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Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield
Abstract
We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Frías). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 ± 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 ± 85 cal yrs BP; ice remained in an inboard position until 7730 ± 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Frías glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion – documented only in stratigraphic sections – between 7730 ± 50 and 7210 ± 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000–5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500–2000 and 1500–1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at ∼700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Frías 1 and Frías 2a, 2b, and 2c. The Onelli and Ameghino glacier valleys also preserve older Holocene moraines. In the Agassiz, Spegazzini, and Mayo valleys, ice of the late-Holocene advances appears to have overridden landforms equivalent in age to Pearson 1. Perito Moreno Glacier is an extreme case in which ice of historical (Pearson 2c) advances overrode all older Holocene moraines. Based on the distribution and number of moraines preserved, we infer that the response to climate differed among the Lago Argentino outlet glaciers during the Holocene. This led us to examine the effects of climatic and non-climatic factors on individual glaciers. As a consequence, we detected an important effect of the valley geometry (hypsometry) on the timing and magnitude of glacier response to climate change. These results indicate that caution is needed in correlating moraines among glacier forefields without firm morpho-stratigraphic and age control. Finally, we note important similarities and differences between the overall moraine chronology in the Lago Argentino basin and that in other areas of southern South America and elsewhere in the Southern Hemisphere.
... ka BP in Potter Cove followed by a glacier readvance at <7.0 cal. ka BP on Potter Peninsula (Strelin et al., 2014) (Figures 3, 5a, 6a and 7e-g). ...
... The Stage 3 readvance was broadly synchronous with two phases of glacier expansion and the reformation of ice shelves on the north-eastern AP (Figure 5f), and in Southern South America between c. 1.5 and 1.1 cal. ka BP (Balco and Schaefer, 2013;Kaplan et al., 2020;Moreno et al., 2018;Strelin et al., 2014) and occurred when a colder conditions existed on the north-eastern AP (Figure 5g) (Mulvaney et al., 2012), but also when composite ice core records from elsewhere in Antarctica show a predominantly warmer phase (Masson et al., 2000). ...
... ka BP which coincided with the transition to colder and more negative SAMlike conditions as the SHW migrated marginally equatorward (Figure 7a-c and g). Glacier readvance(s) on KGI are regionally coherent with readvances on the eastern AP (Kaplan et al., 2020;Figure 5f) and in Patagonia at c. 7 ka (Reynhout et al., 2019;Strelin et al., 2014), implying a common forcing mechanism. ...
To provide insights into glacier-climate dynamics of the South Shetland Islands (SSI), NW Antarctic Peninsula, we present a new deglaciation and readvance model for the Bellingshausen Ice Cap (BIC) on Fildes Peninsula and for King George Island/Isla 25 de Mayo (KGI) ~62°S. Deglaciation on KGI began after c. 15 cal. ka BP and had progressed to within present-day limits on the Fildes Peninsula, its largest ice-free peninsula, by c. 6.6–5.3 cal. ka BP. Probability density phase analysis of chronological data constraining Holocene glacier advances on KGI revealed up to eight 95% probability ‘gaps’ during which readvances could have occurred. These are grouped into four stages – Stage 1: a readvance and marine transgression, well-constrained by field data, between c. 7.4 and 6.6 cal. ka BP; Stage 2: four probability ‘gaps’, less well-constrained by field data, between c. 5.3 and 2.2 cal. ka BP; Stage 3: a well-constrained but restricted ‘readvance’ between c. 1.7 and 1.5 cal. ka BP; Stage 4: two further minor ‘readvances’, one less well-constrained by field data between c. 1.3 and 0.7 cal. ka BP (68% probability), and a ‘final’ well-constrained ‘readvance’ after <0.7 cal. ka BP. The Stage 1 readvance occurred as colder and more negative Southern Annular Mode (SAM)-like conditions developed, and marginally stronger/poleward shifted westerly winds led to more storms and precipitation on the SSI. Readvances after c. 5.3 cal. ka BP were possibly more frequent, driven by reducing spring/summer insolation at 62°S and negative SAM-like conditions, but weaker (equatorward shifted) Westerlies over the SSI led to reduced storminess, restricting readvances within or close to present day limits. Late Holocene readvances were anti-phased with subaquatic freshwater moss layers in lake records unaffected by glaciofluvial inputs. Retreat from ‘Neoglacial’ glacier limits and the recolonisation of lakes by subaquatic freshwater moss after 1950 CE is associated with recent warming/more positive SAM-like conditions.
... Glaciers are sensitive to climatic variations, and glacial landforms indirectly preserve information about past climate (Leger et al., 2021). Many Patagonian glaciers record multiple past advances through frontal moraines (Davies et al., 2020;Kaplan et al., 2016;Reynhout et al., 2019;Strelin et al., 2014), corresponding to times of higher precipitation or lower temperatures. Numerical modeling of past glacier extents under a suite of different climatic scenarios has been used to quantitatively constrain past precipitation and temperature ranges (Leger et al., 2021), although qualitative correlations between glacier extent and climatic conditions are more common (Kaplan et al., 2016;Strelin et al., 2014;Warren, 1993). ...
... Many Patagonian glaciers record multiple past advances through frontal moraines (Davies et al., 2020;Kaplan et al., 2016;Reynhout et al., 2019;Strelin et al., 2014), corresponding to times of higher precipitation or lower temperatures. Numerical modeling of past glacier extents under a suite of different climatic scenarios has been used to quantitatively constrain past precipitation and temperature ranges (Leger et al., 2021), although qualitative correlations between glacier extent and climatic conditions are more common (Kaplan et al., 2016;Strelin et al., 2014;Warren, 1993). Reynhout et al. (2019) proposed that variations in SAM phase have paced Holocene glacier fluctuations in Patagonia by controlling the local precipitation and temperature. ...
... Studies with both a high temporal resolution and temporal coverage greater than 1000 years (Abram et al., 2014;Elbert et al., 2012;Lara et al., 2020;Moreno et al., 2014) show limited agreement, and are too spatially far apart for a consensus Patagonian paleoclimate reconstruction. Our best understanding of past SAM changes comes from an agreement between Southern Patagonian pollen assemblage changes (Moreno et al., 2014) and glacial fluctuations (Kaplan et al., 2016;Reynhout et al., 2019;Strelin et al., 2014), which suggest an approximately 200-year duration of SAM-positive phases. ...
... On the eastern, leeward, side of the SPI, terrestrial archives of glacier variability are abundant (Davies et al., 2020) and numerous moraine systems have been dated through lichenometry (Garibotti and Villalba, 2009), dendrochronology (Masiokas et al., 2009a), radiocarbon (Mercer, 1968;Moreno et al., 2009;Strelin et al., 2014Strelin et al., , 2011, or cosmogenic nuclide exposure-age dating (Kaplan et al., 2016;Moreno et al., 2009;Reynhout et al., 2019;Strelin et al., 2014). As a result, postglacial fluctuations along the eastern side of the icefield are relatively well constrained. ...
... On the eastern, leeward, side of the SPI, terrestrial archives of glacier variability are abundant (Davies et al., 2020) and numerous moraine systems have been dated through lichenometry (Garibotti and Villalba, 2009), dendrochronology (Masiokas et al., 2009a), radiocarbon (Mercer, 1968;Moreno et al., 2009;Strelin et al., 2014Strelin et al., , 2011, or cosmogenic nuclide exposure-age dating (Kaplan et al., 2016;Moreno et al., 2009;Reynhout et al., 2019;Strelin et al., 2014). As a result, postglacial fluctuations along the eastern side of the icefield are relatively well constrained. ...
... (b) Overview map of the Southern Patagonian Icefield (SPI) and the adjacent fjord region. Glaciers investigated in this study are indicated in red (# 8e10), those investigated by Mercer (1970) in gray (# 3e6), by Reynhout et al. (2019) in yellow (#7), and by Kaplan et al. (2016) and Strelin et al. (2014) in dark blue (# 11e18). The western limits of the Patagonian Ice Sheet during the local LGM (orange line) and of the SPI at 13 kyr BP (dotted white line) are from Davies et al. (2020). ...
Postglacial fluctuations of Southern Patagonian Icefield (SPI) glaciers are well constrained on the leeward side of the Andes, but they remain mostly unknown on the windward side of the icefield, where most glaciers are marine-terminating. Here, we reconstruct the postglacial fluctuations of the HPS19, Penguin, and Europa glaciers along the hyperhumid western side of the SPI using a multi-proxy sedimentological and geochemical analysis of a 12.2 m long sediment core from Wide Channel (50°S). Results show that the glaciers retreated into Penguin and Europa fjords by 11.2 cal kyr BP and that they were relatively stable and marine-terminating between 11.2 and 5.8 cal kyr BP. Thereafter, they fluctuated rapidly, with four marked episodes of glacier shrinkage at 5.8-4.8, 3.9-2.4, 1.0-0.2 cal kyr BP, and during the 20th century. Although the HPS19, Penguin, and Europa glaciers were calving into Penguin and Europa fjords during most of the Holocene, our data suggest that they retreated to land-based positions between 5.8 and 4.8 cal kyr BP. The comparison of our sediment record with geological archives from both sides of the Patagonian icefields (46-56°S) suggests synchronous glacier variability on multi-centennial timescales during the Neoglacial period, which is particularly clear after 2.5 cal kyr BP. We conclude that western SPI outlet glaciers remained relatively stable during the first half of the Holocene but fluctuated considerably during the Neoglacial period, and that they retreated to locations further inland than today during the first retreat of the Neoglacial period between 5.8 and 4.8 cal kyr BP.
... Our understanding of the climatic evolution of the southern mid-latitudes during and since the last ice age has benefited from a flurry of paleoclimate research in southern Patagonia and Tierra del Fuego (49 -55 S) over the last decades (Borromei and Quattrocchio, 2008;Borromei et al., 2010;Candel et al., 2020;Coronato et al., 2022;Fern andez et al., 2013Kaplan et al., 2016;Kilian et al., 2007;Kilian and Lamy, 2012;Lamy et al., 2010;Laprida et al., 2021;Markgraf and Huber, 2010;Mancini, 2009;Mansilla et al., 2016Mansilla et al., , 2018Mayr et al., 2007;McCulloch et al., 2019McCulloch et al., , 2020McCulloch et al., , 2021Moreno et al., 2009Moreno et al., , 2010Moreno et al., , 2012Moreno et al., , 2018aMoreno et al., , 2018bMoreno et al., , 2021aMoy et al., 2011;Quade and Kaplan, 2017;Recasens et al., 2015;Sagredo et al., 2011;Strelin et al., 2011Strelin et al., , 2014Sch€ abitz et al., 2013;Tonello et al., 2009;Unkel et al., 2010;Villa-Martínez and Moreno, 2007;Waldmann et al., 2010;Wille and Sch€ abitz, 2009;Zolitschka et al., 2013). Although major advances have shed light on the functioning of the terrestrial and marine paleoenvironments, some subjects remain elusive and, in some instances, compounded by unconstrained geological and ecological assumptions among diverse depositional environments (Kilian and Lamy, 2012;Moreno et al., 2018a). ...
... (d) Lago Cipreses principal component 1 (PC1) score with positive (negative) anomalies in light blue (red) shading (this study). (e) 10 Be cosmogenic dates from Glaciar Torre (i; Reynhout et al., 2019), 14 C and 10 Be dates from Lago Argentino (ii and iii, respectively; Strelin et al., 2014;Kaplan et al., 2016), along with the recalibrated chronology of Cipreses Cycles using SHcal20 (iv; Moreno et al., 2018b). For (i) and (iii), we show the arithmetic mean (red line) with 1s uncertainty (light blue box) crossed by the peak age (blue line) and median age (green line). ...
... In total, the first two phases revealed by the diatom record in L. Cipreses are directly compatible with the pan-Patagonian Early Holocene Westerly Minimum (EHWM) reported by Moreno et al. (2021a) and opposite to the SWW early Holocene maximum inferred from sites near Gran Campo Nevado ( Fig. 1; Lamy et al., 2010). Consistent with this triphasic structure, exposure-age chronologies from Glaciar Torres (Reynhout et al., 2019) and other glaciers adjacent to Lago Argentino (Strelin et al., 2014) provide evidence for glacier advances during the precursor and exit phases but largely absent during the acute phase (Fig. 9e). Furthermore, recent palynological evidence from the Cerro Benítez site, located~35 km southeast of L. Cipreses, indicates forest opening and low bog surface wetness between~8.7-7.2 cal. ...
Conflicting, even opposite interpretations on the evolution of the Southern Westerly Winds (SWW) are evident in paleoenvironmental records from southwestern Patagonia since the last ice age. These divergences call for new approaches utilizing different, ideally independent indicators of paleoenvironmental/paleoclimatic change from sensitive sites in climatically relevant locations. Here we present a multidecadally resolved diatom record from Lago Cipreses (51S), a small closed-basin lake located in a bedrock depression along the eastern foothills of the southern Patagonian Andes. The hydrological balance evolution of this isolated lake affords a direct tie with SWW intensity in a mountainous sector where zonal wind strength and local precipitation are highly correlated. We detect cold-tolerant diatoms (small fragilarioids) between ~14-11.9 cal. ka BP followed by a shift to planktonic assemblages (Discostella pseudostelligera, Aulacoseira spp.) under warmer Holocene conditions. Diatom assemblages indicative of stratified water-column conditions (Discostella pseudostelligera, Achnanthidium aff tepidaricola, Achnanthidium sieminskae) reached their maximum stability between ~9.1-7.4 cal. ka BP. Stronger water-column mixing is evident by an abrupt species turnover to Aulacoseira spp. between ~7.4-3.1 cal. ka BP, superimposed on centennial-scale alternations between assemblages since ~6.1 cal. ka BP. Cold-tolerant diatoms resurge at ~3.1 cal. ka BP and persist until the present. Our record offers assemblage-based evidence we interpret as sub-centennial to multimillennial scale changes in hydroclimate indicative of: (i) strong SWW influence between ~14-11.9 cal. ka BP, (ii) a transition between ~11.9-11.3 cal. ka BP to weak SWW influence between ~11.3-6.5 cal. ka BP, with a SWW minimum between ~9.1-7.4 cal. ka BP, and (iii) strong SWW influence since ~6.5 cal. ka BP, with a Holocene SWW maximum since ~3.1 cal. ka BP. We posit that enhanced hydroclimate variability since ~6.1 cal. ka BP attests to the onset of Southern Annular Mode-like changes at centennial-to sub-centennial timescales. We detect a remarkably coherent and synchronous response of terrestrial and aquatic ecosystems at local scale since ~14 cal. ka BP, highlighting the overriding importance of variations in SWW influence in terrestrial and aquatic environments at multiple timescales.
