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Rapid worldwide growth of glacial lakes since 1990

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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.
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https://doi.org/10.1038/s41558-020-0855-4
1School of Interdisciplinary Arts and Sciences, University of Washington Tacoma, Tacoma, WA, USA. 2Department of Geology, University of Dayton,
Dayton, OH, USA. 3Planetary Science Institute, Tucson, AZ, USA. 4COMET, School of Earth & Environment, University of Leeds, Leeds, UK. 5British Columbia
Ministry of Forests, Lands, Natural Resource Operations and Rural Development, Government of British Columbia, Prince George, British Columbia,
Canada. 6Global Systems Institute, University of Exeter, Exeter, UK. 7Met Office Hadley Centre, Exeter, UK. 8College of Life and Environmental Sciences,
University of Exeter, Penryn, UK. 9Present address: Water, Sediment, Hazards and Earth-surface Dynamics (WaterSHED) Laboratory, Department of
Geoscience, University of Calgary, Calgary, Alberta, Canada. 10Present address: Department of Atmospheric Science, University of Alabama in Huntsville,
Huntsville, AL, USA. e-mail: daniel.shugar@ucalgary.ca
Glaciers are sensitive to climate change1. In many locations,
enhanced glacier mass loss is supporting the growth of
ice-marginal, moraine-dammed and supraglacial lakes24.
These lakes exist in a variety of forms (for example, see Fig. 25 in ref. 5)
and can accelerate glacier mass loss and terminus retreat69 due to
calving. Lake-calving glaciers tend to flow more slowly, are less cre-
vassed and calve less regularly than tidewater glaciers in otherwise
similar environments for reasons that are only partly understood10.
Further, glacial lake growth, once initiated, can decouple from
climate and cause the rapid retreat of glaciers (for examples, see
refs. 3,11,12) due to positive feedback as glacial lakes develop adjacent
to or at the termini of downwasting glaciers and induce rapid melt-
ing. The positive feedback is interrupted when the glacier retreats
out of the lake or the lake drains. As glacial lakes drain, they can
cause sudden hydrologic and geomorphic change1315. Glacial
lake outbursts can pose a risk to people and infrastructure down-
stream1619. However, some glacial lakes are an economic resource
where engineering can mitigate hazards, produce hydroelectric
power and better regulate water outflow20,21.
Although glacial lake change across individual basins (for exam-
ples, see refs. 22,23) or regions (for examples, see refs. 2428) has been
mapped previously, no global assessment has been carried out to
investigate glacial lake occurrence or evolution. Recent develop-
ments in ‘big data’ cloud computing and geomatics29,30 have enabled
automated mapping that can use vast archives of satellite data,
yielding a step change in the understanding of global changes to
the cryosphere31.
Glacial lakes temporarily store meltwater, a process that is cur-
rently neglected in models addressing the hydrological responses
of glaciers to climate change32 and calculations of sea level rise33.
Because no global assessment of glacial lake area or volume has pre-
viously been undertaken, the volume of water stored in these lakes
and the temporal trend of glacial lake storage have not been known.
As a result, the role of terrestrial interception in modulating global
sea level rise has been difficult to estimate.
Here, we quantify glacier lake areas and volumes on a nearly
global scale (see red dashed boxes in Fig. 1) using a data cube built
from 254,795 Landsat scenes from 1990 to 2018 using a normalized
difference water index-based model implemented in Google Earth
Engine (see Methods). The images are aggregated by epoch and ver-
ified for complete coverage of glacier proximal areas to avoid biases
related to differing spatio-temporal image densities. The model
identifies and outlines surface water, which is then filtered by a set
of variables to retain only glacial lakes (supraglacial, proglacial and
ice-marginal). We then use empirical scaling relations34 to estimate
the total glacial lake volume from the measured lake areas to bet-
ter constrain how terrestrial storage of glacial meltwater is changing
decadally and how global sea level is affected. The data also provide
a useful benchmark for assessing regional glacial hazards and vari-
ability in lake evolution.
The global distribution of glacial lakes
The number and size of glacial lakes have grown rapidly over the
past few decades (Figs. 1 and 2). In the 1990–1999 timeframe (see
Methods), 9,414 glacial lakes (>0.05 km2) covered approximately
5.93 × 103 km2 of the Earth’s surface, which together contained
~105.7 km3 of water. As of 2015–2018, the number of glacial lakes
globally had increased to 14,394 (Fig. 1), a 53% increase over
1990–1999. These had grown in total area by 51% to 8.95 × 103 km2,
and their estimated volume had increased by 48% to 156.5 km3
Rapid worldwide growth of glacial lakes since
1990
Dan H. Shugar 1,9 ✉ , Aaron Burr1, Umesh K. Haritashya 2, Jeffrey S. Kargel3, C. Scott Watson 4,
Maureen C. Kennedy 1, Alexandre R. Bevington 5, Richard A. Betts6,7, Stephan Harrison8 and
Katherine Strattman2,10
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 gla-
cial 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.
NATURE CLIMATE CHANGE | VOL 10 | OCTOBER 2020 | 939–945 | www.nature.com/natureclimatechange 939
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... Rising summer temperatures, coupled with heterogeneous precipitation patterns, intensities, and trends, have significantly impacted the sensitive Himalayan glaciers [1,2]. This has resulted in an abrupt retreat of glaciers, which, in turn, has caused an increase in both the number and size of glacial lakes in the Himalayas [3][4][5][6]. These glacial lakes are susceptible to triggering by mass movements (avalanches and rockfalls), precipitation, earthquakes, internal moraine degradation, and seepage [7][8][9], which can rapidly rivers in Tibet, whereas Bhotekoshi and Trishuli in Nepal), which act as essential corridors to transmit warm and humid air from the Indian Ocean to TAR. ...
... Former studies that carried out process-driven susceptibility assessment of GLOF used recent inventory to quantify glacial lake areas [36]. We argue that using a recent glacial lake area, most of which has been subjected to growth since 1990 [6], cannot represent the actual scenario before GLOF. For example, a larger lake is more exposed to potential mass movement than a smaller lake, and vice versa [89]. ...
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