Late glacial climate evolution in the Patagonian Andes (44–47° S) from alpine glacier modelling

Numerical glacier models applied to moraine chronologies provide an opportunity to quantify past climate change. Here we apply a two-dimensional coupled mass balance – ice flow model to well-dated moraine sequences deposited by former alpine glaciers at two central Patagonian sites: Cerro Riñón (43.97°S, 71.64°W) and Río Tranquilo (47.50°S, 72.38°W), to reconstruct the local temperatures during both the Antarctic Cold Reversal (14.7–13 ka) and the Younger Dryas (12.9–11 ka). Modelled temperature anomalies during the Antarctic Cold Reversal are −2.6 ± 0.4 °C at 44°S, and −2.9 ± 0.6 °C at 47°S. At both locations this cold event is followed by temperature increases of +0.6–0.7 °C or precipitation reductions of c. 20% to drive glacier retreat to moraines deposited during Younger Dryas time. The consistent climatic anomalies between these two latitudes suggest this region of Patagonia was responding to a common climatic event. Further, the late-glacial temperature anomalies found here compare well to those determined by similar glacier modelling techniques in New Zealand, at 43–44° S. These results support a trans-Pacific response throughout the southern mid to high latitudes (43–47° S) during the ACR that is best explained by a northward expansion of the south westerly winds.