... However, the beginning of the late Holocene is marked by a global cooling trend (Neoglacial) leading to glacier advances and sea surface temperature decrease in different places in the world (e.g., Jerardino, 1995;Sepúlveda et al., 2009;Aniya et al., 2013;Solomina et al., 2015). SST estimates in the SJG records indicate a slight cooling after 4 cal ka BP, but the onset of the cooling dates from 7 cal ka BP, which is consistent with previous study based on glacier history showing that the onset of cooling has started much earlier, at about 7730 cal BP in Patagonia, marking the beginning of successive glacier advances ( Fig. 7; Strelin et al., 2014;Kaplan et al., 2016). ...
... The marine records of Pacific and Atlantic oceans at high southern latitudes show drastic changes with a cooling trend during this period (Fig. 10, Bianchi and Gersonde, 2004;Kaiser et al., 2005). Indeed, this interval corresponds to the Antarctic and Younger Dryas cold reversals that led to glacier advances in the Southern Hemisphere (Bianchi and Gersonde, 2004;Kaiser et al., 2005;Strelin et al., 2014;Quade and Kaplan, 2017), probably as a result of northward shift of the SWWB. ...
... The SWWB shift in the middle Holocene is consistent with reduced moisture over southern Patagonian and the interruption of the wind driven-upwellings in the high latitudes of the South Atlantic sector (Anderson et al., 2009;Lamy et al., 2010). Such northward migration of the core of the SWWB might have led to the onset of cold conditions in Southern South America, which caused glacier advances after 7730 cal ka BP (Strelin et al., 2014;Kaplan et al., 2016). ...
We use pollen and dinocyst assemblages from three sedimentary sequences of the San Jorge Gulf (SJG) to document the vegetation history of the extra-Andean/eastern Patagonia (Argentina), and the latitudinal variations of the Southern Westerly Wind Belt (SWWB) in relation with ocean changes during the Late Pleistocene and Holocene. Our results suggest that prior to 14 cal ka BP, the vegetation of the SJG was dominated by halophytic taxa probably related to arid conditions in coastal environments. After 14 cal ka BP, pollen data suggest the development of shrub and herb vegetation in the Patagonian steppe then characterized by semi-arid conditions. The 14 cal ka BP transition is marked by increasing Nothofagus pollen abundances, suggesting strong westerlies at the onset of the Antarctic Cold Reversal (ACR). This transition is also marked by the occurrence of marine palynomorphs (dinocysts, organic linings of foraminifers), which relate to sea-level rise. The dinocyst assemblages allowed us to quantitatively estimates changes in summer sea-surface temperature (SST) and annual net primary productivity. Between 14 and 10.8 cal ka BP, which encompasses the glacial termination and the early Holocene, dinocyst assemblages are dominated by Operculodinium centrocarpum (∼82%) and Spiniferites mirabilis (∼8%) that suggest warmer conditions than at present. The transition from early to middle Holocene was marked by high SWWB intensity as suggested by pollen assemblages, and an increase of heterotrophic taxa such as Brigantedinium spp., Echinidinium sp., Dubridinium sp., and the cysts of Polykrikos kofoidii, suggesting increased primary productivity and gradual cooling of surface water. After 4 cal ka BP, pollen data suggest a decrease in the SWWB intensity that correlates with glacier advances in Patagonia and a further decrease in summer SST in the SJG.
... Un problema que ha tenido especial relevancia en la discusión de dichas etapas, ha sido el abandono o uso discontinuo de ciertas zonas y el reposicionamiento de los grupos humanos en función de los cambios climáticos registrados durante el Holoceno medio-tardío (Borrero & Franco, 2000;Franco et al. 2004;Franco et al. 2018). Para dichos momentos se ha registrado una relación inversa de las precipitaciones entre la zona ubicada al este del área y la zona cercana a los Andes (Mancini, 2002;Tonello et al. 2009en Franco et al. 2018Mancini et al. 2013;Ohlendorf et al. 2014;Strelin et al. 2014). En consecuencia, se ha sugerido que el cambio ambiental influyó en la movilidad y los tipos de asentamientos al oeste y al este del Lago Argentino (Franco et al. 2016(Franco et al. , 2018. ...
... Sin embargo, para el momento en que RB1 registra evidencias humanas -hace ca. 350 años AP nuevamente se registran condiciones más áridas en la estepa (Tabla 1), (Aniya, 2013y Strelin et al. 2014en Franco et al. 2018. ...
... 450 años cal. AP, el cual se reflejó en un aumento de la humedad en los Andes, acompañado de condiciones más áridas en la estepa (Aniya, 2013;Strelin et al. 2014en Franco et al. 2018. ...
ln this paper we perform an exploratory study of the formation processes involved in the case of RB1 site, based on the analysis of the zooarchaeological record of stratified layers dated between ca. 4.200 and 350 years BP. To do that, we evaluated the degree of intervention of different agents and studied the preservation and the integrity of the zooarchaeological record in relation to changes in site morphology, to be able to discuss the human role in the formation of assemblages. The results indicate that humans were the main accumulator agent, and their actions have varied throughout the analyzed sequence. The zooarchaeological record suggests changes in the preservation of bone remains, which, according to the results are closely related to environmental variations in the area.
... Un problema que ha tenido especial relevancia en la discusión de dichas etapas, ha sido el abandono o uso discontinuo de ciertas zonas y el reposicionamiento de los grupos humanos en función de los cambios climáticos registrados durante el Holoceno medio-tardío (Borrero & Franco, 2000;Franco et al. 2004;Franco et al. 2018). Para dichos momentos se ha registrado una relación inversa de las precipitaciones entre la zona ubicada al este del área y la zona cercana a los Andes (Mancini, 2002;Tonello et al. 2009en Franco et al. 2018Mancini et al. 2013;Ohlendorf et al. 2014;Strelin et al. 2014). En consecuencia, se ha sugerido que el cambio ambiental influyó en la movilidad y los tipos de asentamientos al oeste y al este del Lago Argentino (Franco et al. 2016(Franco et al. , 2018. ...
... Sin embargo, para el momento en que RB1 registra evidencias humanas -hace ca. 350 años AP nuevamente se registran condiciones más áridas en la estepa (Tabla 1), (Aniya, 2013y Strelin et al. 2014en Franco et al. 2018. ...
... 450 años cal. AP, el cual se reflejó en un aumento de la humedad en los Andes, acompañado de condiciones más áridas en la estepa (Aniya, 2013;Strelin et al. 2014en Franco et al. 2018. ...
En este trabajo realizamos un estudio exploratorio de los procesos de formación del sitio RB1, a partir del análisis del registro zooarqueológico comprendido en capas estratificadas entre ca. 4.200 y 350 años AP. Para ello evaluamos el grado de intervención de diferentes agentes y estudiamos la preservación e integridad del registro en relación con los cambios en la morfología del sitio para discutir el rol humano en la formación de los conjuntos. Los resultados indican que el ser humano habría sido el principal agente acumulador y que su accionar habría variado a lo largo de la secuencia analizada. A su vez, el registro faunístico sugiere cambios en la preservación de los restos óseos, los cuales se encuentran en estrecha relación con las variaciones ambientales del área.
... The eastern margin of the SPI consisted of four main ice lobes, which are constrained chronostratigraphically. In the studied area, the Lago Argentino Lobe is one of them (Kaplan et al., 2016;Strelin et al., 2011Strelin et al., , 2014. ...
... There is extensive work on the Puerto Bandera moraines which constrains late-glacial recession (Strelin and Malagnino, 2000;Strelin et al., 2011). The ice dynamics during Holocene times are dated on the Herminita Peninsula, around Lago Pearson and around Lago Frías ( Fig. 1; Strelin et al., 2014;Kaplan et al., 2016). ...
... The history of deglaciations in the southern arms of Lago Argentino during the late-glacial is presented by Strelin et al. (2011Strelin et al. ( , 2014 and Kaplan et al. (2011). The oldest minimum limiting age of 12,660 cal yrs BP corresponds to the plant colonization of spillways "M" and "A" of Brazo Rico (sector 3 in Strelin et al., 2011), located in the eastern margin of the Brazo Rico (Fig. 4). ...
Lago Argentino hosts various calving glaciers, including the most famous Perito Moreno. Although the onland late-glacial glacier dynamics is rather well constrained, its submerged evidences remains largely unknown. A detailed analysis of high-resolution seismic reflection profiles acquired in the southern arms of Lago Argentino has allowed the identification of several unconformities within the lacustrine sedimentary infill. Four seismostratigraphic sequences have been identified in Brazo Rico and three in Brazo Sur. These sequences are separated by three erosive unconformities in Brazo Rico and two in Brazo Sur, and reflect the sedimentation of a pre-Holocene deep basin in a proglacial lake. The older unconformities were developed as consequence of mass movements, possibly triggered by seismicity in the area. The younger erosive unconformities were correlated with the “Pearson 1a/Frias 1 advance”, the major glacier advance in the mid-Holocene. This study highlights the importance of the glaciolacustrine sediments, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of the glacier Perito Moreno, which in a warming climate is relatively stable.
... The Upsala Channel, a valley shaped by glacier erosion, has a depth of approximately 600 m along the dale (Naruse and Skvarca, 2000;Sugiyama et al., 2016), and on its eastern margin it borders with the Herminita Peninsula (approximately 250 m ASL). On its western side, it borders with the first foothills of the Andes (Feruglio, 1944) (approximate 800 m ASL), covered by moraines of Pearson I and II systems, deposited during the Holocene epoch, shortly after the Last Maximum Glacial (Strelin et al., 2014). ...
... This Western Patagonia region has a very humid climate with a seasonal annual precipitation cycle ranging from 5000 to 10,000 mm per year (Garreaud et al., 2013), and one of the most dramatic precipitation gradients on Earth (Carrasco et al., 2002;Smith and Evans, 2007). Different levels of freezing appear above1km ASL; while the Pacific flank and the summit of the Patagonian Andes receive abundant precipitation (Casassa and Rivera, 1999), the precipitation descends eastward to 200 mm in the city of El Calafate (Strelin et al., 2014). The climate is characterized by cool summers and determined by strong western winds (Weischet, 1996) as a consequence of the southward shift of the subtropical anticyclone and the rise in the latitudinal pressure gradient (Strelin et al., 2014). ...
... Different levels of freezing appear above1km ASL; while the Pacific flank and the summit of the Patagonian Andes receive abundant precipitation (Casassa and Rivera, 1999), the precipitation descends eastward to 200 mm in the city of El Calafate (Strelin et al., 2014). The climate is characterized by cool summers and determined by strong western winds (Weischet, 1996) as a consequence of the southward shift of the subtropical anticyclone and the rise in the latitudinal pressure gradient (Strelin et al., 2014). However, the average annual air temperature is of~6°C on both sides of the mountain range (Carrasco et al., 2002). ...
... In the study area, Middle and Late Holocene glacier fluctuations are well represented by widespread moraine belts fringing the SPIF (R€ othlisberger, 1986;Masiokas et al., 2009;Strelin et al., 2014;Kaplan et al., 2016;Davies et al., 2020). Prior to the formation of Late Holocene glacier limits, which are the focus of this study (Fig. 1), ice retreated from the Late Glacial frontal limits (García et al., 2012) at the eastern end of Torres del Paine National Park, around 13 kyr B.P. or soon after (Moreno et al., 2009). ...
... advances at ca. 1100e1400 yr. B.P. have been reported in other Patagonian glaciers including SPIF outlet glaciers nearby at Lago Argentino and Cordillera Darwin (e.g., Strelin et al., 2014;Kaplan et al., 2016;Aniya, 1995;Hall et al., 2019), suggesting that SPIF outlet glaciers in Torres del Paine probably also did advance at about this time. Nonetheless, more data are required to confirm this SPIF expansion in Torres del Paine. ...
... Prominent Mid-Holocene advances in the region between about 7000 and 4000 yr. B.P. are recorded just to the north around the Lago Argentino and Torre Glaciers (49-50 S) (Aniya, 1995;Mercer, 1970;Strelin et al., 2014;Kaplan et al., 2016;Reynhout et al., 2019). Farther north, the Río Tranquilo Glacier (Monte San Lorenzo, 47 S deposited the RT6 moraine by 5.7 ± 0.1 ka (Sagredo Fig. 6. ...
Southern Hemisphere Holocene glacier chronologies are important for unraveling past climate change, mid-to-high latitude teleconnections, and regional to global climate forcing. At present, a significant number of glacier chronologies for Patagonia are based on ¹⁴C dating, which may afford only maximum- or minimum-limiting dates. Here, we combine geomorphology and stratigraphy with radiocarbon (¹⁴C) and beryllium-10 (¹⁰Be) surface exposure-age dating at three outlet glaciers, Zapata, Tyndall, and Pingo. These glaciers drain the southernmost tip of the Southern Patagonian Ice Field at Torres del Paine National Park, Chile (51°S). After an expansion that we date at 3200 yr. B.P., the Torres del Paine glaciers expanded to their last major Late Holocene maxima at 600 and 340 yr. B.P., with the final dated readvance after 190 yr. B.P. We use these data, together with other Patagonian glacier records, to define the early, mid and final glacial stages of the last millennium. These cold events were separated by warm conditions that allowed the Nothofagus forest to colonize deglaciated land. The presence of near-concurrent glacier fluctuations in Patagonia and Antarctic Peninsula indicates widespread cooling punctuated the Late Holocene, including the last millennium, across much of the extratropical Southern Hemisphere. We link this cooling to cold oceanographic-atmospheric conditions forced by a northern shift or intensification of the Southern Westerly Winds. Such scenario increased northward advection of cold Antarctic circumpolar water along western Patagonia and favored decreased upwelling of warm circumpolar deep water together with expanded sea ice around the Antarctic Peninsula.
