EXPLORING SUBAQUEOUS GLACIAL ENVIRONMENTS: WATER TEMPERATURE INFLUENCES ON LAKE-TERMINATING GLACIERS AT MENDENHALL LAKE, AK

Proglacial lakes primarily form due to glacial retreat over overdeepened basins where water is entrained by moraine dams. These lakes are growing in number and size worldwide with the total area of proglacial lakes increasing by 50% between 1990-2018. Despite their ongoing expansion, there is currently no consensus on how proglacial lakes with lake-terminating glaciers influence the glaciers that feed them, or even if they do. Here we explore a proglacial lake/glacier system in southeast Alaska, Mendenhall Lake and Glacier, which are popular and accessible recreation sites near Juneau, AK. The lake has increased in area by 25% since 1984 as the glacier retreated landward. To investigate the lake’s influence on the glacier, we analyze lake water temperature observations between 2010-2014, lake level data, atmospheric conditions, and remote-sensing derived glacial retreat rates. Using these disparate datasets, we discuss how seasonal temperature fluctuations influence the glacial retreat of Mendenhall Lake. The lake exhibits daily and seasonal fluctuations that range from 0–3°C, with a general cooling pattern throughout the water column as summer progresses. In addition, vertical temperature gradients vary sporadically, potentially indicating pulses of glacial discharge entering the lake as glacial lake outburst floods are known to occur here. By synthesizing these data together, we aim to disentangle the physical processes controlling lake-terminating glacier behavior and motivate future work in proglacial lake systems. More intensive study of Alaskan lake/glacier systems from both above and below water will be useful as analogues for impossible to reach locations (e.g., Greenland) and to inform remote-sensing data.