 2001 and 2011, only few glaciers (Leones, Nef, Pared Sur and Soler) located on the eastern side of the NPI have been stable. Glaciers located on the western side of the NPI suffered a stronger wasting compared to the glaciers located on the eastern side.
Overall, over the ablation areas of the NPI (below 1150 m a.s.l.) a more rapid thinning of 2.6 m yr<sup>−1</sup> occurred between 2000 and 2005 yr compared to the period 1975–2000, in which a mean thinning of 1.7 m yr<sup>−1</sup> was measured for the same zones of the NPI. For the whole period (1975–2005) the most important thinning of the ablation areas has been estimated for HPN-1 Glacier (4.4 m yr<sup>−1</sup>) followed by Benito (3.4 m yr<sup>−1</sup>), Fraenkel (2.4 m yr<sup>−1</sup>), Gualas (2.1 m yr<sup>−1</sup>) and Acodado glaciers, all of them located on the western side of the NPI.
Between 2001 and 2011, a noteworthy retreat of 1.9 km was experienced by Gualas Glacier and by Reichert Glacier with 1.6 km, both located on the north-western side of the NPI. On the south-western side of the NPI, during the same decennia, Steffen Glacier experienced a remarkable retreat of 1.6 km as well. During the 2001–2011 period, Steffen Glacier more than doubled its rate of retreat (compared to the 1979–2001 period) and experienced the disintegration of its main front as well as a lateral tongue that retreated 3.1 km. The most significant retreat observed on the eastern side was experienced by Colonia Glacier (1 km).
Area loss was also relevant during the period 2001–2011. Overall, the icefield experienced a reduction of 50.6 km<sup>2</sup> which represents a 1.3 % relative to the surface area calculated for 2001 yr. The most remarkable surface reduction was observed for HPN-1 Glacier that lost 3.2 % of its surface estimated in 2001, followed by Steffen Glacier (2.8 %).
We suggest that the glacier shrinking observed in the NPI is controlled firstly by atmospheric warming, as it has been reported in this area. Nevertheless, updated climatic studies are needed in order to confirm this suggestion. If the detected past climate trends persist, in the future, glaciers of the NPI will continuous or even increase their rate of shrinking generating important consequences for this region like the production of Glacier Lake Outburst Flood events or the decrease of the melt-water runoff in the long-term future.
The melting of mountain glaciers and ice caps is expected to contribute significantly to sea-level rise in the twenty-first century, although the magnitude of this contribution is not fully constrained. Glaciers in the Patagonian Icefields of South America are thought to have contributed about 10% of the total sea-level rise attributable to mountain glaciers in the past 50 years. However, it is unclear whether recent rates of glacier recession in Patagonia are unusual relative to the past few centuries. Here we reconstruct the recession of these glaciers using remote sensing and field determinations of trimline and terminal moraine location. We estimate that the North Patagonian Icefield has lost 103+/-20.7km3 of ice since its late Holocene peak extent in AD 1870 and that the South Patagonian Icefield has lost 503+/-101.1km3 since its peak in AD 1650. This equates to a sea-level contribution of 0.0018+/-0.0004mmyr-1 since 1870 from the north and 0.0034+/-0.0007mmyr-1 since 1650 from the south. The centennial rates of sea-level contribution we derive are one order of magnitude lower than estimates of melting over the past 50 years, even when we account for possible thinning above the trimline. We conclude that the melt rate and sea-level contribution of the Patagonian Icefields increased markedly in the twentieth century.
A combination of remotely sensed data, field mapping, bathymetric survey and geophysical soundings is used to describe the recent changes in the terminal area of Petrov glacier, the largest glacier in the Akshiirak massif, central Tien Shan. According to our results, three periods of accelerated glacier retreat (1977–80, 1990–95 and 2008–09) can be distinguished since 1977. The largest recession occurred in 1990–95 when the glacier retreated by 54 AE 8 m a –1 . Accelerated glacier retreat affected the enlargement rate of Petrov lake, which increased by 0.04–0.1 km 2 a –1 and by 1.3–2.2 Â 10 6 m 3 a –1 in the last three decades. Since 1995, the mean annual retreat rate of the lake-calving northern glacier section has been up to three times higher than the retreat rate of the land-terminating southern section. The calving flux ranged from 2.5 to 4.6 Â 10 6 m 3 a –1 in 2003–09, resulting in a total glacier mass loss of (17.7 AE 0.4) Â 10 6 m 3 . The calving terminus of Petrov glacier was >65 m thick in 2009 according to ground-penetrating radar measurements.
