Snow albedo at Alerce Glacier, Argentina: effect of PM, snow grain size and cloud cover

VILLARROSA, GUSTAVO; BAJANO, HECTOR; RUIZ, L.; CENLIN, HE; DAWIDOWSKI, LAURA; OUTES, VALERIA; BAJANO, FACUNDO

Montreal

Congreso; 27th IUGG 2019; 2019

The influence of Black Carbon (BC) and other particulate matter (PM) on glacier melting is of great interest currently (1), but there are ongoing discussions on its magnitude, due to controversy on the appropriate methodology of simulation of this effect. Specially, there is a lack of sufficient experimental data regarding different physical and chemical processes involved in the aforementioned interaction (1, 2). Hence, online modules that incorporate this effect in general atmospheric circulation models still provide diverging results.We present preliminary results of two field campaigns (2016 and 2017) in Alerce glacier, Cerro Tronador, Argentina, including measurements of surface albedo, PM content, and volcanic ashes identification. The glacier surface shows a wide range of albedo values (from α ≈ 0,8 for clean, fresh snow to α ≈ 0,25 for snow patches with high PM content), which can be explained through season variability, detailed topography, winds, etc. Microscope analysis show that volcanic ashes from an eruption in 2015 severely influence the PM content even two years after the original ashes deposition, probably due to local or regional ashes resuspension in the atmosphere and to persistence of large particles in the surface layers of the glacier. Albedo measurements have been contrasted with SNICAR albedo model (2, 3), which has been modified to take into account the varying cloud cover over the region. Model sensitivity studies have helped to show the effect of key parameters (PM content, snow grain size, direct and diffuse radiation, snow layer thickness) on the observed albedo.