An early Holocene westerly minimum in the southern mid-latitudes

Moreno, Patricio I.; Henríquez, W.I.; Pesce, O.H.; Henríquez, Carla A.; Fletcher, Michael Shawn; Garreaud, René; Villa-Martínez, Rodrigo

doi:10.1016/j.quascirev.2020.106730

Cited by 27 publications

(22 citation statements)

References 37 publications

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“…This climatic scenario differs from the cold and dry conditions that prevailed during the formation of the N5 deltas in LCP, constrained between ∼20.7-19.3 ka, and the relatively temperate, and intermediate-precipitation N4 phase constrained between ∼19.3-14.8 ka. We note that the end of the N3 phase at ∼11.3 ka occurred shortly after the warm pulse and decline in SWW influence that initiated the Holocene at pan Patagonian scale (∼11.7 ka) (Moreno et al, 2021).…”

Section: Climatic Implicationsmentioning

confidence: 79%

Evolution of Glacial Lake Cochrane During the Last Glacial Termination, Central Chilean Patagonia (∼47°S)

et al. 2022

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Large ice-dammed lakes developed along the eastern margin of the Patagonian Ice Sheet (PIS) during the Last Glacial Termination (T1). Their spatial/temporal evolution, however, remains poorly constrained despite their importance for deciphering fluctuations of the shrinking PIS, isostatic adjustments, and climate forcing. Here we examine the distribution and age of shoreline features deposited or sculpted by Glacial Lake Cochrane (GLC) in the Lago Cochrane/Pueyrredón (LCP) basin, Central Patagonia, following recession of the LCP glacier lobe from its final Last Glacial Maximum (LGM) moraines. GLC drained initially toward the Atlantic Ocean and continuing ice shrinking opened new drainage routes allowing the discharge toward the Pacific Ocean. We identify five clusters of lake terraces, shorelines, and deltas between elevations ∼600–500 (N5), ∼470–400 (N4), ∼360–300 (N3), ∼230–220 (N2), and ∼180–170 masl (N1) throughout the LCP basin. The distribution of these clusters and associated glaciolacustrine deposits provide constraints for the evolving position of the damming glacier bodies. Elevation gradients within the landform clusters reveal glacio-isostatic adjustments that enable us to quantify the magnitude of deglacial rebound and construct isostatically corrected surfaces for the different phases in the evolution of GLC. Our chronology, based principally on radiocarbon dates from lake sediment cores and new OSL dating, suggests that these phases developed between ∼20.7–19.3 ka (N5), ∼19.3–14.8 ka (N4), ∼14.8–11.3 ka (N3), and shortly thereafter (N2 and N1). The N3 landforms are the most ubiquitous, well-preserved, and voluminous, attributes that resulted from a ∼3,500-year long period of glacial stability, enhanced sediment supply by peak precipitation regime, and profuse snow and ice melting during the most recent half of T1. This scenario differs from the cold and dry conditions that prevailed during the brief N5 phase and the moderate amount of precipitation during the N4 phase. We interpret the limited development of the N2 and N1 landforms as ephemeral stabilization events following the final and irreversible disappearance of GLC after N3. This event commenced shortly after the onset of an early Holocene westerly minimum at pan-Patagonian scale at ∼11.7 ka, contemporaneous with peak atmospheric and oceanic temperatures in the middle and high latitudes of the Southern Hemisphere.

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Section: Climatic Implicationsmentioning

confidence: 79%

Evolution of Glacial Lake Cochrane During the Last Glacial Termination, Central Chilean Patagonia (∼47°S)

et al. 2022

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“…A stronger SHW during the mid-Holocene coincides with an intensification of the westerlies recorded by other palaeorecords in Patagonia (e.g. Moreno et al, 2018Moreno et al, , 2021. The details of this are not fully known, but it has been suggested that this intensification is linked with a southward deflection of the SHW by the South Pacific High (Mayr et al, 2007 and references therein), while modelling results imply that this displacement can also be driven by a decrease in sea-ice (Hudson and Hewitson, 2001).…”

Section: Long-distance Pollen Signalmentioning

confidence: 60%

Pollen evidence of variations in Holocene climate and Southern Hemisphere Westerly Wind strength on sub-Antarctic South Georgia

et al. 2021

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The Southern Hemisphere Westerlies (SHW) play a major role in the global climate system. The winds drive ocean circulation and affect the Southern Oceans’ ability to take up atmospheric CO2. Recently, the SHW core belt has strengthened and shifted south, but there is an insufficient understanding of its long-term behaviour. Palaeoclimatic records are key for capturing long-term variability through the SHW’s effect on surface temperature and moisture availability. However, terrestrial records are sparse in the Southern Hemisphere. We use a palynological record from Lake Diamond on sub-Antarctic South Georgia to provide reconstructions of vegetation and climate for the last ~10,000 years. Influx of long-distance transported pollen is used as a measure of surface wind strength. Changes in relative pollen abundance of native taxa occupying either upland (cold) or lowland (warm) environments indicate local climatic variability. On South Georgia, we find long-distance transported pollen from South American taxa, mainly Nothofagus and Ephedra. They show a general increase in abundance throughout the Holocene, with peak influxes between 5700–5400, 2800–1500 and 1000–500 cal yr BP. These intervals coincide with colder periods inferred from the palynological record, suggesting that SHW variation and temperature on South Georgia are highly connected. Agreement with palaeoecological records from eastern Patagonia show that climatic changes have been regionally consistent. The record from Lake Diamond further illustrates the importance of remote islands in contributing to a deeper understanding of atmospheric circulation and climatic variability in the sub-Antarctic.

