Journal Article

An Examination of Water‐Related Melt Processes in Arctic Snow on Tundra and Sea‐Ice

Pinzner, Anika, Mahoney, Andrew R., Delamere, Jennifer S., Sturm, Matthew

2024

Overview

From April through June in 2019 and 2022, we monitored snow melt at three sites near Utqiaġvik, Alaska. Along 200‐m lines we measured snow depth, density, stratigraphy, snow‐covered area, and spectral albedo. Site 1 (ARM) was sloped tundra drained by water tracks. Site 2 (BEO) was flat polygonal tundra. Site 3 (ICE) was on undeformed landfast sea ice. All three sites were within a 6 km radius. Despite similar pre‐melt snow distributions and weather, the melt progression differed markedly between sites. In 2019, by mid‐melt, there was 40% less snow‐covered area at ARM versus ICE, and 34% less snow‐covered area at ARM versus BEO. The 2022 melt started 2 weeks later than in 2019 and was rapid, so smaller differences in snow‐covered areas developed. In both years meltout dates varied by up to 25 days between sites, and more than 20 days within sites, with melt rates at locations only meters apart differing by up to a factor of seven. This melt diachroneity led to highly heterogeneous meltout patterns at all three sites. Our measurements and observations indicate that, in addition to reductions in snow reflective properties and wind‐driven heat advection, the fate of meltwater plays a key role in producing melt diachroneity. We identify seven snow‐water mechanisms that can enhance or inhibit melt rates, all largely controlled by the local topography and the nature of the substrate. These mechanisms are important because the most rapid changes in albedo coincide with the peak of water‐snow melt interactions. Plain Language Summary We observed in detail snow melt on two different tundra locations and one sea ice location in Arctic Alaska in the spring of 2019 and 2022. During the melt season, these landscapes go from reflecting over 80% of the sunlight to less than 20%, a transition that impacts the global climate. Our observations showed that while warming weather is what ultimately controls snowmelt, the re‐freezing and flow of meltwater within the snowpack, plays a crucial role in controlling local melt rates of individual snow patches. These water‐related melt mechanisms, together with wind‐driven laterally advected air and the reflective properties of the snow, largely control the date individual snow patches disappear, and therefore, when the most rapid changes in solar reflectivity will take place. Key Points Water‐related processes in snow can promote or impede lateral advection of heat and mass, enhancing or inhibiting melt in the Arctic The composition and topography of the substrate govern the nature of the water‐snow interactions and thereby influence meltout patterns The most rapid and largest changes in surface albedo happen just prior to the snow‐free date when water‐snow melt mechanisms reach a peak

• Publisher: John Wiley & Sons, Inc,American Geophysical Union (AGU),Wiley
• Subject: Advection / Alaska / Albedo / Albedo (solar) / Arctic region / Arctic sea ice / Arctic snow / Cold / Freezing / Global climate / Heat / Heat transport / Ice / Measuring instruments / melt / Meltwater / Radiation / Reflectance / Sea ice / Snow / Snow accumulation / Snow depth / Snowmelt / Snowpack / Spectral albedo / Stratigraphy / Substrates / Sunlight / Taiga & tundra / Topography / Tundra / Water / Weather / Wind