Late glacial and Holocene climate variability, southernmost Patagonia

McCulloch, Robert; Blaikie, James; Jacob, Bárbara; Mansilla, Claudia A; Morello, Flavia; Pol‐Holz, Ricardo De; Román, Manuel San; Tisdall, Eileen; Torres, Jimena

doi:10.1016/j.quascirev.2019.106131

Cited by 30 publications

(29 citation statements)

References 60 publications

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“…Even if it is unclear whether this could also have caused the gap in the Lake Diamond record, drier conditions would stop peat growth and inwash of sediments to the lake. A diatom inferred lake level low stand in Laguna Potrok Aike from 8700 to 7300 cal yr BP (Wille et al, 2007) and retreat of Nothofagus woodland in Southern Patagonia (Mansilla et al, 2018; McCulloch et al, 2020) suggest that warm and dry conditions prevailed in the south Atlantic region.…”

Section: Discussionmentioning

confidence: 99%

“…However, shifts in the forest-steppe ecotone in southern Patagonia occurred throughout the Holocene (Mansilla et al, 2018), thereby affecting the taxonomic composition of the LDT pollen flux. The eastward extend of the precipitation-sensitive Nothofagus forest has varied substantially following dry/wet phases related to weak/strong SHW intervals (Mansilla et al, 2018;McCulloch et al, 2020;Moreno et al, 2010Moreno et al, , 2014. This could amplify the Nothofagus pollen influx to Lake Diamond during periods of strong SHW.…”

Section: Long-distance Pollen Signalmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Long-distance Pollen Signalmentioning

confidence: 99%

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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“…Ice-lobes from the Cordillera Paine extended out beyond the eastern end of Lago del Toro forming complex terminal moraine systems, scouring deep lake basins such as Lago del Toro, while reaching their maximum advance limits at the l-LGM (limit A 1 in Figure 2A) (Sagredo et al, 2011;García et al, 2012;García et al, 2014;García et al, 2018;Davies et al, 2020). At the global-Last Glacial Maximum (g-LGM), c. 26.5-19 ka, the Southern Patagonian Ice Sheet was more than 200 km wide and over 1800 km long, yet it reached only half its maximum Marine Isotope Stage 3 extent due to milder winters and drier conditions associated with a weaker, broader, and equatorward shifted Southern Westerly wind belt that extended into the midlatitudes (McCulloch and Davies, 2001;Kaplan et al, 2007;Kaplan et al, 2008;García et al, 2014;Darvill et al, 2015;Glasser et al, 2017;García et al, 2018;Davies et al, 2020;McCulloch et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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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“…last 4200 years) evidenced only minor environmental shifts compared to the substantial climatic, ecological and geomorphological changes that took place during the Holocene (e.g. Ariztegui et al, 2008; Iglesias et al, 2014; Lara et al, 2020; McCulloch et al, 2020; Moreno et al, 2018). However, if considering the last millennia individually, some significant decadal-to-centennial timescale environmental changes are observed (e.g.…”

Section: Introductionmentioning

confidence: 99%

Disentangling the Medieval Climatic Anomaly in Patagonia and its impact on human societies

et al. 2022

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This paper revises paleoenvironmental data from Patagonia (southern South America) to discuss the occurrence, characteristics, and human impact of the Medieval Climatic Anomaly (MCA). The analysis of continuous paleoenvironmental archives with multidecadal-to-centennial resolution is based on a quality assessment regarding data interpretation, chronological control, and time range adequacy within the MCA lapse. After applying this three-stepped quality filters on the total dataset ( N = 48), 18 cases can accurately be ascribed to the MCA. Except for two sites indicating wetter conditions, these records show dry and/or warm conditions between ca. 750 and 1350 CE (core period at ca. 800–1200 CE). Even though MCA records come mostly from forests and forest-steppe ecotones, all previous archeological hypotheses about the MCA effects on past hunter-gatherers were proposed for the steppes, particularly in southern sectors, thus requiring an assessment of the source of the signal, their synchronicity and causality between human-environmental processes. In the southern steppe, paleoenvironmental records partially overlapping with the MCA time window actually show a predominance of wet conditions between 47° and 50° S, whereas a generalized aridity is recorded in southern tip of the continental Patagonia between 51° and 52° S. Thus, a complex scenario of landscape fragmentation can be supported in the southern steppes during the MCA, produced not only by enhanced aridity in dry environments, but also because of the presence of wet and more resilient areas. This landscape heterogeneity must be considered to deepen the understanding of behavioral changes contemporaneous to the MCA. However, a scenario of demographic growth suggested around 1000 CE for the entire Patagonia could have promoted human changes similar to those expected for the MCA. Finally, no-archeological discussions linked to the MCA were developed for forest regions, despite their robust paleoenvironmental records, implying that changes in proxy data might not have necessarily involved important environmental changes.

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Late glacial and Holocene climate variability, southernmost Patagonia

Cited by 30 publications

References 60 publications

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

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

Disentangling the Medieval Climatic Anomaly in Patagonia and its impact on human societies

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