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“…Dating of moraines and shorelines; changes in basin topography (García et al, 2012;García et al, 2014;García et al, 2018); multi-proxy, isotopic, and pollen analysis of lake and marine sediment records (Huber et al, 2004;Fletcher and Moreno, 2012;Mayr et al, 2013;Zolitschka et al, 2013;Moreno et al, 2018;McCulloch et al, 2020;Moreno et al, 2021); and larger-scale regional data compilations (Glasser et al, 2008;Davies et al, 2020;Palacios et al, 2020) have been used to reconstruct past glacier extent and deglaciation in Patagonia (Figure 3), with many studies linking glacier advance and retreat to past changes in precipitation and SWW intensity and/or latitudinal position over Southern South America (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…The lake level history of Lago del Toro and the Holocene vegetational history of the surrounding area are detailed and well-studied (Figure 3, reference nos. 7-15 for summary) (García et al, 2012;Solari et al, 2012;García et al, 2014;García et al, 2018;Moreno et al, 2018;Moreno et al, 2021). A large ice-dammed proglacial lake, palaeo-Lago Tehuelche, once covered Lago del Toro and Lago Sarmiento sometime after c. 38 ka but before c. 17.6-16.8 ka; that is, between the l-LGM and g-LGM (Sagredo et al, 2011;Moreno et al, 2012;García et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…No post-LGM chronology has been established for these moraines or those along the southern margin of Lago del Toro, adjacent to Lago Pato (Figures 2A,B). Glacier advances were driven by the alignment of the SWW over 51-52 °S, which persisted between c. 13.4 and 11.3 ka as ACR glaciers retreated, but then became weaker, more diffuse, or poleward shifted during the "Early Holocene Westerlies Minimum" (Mayr et al, 2013;Quade and Kaplan, 2017;Moreno et al, 2018;Zolitschka et al, 2018;McCulloch et al, 2020;Moreno et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Late Glacial and Holocene Palaeolake History of the Última Esperanza Region of Southern Patagonia

et al. 2022

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We undertook multi-proxy analyses on two sediment cores from Lago Pato, a small lake basin at 51°S topographically separated from Lago del Toro in Torres del Paine (TdP), to provide insights into glacier dynamics and lake-level change in the TdP and Última Esperanza region over the last ∼30,000 cal a BP (30 ka). Lago Pato is situated in a region overridden by the Southern Patagonian Ice Field during the Last Glacial and in a transitional climatic zone of Southern Patagonia sensitive to seasonal- to millennial-scale changes in the Southern Hemisphere Westerly Winds (SWW). Results show that a deep ice-dammed and enlarged palaeolake encompassed Lago del Toro and Lago Pato c. 30–20 ka after the ice had retreated from local-Last Glacial Maximum (l-LGM) limits at c. 48–34 ka and during the build-up to the global-Last Glacial Maximum (g-LGM), c. 26–19 ka. Gaps in both sediment records between c. 20–13.4 ka and c. 20–10 ka suggest hiatuses in sediment accumulation during the g-LGM and Antarctic Cold Reversal (ACR) readvances and/or removal by lake lowering or flushing during the Late Glacial–early Holocene. The palaeolake level dropped from >100 m a.s.l. to ∼40–50 m a.s.l. towards the end of the ACR c. 13.4–13.0 ka, creating a shallower glaciolacustrine environment dammed by an ice tongue in the Estancia Puerto Consuelo–Última Esperanza fjord. Further lowering of the enlarged palaeolake level occurred when the ice thinned to <40 m a.s.l., eventually isolating Lago Pato from Lago del Toro and glaciogenic sediment input at c. 11.7 ka. After isolation, the ecology and water levels in Lago Pato became sensitive to regional climate shifts. The shallow, stable, and highly anoxic environment that developed after c. 11.7 ka is associated with weaker (or poleward shifted) SWW at 51°S and was replaced at c. 10 ka by an increasingly productive shallow-littoral lake with a variable lake-level and periodic shifts in anoxic-oxic bottom water conditions and ratios of benthic-planktonic diatoms. A more open Nothofagus forest, established at c. 8.6–7.5 ka, and more arid conditions c. 7.5–5.7 cal ka BP are linked to another phase of weaker (or poleward shifted) SWW at 51°S. More persistently wet conditions from c. 5.7 ka, with extensive closed Nothofagus forests and planktonic diatoms dominant, are associated with stronger (or equatorward shifted) SWW over 51°S. The abrupt return of benthic-to-tychoplanktonic diatoms after c. 3 ka reflects enhanced SWW at 51°S. Increasingly stable lacustrine and littoral wetland conditions established in the last ∼500 years reflect weaker SWW and lasted until recent decades.

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An early Holocene westerly minimum in the southern mid-latitudes

Cited by 27 publications

References 37 publications

Evolution of Glacial Lake Cochrane During the Last Glacial Termination, Central Chilean Patagonia (∼47°S)

Evolution of Glacial Lake Cochrane During the Last Glacial Termination, Central Chilean Patagonia (∼47°S)

Pollen evidence of variations in Holocene climate and Southern Hemisphere Westerly Wind strength on sub-Antarctic South Georgia

Late Glacial and Holocene Palaeolake History of the Última Esperanza Region of Southern Patagonia

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