... 12.000 años cal AP. Numerosas investigaciones en Patagonia Austral y en la Península Antártica han señalado la existencia de cambios considerables en la extensión de los glaciares, en la temperatura y en las precipitaciones durante el I N P R E S S Holoceno (Bentley et al., 2009;Tonello et al., 2009;Massaferro et al., 2013;Strelin et al., 2014;Kaplan et al., 2016). La variabilidad climática del Holoceno ha sido adjudicada a la ocurrencia de eventos asociados a diferentes escalas temporales y asociados a diferentes mecanismos de acción. ...
... La acción de los antiguos glaciares pleistocénicos en Patagonia se evidencia en la forma de los relieves andinos, caracterizados por valles grandes y cuencas profundas. Numerosos autores han estudiado y reconstruido los momentos de avances y retrocesos de los glaciares del suroeste de Patagonia durante el Último Máximo Glacial (UMG) y sus fluctuaciones durante el Holoceno (Mercer, 1982;Wenzens y Wenzens, 1998;Strelin y Malagnino, 2000;Glasser et al., 2004;Masiokas et al., 2009;Aniya, 2013;Strelin et al. 2014). En general, para el sudoeste de Patagonia, los autores coinciden que el campo de hielo se extendía hasta la margen oriental de los lagos San Martín, Viedma y Argentino durante el UMG. ...
... En general, para el sudoeste de Patagonia, los autores coinciden que el campo de hielo se extendía hasta la margen oriental de los lagos San Martín, Viedma y Argentino durante el UMG. En particular, en el área del Lago Argentino, las morrenas de Puerto Banderas corresponden a avances glaciares alrededor de 13.000 años cal AP (Strelin et al., 2014). Desde ese momento, las grandes masas glaciares habrían retrocedido hasta posiciones cercanas a las actuales, presentando oscilaciones durante diferentes períodos (ej. ...
Paleoecological studies in Patagonia provide information about vegetation and climate changes occurred during the Holocene. The climatic evolution of this region offers a unique opportunity to study the environmental variability as well as the ecosystem variations. The dynamic of the forest ecosystems is modulated by the occurrence of disturbances. Fires are one of the most important disturbances in temperate forest ecosystems, and its study allows contrasting independently about the changes experienced by ecosystems. In addition, in Patagonia, environmental and postglacial vegetation changes have been determined by variations in the temperature and westerlies winds. In order to reconstruct changes experienced by the forest ecosystem and patterns of plant diversity during the Holocene, in relation to Postglacial dynamics, natural and anthropic disturbances in the Lake Argentino, pollen and charcoal were studied in a sedimentary sequence at Península Avellaneda. Pollen assemblages suggest non-cyclic changes in plant diversity during the Holocene. The highly diverse cold grass-shrub communities dominated the area up to the Early Holocene, when they were displaced upland by less diverse forest and steppes. Also, The Early and Midd-Holocene was characterized by opposite variations of hydric balance between Andean and extra-andean plant communities present between 48° and 50° S, whereas fire activity occurs synchronously between forest (Andean) and steppe communities (Extra-andean). Late Holocene is characterized by different proxy signals depending on the geographical location of the paleoecological records. To conclude, this work provides a better understanding of the fossil pollen record by its comparison with modern surface pollen samples along an altitudinal vegetation gradient.
... The eastern margin of the Southern Patagonian Icefield consisted of four main ice lobes, which are constrained chronostratigraphically by radiocarbon and cosmogenic ages. From north to south these are the O'Higgins/San Martin lobe (Glasser et al., 2011b;Wenzens, 2005), Lago Viedma and Lago Argentino lobes (Ackert et al., 2008;Kaplan et al., 2016;Strelin et al., 2011Strelin et al., , 2014Wenzens, 1999), and, south of Cordon de los Baguales, the Torres del Paine/Río Coyle and del Toro lobes García et al., 2018;Moreno et al., 2009) (Fig. 24). The Bella Vista/Ultima Esperanza lobe is discussed in the Gran Campo Nevado section. ...
... However, extensive work on the Puerto Bandera moraines constrains Late Glacial recession from these outer moraines (Ackert et al., 2008;Strelin and Malagnino, 2000;Strelin et al., 2011). Holocene ice dynamics of the Lago Argentino lobe are well dated on the Herminita Peninsula, around Lago Pearson and around Lago Frías Strelin et al., 2014). ...
... At 20 ka, the extent of many outlet lobes is uncertain. The Torres del Paine/Río Coyle Lobe is well dated at the TDP I moraines around Lago del Toro to 21.3 Fig. 24. A. Glaciers, lakes and rivers of the Southern Patagonian Icefield (48°-52°S), and published chronology (ka) and geomorphology (Ackert et al., 2008;Ashworth et al., 1991;Casassa et al., 1997;Dowdeswell et al., 2016a;Fogwill and Kubik, 2005;García et al., 2012;García et al., 2018;Glasser et al., 2011b;Horta et al., 2019;Kaplan et al., 2016;Lastras and Dowdeswell, 2016;Marden and Clapperton, 1995;Masiokas et al., 2008;Mercer, 1965Mercer, , 1968Mercer, , 1976Moreno et al., 2009;Sagredo et al., 2011;Strelin et al., 2014;Wenzens, 1999Wenzens, , 2005Wenzens, , 2006. Mean 10 Be ages of moraines are shown in pink crosses. ...
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.
... The most outstanding features in the reconstruction presented here are two major warm periods between 3140e2800 BC and 70 BC e 150 AD (5159e4819 and 2089e1869 years ago, respectively, counted from 2019 to facilitate comparisons with glacier records based on 10 Be dated moraines). During these warm periods, no glacier advances have been reported for Patagonia (Aniya, 2013;Kaplan et al., 2016;Strelin et al., 2014, Fig. 5A). ...
... These cold periods are, respectively, 5269e5159; 4819e4689; 4549e4379 and 2309-2089 years ago. The first three overlap in timing with the largest glacier expansions reported for southern Patagonia based on a 10 Be-dated chronology from Holocene moraines (Kaplan et al., 2016), and the 290e70 BC cold period is consistent with the latter portion of glacier expansion (Strelin et al., 2014, Fig. 5A). Aniya (1995) identified a glacier advance ca. ...
... In the last 2000 years, cold periods are less prominent and shorter compared to the earlier part of the reconstruction (Fig. 5A). The last four cold periods identified for AD 150e310, 655e730, 1180e1350 and 1530e1670 are concurrent with glacier advances reported by Strelin et al. (2014), and partially coincide with Kaplan et al. (2016, Fig . 5A). ...
It is widely documented that the Earth's surface temperatures have increased in recent decades. However , temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC e 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140 e2800BC and 70BC e 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959e2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432e434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At inter-annual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Ni~ no Southern Oscillation (ENSO) and longer oscillations. Our study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems.
... However, existing data from South America suggest that this interpretation of interhemispheric asynchrony may be too simplified. Adjacent to the South Patagonian Icefield, a date of wood from within a landslide deposit indicates that glaciers near Lago Argentino in southern South America had retreated close to present-day positions by~9200 yr BP (Strelin et al., 2014). Thus, it is worth examining whether there are important differences in glacier behavior between southernmost South America and New Zealand during the Holocene that may reflect regional patterns of oceanic and atmospheric circulation. ...
... The Marinelli record shows similarities to those from the southern part of the South Patagonian Icefield (Table 4). Based on a calibrated radiocarbon age of wood enclosed in a landslide deposit, Strelin et al. (2014) inferred extensive early Holocene deglaciation of the Agassiz Este Glacier in the Lago Argentino basin by 9200 yr BP. After an advance at 7210e7730 yr BP (Strelin et al., 2014), glaciers at Lago Argentino expanded to their maximum Holocene extent at 5000e6000 yr BP (Strelin et al., 2014;Kaplan et al., 2016). ...
... Based on a calibrated radiocarbon age of wood enclosed in a landslide deposit, Strelin et al. (2014) inferred extensive early Holocene deglaciation of the Agassiz Este Glacier in the Lago Argentino basin by 9200 yr BP. After an advance at 7210e7730 yr BP (Strelin et al., 2014), glaciers at Lago Argentino expanded to their maximum Holocene extent at 5000e6000 yr BP (Strelin et al., 2014;Kaplan et al., 2016). This latter event may have been replicated at Fiordo Marinelli when the glacier overrode Section 17 at 6650 yr BP (Table 4). ...
Records of past variability afford context for evaluating present-day glacier behavior and for testing hypotheses of climate change. Here, we use 69 radiocarbon dates of wood and other organic materials in association with glacial deposits to document the behavior of Ventisqueros Marinelli and Brooks in Cordillera Darwin over the past ∼17,000 years. Recession from the last glacial maximum was early, with most occurring prior to 17,000 yr BP. Any glacial resurgence during the Antarctic Cold Reversal must have terminated within the bounds of Holocene ice fluctuations. By early Holocene time, Ventisquero Marinelli had retreated such that it was no more extensive than it was in AD 1992. We identify several subsequent glacier readvances, but also note long periods of restricted ice extent, particularly in the mid-Holocene. There were times when Holocene glaciers must have been smaller than at present. Our new record from Marinelli shows similarities to other reconstructions of Holocene glacier variation from southern South America, such as at Mt. Sarmiento and the South Patagonian Icefield, suggesting an underlying climate signal. The overall implication is of substantial early Holocene deglaciation followed by repeated advances interspersed with periods of recession when ice extent was smaller than at present. This general pattern of glacier behavior appears to differ from that of New Zealand's Southern Alps and points to the value of a geographic spread of datasets to elucidate the pattern of Southern Hemisphere climate during the Holocene.
... Paleoglacier studies in southern Patagonia (defined here as South America between 46 and 53 S) reveal a glacial chronology different from those in New Zealand and the Northern Hemisphere. Several models of "Neoglaciation" have been proposed, often dissimilar from each other, although all suggest that an early Holocene warm period was followed immediately by mid-Holocene glacier maxima and progressively smaller glaciations in the mid-to late-Holocene (Mercer, 1965;Clapperton and Sugden, 1988;Glasser et al., 2004;Aniya, 2013;Strelin et al., 2014;Kaplan et al., 2016). Although this pattern differs from the progressively less-and moreextensive Holocene glaciations in New Zealand and the Northern Hemisphere, respectively, early workers (Porter and Denton, 1967;Mercer, 1982) drew implicit parallels across the polar hemispheres by defining the Patagonian record in terms of a warm "Hypsithermal" followed by a colder "Neoglacial" period (Porter, 2000). ...
... Lags of centuries to millenniador periods of erosion between initial and subsequent colonizationdcan result in valid limiting ages of low precision. New age constraints of previously dated moraines in Patagonia have demonstrated that the original minimum-limiting ages often underestimated the true age of the landform by thousands of years, for instance at Peninsula Herminita (Aniya and Sato, 1995;Strelin et al., 2011;Kaplan et al., 2016), Lago Pearson (Mercer, 1965;Kaplan et al., 2016), and at Glaciar Frías (Mercer, 1976;Strelin et al., 2014;Kaplan et al., 2016). ...
... 1a and 51 S). These constitute the most thorough records of directly-dated glacier fluctuations since late-glacial time in the region (Strelin et al., 2014;Kaplan et al., 2016). These records from Lago Argentino show glacier expansions during the ACR and at 6100 ± 390, 4450 ± 220, 2300-2000, 1400 ± 110, 600-500, 360 ± 30, and 240 ± 20 yr BP (Fig. 2b). ...
... La cuenca del Upsala presenta una combinación de procesos glaciales y paraglaciales, constituyendo un ambiente complejo. Se han realizado investigaciones de la geomorfología glaciar del CHPS (Caldenius, 1932;Malagnino y Strelin 1992;Glasser et al., 2005Glasser et al., , 2008Aniya et al., 2007;Glasser y Ghiglione, 2009;Strelin et al., 2014), pero existe una carencia de estudios en la cuenca del Upsala, de la geomorfología paraglacial, asociada a la inestabilidad de las laderas. ...
... Estas masas de hielo comenzaron a sufrir una disminución en su superficie, producto de la intervención de varios factores, dejando como consecuencia un paisaje modelado por la acción glaciar y pendientes cubiertas por depósitos glaciogénicos. En la cuenca del lago Argentino los glaciares comenzaron a retroceder en el Holoceno temprano (Strelin et al., 2014). El canal Upsala es uno de estos valles modelados por el hielo, con una profundidad de ~600 m en el frente del glaciar Upsala (Naruse y Skvarca, 2000;Sugiyama et al., 2016) y sus alrededores como los valles del río Moyano, río Norte, península Herminita, bahía Onelli y canal Spegazzini (Fig. 1). ...
... El canal Upsala es uno de estos valles modelados por el hielo, con una profundidad de ~600 m en el frente del glaciar Upsala (Naruse y Skvarca, 2000;Sugiyama et al., 2016) y sus alrededores como los valles del río Moyano, río Norte, península Herminita, bahía Onelli y canal Spegazzini (Fig. 1). Hacia el oeste del canal aparecen las primeras estribaciones de la zona Andina, cubiertas con depósitos de los sistemas morrénicos Pearson I y II (Strelin et al., 2014). ...
The worldwide retreat and thinning of glaciers in recent decades have a direct impact on the stability of the slopes. The Upsala glacier basin and the glaciers of the North Branch of Argentino Lake have suffered a marked retreat, generating valleys with steep slopes and covered with unstable moraine deposits. Therefore, the slopes are strongly destabilized, favoring the generation of paraglacial geomorphological processes. The main goal of this study is to identify and analyze the paraglacial geomorphology associated with instability processes. We analysis the area through the combination of morphometric parameters and intervening factors that condition and trigger these processes by satellite images. The results show that paraglacial geomorphology is influenced by the combination of: (i) terrain morphometric parameters as, among others, terrain elevations exceeding 700 m ASL, average slopes with a range between 25º-45º, east-northwest slopes aspects with greater insolation, concave curvature of the terrain and slight to moderate roughness (0.40-0.65); (ii) conditioning factors, moraine material deposited by glaciers, weathered rock outcrops and vegetation cover; (iii) triggering factors, groundwater infiltration by proglacial lagoons and surface infiltration by rainfall, thaw and runoff, variation of air and soil temperatures and variation of lake level. In conclusion, the slopes with the greatest paraglacial geomorphological processes resulting from mass removal processes are those in direct contact with the Upsala, Bertacchi and Cono glaciers, the western slope of the Upsala channel and some areas of the Moyano and Norte valleys. The area is characterized by a combination of glacial and paraglacial environments, each being an integral part of the evolution of the environment.
