The hydrologic and geochemical contributions from snow to streamflow in the McMurdo Dry Valleys of Antarctica

Abstract

The glacial meltwater streams in the McMurdo Dry Valleys (MDVs), Antarctica only flow during the austral summer and contain abundant algal mats which grow at the onset of flow. Their relative abundance in stream channels of this polar desert make the streams biogeochemical hot spots. The MDVs receive minimal precipitation as snow, which is redistributed by wind and deposited in distinct locations, some of which become persistent snow patches each year. Previous studies identified that MDV streamflow comes from a combination of glacier ice and snow, although snow was assumed to contribute little to the overall water budget. This study uses a combination of satellite imagery, terrain analysis, and field measurements to determine where snow patches accumulate and persist across MDV watersheds, and to quantify the potential hydrologic and biogeochemical contributions of snow patches to streams. Watersheds near the coast have the highest snow‐covered area and longest snow persistence. Many of these snow patches accumulate within the stream channels, which results in the potential to contribute to streamflow. During the summer of 2021–2022, stream channel snow patches had the potential to contribute anywhere between <1% and 90% of the total annual discharge in Lake Fryxell Basin streams, and may increase with different hydrometeorological conditions. On average the potential inputs from snow patches to streamflow was between 12% and 25% of the annual discharge during the 2021–2022 season, as determined by snow area and SWE. Snow patches in the majority of the watersheds had higher nitrogen and phosphorous concentrations than stream water, and six streams contained snow with higher N:P ratios than the average N:P in the stream water. This suggests that if such patches melt early in the summer, these nutrient and water inputs could occur at the right time and stoichiometry to be crucial for early season algal mat growth.

Habitat suitability of biocrust communities in a cold desert ecosystem

“…Snow patches provide benefits beyond moisture availability, and therefore serve as preferential microhabitats for biocrusts and other organisms in Antarctica (Kappen, 1985 ; Power, Salvatore, Sokol, et al., 2024 ) and other ecosystems outside of Antarctica (Hao et al., 2020 ; Hui et al., 2022 ; Ladrón de Guevara & Maestre, 2022 ; Yang et al., 2023 ; Zhang et al., 2021 ). For example, snow cover reduces temperature extremes in underlying soil (Schimel et al., 2004 ), supplies nutrient inputs (Wright et al., 2024 ), and likely provides refuge for biocrusts from both eolian scouring during common extreme wind events (e.g., Beane, 2021 ; Nylen et al., 2004 ; Obryk et al., 2020 ) and intense UV‐radiation (e.g., Bernhard & Stierle, 2020 ; Farman et al., 1985 ; McKnight et al., 1999 ).…”