The large MIS 4 and long MIS 2 glacier maxima on the southern tip of South America

Peltier, Carly; Kaplan, Michael R.; Birkel, S. D.; Soteres, Rodrigo L.; Sagredo, Esteban A.; Aravena, Juan Carlos; Araos, José; Moreno, P. I.; Schwartz, Roseanne; Schaefer, Joerg M.

doi:10.1016/j.quascirev.2021.106858

Cited by 45 publications

(40 citation statements)

References 73 publications

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“…To summarise, empirical data including this study suggest that major middle-to-late Pleistocene cycles of SH midlatitude glaciers and ice sheets appear to be coeval with NH glaciers and ice sheets, but out-of-phase with local mid-latitude summer insolation intensity (Putnam et al, 2013;Peltier et al, 2021), traditionally thought to be the primary driver of middle-to-late Pleistocene glacial expansion/demise cycles (Mercer, 1984). However, recent hypotheses suggest that this paradox might be explained by the potentially more dominant climate-forcing effect of the seasonality and seasonal-duration expressions of SH insolation, through their impact on atmospheric temperature, the position of the SWW belt and Subtropical Front, Antarctic sea ice extent, and Southern Ocean stratification and CO2 storage-and-release feedback mechanisms.…”

Section: Climatic and Orbital Drivers Of Sh Glaciations -Hypothesesmentioning

confidence: 80%

“…In southeastern Patagonia, moreextensive-than MIS 2 advances were also dated to MIS 4 and 3 using TCN exposure dating (e.g. Darvill et al, 2016;García et al, 2018;Peltier et al, 2021). We argue that while the RC outlet glacier most likely advanced during the MIS 4 and 3 cooling events, these intervals were relatively short-lived, impeding the PIS from becoming locally thick enough to allow the RC outlet glacier to advance along its retrograde bed slope and generate an extensive advance.…”

Section: Synthesis: the Timing Of Patagonian Glaciationsmentioning

confidence: 91%

“…However, more accurate dating of younger PIS outlet-glacier advances occurring during the global LGM (MIS 2; e.g. Peltier et al, 2021), including the RC outlet glacier (RC III-VII; Leger et al, 2021a), has shown that these later SH glacier advances, and also SSTs and Antarctic atmospheric temperature depressions, were anti-phased with SH summer insolation intensity, and were instead coeval with high SH seasonality and winter duration. Consequently, it is plausible that the PIS advanced at ~280 ka (RC 0) and ~255 ka (RC I), when SH summer insolation intensity was high, but when SH winters were cold and long.…”

Section: The Mis 8 Glaciationsmentioning

confidence: 99%

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A cosmogenic nuclide-derived chronology of pre-Last Glacial Cycle glaciations during MIS 8 and MIS 6 in northern Patagonia

Leger

Hein

Rodés

et al. 2022

Preprint

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Abstract. The precise environmental mechanisms controlling Quaternary glacial cycles remain ambiguous. To address this problem, it is critical to better comprehend the drivers of spatio-temporal variability in ice-sheet evolution by establishing reliable chronologies of former outlet-glacier advances. When spanning multiple glacial cycles, such chronologies have the capacity to resolve conundrums on interhemispheric phasing of glaciations and climate events. In southern Argentina, reconstructions of this kind are achievable, as Quaternary expansions of the Patagonian Ice Sheet have emplaced a well-preserved geomorphological record covering several glacial cycles. Moreover, robust ice-sheet reconstructions from Patagonia are powerful barometers of former climate change, as Patagonian glaciers are influenced by the Southern Westerly Winds and its coupled Antarctic Circumpolar Current. Former shifts in these circulation mechanisms are essential to better constrain, as they may have played a critical role in pacing regional and possibly global Quaternary climate change. Here, we present a new set of cosmogenic 10Be and 26Al exposure ages from pre-Last Glacial Cycle moraine boulder, glaciofluvial outwash cobble and bedrock samples. This dataset constitutes the first direct chronology dating pre-LGM glacier advances in northern Patagonia, and completes our effort to date the entire preserved moraine record of the Río Corcovado valley system (43° S, 71° W). We find the outermost margins of the study site depict at least three distinct pre-Last Glacial Cycle glaciations occurring at 284 ± 7 ka, 257 ± 7 ka, and 147 ± 4 ka. Combined with the local LGM chronology, we discover that a minimum of four distinct Pleistocene glaciations occurred during Marine Isotope Stages eight, six, and two in northern Patagonia. Evidence for stage four and three deposits were not found at the study site, which illustrates former longitudinal and latitudinal asynchronies in Patagonian Ice Sheet mass balance during these stages. We find the most extensive middle-to-late Pleistocene expansions of the Patagonian Ice Sheet appear to be out-of-phase with local summer insolation intensity, but synchronous with orbitally-controlled periods of longer and colder winters. Our findings thus enable to explore the potential roles of seasonality and seasonal duration in driving southern mid-latitude ice-sheet mass balance and facilitate novel glacio-geomorphological interpretations for the study region. They also provide empirical constraints of former ice-sheet extent and dynamics that are essential to calibrating numerical ice-sheet and glacial isostatic adjustment models.