... The Upsala Channel, a valley shaped by glacier erosion, has a depth of approximately 600 m along the dale (Naruse and Skvarca, 2000;Sugiyama et al., 2016), and on its eastern margin it borders with the Herminita Peninsula (approximately 250 m ASL). On its western side, it borders with the first foothills of the Andes (Feruglio, 1944) (approximate 800 m ASL), covered by moraines of Pearson I and II systems, deposited during the Holocene epoch, shortly after the Last Maximum Glacial (Strelin et al., 2014). ...
... This Western Patagonia region has a very humid climate with a seasonal annual precipitation cycle ranging from 5000 to 10,000 mm per year (Garreaud et al., 2013), and one of the most dramatic precipitation gradients on Earth (Carrasco et al., 2002;Smith and Evans, 2007). Different levels of freezing appear above1km ASL; while the Pacific flank and the summit of the Patagonian Andes receive abundant precipitation (Casassa and Rivera, 1999), the precipitation descends eastward to 200 mm in the city of El Calafate (Strelin et al., 2014). The climate is characterized by cool summers and determined by strong western winds (Weischet, 1996) as a consequence of the southward shift of the subtropical anticyclone and the rise in the latitudinal pressure gradient (Strelin et al., 2014). ...
... Different levels of freezing appear above1km ASL; while the Pacific flank and the summit of the Patagonian Andes receive abundant precipitation (Casassa and Rivera, 1999), the precipitation descends eastward to 200 mm in the city of El Calafate (Strelin et al., 2014). The climate is characterized by cool summers and determined by strong western winds (Weischet, 1996) as a consequence of the southward shift of the subtropical anticyclone and the rise in the latitudinal pressure gradient (Strelin et al., 2014). However, the average annual air temperature is of~6°C on both sides of the mountain range (Carrasco et al., 2002). ...
We present results of the estimation of surface changes associated with slope instability processes on the Upsala Channel by remote sensing and statistic techniques. Hillslopes, involving lateral moraines, of Upsala Channel at the Argentino Lake have become potentially unstable due to the retreat of Upsala Glacier during the last century. The glaciation and deglaciation processes modify the tensions on the slope stability and may generate landslide processes. A landslide movement destroyed the western edge of the Upsala Channel in February 2013. In addition, the region represents a great tourist attraction usually ships navigate through the Upsala Channel seeing impressive landscapes, especially the Upsala Glacier, stand out. Due to this risky situation the necessity of increasing the knowledge in the area has arisen but has not been addressed yet. Therefore, the main goal of the present study is to investigate the multivariate statistical techniques by the principal component analysis (PCA) and discriminative analysis (DA) in four testing areas (TASn). Besides, we include Pearson's correlation coefficient (PCC) and normal distribution (ND) to determine whether the testing areas suffered slope movements or were temporally stable. The study is based on Landsat optical satellite images, acquired during the period from October 2001 to April 2015. The results show that TAS1,2,4 are less stable, whereas TAS5 is a more stable area as compared to another TAS. The PC1 and PC2 principal components explained the total variability of the 76% data. The total apparent error of DA reached 2.2% points. The PCC achieved a positive trend during the years when movement on the slope surface was not observed; while during the periods when slope instability was observed, the correlation showed a negative trend. The TASn that had shown a different behavior presented contrasted Gaussian bells; they are more flattened in those years with instability events.
... In our environmental research, for the Andes, we have borrowed heavily from the precipitation model of Tonello et al. (2009) based on pollen data from Cerro Frias (CF) south of Lake Argentino and the works of Moreno et al. (2009), Aniya (2013, and Strelin et al. (2014), who have documented periods of glacier advance in the Southern Patagonia Ice Field (SPIF). For the steppe east of the Andes, we have utilized data in Ohlendorf et al. (2014) on Laguna Cháltel. ...
... 5500-3000 cal BP was the longest, more or less continuous period of increased moisture in the Andes during the Holocene. It was accompanied by lower South Atlantic SSTs (sea surface temperatures), more persistent Antarctic sea ice and multiple periods of glacier advance in the SPIF (Hodell et al. 2001;Moreno et al. 2009;Aniya 2013;Strelin et al. 2014) (Fig. 14.3e, h, j). The most abundant evidence of human occupation at ChM2 (Mehl the Andes were relatively wet throughout Period I but may have been a little drier ca. ...
... We have not recovered evidence of human occupation in the Lake Argentino area during what appears to have been a very prominent 400-year dry period in the Andes. Aniya (2013) and Strelin et al. (2014) suggest glacier advances during the first 300 years of this period (Fig. 14.3f, g), but there is no evidence of wetter conditions or human settlement in western areas at this time. In contrast, Moreno et al. (2009) suggest that the period of glacier advances late in Period II ended around 2200 cal BP. ...
The Hoabinhian is a distinctive Pleistocene stone artefact technology of mainland and island Southeast Asia. Its relationships to key patterns of technological change both at a global scale and in adjacent regions such as East Asia, South Asia and Australia are currently poorly understood. These key patterns are important indicators of evolutionary and demographic change in human prehistory so our understanding of the Hoabinhian may be substantially enhanced by examining these relationships. In this paper I present new evidence of ancient Hoabinhian technology from Northwest Thailand and examine connections between Hoabinhian technology and the innovation of other important Pleistocene technological processes such as radial core geometry. I present some claims about the evolutionary significance of the Hoabinhian and recommend future research priorities.
... Evidence of the Stage 1 readvance and a marine transgression, when relative sea-level was ~15 m a.s.l. after 7.5-7.0 ka cal BP in Potter Cove (Strelin et al., 2014) Data constraining RSL from the SSI are more complex than other locations across Antarctica, and several different RSL curves have been suggested for the SSI (Pallàs et al., 1997;Bentley et al., 2005;Hall, 2010;Roberts et al., 2011;Watcham et al., 2011;Simms et al., 2012;2021;Johnson et al., 2021). Bentley et al. (2005) initially proposed that RSL declined from an undated early-mid Holocene marine limit of ~16-18 m above present sea-level (henceforth, m a.s.l.) in a discontinuous manner, interrupted at 14.5-16 m a.s.l. by a redavance between 5.8-3.0 ka cal BP). ...
... The Stage 3 readvance was broadly synchronous with two minor phases of glacier expansion on the north-eastern AP (Kaplan et al., 2020) (Figure 5E), in Southern South America between c. 1.5 and 1.1. ka cal BP (Strelin et al., 2014;Moreno et al., 2018), and a predominantly warmer phase in composite ice core records from elsewhere in Antarctica (Masson et al., 2000). ...
The timing of mid–late Holocene deglaciation and glacier readvances on the South Shetland Islands, northern Antarctic Peninsula has been long debated. We used a combined geomorphological, chronological, and palaeolimnological approach to develop a new readvance model for the Bellingshausen Ice Cap (BIC) on the Fildes Peninsula, King George Island/Isla 25 de Mayo, South Shetland Islands, NW Antarctic Peninsula. Results show that retreat to within present-day limits occurred by c. 6 ka, as spring/summer insolation at 62 °S peaked. Probability density analysis of new and previously published chronological data (n=80) from across Fildes Peninsula and King George Island identified up to eight probability ‘gaps’ when glacier readvances might have occurred: 1) a well-defined readvance (with a marine transgression) between c. 7.4–6.6 ka cal BP; 2–5) four possible readvances between c. 5.3–4.8 ka cal BP, 4.5–3.9 ka cal BP, 3.3–3.0 ka cal BP and/or 2.6–2.2 ka cal BP; 6) a well-defined readvance at 1.7–1.3 ka; 7–8) well-defined readvances between c. 1.3–0.7 and after <0.7 ka cal BP. Mid-late Holocene readvances of the BIC on the Fildes Peninsula were limited to within or around the current ice margin. Prior to c. 5 ka cal BP, readvances were initiated during phases of reduced global solar irradiance, with colder and more humid negative Southern Annular Mode (SAM)-like conditions. After c. 5 ka, a declining trend in insolation at 62 °S led to persistently colder/ wetter and more negative SAM-like conditions that likely drove late Holocene readvances.
... Extensive on October 23, 2020 http://advances.sciencemag.org/ Downloaded from glacier advances occurred at a similar latitude in Patagonia between 6.0 to 4.0 ka BP (38)(39)(40). These recent well-dated chronologies revise the timing of neoglacial cooling in the region to 6.0 ka BP, approximately 1000 years before previous interpretations (41). ...
... The potential faunal shift indicated by the change in the bio-element assemblage at ~2.0 ka BP (Fig. 2, A to F) occurred after a 2°C warming of February SSTs at 50°S in the South Atlantic Ocean (37) and enhanced SWW over Tierra Del Fuego at 1.75 ka BP (30). It also coincides with west Antarctic Peninsula SST warming (50), a highly variable ENSO state, a longer duration of sea ice presence in the eastern South Atlantic (37), and regional cooling (38,51). Without knowing species compositions, it is difficult to identify a causal mechanism for the apparent turnover, but it may reflect poleward range shifts in seabird species as ocean temperatures warmed. ...
The coastal tussac (Poa flabellata) grasslands of the Falkland Islands are a critical seabird breeding habitat but have been drastically reduced by grazing and erosion. Meanwhile, the sensitivity of seabirds and tussac to climate change is unknown because of a lack of long-term records in the South Atlantic. Our 14,000-year multiproxy record reveals an ecosystem state shift following seabird establishment 5000 years ago, as marine-derived nutrients from guano facilitated tussac establishment, peat productivity, and increased fire. Seabird arrival coincided with regional cooling, suggesting that the Falkland Islands are a cold-climate refugium. Conservation efforts focusing on tussac restoration should include this terrestrial-marine linkage, although a warming Southern Ocean calls into question the long-term viability of the Falkland Islands as habitat for low-latitude seabirds.
... In general, calculated temperatures for the Late Holocene showed significant differences when compared to the modern shell, which showed lower mean temperatures when compared to the modern shell (~18-19 °C and ~ 21 °C, respectively). Even if those values coincide with the cooler temperature pulses interpreted by other authors in Patagonia during the Late Holocene (Schäbitz, 1994;Villalba, 1994;Meyer and Wagner, 2008;Boretto et al., 2013;Strelin et al., 2014) we would be very careful to derive such an interpretation from single shell specimens each representing a slice of a few years, within an interval of a few hundred years. It however very much justifies future studies focussing in more detail at specific time intervals in the past using A. purpurata as an archive. ...
... A more detailed look into the stable isotope analyses in Holocene shells will then be needed in order to distinguish if environmental changes are more likely to occur due to local variations or global climate changes and which time scale these changes occur. Some environmental events during the Late Holocene, such as temperature variability, were reported for Patagonia: Neoglacial pulses, the Medieval Warm Period and the Little Ice Age (Schäbitz, 1994;Villalba, 1994;Iriondo and Garcia, 1993;Cioccale, 1999;Prevosti et al., 2004;Meyer and Wagner, 2008;Boretto et al., 2013;Strelin et al., 2014;among others). All these climatic changes registered by different archives (pollen, tree-rings, glacial records, aeolian deposits, fossil soils, biogeographic records, etc.) were interpreted as variations in temperature, humidity as well as rainfall frequency. ...
Amiantis purpurata is a common warm-temperate water bivalve species distributed from southern Brazil to northern Patagonia, Argentina, which has a rich and well preserved fossil record in the San Matías Gulf (SMG) dating back to the late Quaternary. This study aims to establish A. purpurata shells as a new palaeoarchive of past marine conditions in South America. We compared the stable oxygen and carbon profiles (δ 18 O shell ; δ 13 C shell) of eleven specimens of A. purpurata from different geological times (modern, Late Holocene and interglacial Late Pleistocene), and additionally present in situ oxygen isotope values of seawater within SMG (δ 18 O water). Using both sets of information, we calculated and reconstructed palaeowater temperatures for the Late Holocene and compared them to modern water temperatures. Our findings indicate that A. purpurata records past environmental parameters such as water temperatures on a seasonal scale and can therefore be considered a suitable candidate for future palaeoenvironmental reconstructions in Northern Patagonia. This study is the first step towards further stable isotope analyses on fossil A. purpurata shells, which will show whether and if so, to what extent, important global climate events such as the Neoglacial (Early Holocene), the Hypsithermal (Middle Holocene) and the Little Ice Age (Late Holocene) occurred in South America.
... The lake level decline in L. Lepué between ~11-7.9 ka was coeval with recession of valley glaciers in the north Patagonian Andes (Moreno et al., 2021b;Sagredo et al., 2018;Soteres et al., 2022a), and peak temperatures in marine core MD07-3088 between ~11.1-7.5 ka in (Haddam et al., 2018) (Fig. 6). A transgressive lake phase ensued at ~7.9 ka suggesting stronger SWW influence, in agreement with a decline in fire activity at regional scale (Moreno et al., 2022 and renewed glacier activity in the Patagonian Andes (Kaplan et al., 2016;Reynhout et al., 2019;Sagredo et al., 2021;Strelin et al., 2014). SST cooling in MD07-3088 began at ~7.5 ka and intensified at ~2.7 ka and ~0.6 ka, culminating in a SST minimum during the 20 th century (Weighted Mean: 11.6 • C) (Haddam et al., 2018) (Fig. 6). ...
