On-site albedo data and their relationship to the long-term evolution of surface morphology in glaciers of Hurd Peninsula, South Shetland Islands, Antarctica

Snow and ice albedo play a crucial role in the mass losses from the NW Antarctic Peninsula and the South Shetlands Islands since absorption of solar radiation is the largest energy source for surface melt in the cryosphere. Snow albedo exhibits a large variation at different time scales (hours, days, seasonal, long-term trend). It has been established that the thickness of the snow/ice layer that affects the albedo varies from 20 cm to 50 cm.   The surface geomorphology of this layer exerts a strong control in the snow albedo evolution over a day because they affect the amount of solar energy received, and the exposure to prevailing winds. In order to discover patterns of variation between snow albedo and surface geomorphology over Hurd Peninsula glaciers at metric scales, we used four DEMs (1957,2000, 2013 and 2019) of 1 m of spatial resolution. In the four DEMs topographical variables (altitude, slope, plan and profile curvature, aspect) and indexes (diurnal differential heating, wind exposition, roughness index) were calculated using QGis_Gdal_SAGA tools.  Because of the high spatiotemporal variability of the snow cover, the albedo data obtained from fixed stations provide a partial picture of the actual field behaviour.  In order to obtain spatially distributed albedo measurements over Hurd Peninsula glaciers, we designed a portable albedometer. The device consists of two pyranometers, one facing the sky and another facing the ground at 1,20m above the ground, working together with a GNSS. The dataloggers of each pyranometer were set up to take a measurement every 5 seconds. Using this equipment, in January of 2018 and 2019 we surveyed the glaciers of Hurd Peninsula along the same tracks but under different weather conditions (fog, clear sky, clouds and clearings). The population of albedo data obtained with this method was about 800 measured points per track per day.  Using QGis we obtained the values of topographical variables and indexes for all the albedo points. Lineal correlations between albedo and topographical variables and indexes were explored. The R² was especially high in the tracks performed during open sky days. There are not significant correlations between DTMs variables and albedo data in tracks performed in foggy days. Moreover, we built a Linear Regression Model (forward stepwise) of open_sky day’s albedo with Adjusted R²= 0.86 and Std. Error of estimate: 0.00428 with diurnal differential heating_2019, altitudes (1957, 2000, 2013), slope_2019 and convexity_2019 as predictive variables. To estimate the surface albedo all across Hurd Peninsula extending linear models using QGis. Also, we calculated the DTM of 1957-2019 altitude changes in meters (Minimum=-32.694, Maximum=53.188, Mean=7.959, StdDev=10.526), which shows strong correlation with albedo of all open sky tracks.  We interpreted these results in relation to the density, structure and state of metamorphism of the snow cover that could represent the layer of snow that affects the albedo in Hurd Peninsula glaciers. The preliminary results seem to indicate that the surface melting intra-annual variability of the Hurd Peninsula glaciers, registered in the glacier surfaces geomorphology, exerts a strong influence on the current albedo.