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[ACC28-P06] Seasonal variations in the thermal structures of proglacial lakes in the Southern Patagonia Icefield
Keywords:calving glacier, proglacial lake, subaqueous melt, Patagonia
Our results in spring showed relatively uniform water temperature and turbidity from the lake surface to the bottom, whereas temperature and turbidity showed steeper vertical gradients in summer. These results are consistent in the two lakes. In summer, water temperature in front of Glacier Upsala (2—4oC) was colder than in spring, because of large amounts of subglacial discharge from the glacier. Turbid and cold water (< 1oC) was found at the deepest part of the lake (> 500 m below the lake surface), which is a strong indication of subglacial meltwater discharge. Contrasting to Glaciar Upsala, cold deep water was missing in the lake of Glaciar Perito Moreno both in summer and spring. In summer, water temperature (6oC) was warmer than in spring by 〜3oC within whole lake, and in particular, warm water layer (〜8oC) observed at the lake surface (<5 m below the lake surface).
These data indicate different thermal structures in front of the two freshwater calving glaciers in Patagonia. The structure is probably dependent on the bathymetry and subglacial discharge. Warmer lake is formed by relatively small amount of subglacial discharge and shallow lake, which should play crucial roles in the melting of calving face below the lake surface.