We report a fossil diatom record from small closed-basin Lago Lepué (43 • S) to examine past changes in freshwater ecosystems and hydrologic balance in northwestern Patagonia since ~18 ka. The record starts with abundant staurosiroids and the heavily silicified Aulacoseira granulata suggesting deep turbulent mixing during a low lake level stand between ~18-16.4 ka. A. distans increased shortly after ~16.4 ka and achieved maximum abundance between ~15.4-13.6 ka, while A. granulata disappeared at ~15.8 ka and A. alpigena rose at ~14.9 ka to its maximum between ~13-12 ka. We infer turbulent, cold, and circumneutral to slightly acid lake conditions contemporaneous with a steady lake level rise that started at ~16.4 ka and culminated between ~13-12 ka. These trends reversed between ~11-7.8 ka with the dominance of Discostella stelligera and staurosiroids, suggesting warmer lake conditions and shallower mixing. Subsequent changes include increases of A. distans with D. stelligera between ~7.8-5.8 ka, dominance of the former between ~5.8-3.3 ka, a rapid increase in A. perglabra at ~3.3 ka, and ensuing diversification of benthic acidophilous species. We infer a rapid lake-level decline between ~11-7.8 ka, with subsequent rising pulses at ~7.8 ka and ~5.8 ka, a multimillennial-scale lake acidifi-cation trend, and overall high lake levels with centennial-scale reversals between ~6-0 ka. Coherent variations in terrestrial and aquatic ecosystem changes recorded in the same core suggest negative hydrologic balance between ~18-16.4 ka and ~11-7.8 ka, positive balance between ~14.9-12 ka and ~6-0 ka, with transitional conditions in the interim, overprinted by millennial-scale changes and enhanced variability since ~6 ka. Covariation with paleoclimate records at regional, pan-Patagonian, and hemispheric scale suggests millennial to centennial-scale variability superimposed upon a multi-millennial pacing of Southern Westerly Wind evolution since ~18 ka.
... Demonstrating this at Lago Argentino is challenging, as it exhibits strong spatial variability and a non-unique relationship between the proxy and climatic variables of interest. In particular the distance between any given location and the glacier fronts has evolved through time due to glacier advance and retreat (Strelin et al. 2014;Kaplan et al. 2016) and the local conditions have fluctuated on centennial timescales due to large-scale climatic systems (Van Wyk de Vries et al. 2023). The strong spatial variability in Lago Argentino is best illustrated by the correlation between DJF wind speed and red PxI in cores 41A and 42A, located within 3 km of each other in a region where the lake is at its narrowest. ...
The quantity and characteristics of sediment deposited in lakes are affected by climate to varying extents. As sediment is deposited, it provides a record of past climatic or environmental conditions. However, determining a direct relationship between specific climatic variables and measurable sediment properties, for instance between temperature and sediment optical reflectance, is complex. In this study, we investigate the suitability of sediment reflectance, recorded as sediment pixel intensity (PxI), as a paleoclimate proxy at a large ice-contact lake in southern Patagonia, Lago Argentino. We also evaluate whether sediment PxI can be used to investigate the present-day climatic drivers of sedimentation across Lago Argentino. First, we show that sediment PxIs relate to underlying sediment composition, and are significantly correlated with XRF-derived major element composition. Secondly, we find that PxIs correlate with both austral summer temperatures and wind speeds, but not with precipitation. PxI timeseries reach the p <0.1 correlation significance threshold for use as a paleo-wind proxy in as many as 6 cores and a paleo-temperature proxy in up to 4 cores. However, high spatial variability and the non-unique relationship between PxI and both temperature and wind speed challenges the necessary assumption of stationarity at Lago Argentino. While not suitable as a paleoclimatic proxy, correlations between PxI and instrumental climate data do chronicle current climatic controls on sediment deposition at Lago Argentino: high summer temperatures enhance settling of coarse, optically dark grains across the lake basin by promoting ice melt and lake stratification, while high wind speeds reduce the settling of fine, optically bright grains in the ice-proximal regions by transporting sediment-rich waters away from the glacier fronts. The assumptions required for quantitative paleoclimatic reconstruction must be carefully evaluated in complex lacustrine environments, but records unsuitable for use as proxies might nevertheless yield valuable information about the drivers of modern sedimentary transport and deposition.
... This environmental situation is contemporaneous with the generation of moraines in Argentino lake basin before 400 and after 300 cal yrs. BP (Strelin et al., 2014) or around 360-240 cal yrs. BP (Kaplan et al., 2016, Fig. 12 A). ...
Environmental changes were reconstructed from a multiproxy synthesis of over 30 localities from the Isla Grande de Tierra del Fuego and Isla de los Estados, southernmost South America. At a local scale, the results from the mountain forest and gently undulating steppe areas were integrated as well as those from the marine environments of the Beagle Channel and the Atlantic coasts. At a regional scale, the results were integrated with those published for the southernmost Andean and Extra-Andean Patagonia and the Antarctic Peninsula. This study focuses on the environmental evolution during the Late Glacial-Holocene transition, the Middle to Late Holocene transgressive-regressive hemicycle and wet-dry oscillations, the Medieval Climate Anomaly, the Little Ice Age, the tephra inputs from the Patagonian Andes, and the recent climatic warming. Most paleoenvironmental changes are related to variations in the latitudinal position and intensity of the Southern Westerly Winds (SWW) while others are associated with astronomical or endogenous forcings. At a strong intensity of the SWW, a greater contribution of humidity to the forest areas and an increase in the rainfall gradient create windy and arid conditions in the steppe. At a weak intensity of the SWW, lower humidity input in the forest areas and the advection of air masses from the Atlantic Ocean promoted humid and slightly windy conditions in the steppe. Similar environmental trends are observed between terrestrial and marine environments in the center and south of Tierra del Fuego, Isla de los Estados and the Antarctic Peninsula, and between the Fuegian steppe and Extra-Andean Patagonia. The paleoclimatic evidence reveal high environmental variability in the last 10,000 years for this sector of the Southern Hemisphere.
... (b) Seismic profiles tracks (magenta lines) within the southern arms of Lago Argentino. Cyan dots correspond to the Puerto Banderas moraine and dated spots from Strelin, Denton, Vandergoes, Ninnemann, and Putnam (2011);Strelin, Kaplan, Vandergoes, Denton, and Schaefer (2014) and Kaplan et al. (2011). (c) Close-up of Lago Roca. ...
Lago Roca is a NE–SW elongated lacustrine body located to the south of Lago Argentino, the largest lake of the UNESCO ‘Los Glaciares’ National Park. An extensive high‐resolution seismic survey carried out within the Lago Roca, integrated with geological information gathered in the area, have allowed to produce: (a) a complete bathymetric map of the lake; (b) a basement topography map and a structural map; and (c) an analysis of the geometry, distribution, and thickness of the sedimentary infill. Two sub‐basins were recognized in Lago Roca, separated by a central basement high that shows a pop‐up structure. The northern and southern margins of the lake basement are bounded by NE–SW trending strike‐slip faults that constitute subsidiary faults strands of the regional structural lineament known as the ‘Lago Argentino transfer fault’. The shallow, low magnitude seismicity recorded in the area supports the interpretation that this fault segment is active at the present. The relative motion along the fault led to the deformation of the sedimentary infill of the lake, which was also affected by several subsidiary normal faults oriented parallel to the Lago Argentino transfer fault. Data show the peculiar asymmetry in the sedimentary filling of Lago Roca, typical of those of pull‐apart basins generated along transform margins. A simplified model for the evolution of Lago Roca is also here proposed, based on the analysed data and the regional tectonic background. A high‐resolution seismic survey carried out within Lago Roca has allowed to produce a bathymetric map of the lake, a basement topography map, and a structural map. Two sub‐basins were recognized separated by a central basement high. Northern and southern margins of the lake basement are bounded by NE–SW trending strike‐slip faults that constitute subsidiary faults strands of the regional structural lineament known as ‘Lago Argentino transfer fault’.
... This decrease in marine influence might have resulted from a combination of decelerated global sea-level rise (Lambeck et al., 2014) and accelerated glacial isostatic uplift in response to glacier recession from their Neoglacial maxima (Fig. 8;Aniya, 2013;Davies et al., 2020). More specifically, this acceleration seems to have mostly occurred after Neoglaciation III (2780 e 1910 cal yr BP; ages calibrated from Aniya, 2013 using SHCal20), and may therefore represent isostatic uplift due to the recession of glaciers on both the Northern and Southern Patagonian Icefields after this particularly extended Neoglacial advance (Bertrand et al., 2012a;Harrison et al., 2008;Mercer, 1982;Siani et al., 2010;Strelin et al., 2014). This paleoenvironmental reconstruction implies that (1) during most of the last 9.1 kyr glacial isostatic adjustment was relatively slow, and (2) that glacial isostatic adjustment accelerated during the late Holocene in response to Neoglacial ice load changes. ...
Our understanding of glacial isostatic rebound across Patagonia is highly limited, despite its importance to constrain past ice volume estimates and better comprehend relative sea-level variations. With this in mind, our research objective is to reconstruct the magnitude and rate of Late Glacial and Holocene glacial isostatic adjustment near the center of the former Patagonian Ice Sheet. We focus on Larenas Bay (48°S; 1.26 km2), which is connected to Baker Channel through a shallow (7.4 m) and narrow (ca. 150 m across) inlet, and hence has the potential to record periods of basin isolation and marine ingression. The pale-oenvironmental evolution of the bay was investigated through a sedimentological analysis of a 9.2 m long radiocarbon-dated sediment core covering the last 16.8 kyr. Salinity indicators, including diatom paleoecology, alkenone concentrations and CaCO3 content, were used to reconstruct the bay's connec-tivity to the fjord. Results indicate that Larenas Bay was a marine environment before 16.5 cal kyr BP and after 9.1 cal kyr BP, but that it was disconnected from Baker Channel in-between. We infer that the postglacial rebound started before 16.5 cal kyr BP and that it outpaced global sea-level rise until slightly before 9.1 cal kyr BP. During the Late Glacial and early Holocene, the center of the former Patagonian Ice Sheet experienced an absolute uplift of ca. 96 m, at an average rate of 1.3 cm/yr. During the remainder of the Holocene, glacial isostatic adjustment continued (ca. 20 m), but at a slower average pace of 0.2 cm/yr. Comparisons between multi-millennial variations in the salinity indicators and existing records of global sea-level rise suggest that the glacial isostatic adjustment rate also fluctuated within these time intervals, likely in response to glacier dynamics. More specifically, most of the glacial isostatic adjustment registered between 16.5 - 9.1 cal kyr BP seems to have occurred before meltwater pulse 1A (14.5 - 14.0 kyr BP). Likewise, it appears that the highest glacial isostatic rebound rates of the last 9.1 kyr occurred during the late Holocene, most likely in response to glacier recession from their Neoglacial maxima. This implies a relatively rapid response of the local solid earth to ice unloading, which agrees with independent modelling studies investigating contemporary uplift. We conclude that the center of the former Pata-gonian Ice Sheet experienced a glacial isostatic adjustment of ca. 116 m over the last 16.5 kyr, and that >80% occurred during the Late Glacial and early Holocene.
... La conexión de la cuenca con el CHPS determinó que los avances neoglaciares aumentaran las condiciones de estacionalidad habituales hacia el oeste (menores temperaturas y mayor carga nival) de los campos de invernada y que se haya generado mayor aridización (Strelin et al. 2014;Kaplan et al. 2016). Eso se tradujo en condiciones de estrés invernal más rigurosas. ...
Luis Alberto Borrero changed the way of producing archaeological knowledge in Patagonia and Tierra del Fuego (as well as beyond). The interrelationship between distributional archaeology and regional taphonomy-two research programs introduced by him 30 years ago-highlights the importance of three analytical units: the region, the artifact and the element (bone). Combined with an epistemology centered on falsifiability, this is the structure for formulating broad questions mostly related to Holocene hunter-gatherer landscape use. Building on this legacy, the article presents a case study of the winter grounds on the north shore of Lake Viedma. It integrates the taphonomic results of guanaco (Lama guanicoe) with those of artifact distribution. Furthermore, we present new radiocarbon dates that frame the analysis of fauna from several archaeological sites located in the deflation hollows of coastal sand dunes. The identification of a similar set of environmental and archaeological conditions to that proposed by Borrero in 1988 in the trampling model he used for guanacos in Tierra del Fuego demonstrates the latter’s relevance to the Viedma Lake region.
... At the head of Lago Argentino, the Upsala glacier at Lago Pearson may have been expanded until close to 1000 yr ago, given one sample age of ∼960 ± 30 (Kaplan et al., 2016). Regardless, in general, Patagonian glaciers reached their maximum Holocene positions earlier, during the middle or early Holocene (Aniya, 2013;Kaplan et al., 2016;Reynhout et al., 2019); the advances of the last millennium started around or after ∼700 yr ago (Strelin et al., 2014;García et al., 2020). ...
In the Cordillera Darwin, southernmost South America, we used ¹⁰ Be and ¹⁴ C dating, dendrochronology, and historical observations to reconstruct the glacial history of the Dalla Vedova valley from deglacial time to the present. After deglacial recession into northeastern Darwin and Dalla Vedova, by ~16 ka, evidence indicates a glacial advance at ~13 ka coeval with the Antarctic Cold Reversal. The next robustly dated glacial expansion occurred at 870 ± 60 calendar yr ago (approximately AD 1150), followed by less-extensive dendrochronologically constrained advances from shortly before AD 1836 to the mid-twentieth century. Our record is consistent with most studies within the Cordillera Darwin that show that the Holocene glacial maximum occurred during the last millennium. This pattern contrasts with the extensive early- and mid-Holocene glacier expansions farther north in Patagonia; furthermore, an advance at 870 ± 60 yr ago may suggest out-of-phase glacial advances occurred within the Cordillera Darwin relative to Patagonia. We speculate that a southward shift of westerlies and associated climate regimes toward the southernmost tip of the continent, about 900–800 yr ago, provides a mechanism by which some glaciers advanced in the Cordillera Darwin during what is generally considered a warm and dry period to the north in Patagonia.
... In order to evaluate the ability of countMYvarves to resolve very fine scale laminations, we use an example from Lago Argentino, a large proglacial lake in southern Patagonia, Argentina (Skvarca and Naruse, 1997;Pasquini and Depetris, 2011;Richter et al., 2016). Three large outlets of the Southern Patagonian Icefield (Glaciar Upsala, Spegazzini and Perito-Moreno) calve directly into this lake, resulting in a large influx of freshly eroded glacial flour (Skvarca et al., 2002(Skvarca et al., , 2003Pasquini and Depetris, 2011;Strelin et al., 2014). The main basin of the lake is separated from these actively calving glaciers by a network of glacial fjords nearly 50 km long, and sedimentation rate in the main basin is dominated by gradual fallout of fine silt to mud-scale particles. ...
