Snow Melt Trajectories and the Evolution of Surface Albedo at Utqiagvik, Alaska

Description

Scientists seek to better quantify high-latitude radiative processes through the study of the seasonal evolution of the surfaces (ground and ice) and the ARM North Slope of Alaska (NSA) atmospheric observatory is well-suited for such studies. The evolution of albedo of this coastal region, from pre-melt through the complete melt of the snow cover, is being examined during the ARM-sponsored Snow Albedo Evolution Campaign (SALVO). SALVO focuses on the terrestrial-sea ice linkage. In the springs of 2019 through 2021, we are measuring the spectral albedo, snow depth, and snow characteristics on a daily basis along 200-m transects near Utqiagvik, Alaska. Three contrasting sites were observed during the spring melt (considered April - June): one transect was located at the ARM NSA Central Facility on the northern coast, one transect was on the tundra 3-km inland, and one transect was on the sea ice of Elson Lagoon.  While the snow cover of all three sites was similar in depth and albedo characteristics at the start of the melt period, each site evolved differently as the snow melted and the substrate (ice vs. tundra) and local micro-topography began to affect the surface conditions. Snow-grain coarsening, which can lower snow albedo considerably, was particularly different at the three sites, with local sub-snow drainage conditions an important secondary control on the site-averaged albedo. On the tundra, which has an albedo less than 0.2 when bare of snow, the results followed expectations with areas of exposed tundra eventually accelerating the rate of snow melt on adjacent snow-covered patches; however, on the sea ice, a number of unusual and unexpected processes occurred (e.g., separation of ice along dirt septum) that delayed melt and combined to keep the albedo high far longer than we had anticipated. This outcome, while preliminary, seems a useful indicator that albedo trajectories under a warming climate may be more complex than we currently think, and we can expect considerable differences in these trajectories on sea ice vs. land.