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Section: Climatic and Orbital Drivers Of Sh Glaciations -Hypothesesmentioning

confidence: 80%

Section: Synthesis: the Timing Of Patagonian Glaciationsmentioning

confidence: 91%

Section: The Mis 8 Glaciationsmentioning

confidence: 99%

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A cosmogenic nuclide-derived chronology of pre-Last Glacial Cycle glaciations during MIS 8 and MIS 6 in northern Patagonia

Leger

Hein

Rodés

et al. 2022

Preprint

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“…Terrestrial geochronologic records show that the maximum extents of the ice lobe fluctuations along the PIS occurred at different times during the last glacial period, suggesting an asynchrony between northern, central and southern Patagonia. Most moraine chronologies have recorded local ice maxima during MIS 2 and MIS 3, but also MIS 4 and MIS 5a (Kaplan et al, 2004;Douglass et al, 2006;Hein et al, 2010;Darvill et al, 2015;García et al, 2018García et al, , 2021Mendelová et al, 2020;Leger et al, 2021;Peltier et al, 2021). This asynchrony of the glacial maximum extensions could be in response to the interaction of different factors, such as shifts of the atmospheric and oceanic frontal systems, Antarctic Sea-ice migration and Southern Ocean stratification (Darvill et al, 2016) and/or topographic controls (Sugden et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

The Last Glacial Maximum and Deglacial History of the Seno Skyring Ice Lobe (52°S), Southern Patagonia

et al. 2022

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There are still many uncertainties about the climatic forcing that drove the glacier fluctuations of the Patagonian Ice Sheet (PIS, 38–55°S) during the last glacial period. A key source of uncertainty is the asynchrony of ice lobe fluctuations between the northern, central, and southern PIS. To fully understand the regional trends requires careful mapping and extensive geochronological studies. This paper presents geomorphological and geochronological reconstructions of the glacial and deglacial landforms formed during the last glacial period at the Seno Skyring lobe, southernmost Patagonia (52°S, 71°W). We present a detailed geomorphological map, where we identify two moraine systems. The outer and older is named Laguna Blanca (LB) and the inner Río Verde (RV). The LB moraines were built subaerially, whereas parts of the RV were deposited subaqueously under the palaeo lake Laguna Blanca, which developed during deglaciation. We conducted surface exposure 10Be dating methods on boulder samples collected from LB and RV glacial margins. The moraine LB III and LB IV formed at 26.3 ± 2.3 ka (n = 5) and 24.3 ± 0.9 ka (n = 3), respectively. For the inner RV moraine, we obtained an age of 18.7 ± 1.5 ka (n = 6). For the palaeo Laguna Blanca evolution, we performed 10Be exposure ages on shoreline berms and optically stimulated luminesce dating to constrain the lake levels, and 10Be depth profile dating on an outwash deposit formed by a partial lake drainage event, which occurred at 22 ± 3 ka. For the RV moraine deglaciation, we performed radiocarbon dating of basal sediments in a peat bog, which indicates that the glacier retreated from the terminal RV moraine by at least c. 16.4 cal kyr BP. Our moraine geochronology shows an asynchrony in the maximum extents and a different pattern of ice advances between neighbouring lobes in southern Patagonia. We speculate that this may be due, at least in part, to the interaction between topography and the precipitation carried by the southern westerly wind belt. However, we found broad synchrony of glacial readvances contemporaneous with the RV moraine.

