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

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

Montreal

Congreso; 27th IUGG General Assembly; 2019

IUGG

The influence of Black Carbon (BC) and other particulate matter (PM) on glaciermelting is of great interest currently, but there are ongoing discussions on itsmagnitude, due to controversy on the appropriate methodology of simulation ofthis effect. Specially, there is a lack of sufficient experimental data regardingdifferent physical and chemical processes involved in the aforementionedinteraction. Hence, online modules that incorporate this effect in generalatmospheric circulation models still provide diverging results.We present preliminary results of two field campaigns (2016 and 2017) in Alerceglacier, Cerro Tronador, Argentina, including measurements of surface albedo,PM content, and volcanic ashes identification. The glacier surface shows a widerange of albedo values (from α ≈ 0,8 for clean, fresh snow to α ≈ 0,25 for snowpatches with high PM content), which can be explained through seasonvariability, detailed topography, winds, etc. Microscope analysis show thatvolcanic ashes from an eruption in 2015 influence the PM content even twoyears after the original ashes deposition, probably due to local or regional ashesresuspension in the atmosphere and to persistance of large particles in thesurface layers of the glacier. Albedo measurements have been contrasted withSNICAR albedo model, which has been modified to take into account thevarying cloud cover over the region. Model sensitivity studies have helped toshow the effect of key parameters (PM content, snow grain size, direct anddiffuse radiation, snow layer thickness) on the observed albedo.