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Long-term continental mean air temperature (MAT) records are rare worldwide, but essential for paleoclimate and paleoenvironmental reconstructions. MAT variability in the south-western Patagonian fjord region (Golfo Almirante Montt; 52°S) during the last ∼14.5 kyr was estimated using a proxy based on soil bacterial lipids applied to a postglacial sediment record shifting between marine and freshwater stages. MAT was around 7 ± 1 °C between 14.5 and 11 kyr, which includes the Antarctic Cold Reversal (ACR; 14.7–13 kyr). The persistent cold temperature beyond the ACR resulted likely from a local cooling effect related to the presence of glaciers from the Southern Patagonian Icefield. Subsequent to a ∼5 °C warming, MAT reached maximum values around 12 ± 1 °C during the Early Holocene (11–8 kyr) and was around 10 ± 1 °C during the Mid- to Late Holocene. A 3–4 °C MAT cooling during the ACR is in close agreement with temperature estimations based on a mass balance - ice flow model applied to glacial moraine sequences located at 44–47°S. The MAT record was combined with the K/Ti proxy for terrigenous input as well as two proxies for vegetation cover based on n -alkane lipids derived from higher plant leaf waxes. These proxies indicate increased humidity between 14.5 and 11 kyr and drier conditions during the Early Holocene in contrast with generally wetter conditions in south-western, coastal Patagonia at this time. A positive Southern Annular Mode and the resulting poleward shift, contraction and strengthening of the Southern Hemisphere Westerly Winds (SWW) south of ∼51°S during the Early Holocene likely triggered wetter conditions on the windward side of the Andes and drier conditions on the leeward side due to a strengthening of foehn winds. During the ACR and the Mid- to Late Holocene, an equatorward shift, a broadening and a weakening of the SWW resulted in wetter conditions in western Patagonia on both sides of the Andes. The MAT and humidity-related postglacial records of Golfo Almirante Montt provide important new insights into the different paleoenvironmental reconstructions based on marine, lake and glacier evidence in southern Patagonia.
Kaiser et al. (Tue,) studied this question.