Annual resolution sediment layers, known as varves, can provide continuous and high-resolution chronologies of sedimentary sequences. In addition, varve counting is not burdened with the high laboratory costs of geochronological analyses. Despite a more than 100-year history of use, many existing varve counting techniques are time consuming and difficult to reproduce. We present countMYvarves, a varve counting toolbox which uses sliding-window autocorrelation to count the number of repeated patterns in core scans or outcrop photos. The toolbox is used to build an annually-resolved record of sedimentation rates, which are depth-integrated to provide ages. We validate the model with repeated manual counts of a high sedimentation rate lake with biogenic varves (Herd Lake, USA) and a low sedimentation rate glacial lake (Lago Argentino, Argentina). In both cases, countMYvarves is consistent with manual counts and provides additional sedimentation rate data. The toolbox performs multiple simultaneous varve counts, enabling uncertainty to be quantified and propagated into the resulting age-depth model. The toolbox also includes modules to automatically exclude non-varved portions of sediment and interpolate over missing or disrupted sediment. CountMYvarves is open source, runs through a graphical user interface, and is available online for download for use on Windows, macOS or Linux at https://doi.org/10.5281/zenodo.4031811 .
... Se registraron avances neoglaciares a lo largo de los últimos 4500 años (Wenzens & Wenzens, 1998) que generaron una mayor estacionalidad en el extremo occidental del lago (Kaplan et al., 2016;Strelin et al., 2014). Esto probablemente causó el uso intermitente o el abandono de este sector de la cuenca. ...
Se presentan los resultados de nuevos trabajos en el bosque de Nothofagus en la localidad de El Chaltén, lindante con el Campo de Hielo Patagónico Sur. El ambiente es marcadamente estacional y el espacio configura un callejón sin salida. Las excavaciones de sitios en bloques La Lagunita-La Fisura, Alero 1 y Alero 2 brindan información sobre tecnología lítica y arqueofaunas que fue complementada con relevamientos de motivos rupestres y el registro de hallazgos aislados. El registro arqueológico muestra baja intensidad de uso y el desarrollo de actividades focalizadas en el mantenimiento de artefactos, mientras que la arqueofauna evidencia procesamiento intensivo. Los tres sitios poseen motivos rupestres zoomorfos que no sugieren diferencias importantes en sus momentos de ejecución. Se propone el uso marginal del bosque por parte de partidas logísticas con individuos equipados. Dos dataciones radiocarbónicas circa 400 años AP muestran la integración tardía de este ambiente a los sistemas cazadores recolectores de la margen Norte del lago Viedma. Una primera comparación en torno al uso del bosque en la margen sur del lago y en cuencas vecinas (lagos San Martín y Argentino) indicaría la existencia de distintos umbrales de marginalidad.
... The Southern Patagonian Icefield (SPI), extending between 48.2 • and 51.6 • S along the Southern Patagonian Andes, responds very sensitively to climatic changes (Mercer, 1976;Strelin et al., 2011Strelin et al., , 2014Glasser et al., 2011;Meier et al., 2018;Lodolo et al., 2020). At present, it is subject to rapid ice-mass loss (Malz et al., 2018;Braun et al., 2019;Richter et al., 2019;Dussaillant et al., 2019;Abdel Jaber et al., 2019). ...
The Southern Patagonian Icefield is located in an area with a complex tectonic-rheological structure and is affected by intense glacial-isostatic adjustment and rapid ice retreat. Geodetic observations of loading effects provide information on earth structure. Perito Moreno Glacier repeatedly dams the Brazo Rico and Brazo Sur branches of Lago Argentino. The rupture of the ice dam applies an intense hydrological load signal which results in an elastic response of the solid earth. We present a modelling procedure to predict loading effects in response to water-level changes in Brazo Rico. The output is compared with site displacements observed by GNSS during the 2016 rupture event. Our results show that water-level changes in Brazo Rico exceeding 5 m produce vertical deformations detectable with GNSS observations. A geodetic observation of loading effects at magnitudes similar to those of the maximum historic event in 1956 could provide meaningful constraints on elastic earth models. We discuss consequences for the determination of accurate deformation rates, implications for our understanding of the intense uplift observed at the Southern Patagonian Icefield, and requirements and prospects for obtaining geodetic observations of the loading effects of future rupture events.
... records could be different glacier responses in the catchments, for instance due to local bed topography, distinct shading situations or glacier hypsometry (e.g. Strelin et al., 2014). One potential way to reconcile results from the Kromer-and Klostertal with results presented in this study is the systematic modeling of Equilibrium Line Altitudes (ELAs), which will be subject of future work. ...
Mountain glaciers are important water resources in Alpine regions and are sensitive to climate change. Reconstructing glacier oscillations improves our understanding of the amplitude and the frequency of climate variability and resolves time periods when the climate system was in transition – from glacial to interglacial conditions at the beginning of the Holocene, and from a naturally controlled system to an anthropogenically influenced system in the course of industrialization.
With this study, we contribute a new Holocene mountain glacier chronology from the Eastern European Alps. The study area, the Ochsental in the Silvretta Massif, features pronounced Holocene moraine ridges and is an important catchment for hydropower production. We present 18 new ¹⁰Be exposure ages of bedrock outcrops (n = 2) and boulders (n = 16). We complement the ¹⁰Be glacier chronology with historical records and instrumental time series and correlate it with pre-existing climate proxy records for capturing ice margin positions at different times during the Holocene. The Ochsental chronology is compared to cosmogenic nuclide moraine records across the European Alps to provide an Alpine-wide perspective on the transition from the Younger Dryas (YD; c. 12.9 to 11.7 ka) to the Holocene (c. 11.7 ka to present).
Results show that glaciers in the Ochsental stabilized at the position of a preserved Holocene moraine c. 9.9 ± 0.7 ka after retreating from their Late Glacial position. This Holocene moraine formation interval is concurrent with a cold spell detected in some climate proxy records in the Swiss and Austrian Alps, the Central European Cold Phase 1 (CE-1). Glaciers were presumably much smaller during the Mid-Holocene and readvanced to a position close to the preserved Early Holocene moraine during the Little Ice Age (LIA; c. 1250 to 1850 CE). LIA ¹⁰Be ages range from 390 ± 20 yrs to 135 ± 5 yrs and point to multiple advances within this time period with most robust evidence for a culmination during the 18th century. The ¹⁰Be record and the historical glacier records overlap and are remarkably consistent, which demonstrates that ¹⁰Be surface exposure dating produces reliable ages even for young glacial deposits. Within the last c. 170 years, Ochsentaler glacier has retreated c. 2.3 km, which highlights the impact of recent warming on Alpine mountain glaciers.
... In particular, we know that many glaciers in the Patagonian Icefield, on South Georgia and James Ross Islands, and along the Antarctic Peninsula receded between ∼ 4500 and 2700 cal. yr BP (Mulvaney et al., 2012;Sterken et al., 2012;Anyia, 2013;Strelin et al., 2014;Kaplan et al., 2016;Oppedal et al., 2018). Peatlands expanded across sub-Antarctica during these times as well (e.g., Yu et al., 2016;Loisel et al., 2017b). ...
Fens and bogs are distinct in terms of their biogeochemistry, water table behavior, and net peat-accumulation regimes. While most peatlands start developing as fens, a large fraction of them eventually shift to bogs in a step-like ecosystem shift. This transition has traditionally been assumed to be primarily controlled by the ecosystem itself (autogenic control). Here we use 90 peat profiles from southernmost South America (SSA) as a case study that illustrates a synchronous, regional-scale shift from fen to bog around 4200 years ago. In light of these results, we propose and discuss conceptual models that link environmental change (allogenic control) as a trigger to the fen-bog transition (FBT). In addition, our stratigraphic analyses show that Sphagnum deposits are associated with greater peat masses, larger soil-carbon stocks, and higher rates of peat-carbon accumulation than their non-Sphagnum counterparts, with Sphagnum bogs being characterized by soil-carbon densities over twice that of non-Sphagnum peatlands (medians = 141 vs. 56 kgC/m2). Since fens and bogs also behave differently in terms of their carbon exchanges with the atmosphere, a better appraisal of the processes involved in the FBT could help elucidate the role of this critical ecosystem shift in the past and future global carbon cycle.
... These rocks formed in a N-S trending compressional phase that created a system of fold and thrust belt developed during distinct stages of the Andean orogeny that occurred until the Pliocene (Ghiglione et al., 2016;Giacosa et al., 2012). During the Quaternary, the glaciers expanded their fronts towards the east (Rabassa et al., 2011;Strelin et al., 2014Strelin et al., , 2011 and both arms of Lago Argentino, along with the other narrow valleys, were entirely covered by ice. The last glaciation, known in the area as El Tranquilo Glaciation (Strelin & Malagnino, 1996), reached its maximum extent at nearly 15 14 C kyr BP (Glasser et al., 2004). ...
Lago Argentino hosts a series of calving glaciers originating from the Southern Patagonian Icefield, the largest temperate ice cap of the southern hemisphere. Brazo Rico and Brazo Sur are two basins located in the southern part of Lago Argentino, where a series of high-resolution seismic profiles have allowed reconstruction of its depositional setting and sedimentary architecture, and to produce the following maps: top of the acoustic basement, top of the glacial sequence, and thickness of the glacio-lacustrine deposits. Data reveal the role of basement highs in the complex dynamic behavior of the two main glaciers, Perito Moreno and Frías glaciers, which fluctuated along Brazo Rico and Brazo Sur since the end of the Last Glacial Maximum. Their advances and retreats are testified by the presence of several moraine fronts buried beneath a generally undisturbed, glacio-lacustrine and lacustrine sequence, which records the depositional history of the southern arms of Lago Argentino.
... The latitudinal shift in air characteristics, especially temperature, plays a role in determining the latitude of the SWW core (Quade & Kaplan 2017). The chironomid-inferred mean annual temperature in Laguna Potrok Aike, the temperature reconstructions for the Antarctic ice-core and the glacier historyof the Lago Argentino basin (50°S) suggest colder temperatures during the ACR and a subsequent increase during the YD (Massaferro & Larocque-Tobler 2013;Strelin et al. 2014;Fig. 8). ...
Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.
... By implication, we infer that at least some cirques in the study area were re-occupied during the ACR. Subsequently, glaciers in the nearby Andes experienced repeated fluctuations throughout the Holocene (e.g., Strelin et al., 2014). We consider that the SBMR cirques, at least those currently occupied by ice, experienced similar variability. ...
The Sierra Baguales Mountain Range, forming the eastern foothills of the Southern Patagonian Andes, has well-developed alpine-glaciated landforms which present an ideal opportunity to study climatic and non-climatic factors that control cirque development and morphology. One hundred and forty-three glacial cirques were studied with reference to 14 morphometric attributes which were analyzed using statistical analysis and GIS methodologies. The cirques were classified into two types using cluster analysis complimented with a composite map based on the attributes, the latter technique that is applied to glacial cirque analysis for the first time. Type 1 cirques are associated with glacial processes isolated from the Southern Patagonian Ice Field (SPIF), developed under locally cold and dry climatic conditions. Type 2 glacial cirques are associated with older, more extensive glacial processes controlled by regional-scale climate variables and the presence of the Pleistocene Ice Sheet. The results show that the development of most of the glacial cirques has been controlled mainly by their aspect, exposure to solar radiation, Southern Hemisphere Westerly winds, and cirque floor slope. Finally, we concluded that our analyses show the evolution of cirques in the Sierra Baguales Mountain Range was not uniform. Cirque glaciers that developed to the west, close to the Southern Patagonian Ice field, have been more dynamic, and therefore their cirques experienced more erosion than those located to the east.
Holocene environmental changes in Patagonia were mostly shaped by unsteady ice-cover recession. Consequently, environmental reconstructions are largely based on discontinuous moraine chronologies from valley deposits. Here, we present a 3 m-long continuous sediment record recovered from Laguna Meseta (LME), a lake located on Meseta Chile Chico. Its altitude and location relative to the North Patagonian Icefield provide a unique opportunity to reconstruct the glacial history and the related environmental dynamics.
Our radiocarbon chronology constrains sedimentation to the last ~10,000 years and provides a minimum age for postglacial ice-free lacustrine conditions due to a westward retreat of the ice cap. Lacustrine productivity reached its maximum at the start of sedimentation and decreased afterwards. Between 5,500 and 4,600 cal yr BP, a major shift towards allochthonous sediment accumulation occurred, caused by an abrupt increase in clastic deposition from basaltic lithologies of the Meseta Chile Chico. This episode correlates with the precipitation-driven mid-Holocene glacier advance of Patagonian glaciers and suggests that conditions were colder/wetter on the Meseta Chile Chico at that time. After 4,600 cal yr BP these conditions continued to supply LME with clastic sediments until a stepped decrease around 900 cal yr BP. Thereupon, lacustrine productivity distinctly increased and stabilized around 300 cal yr BP. Our findings indicate that environmental conditions on Meseta Chile Chico were mainly controlled by precipitation variability during regional oscillations of the Southern Hemisphere Westerly Winds over the last 10 ka.
In order to understand the paleogeographic evolution of Viedma Lake (252 masl) sedimentary sequences with glaciolacustrine and lacustrine strata between 307 masl and 266 masl and bathymetric fluctuations between 27 ka. and 2.4 ka. were identified. The paleoenvironmental interpretation of the stratigraphic profiles was carried out based on the analysis of facies and their associations. The oldest age was recorded at 301 masl (27 ka) and the youngest corresponds to 266 masl (2.4 ka). The record of 27 ka was compared with another dated record of the Tar-San Martin Lakes basin showing that Viedma – Tar-San Martín Lakes were formed at similar ages. Taking into account that the deposits of Bahía Túnel are located at 266 masl and that the level of the lake would be above this height, it is proposed that this lake level would have restricted the movement of hunter-gatherer populations along the coast and to the west. From 2.4 ka on a new space started to be available for these populations broadening the wintering grounds (≤400 masl). The chronology of the archaeological record found in this new space fits the proposed paleogeographic evolution. This paper complements the research on the evolution of lacustrine systems in the Patagonian Mountain range and broadens the discussion of human mobility in the Viedma Lake basin during the Holocene.