Abstarct
To investigate the impact of proglacial lake formation on the dynamics and evolution of glaciers, we measured the ice motion of the terminal part of Rhonegletscher, Switzerland, where a lake formed in 2005. In 2009, the flow velocity near the terminus was >20 m a ⁻¹ . One of the survey stakes tripled its velocity between 2006 and 2007. Since the lake water pressure was consistently close to the ice overburden pressure, it is likely that the high subglacial water pressure enhanced the basal ice motion. The estimated flow velocity due to ice shearing was negligibly small; almost 100% of the horizontal velocity near the terminus was caused by basal sliding. The longitudinal strain rate was large, 0.064 a –1 , indicating that much of the glacier thinning was due to ice dynamics. The region of ice flotation adjacent to the lake expanded between 2008 and 2009 as a result of glacier thinning. Accordingly, a huge uplift of the surface was observed in 2009. It is clear from the vertical ice motion as well as visual observations that the marginal part of the glacier began to float. The ice-thinning rate in the studied area from 2008 to 2009 was 3.4 ma –1 , larger than previous estimates.
Changes in the area and bathymetry of Imja Glacial Lake and in the elevation of its damming moraine, Khumbu region, Nepal Himalaya are investigated. Previously reported changes in the lake area have been updated by multi-temporal ASTER images, which revealed a decreased expansion rate after 2000. A provisional expansion of the lake observed in 2004, from which some studies concluded an accelerated lake expansion due to global warming, has, from 2005, subsided to the glacier surface. Bathymetric changes for the period 1992–2002 that were first obtained for Himalayan glacial lakes suggest that the melting of debris-covered ice beneath the lake is insignificant in terms of the increase in lake volume, and that the retreat of a glacier in contact with the lake by calving is essential for the lake's expansion. Changes in the height of a damming moraine for the period 2001–2007 suggest a continuous surface lowering near the lake, though the lowering rates are smaller than those for the period 1989–1994.
The dominant spatial and temporal patterns of a network of 23 homogenous instrumental rainfall records of Southern South America were analysed and used to define four regional annual precipitation series: (1) Northwestern Patagonia (1950–2000) with nine stations from both side of the Andes between 41 and 44°S; (2) Central Patagonia (1950–2000) with five Chilean stations between 45 and 47°S; (3) Patagonian plains–Atlantic (1961–2000) with five Argentinean stations spread between 43 and 50°S and from the eastern foothills of the Andes to the Atlantic coast and (4) Southern Patagonia (1950–2000) with four stations east of the Andes, near the Strait of Magellan between 51 and 53°S. Unique patterns were also identified for two of the southernmost stations in Ushuaia and Evangelistas (EVA). Time series analysis of these regional patterns shows marked decadal variability for Northwestern and Central Patagonia, 3–7 years oscillations for the Patagonian plains–Atlantic region and a strong biannual oscillation mode for Southern Patagonia. Regional annual rainfall appears to be strongly influenced by Antarctic circulation modes (Antarctic Oscillation Index), whereas the El Niño-Southern Oscillation (ENSO) influence on rainfall variability is less evident. Highly significant correlation of precipitation on the west coast of Patagonia with the pressure gradient between the subtropical eastern Pacific and the high-latitude south eastern Pacific is confirmed. Copyright © 2008 Royal Meteorological Society
Recent climate changes have had a significant impact on the high-mountain glacial environment. Rapid melting of glaciers has resulted in the formation and expansion of moraine-dammed lakes, creating a potential danger from glacial lake outburst floods (GLOFs). Most lakes have formed during the second half of the 20th century. Glaciers in the Mount Everest (Sagamartha) region, Nepal, are retreating at an average rate of 10–59 m a –1 . From 1976 to 2000, Lumding and Imja Glaciers retreated 42 and 34 m a –1 , respectively, a rate that increased to 74 m a –1 for both glaciers from 2000 to 2007. During the past decade, Himalayan glaciers have generally been shrinking and retreating faster while moraine-dammed lakes have been proliferating. Although the number of lakes above 3500 m a.s.l. has decreased, the overall area of moraine-dammed lakes is increasing. Understanding the behaviour of glaciers and glacial lakes is a vital aspect of GLOF disaster management.
