Rapid glacier recession at Monte San Lorenzo (Patagonia) in response to abrupt Southern Hemisphere warming 13.0-12.0 ka

Mid-latitude Patagonian glaciers are sensitive to changes in the complex coupled ocean-atmospheric climate system of the Southern Hemisphere, and in particular changes in temperature and precipitation through shifts in the latitudinal position of the austral westerlies. Here, we investigate glacier response to a period of rapid climate warming immediately post-dating the Antarctic Cold Reversal (ACR). We present new cosmogenic nuclide surface exposure ages, alongside previously published ages, from glacially transported boulders to date a sequence of 13 ice margins formed in the northern outlet valleys of the Monte San Lorenzo ice cap (47.3°S). The dataset constrains glacier recession of 31.7 km over a period of ~1.0 kyr from 13.2 ± 0.4 ka (the end of the ACR) to 12.1 ± 0.4 ka. The average rate of recession was 35.2 m yr-1 over this 1.0 ka period, increasing from 12.75 m yr-1 at the start of the record (moraines M1 to M4) to 50 m yr-1 from M9 to M12. This recession likely occurred during a period of rapid warming when the austral westerlies shifted polewards, possibly during a persistent positive phase of the Southern Annular Mode (SAM), which reduced solid precipitation and decreased accumulation. It is likely that ice extent stabilised during the Holocene, with ice occupying the M13 moraine during repeated Holocene neoglacials, before anthropogenic warming caused recession at a rate of 55.5 m yr-1 from 1985 to 2016.This dataset sheds light onto the key drivers of satellite ice-caps around the Patagonian Andes and demonstrates mass balance sensitivity to temperature and precipitation.