The Patagonian Andes were affected by a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene. Deciphering drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern terrace formation is investigated from the Laguna del Viedma valley as a modern analogue of Late Quaternary landscape evolution in Patagonia. The aim of the research was to constrain the timing of terrace formation following lake level fall of the Laguna del Viedma over a 35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from 1985-2019 to document glacier and lake changes in the study area; 2) map landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations. In total seven terrace surfaces were distinguished, with the oldest four pre-dating the ALOS PALSAR DEM (February 2000) used. Landform evidence shows the highest, and vegetated, T1 terrace surface (+40-75 m) grades to the highest lake level and was likely the elevation of the valley floor during Holocene neoglacials. Viedma glacier recession then led to a phase of lake regressions/transgressions with an overall trend of lake level fall. The DEM shows ~20 m incision from the 1985 floodplain level (T3) to the T4 level floodplain by 2000. This constrains a minimum rate of incision of 1.33 m/yr, however, the satellite time series demonstrates rapid T3 terrace formation, with evidence for mass movements contributing to lateral terrace erosion by 1986. The implications of the data-are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within many large river systems of the Patagonian Andes from 42-52⁰ S. The data herein demonstrate that base level falls from sudden lake drainage events were likely a major driver of rapid landscape change in Patagonia during deglaciation.
The Patagonian glaciations developed since the latest Miocene (ca. 6 Ma) in multiple events, of varied duration and intensity. Most of the present glacial landscape is the outcome of the glacial modelling during the Pleistocene, since the Great Patagonian Glaciation (GPG; ca. 1 Ma). The Patagonian Andes were covered by a continuous mountain ice sheet, from 37º S to Cape Horn (56º S) in at least five major glaciations for more than 15 cold events in the last million years. The present drainage network was developed after the Last Glacial Maximum (LGM; ca. 24 cal. ka BP), particularly those cases with drainage reversal, when the glaciers began to melt due to global climatic changes. The environmental impact of Pleistocene glaciations extended all over Patagonia. The knowledge about the Last Glaciation, the Late Glacial and Holocene glaciations is very important because the human settling of the Patagonian landscape as we know it took place during this period. Moreover, the human colonization of Patagonia took place sometime after the Last Glacial Maximum and during the Late Glacial (ca. 18,000 to 10,000 years ago) and it was completed along the entire Early Holocene.
We map the glacial geomorphology of the former Patagonian Ice Sheet between 44°S and 46°S. Building on previous work, our map covers a ∼50,000 km² region of west-central Patagonia. The study area includes the eastward-flowing Río Pico, Río Caceres, Río Cisnes, Lago Plata-Fontana, El Toqui, Lago Coyt/Río Ñirehuao, Simpson/Paso Coyhaique, and Balmaceda palaeo-outlet glaciers, adjacent valleys, and the Andean Cordillera. The inventory contains >70,000 individual landforms mapped from remotely-sensed imagery and field surveys. Mapping was classified into ice-marginal (e.g. moraine ridges, trimlines), subglacial (e.g. glacial lineations, flutes), glaciolacustrine (e.g. palaeolake shorelines, perched deltas), glaciofluvial (e.g. proglacial outwash plains, meltwater channels), and non-glacial (e.g. palaeochannels, landslides or slumps) landform groups. The new map will inform future interpretations of regional glacier dynamics, and the development of robust geochronological datasets that test the timing of glaciation and deglaciation.
Geological climate archives from the Holocene Epoch provide baseline information concerning natural climate variability. Temperate mountain glacier extent is sensitive to summer air temperature, thus geological records of past glacier length changes are a useful proxy for this climatic variable. Here we present a new cosmogenic ¹⁰Be chronology of glacier length changes at Dart Glacier in the Southern Alps, New Zealand. Prominent moraines deposited 321 ± 44 yr ago (n = 11) and 7.8 ± 0.3 ka (n = 5) show glaciers during the Little Ice Age were less extensive than during the early Holocene. This pattern of net Holocene glacier retreat is consistent with emerging data from other catchments in New Zealand and across the southern mid-latitudes. Using the physical framework of a transient global climate model simulation, we suggest that cool summers in the early Holocene were promoted by the local summer insolation minimum, together with low atmospheric greenhouse gas concentrations, causing an early Holocene austral glacial maximum. An insolation-driven reduction in seasonality at southern mid-latitudes may reconcile differences between early Holocene temperature reconstructions where climate proxies have different seasonal sensitivities. We suggest that rising greenhouse gas concentrations after 7 ka caused regional-scale glacier retreat and appear to be the dominant driver of multi-millennial summer temperature trends in the southern mid-latitudes during the present interglacial.
The aim of this paper is to describe and discuss the strategies and technology implemented by Late Holocene hunter-gatherers to hunt their most prominent animal resources, guanaco (Lama guanicoe) and choique (Rhea pennata pennata), in different settings in the north margin of Lake Viedma (Santa Cruz province, Argentina). In order to do that, we use archaeological distributional data from different altitudinal levels, namely lakeshore dunes (255–275 m.a.s.l), mid-altitude plains or pampas (276–900 m.a.s.l.), and Del Tobiano basaltic plateau (≥900 m a.s.l.). The pampas, particularly the grounds below 400 m.a.s.l., may have been used by both species as their wintering grounds (although their permanence in this environment could have occurred throughout the year), while the mid-altitude plains and the plateau seem to have been primarily used by the guanaco as grazing and calving grounds from late spring to early fall, the months in which most of its surface is free of snow. Likely, differences in seasonality, topography and use of these environments by the guanaco and choique social groups may have forced people to adopt different hunting strategies, tactics and weaponry. Frequency variations in the presence of projectile points and bolas at different altitudinal levels have been observed. In the pampas, evidence suggests that guanaco hunting was aided by the use of bow and arrows and/or throwing weapons, such as spears and bolas, the latter likely also used in the hunting of choique. In the plateau, on the other hand, guanaco hunting tactics involved the use of blinds either by individuals or small groups of hunters who were mainly equipped with throwing weapons and/or bow and arrows. The archeological record of the plateau shows a logistic hunting-oriented strategy as well as a residential use during summer months. Artifact density and variety at lakeshore dunes suggest a greater intensity of occupation of these grounds, probably linked to a more residential use—either seasonal (fall/winter) or year-round—made possible by the availability, although in variable density throughout the year, of guanaco and choique. Consequently, the regional archeological landscape exhibits evidence of integration and complementarity of the different altitudinal levels in the northern margin of the Lake Viedma, at least during the Late Holocene.
Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the canal de Los témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of the "Herminita advance" identified and dated onland. We interpret these bedforms as the evidence of the most pronounced advance of Perito Moreno glacier during the mid-Holocene cooling event that characterized this sector of the Southern Hemisphere. this study highlights the importance of subaqueous glacial bedforms, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of glaciers like Perito Moreno that in a warming climate are relatively stable.
Peatlands have been important terrestrial carbon reservoirs throughout the Holocene, yet whether these ecosystems will become stronger or weaker carbon sinks in the future remains debated. While surface peat layers (acrotelm) have a greater apparent rate of carbon accumulation than deeper, millennial‐aged peat (catotelm), it is difficult to project how much more aerobic decomposition will take place before the younger surface cohorts join the older deeper ones. Studies have suggested that warming could lead to weakened carbon accumulation in peatlands due to enhanced aerobic decay in the acrotelm, which would lead to a slower transfer of peat into the catotelm, if any. Conversely, other studies have suggested increased C accumulation in the acrotelm and thus, larger long‐term carbon transfer into the catotelm under warming conditions because of greater plant productivity and faster peat accumulation. Improving our predictions about the rate of present and future peatland development is important to forecast feedbacks on the global carbon cycle and help inform land management decisions.
In this study, we analyzed two peat cores from southern Patagonia to calculate their long‐ vs. short‐peat carbon accumulation rates. The acrotelm rates were compared to the catotelm peat carbon legacies using an empirical modeling approach that allows calculating the future catotelm peat storage based on today’s acrotelm characteristics, and thus predict if those recent rates of carbon accumulation will lead to greater or weaker long‐term carbon storage in the future. Our results indicate that, depending on local bioclimatic parameters, some peatlands may become stronger carbon sinks in the future, while others may become weaker. In the case of this study, the wetter site is expected to increase its carbon‐sink capacity, while our prediction for the drier site is a net decrease in carbon sequestration in the coming decades to centuries.
Lago Argentino hosts various calving glaciers, among them the famous Perito Moreno. Whereas the onland late Pleistocene-Holocene glacial history is rather well constrained, the submerged glacier-related features were until now undisclosed. Here we present a series of high-resolution seismic profiles revealing moraine bodies associated with the late-glacial glacier dynamics and the first bathymetric map of the Brazo Rico and Brazo Sur, the two southern arms of Lago Argentino. At the eastern termination of Brazo Rico, we identified at the lake floor the submerged expression of the Puerto Bandera 3 moraine mapped onshore, which represents the oldest event (12,660 ± 70 cal yr BP oldest minimum age) recognized in this lake arm, and seven other younger events expressed by a series of terminal and recessional moraines. Along the Brazo Sur, few moraine bodies have been imaged by seismic data. Here, the youngest temporal constraint comes from the Frías moraine (ca. 6000 cal yr BP), which closes off the southern end of the Brazo Sur. At the confluence of the two arms, the Perito Moreno and the former Frías glacier merged and flowed toward east during their late-glacial maximum advance (i.e., Puerto Bandera 1 moraine). The subaqueous evidence of moraine bodies testifies to the occurrence of previously undocumented pulses of the Perito Moreno and former Frías glaciers within the general phase of late Pleistocene-Holocene regression.
We obtained 49 new 10 Be ages that document the activity of the former Northern Antarctic Peninsula Ice Sheet, and subsequently the James Ross Island Ice Cap and nearby glaciers, from the end of the last glacial period until the last ∼100 years. The data indicate that from >11 to ∼8 ka marked recession of glacier systems occurred around James Ross Island, including tidewater and local land-terminating glaciers. Glaciers reached heads of bays and fjords by 8-7 ka. Subsequently, local glaciers were larger than present around (at least) 7.5-7 ka and ∼5-4 ka, at times between 3.9 and 3.6 ka and just after 3 ka, between ∼2.4 and ∼1 ka, and from ∼300 to ∼100 years ago. After deglaciation, the largest local glacier extents occurred between ∼7 ka and ∼4 ka. Comparison with other paleoclimate records, including of sea ice extent, reveals coherent climate changes over ∼15 • of latitude. In the early Holocene, most of the time a swath of warmth spanned from southern South America to the Antarctic Peninsula sector. We infer such intervals are times of weakening and/or poleward expansion of the band of stronger westerlies, associated with contraction of the polar vortex. Conversely, increased sea ice and equatorward expansion of the westerlies and the polar vortex favor larger glaciers from Patagonia to the Antarctic Peninsula, which typically occurred after ∼8 ka, although warm stretches did take place. For example, on the Antarctic Peninsula and in Patagonia the interval from 4 to ∼3 ka was typically warm, but conditions were not uniform in either region. We also infer that reduced and expanded glacier extents in Patagonia and the eastern Antarctic Peninsula tend to occur when conditions resemble a persistent positive and negative southern annular mode, respectively.
The Magallanes-Tierra del Fuego region, Southern Patagonia (53-56°S) features a plethora of fjords and remote and isolated islands, and hosts several thousand glaciers. The number of investigated glaciers with respect to the multiple Neoglacial advances is based on a few individual studies and is still fragmentary, which complicates the interpretation of the glacial dynamics in the southernmost part of America. Schiaparelli Glacier (54°24′S, 70°50′W), located at the western side of the Cordillera Darwin, was selected for tree-ring-based and radiocarbon dating of the glacial deposits. One focus of the study was to address to the potential dating uncertainties that arise by the use of Nothofagus spp. as a pioneer species. A robust analysis of the age-height relationship, missing the pith of the tree (pith offset), and site-specific ecesis time revealed a total uncertainty value of ±5-9 years. Three adjacent terminal moraines were identified, which increasingly tapered towards the glacier, with oldest deposition dates of 1749 ± 5 CE, 1789 ± 5 CE, and 1867 ± 5 CE. Radiocarbon dates of trunks incorporated within the terminal moraine system indicate at least three phases of cumulative glacial activity within the last 2300 years that coincide with the Neoglacial phases of the Southern Patagonian Icefield and adjacent mountain glaciers. The sub-recent trunks revealed the first evidence of a Neoglacial advance between ~600 BCE and 100 CE, which so far has not been substantiated in the Magallanes-Tierra del Fuego region.
The Medieval Climate Anomaly (MCA) is a climatic perturbation with a core period of 1000-1200 AD that is
well-recognized in the Northern Hemisphere (NH). Its existence in the Southern Hemisphere (SH) and the level
of synchronicity with the NH is still a matter of debate. Here we present a palaeotemperature synthesis for South
America encompassing the past 1500 years based on multiproxy data from 76 published land and marine sites.
The data sets have been thoroughly graphically correlated and the MCA trends palaeoclimatologically mapped.
The vast majority of all South American land sites suggest a warm MCA. Andean vegetation zones moved upslope,
glaciers retreated, biological productivity in high altitude lakes increased, the duration of cold season ice
cover on Andean lakes shortened, and trees produced thicker annual rings. Similar MCA warming occurred in
coastal seas, except in the year-round upwelling zones of Peru, northern Chile and Cabo Frio (Brazil) where
upwelling processes intensified during the MCA due to changes in winds and ocean currents. MCA warming in
South America and the NH appears to have occurred largely synchronous, probably reaching comparable intensities.
Future studies will have to address major MCA data gaps that still exist outside the Andes in the central and
eastern parts of the continent. The most likely key drivers for the medieval climate change are multi-centennial
Pacific and Atlantic ocean cycles, probably linked to solar forcing.