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“…Palaeo-climate proxy data from northwestern Patagonia suggest a return to colder, wetter conditions in the late LGM, between ∼19.5 and ∼18 ka, during which it is hypothesised that the SWW locally reached their maximum LGM influence (Denton et al, 1999;Moreno et al, 2018). Moreover, numerous late-LGM expansion and/or stabilisation events have been reported for several Patagonian and New Zealand glaciers at ∼17-18 ka (e.g., Denton et al, 1999;Kaplan et al, 2007Kaplan et al, , 2008Shulmeister et al, 2010Shulmeister et al, , 2019Murray et al, 2012;Putnam et al, 2013;Moreno et al, 2015;Mendelová et al, 2020a;Davies et al, 2020;Peltier et al, 2021), which suggest a somewhat synchronous late-LGM glacial response across the southern mid-latitudes. However, recent geochronological evidence from the northeastern sector of the former Patagonian Ice Sheet (PIS) does not fit this pattern.…”

Section: Introductionmentioning

confidence: 99%

Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation

et al. 2021

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The last glacial termination was a key event during Earth’s Quaternary history that was associated with rapid, high-magnitude environmental and climatic change. Identifying its trigger mechanisms is critical for understanding Earth’s modern climate system over millennial timescales. It has been proposed that latitudinal shifts of the Southern Hemisphere Westerly Wind belt and the coupled Subtropical Front are important components of the changes leading to global deglaciation, making them essential to investigate and reconstruct empirically. The Patagonian Andes are part of the only continental landmass that fully intersects the Southern Westerly Winds, and thus present an opportunity to study their former latitudinal migrations through time and to constrain southern mid-latitude palaeo-climates. Here we use a combination of geomorphological mapping, terrestrial cosmogenic nuclide exposure dating and glacial numerical modelling to reconstruct the late-Last Glacial Maximum (LGM) behaviour and surface mass balance of two mountain glaciers of northeastern Patagonia (43°S, 71°W), the El Loro and Río Comisario palaeo-glaciers. In both valleys, we find geomorphological evidence of glacier advances that occurred after the retreat of the main ice-sheet outlet glacier from its LGM margins. We date the outermost moraine in the El Loro valley to 18.0 ± 1.15 ka. Moreover, a series of moraine-matching simulations were run for both glaciers using a spatially-distributed ice-flow model coupled with a positive degree-day surface mass balance parameterisation. Following a correction for cumulative local surface uplift resulting from glacial isostatic adjustment since ∼18 ka, which we estimate to be ∼130 m, the glacier model suggests that regional mean annual temperatures were between 1.9 and 2.8°C lower than present at around 18.0 ± 1.15 ka, while precipitation was between ∼50 and ∼380% higher than today. Our findings support the proposed equatorward migration of the precipitation-bearing Southern Westerly Wind belt towards the end of the LGM, between ∼19.5 and ∼18 ka, which caused more humid conditions towards the eastern margins of the northern Patagonian Ice Sheet a few centuries ahead of widespread deglaciation across the cordillera.

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The large MIS 4 and long MIS 2 glacier maxima on the southern tip of South America

Cited by 45 publications

References 73 publications

A cosmogenic nuclide-derived chronology of pre-Last Glacial Cycle glaciations during MIS 8 and MIS 6 in northern Patagonia

A cosmogenic nuclide-derived chronology of pre-Last Glacial Cycle glaciations during MIS 8 and MIS 6 in northern Patagonia

The Last Glacial Maximum and Deglacial History of the Seno Skyring Ice Lobe (52°S), Southern Patagonia

Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation

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