Glacier expansion in central Patagonia during the Antarctic Cold Reversal followed by retreat and stabilisation during the Younger Dryas

• Published in: Quaternary Science Reviews
• Main Authors: Mendelova, Monika, Hein, Andrew S, Rodes, Angel, Smedley, Rachel K, Xu, Sheng
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier BV 2020
• Subjects: Antarctic; Belgrano; Pacific; Patagonia; The Antarctic; Antarc*; Ice cap; Ice Sheet
• Online Access: http://livrepository.liverpool.ac.uk/3063840/; https://doi.org/10.1016/j.quascirev.2019.106047; http://livrepository.liverpool.ac.uk/3063840/1/Mendelova%20et%20al.%20ACR.pdf

The spatial-temporal footprint of millennial-scale climate events during the last glacial-interglacial transition can yield insights into the underlying drivers of climate change, but remains poorly resolved in Patagonia. Here, we assess the glacier response to abrupt cold events and palaeolake evolution using geomorphological mapping along with 10Be ages and optically stimulated luminescence ages from near Lago Belgrano (47.9° S) on the eastern side of Monte San Lorenzo. The former Belgrano glacier was sustained by a climatically sensitive ice cap, making the site ideal for investigating the glacier response to abrupt cold reversals. Our data reveal an extensive re-advance at 13.1 ± 0.6 ka, consistent with cooling and increased precipitation during the Antarctic Cold Reversal (ACR). Subsequently, ice retreated by at least 10 km and created an ice-dammed proglacial lake in the Belgrano valley. Rapid recession was punctuated by smaller advances/still-stands sufficient to maintain an ice-dam for the palaeolake and deposit a lateral moraine dated at 12.4 ± 0.3 ka during the Younger Dryas (YD). The final withdrawal of glaciers to the mountains allowed the palaeolake to drain and resulted in an Atlantic/Pacific drainage reversal. This marks the final separation of the Patagonian Ice Sheet into the individual ice fields at the YD-Holocene transition. Our data demonstrate the dominant ACR climate signal in central Patagonia, but also reveals a co-occurrence of the northern hemisphere YD signal, albeit of smaller magnitude. The ACR re-advance was primarily climatically controlled, but its relative magnitude was likely a consequence of ice divide migration and ice flow re-routing during the break-up of the Patagonian Ice Sheet.