Comparing the response to meteorological drivers at Taylor and Commonwealth glacier, McMurdo Dry Valleys, Antarctica.

In the McMurdo Dry Valleys (MDV) of Antarctica thrives a unique ecosystem under extreme cold and dry conditions. The limited snowfall that falls on the valley floor quickly sublimates and therefore glacial melt is the most important input to the streams and ice-covered lakes that provide water for the ecosystem. Understanding what drives the variability and changes in glacial meltwater is therefore of great importance to foresee ecosystem changes in a warming world. To assess the temporal variability and meteorological drivers of glacial melt in Taylor Valley, a 22-year surface energy balance (SEB) record is constructed for Taylor and Commonwealth glacier. Automatic weather station observations from the Long-term Ecological Research (LTER) Program in the ablation zone of each glacier are gap filled and completed using locally-tuned parameterisations. The two SEB records are compared to understand the different response of two nearby glaciers (~30 km apart) to local and regional climate forcing. The more melt dominated Commonwealth glacier shows strong seasonal variability in ablation. The closer proximity of Commonwealth glacier to the ocean leads to more rapid changes in albedo as controlled by summer snowfall events. Not only does the presence of snow but also the larger variability in ice albedo compared to Taylor glacier explains much of the seasonal variability in melt. Another major driver of melt are the number of degree days above freezing for both glaciers, which is strongly linked to foehn wind events in Taylor Valley. The further inland Taylor glacier experiences drier and windier conditions and therefore sublimation dominates ablation and melt occurrence. Cloud cover and snowfall in summer switch off glacial melt in summer on both glaciers. We have also used ERA5 fields to study the moisture sources of the MDV precipitation and clouds. This will help us understand how changes in moisture and regional circulation patterns might impact the MDV glaciers and ecosystem in a warming climate.