The purpose of the present work was to investigate variations in the surface areas of lakes in the north-east sector of Sagarmatha National Park (Nepal) at the end of the 20 th century, through comparison of the Mount Everest maps based on a survey done in the early 1980s, and the official Map of Nepal based on a survey done at the beginning of the 1990s. The analysis of the changes occurring between the 1980s and the 1990s in the surface areas and distribution of lakes in the north-east sector of SNP reveals that lake areas substantially increased, by 15.4 (-5.5; +5.7)% (median 12.5%), within hydrographic basins that included a certain amount of glacial cover. In fact, 96% of the lakes whose surface area increased are located in glacial basins. Conversely, the majority of the lakes without glacial cover in their catchment showed a reduction in surface area, and in many cases disappeared (83% of the lakes that disappeared were situated in basins without glaciers). This different behaviour of these two types of lakes, though observed over a short time span, would appear to be consistent with the consequences of temperature increases recorded from the beginning of 1980s on a global and local scale. The digital tool produced (Limnological Information System, LIS) as part of this work is intended to provide a useful platform for extending the analysis to entire area of SNP, as well as for subsequent comparisons based on earlier maps or more recent satellite images.
Five similar glacial-lake outburst floods (GLOFs) occurred in April, October, December 2008, March and September 2009 in the
Northern Patagonia Icefield. On each occasion, Cachet 2 Lake, dammed by the Colonia Glacier, released circa 200-millionm3 water into the Colonia River. Refilling has occurred rapidly, such that further outbreak floods can be expected. Pipeflow
calculations of the subglacial tunnel drainage and 1D hydraulic models of the river flood give consistent results, with an
estimated peak discharge surpassing 3,000m3s−1. These floods were larger in magnitude than any flood on record, according to gauged data since 1963. However, geomorphological
analysis of the Colonia valley shows physical evidence of former catastrophic outburst floods from a larger glacial-lake,
with flood discharges possibly as high as 16,000m3s−1. Due to potential impacts of climate change on glacier dynamics in the area, jökulhlaups may increase future flood risks
for infrastructure and population. This is particularly relevant in view of the current development of hydropower projects
in Chilean Patagonia.
KeywordsJökulhlaup-Outburst flood-Patagonia-Glacial-lake-Climate change
An interdisciplinary study of glacier-related hazards in the Petrov lake region (Ak-Shiirak Range, the Inner Tien-Shan, Kyrgyzstan) has been undertaken to identify potential dangers to the area. A cooperative effort from experts in the fields of hydrology, glaciology, geomorphology and geophysics has been employed in this study. For the hazard assessment, evolution of the Petrov glacier and lake was reconstructed using historical reports, aerial photographs and satellite images. Geomorphological mapping and geophysical soundings was applied to the lake territory and the moraine dam. This has identified potentially hazardous areas of the dam including subsurface drainage zones and cracks that could cause a sudden extremely high discharge. In the
past three decades, the Petrov lake has doubled in size, while in recent years, its area has been increasing by more than 92,000 square metres per year. Although there is no evidence for an imminent outburst, the dramatic increase in the lake’s size emphasizes the importance of this study.