Resumen. Las reconstrucciones del pasado se tornan más objetivas si se considera el mayor número de indicadores posible. En especial, las reconstrucciones ambientales de los últimos 20.000 años son importantes para el entendimiento de la dinámica de los sistemas naturales. Los macrofósiles vegetales tienen características que complementan el análisis polínico, permitiendo una mejor reconstrucción de la vegetación cuando se estudian en conjunto. El registro de macrofósiles acredita la llegada y la colonización local de los taxones durante el Holoceno, mientras que el registro de polen proporciona información a nivel regional. Esta información es valiosa en la reconstrucción de la vegetación local y en la determinación de los cambios en el límite de los bosques. Con el interés de realizar comparaciones directas entre el contenido de macrofósiles vegetales y de polen provenientes del mismo testigo, se analizaron tres secuencias de turbales del área del Lago Argentino previamente estudiadas. Esta integración permitió realizar una reconstrucción local y regional de los cambios en la vegetación y condiciones paleoambientales para los últimos 13.000 años cal. AP. Estos resultados ilustran como el análisis de macrofósiles vegetales (análisis taxonómicos, tafonómicos y estadísticos) en combinación con el análisis polínico proporciona un mejor entendimiento de la historia de la vegetación del área del Lago Argentino, sudoeste de Patagonia.
Palabras clave. Polen. Macrorrestos vegetales. Mallín. Lago Argentino. Cuaternario tardío.
Abstract. CONTRIBUTION OF PLANT MACROFOSSILS ANALYSIS TO THE PALEOECOLOGY RECONSTRUCTION IN RELATION TO POLLEN RECORDS FROM HOLOCENE PEATLAND SEQUENCES OF PATAGONIA, ARGENTINA. Reconstructions of the past become more objective when the largest number of possible indicators is used. Environmental reconstructions of the last 20,000 years are important to understand the dynamics of natural systems. Plant macrofossils have features that complement pollen analysis, adding new dimensions when studied in conjunction. Plant macrofossils credit the arrival and local colonization of taxa during the Holocene, while pollen records provide information at a regional level. This information is valuable in the reconstruction of local vegetation and in the determination of changes in the tree line. In order to compare plant macrofossil and pollen from the same core, three peatland sequences from Lago Argentino area previously studied were analyzed. This integration allowed a local and regional reconstruction of vegetation and paleoenvironmental conditions for the last 13,000 cal. yr BP. These results provide an example of how plant macrofossil analysis (taxonomic, taphonomic, and statistical analysis) in combination with pollen analysis results in a better understanding of the vegetation history of Lago Argentino area, southwest Patagonia.
Key words. Pollen. Plant macroremains. Mire. Lago Argentino. Late Quaternary.
A simple equation is derived relating the net mass-balance and hypsometric curves of a steady-state valley glacier. It is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions. Examples are given which show that area-based indices (e.g. AAR) for estimating the equilibrium line altitude (ELA) may be subject to a substantial built-in variance because they implicitly rely upon similarity of glacier shape and regimen over a region. If accurate topographic maps are available, the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass-balance gradients. Alternatively, if similar information is available concerning regional glacier regimen, disparate extents and responses may be collectively utilized to estimate values of ELA or to infer climatic influence, taking glacier hypsometry into account.
A survey of some relict and active landforms in the Lachman and Rink Crags areas of NW James Ross Island on the Antarctic Peninsula has yielded new evidence that provides a better understanding of the Holocene morphoclimatic evolution of this currently deglaciated sector of James Ross Island. Six Holocene (mainly land-grounded) glacial advances were delimited by these morphological and stratigraphic studies, dated at 6700–6400, 4900–4400, and shortly after 3900 14C yr B.P., with three more recent advances, dated by regional correlations, that occurred between the Holocene regional climatic optimum (3900–3000 14C yr B.P.) and the Little Ice Age (ca. 300 14C yr B.P.). In some cases, ice-cored rock glacier formation followed the younger glacier advances. In recent decades, the significant climatic warming recorded in the NE region of James Ross Island has produced a number of changes in the periglacial and glacial landforms. Stone-banked terraces and lobes have developed in the Rink Crags, and protalus rampart formation has ceased in favor of protalus lobe development in the Cerro Triple area. Conical depressions filled with water have also increased in area over the surface of the Lachman II ice-cored rock glacier, threatening to destroy this landform.
The Patagonian icefields are the largest mid-latitude ice masses and yet few glaciological data exist for them. The presence of the Andes lying athwart the westerlies makes for a dynamic glacial system with steep balance gradients and west-east equilibrium-line altitude gradients. The overall trend during the 20th century has been glacier retreat. However, whereas most eastern outlets retreated consistently from the beginning of the century, recession on the west began later, has been interrupted by readvances, and most recently has accelerated markedly, reaching higher mean rates of retreat than those on the east. This contrast may result from a predominantly precipitation-controlled mass-balance regime in the west and a dominant temperature control in the east. Superimposed on these contrasts is the anomalous behavior of certain calving glaciers, the oscillations of which contrast in magnitude, timing and sign with each other and with noncalving glaciers, and which in many cases do not relate directly to climate change. Two large calving outlets are at or near their Neoglacial maxima. The tantalizing fragments of information that exist suggest that there is a rich glaciological source to be mined in Patagonia yielding insights into glacioclimatic interactions, calving dynamics, Holocene climate change and the role of topography in controlling glacier behavior. 118 refs., 13 figs., 2 tabs.
The timing and magnitude of postglacial climatic changes around the globe provide insights into the underlying drivers of natural climate change. Using geomorphologic mapping of moraines, ¹⁰Be surface-exposure dating, snowline reconstructions, and numerical modeling, we quantified glacier behavior during Late Glacial (15–11.5 ka) and Holocene (the past ∼11.5 k.y.) time in the Ben Ohau Range, New Zealand. Glaciers were more extensive during the Antarctic Cold Reversal (ACR), than subsequently, and the margins underwent a punctuated net withdrawal over the Holocene. Numerical modeling experiments that achieve the best fit to the moraines suggest that air temperature during the ACR was between 1.8 °C and 2.6 °C cooler than today, with similar (±20%) prescribed precipitation. After the ACR, a net snowline rise of ∼100 m through the Younger Dryas stadial (12.9–11.7 ka) was succeeded by a further “long-term,” or net, rise of ∼100 m between ∼11 k.y. and ∼500 yr ago. Glacier snowline records in New Zealand show generally coherent Late Glacial and Holocene climate trends. However, the paleoclimate record in the southwest Pacific region shows important differences from that in the Northern Hemisphere.
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.
The Southern Patagonia Icefield (SPA) is located at mid-latitudes in southern South America, which is dominated by the westerly regime and frontal systems. This results in a high frequency of cloudy days (more than 70% of the time) and precipitation events. Analysis of air temperature and precipitation data from southern meteorological stations for the past century indicate and overall warming and decrease in precipitation until the mid-80´s, but not significant changes are observed afterwards. In fact, the coastal stations show an increase in precipitation after the 1980´s. The mid-term behavior of the atmospheric variables introduces uncertanties in predicting the consequences of future climate change in southern South America.
Glacial geologic evidence indicates that glaciers throughout the Andes and Antarctica fluctuated during the Holocene. Radiocarbon dating and other age determinations suggest that glaciers readvanced significantly only during the last 5 ka, reaching positions from several 100 m to a few kilometres beyond their present limits. In South America tenuous evidence from radiocarbon dates, with dendrochronological data and environmental interpretations from pollen analyses indicate four main periods of Neoglacial advance, culminating 5000-4000 BP, 3000-2000 BP, 1300-1000 BP, and 15th-late 19th centuries; smaller advances may have occurred at ca. 8400 BP, ca. 7500 BP, and ca. 6300 BP. The meagre data are consistent in indicating broad synchrony throughout the Andes during the last 5 ka, suggesting response to global climatic changes. Anomalies exist in Patagonia where some tide-water glaciers reached their maximal Holocene limits recently this century.
Investigations carried out in the Ema Glacier valley, Tierra del Fuego, on the eastern side of Monte Sarmiento Massif, enable the recognition of five Holocene glacial events. The oldest glacial advance deposited the so-called external moraines of Ema Glacier, with a probable occurrence between 6000 and 5000 14 C y BP without discarding the potential for these deposits to be from Lateglacial time. The remaining four readvances built up a complex inner moraine system named informally internal moraines of Ema Glacier. The oldest recognized till unit that constitutes this proximal moraine system was deposited shortly before 3135 14 C y BP, when glaciolacustrine sedimentation took place during glacier recession. Subsequent glacial advances accumulated till at about 1288 14 C y, shortly after 695 14 C y, and between 379 14 C y and 60 y BP. This chronology of Holocene glacier events coincides with and is well complemented by the one established by other authors for Fiordo Pía at Cordillera Darwin, 75 km to the east. The Ema-Pía chronology is used to calibrate tentatively a series of moraine belts previously identified in the mountain ranges adjacent to Ushuaia, 150 km SE of the surveyed region. A comparative chart shows that the chronological data obtained for the neoglacial readvances in Tierra del Fuego are in accordance with those for the southern Patagonian Andes further north. It follows that the Holocene behavior of the glaciers in the Andean region of Tierra del Fuego and southern Patagonia is essentially a response to the same regional climate change.
This paper presents the evidence for Late Pleistocene and Holocene palaeoclimate and glacier fluctuations of the two major icefields in Patagonia, the Hielo Patagónico Norte (47°00′S, 73°39′W) and the Hielo Patagónico Sur (between 48°50′S and 51°30′S). The palaeoenvironmental evidence suggests that glaciers still covered large areas of Patagonia at approximately 14,600 14C years BP. Uniform and rapid warming took place after 13,000 14C years BP, with no unequivocal evidence for climate fluctuations equivalent to those of the Northern Hemisphere Younger Dryas cooling event (the Younger Dryas Chronozone, dated to 11,000–10,000 14C years BP (12,700–11,500 cal. years BP). During the early Holocene (10,000–5000 14C years BP) atmospheric temperatures east of the Andes were about 2 °C above modern values in the period 8500–6500 14C years BP. The period between 6000 and 3600 14C years BP appears to have been colder and wetter than present, followed by an arid phase from 3600 to 3000 14C years BP. From 3000 14C years BP to the present, there is evidence of a cold phase, with relatively high precipitation. West of the Andes, the available evidence points to periods of drier than present conditions between 9400–6300 and 2400–1600 14C years BP. Holocene glacier advances in Patagonia began around 5000 14C years BP, coincident with a strong climatic cooling around this time (the Neoglacial interval). Glacier advances can be assigned to one of three time periods following a ‘Mercer-type’ chronology, or one of four time periods following an ‘Aniya-type’ chronology. The ‘Mercer-type’ chronology has glacier advances 4700–4200 14C years BP; 2700–2000 14C years BP and during the Little Ice Age. The ‘Aniya-type’ chronology has glacier advances at 3600 14C years BP, 2300 14C years BP, 1600–1400 14C years BP and during the Little Ice Age. These chronologies are best regarded as broad regional trends, since there are also dated examples of glacier advances outside these time periods. Possible explanations for the observed patterns of glacier fluctuations in Patagonia include changes related to the internal characteristics of the icefields, changes in the extent of Antarctic sea-ice cover, atmospheric/oceanic coupling-induced climate variability, systematic changes in synoptic conditions and short-term variations in atmospheric temperature and precipitation.
This paper presents an updated, extensive review of glacier fluctuations during the past 1000 years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼ 17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110 years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations.
Recent measurements on dendrochronologically-dated wood from the Southern Hemisphere have shown that there are differences between the structural form of the radiocarbon calibration curves from each hemisphere. Thus, it is desirable, when possible, to use calibration data obtained from secure dendrochronologically-dated wood from the corresponding hemisphere. In this paper, we outline the recent work and point the reader to the internationally recommended data set that should be used for future calibration of Southern Hemisphere ¹⁴C dates. This article has been published in the journal: Radiocarbon. © 2004 by the Arizona Board of Regents on behalf of the University of Arizona. Used with permission.
Cosmogenic nuclide surface-exposure dating reveals that glaciers in southern South America (46degreesS) advanced ca. 8.5 and 6.2 ka, likely as a result of a northward migration of the Southern Westerlies that caused an increase in precipitation and/or a decrease in temperature at this latitude. The older advance precedes the currently accepted initiation of Holocene glacial activity in southern South America by similar to3000 yr. Both of these advances are temporally synchronous with Holocene climate oscillations that occurred in Greenland and the rest of the world. If there are causal links between these events, then rapid climate changes appear to be either externally forced (e.g., solar variability) or are rapidly propagated around the globe (e.g., atmospheric processes).
Vive La Différence
How closely do climate changes in the Northern and Southern Hemispheres resemble each other? Much discussion has concentrated on the Holocene, the warm period of the past 11,500 years in which we now live, which represents a baseline to which contemporary climate change can be compared. Schaefer et al. (p. 622 ; see the Perspective by Balco ) present a chronology of glacial movement over the last 7000 years in New Zealand, which they compare to similar records from the Northern Hemisphere. Clear differences are observed between the histories of glaciers in the opposing hemispheres, which may be owing to regional controls. Thus, neither of two popular arguments—that the hemispheres change in-phase or that they change in an anti-phased manner—appear to be correct.
Digital elevation models of the Northern and Southern Patagonia Icefields of South America generated from the 2000 Shuttle
Radar Topography Mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers.
During the period 1968/1975–2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.042 ± 0.002 millimeters
per year. In the more recent years 1995–2000, average ice thinning rates have more than doubled to an equivalent sea level
rise of 0.105 ± 0.011 millimeters per year. The glaciers are thinning more quickly than can be explained by warmer air temperatures
and decreased precipitation, and their contribution to sea level per unit area is larger than that of Alaska glaciers.
We present here a review of the current glaciological knowledge of the Southern Patagonia Icefield (SPI). With an area of 13,000 km2 and 48 major glaciers, the SPI is the largest ice mass in the Southern Hemisphere outside of Antarctica. The glacier inventory and recent glacier variations are presented, as well as ice thickness data and its variations, ice velocity, ablation, accumulation, hydrological characteristics, climate changes and implications for sea level rise. Most of the glaciers have been retreating, with a few in a state of equilibrium and advance. Glacier retreat is interpreted primarily as a response to regional atmospheric warming and to a lesser extent, to precipitation decrease observed during the last century in this region. The general retreat of SPI has resulted in an estimated contribution of 6% to the global rise in sea level due to melting of small glaciers and ice caps. Many glaciological characteristics of the SPI, in particular its mass balance, need to be determined more precisely.