Summer valley-floor snowfall in Taylor Valley, Antarctica from 1995–2017

Abstract. In polar, coastal areas like Taylor Valley, snowfall is predicted to increase under warming conditions as reduced sea ice increases open water area and evaporation potential, thereby creating conditions that would facilitate precipitation. Taylor Valley is a mosaic of glaciers, valley-bottom ice-covered lakes, ephemeral streams and dark, rocky soils. Ecosystems are both light- and nutrient-limited and rely on seasonally available liquid water. Although Taylor Valley receives minimal snowfall annually, light snow cover during summer months reduces radiation for primary productivity and slows melting by increasing the local albedo. Snowfall has been measured at four sites in Taylor Valley since 1995. Daily photographs at the Lake Hoare station in the central portion of the valley record snow cover since 2007 and augment the automated precipitation measurements. Here, we focus on valley-floor snowfall due to its effect on ecosystems in the valley-bottom lakes and streams. Precipitation increased by 3 mm water equivalent (w.e.) a⁻¹ from 1995 to 2009, then decreased by 1 mm w.e. a⁻¹ through 2017. Since 2009, annual snowfall in Taylor Valley ranges from 1 to 30 mm w.e. High snowfall during the Spring near the coast is indicative of high summer snowfall at the more inland Lake Bonney station (r² = 0.66; p < 0.05). In contrast, the average fraction of days with snow on the ground tripled at Lake Hoare after 2011, primarily during Spring and Fall. Fall snow persistence at Lake Hoare has been increasing by ~ 1 day per year since the start of the record in 2007, although Spring snow cover exhibits no trend. In agreement with previous studies, regression analysis revealed no correlation of snow cover or snowfall with sea ice extent or mean temperatures. Strong seasonality and interannual variability underscores the complexity of precipitation and snow persistence controls in Taylor Valley. In regions where snow cover contributes more to the radiation budget than the hydrologic budget, photographs are the most reliable method for monitoring precipitation. The results of this study highlight the importance of continued monitoring of precipitation throughout Taylor Valley. The establishment of coastal and inland snow cover monitoring stations would augment point observations of snow cover and add spatial complexity to our present understanding of the expected hydrologic and ecosystem response to climate change in Taylor Valley.