Glaciar León is a temperate, grounded outlet of the eastern North Patagonian Icefield (NPI). It terminates at an active calving margin in Lago Leones, a 10 km long proglacial lake. We take a multidisciplinary approach to its description and use ASTER imagery and clast sedimentology to describe the geomorphology of the glacier and its associated moraines. We date periods of glacier retreat over the last 2500 years using a combination of lichenometric, dendrochronological, cosmogenic and optically stimulated luminescence techniques and show that the glacier receded from a large terminal moraine complex some 2500 years ago and underwent further significant recession from nineteenth-century moraine limits. The moraine dates indicate varying retreat rates, in conjunction with significant downwasting. The bathymetry of Lago Leones is characterized by distinct ridges interpreted as moraine ridges that dissect the lake into several basins, with water depths reaching 360 m. The fluctuations of Glaciar León appear to have been controlled by the interplay between climatic forcing and calving dynamics. NERC; University of St Andrews; American Alpine Club; British Geomorphological Research Group; Dudley Stamp Memorial Trust; Royal Scottish Geographical Society; Quaternary Research Association; Carnegie Trust for the Universities of Scotland
BGRに掲載された論文の著作権は原則として社団法人日本雪氷学会に帰属する。 （日本雪氷学会著作権規程） The major results of the Glaciological Research Project in Patagonia (GRPP) ,2003-2005, whichtargeted Glaciar Exploradores of the Hielo Patagonico Norte (HPN) and Glaciar Perito Moreno of theHielo Patagonico Sur (HPS), were reported. Studies at Glaciar Exploradores include recent glacialchronology, glacier flow measurements with D-GPS, meteorological measurements with an AWS andhydrological measurements at the outlet stream. Three moraine systems were recognized, and mostrecent two of them were formed sometime between the 12th and 17th century and the early to mid-19thcentury. The annual glacier flows in the area within 5km from the terminus ranged 48 to 138m in 2003-2004. Strong emergence velocity was observed near the terminus. The annual precipitation near theterminus was close to 3000mm,the mean annual air temperature was 7.5C and the annual specific runoffwas about 6200mm in 2005. Also the variations of 21 outlet glaciers of the HPN from 1944/45 to 2004/05were presented with their notable characteristics. The area loss due to recession in 60 years amountedto ca. 100km2, of which close to 30% was accounted by Glaciar San Quintin, the largest glacier of the HPN.At Glaciar Perito Moreno, observations and measurements were carried out for flow, strain gridand meteorological measurements, and calving activities. Flow velocity per day in December 2004ranged 3.95 to 0.53m, with the average of 1.66m at the calving front. At the middle reach, the averagedaily flow velocity was 1.5m, and the profile survey revealed that the inner zone maintained thickerconditions, but with no significant trend of additional thickening. The annual mean temperaturenear the EL (ca. 1350m) was 1.0C, while that at near the terminus was 6.3C in 2005.
Failures of glacial lake dams can cause outburst floods and represents a serious hazard. The potential danger of outburst floods depends on various factors like the lake's area and volume, glacier change, morphometry of the glacier and its surrounding moraines and valley, and glacier velocity. Remote sensing offers an efficient tool for displacement calculations and risk assessment of the identification of potentially dangerous glacial lakes (PDGLs) and is especially helpful for remote mountainous areas. Not all important parameters can, however, be obtained using spaceborne imagery. Additional interpretation by an expert is required. ASTER data has a suitable accuracy to calculate surface velocity. Ikonos data offers more detail but requires more effort for rectification. All investigated debris-covered glacier tongues show areas with no or very slow movement rates. From 1962 to 2003 the number and area of glacial lakes increased, dominated by the occurrence and almost linear areal expansion of the moraine-dammed lakes, like the Imja Lake. Although the Imja Lake will probably still grow in the near future, the risk of an outburst flood (GLOF) is considered not higher than for other glacial lakes in the area. Potentially dangerous lakes and areas of lake development are identified. There is a high probability of further lake development at Khumbu Glacier, but a low one at Lhotse Glacier.
Lake Arsine, a pro-glacial lake in the French Alps, first appeared 30 years ago and has since been growing steadily. In 1985, it reached an area of 5.9 ha, a maximum depth of 39 m, and a volume of 0.8 × 106 m3. This lake is dammed partially by a glacial moraine and partially by a tongue of dead ice covered by a moraine 1–2 m thick. The glacier calves into the lake, which collects all the melt water from the surrounding glacial area of 250 ha. No open outlet exists and seepage reaches a value of 5 × 106 m3 year−1. A 1 year water balance shows that seepage increases rapidly with water level, from less than 0.03 m3 s−1to more than 0.75 m3 s−l for a rise in water level of 10 m. The seasonal lake-volume fluctuations of 0.5 × 106 m3 are small compared with the inflow volume of 5 × 106 m3.
