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

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.

南极洲麦克默多干谷（MDV）的冰川融水溪流仅在南半球夏季流动，其中含有大量在水流开始时生长的藻垫。它们在这片极地沙漠的河道中相对丰富，使这些溪流成为生物地球化学热点。麦克默多干谷的降雪量极少，雪被风重新分配并沉积在不同的位置，其中一些位置每年都会形成持久的积雪区。先前的研究确定，麦克默多干谷的溪流流量来自冰川冰和雪的共同作用，尽管雪被认为对总体水量平衡贡献很小。本研究结合卫星图像、地形分析和实地测量，以确定麦克默多干谷流域内积雪区在何处积累并持续存在，并量化积雪区对溪流可能产生的水文和生物地球化学贡献。沿海附近的流域积雪覆盖面积最大，积雪持续时间最长。许多积雪区在河道内积累，这有可能为溪流流量做出贡献。在2021 - 2022年夏季，弗莱克塞尔湖盆地溪流中，河道积雪区对年总径流量的潜在贡献在<1%到90%之间，并且可能会随着不同的水文气象条件而增加。根据积雪面积和雪水当量确定，在2021 - 2022年季节，积雪区对溪流流量的潜在输入平均占年径流量的12%到25%。大多数流域的积雪区氮和磷的浓度高于溪水，并且六条溪流中积雪的氮磷比高于溪水中的平均氮磷比。这表明，如果这些积雪区在夏季早期融化，这些营养物质和水的输入可能会在合适的时间和化学计量比下发生，对早期藻垫生长至关重要。