Insight into glacier evolution, proglacial lake dynamics, and paleoclimate from Lago Argentino, Patagonia

Proglacial lakes provide valuable records of paleoclimate, volcanism, and glaciation. We present results from spatially extensive coring of Lago Argentino, a 1500 km² proglacial lake on the eastern margin of the Southern Patagonian Icefield (SPI). We recovered forty-seven sediment cores from water depths up to 600 m. Detailed analysis of this sediment reveals annual laminations – known as varves – which we use to build a high-resolution age-depth model for each core.

In this presentation, we discuss the insight gained into varve formation mechanisms, paleoclimate, and glacier change in the Lago Argentino basin of the Southern Patagonian Icefield. Firstly, we show that varves form by three distinct mechanisms across Lago Argentino (~west to east): a seasonal cycle in glacial sediment influx, a seasonal cycle in lake mixing, and a seasonal cycle in fluvial sediment influx. Second, we examine the evidence for recent glacier fluctuations across Lago Argentino. We find evidence that glaciers were locally larger early in the last millennium than during the Little Ice Age. Finally, we examine the periodicity of sediment mass accumulation rate and find dominant decadal to centennial periodicities (35, 80, 150 and 200 years). We relate periodicities in sediment accumulation to periodicities in known climatic drivers, specifically the Southern Annular Mode. These results provide new insight into multiannual glacial change and sedimentation dynamics in a complex glacio-lacustrine system and highlight the value of proglacial lake records for understanding present-day glacier change.