Progressive clogging of the bottom by glacial flour has led to a gradual rise of 8 m in 16 years in the summer level, while at the same time the height of the dam has decreased by 10 m due to the melting of dead ice. Consequently, by the end of July 1985 the freeboard was only 2 m and overflow on to the dead ice was thought likely to occur in the very near future. To eliminate this flood hazard, a 250 m long channel was dug in an ice-free zone which had been profiled by geophysical prospecting. This work was carried out between 14 April and 13 June 1986, in order to benefit from the low winter water level.
Geotechnical studies of the moraine have shown that no large landslide is to be feared. A crude model of the waves created by calving shows that the new water level is safe and the channel is capable of handling the maximum likely discharge of 15 m3 s−1 resulting from the highest possible wave of 3.5 m.
Vatnajökull, Iceland, is the Earth’s most studied ice cap and represents a classical glaciological field site on the basis of S. Pálsson’s seminal glaciological field research in the late 18th century. Since the 19th century, Vatnajökull has been the focus of an array of glaciological studies by scientists from many nations, including many remote-sensing investigations since 1951. Landsat-derived positions of the termini of 11 outlet glaciers of Vatnajökull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973–92. The largest changes during the 19 year period (1973–92) occurred in the large lobate, surge-type outlet glaciers along the southwestern, western, and northern margins of Vatnajökull. Tungnaárjökull receded −1413 ± 112 m (−1380 ± 1 m from ground observations), and Brúarjökull receded −1975 ± 191 m (−2096 ± 5 m from extrapolated ground observations) between 1973 and 1992. Satellite images can be used to delineate glacier margin changes on a time-lapse basis, if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance/recession is larger than maximum image pixel size. “Local knowledge” of glaciers is critically important, however, in the accurate delineation of glacier margins on Landsat images.
The retreat of glaciers since 1927 in Cordillera Blanca has produced dangerous lakes at the front of many glaciers. All the known data, most of them unpublished, are reviewed. The known aluviones are listed, and those of Chavin, Quebrada Los Cedros and Artesoncocha described in full. In these three cases a breach in the front moraine came from big ice falls into the lake. The protective devices made on the outlets are described, as well as the effects of the big earthquake on 31 May 1970. In the case of Laguna Parón, which keeps its level thanks to infiltrations, the fluctuations of the discharge of the springs as related to the level of the lake from 1955 to 1969 are reported. The projects for lowering the level of Laguna Parón and for emptying Safuna Alta are described. The latter partially emptied in fact by piping after the earthquake, allowing a final solution.
In western Canada, existing and former lakes dammed by landslides, moraines, and glaciers have drained suddenly to produce floods, orders of magnitude larger than normal streamflows. Landslide dams consisting of failed bedrock generally are stable, whereas those comprising Quaternary sediments or volcanic debris fail soon after they form, typically by overtopping and incision. Moraine dams are susceptible to failure because they are steep-sided and consist of loose, poorly sorted sediment. Irreversible rapid incision of a moraine dam may result from a large overflow associated with a severe rainstorm, avalanche, or rockfall. Some glacier-dammed lakes drain suddenly through englacial and subglacial tunnels to produce large floods. -from Authors
Describes research into the lake situated at the end of the Petrov glacier on the north-western slope of the Ak-Shiyrak massif in Tien-Shan. The lake was not formed until about 1870 and cannot be more than about 110 years old. At the present time it is increasing in size at approximately the same rate as the glacier is retreating.-translated by P.Cooke
An approach for semi-automatic lake detection based on multispectral optical remote sensing data and digital elevation models (DEM) is presented in this contribution. After preprocessing of the satellite images, all data are processed in a Geographic Information System (GIS). Preliminary hazard assessment of the detected lakes in a test region was performed: Potential ice avalanches and debris fl ows originating in glacier lake outbursts are modeled by means of hydrological fl ow-routing models. The strength of the presented methods is the ability to quickly create an overview of the glacier lake situation and related hazard potentials over large regions. With few adjustment works, the presented approach can be applied to mountain regions all over the world.