Physical Controls on the Hydrology of Perennially Ice-Covered Lakes, Taylor Valley, Antarctica (1996-2013)

The McMurdo Dry Valleys, Antarctica, are a polar desert populated with numerous closed-watershed, perennially ice-covered lakes primarily fed by glacial melt. Lake levels have varied by as much as 8 m since 1972 and are currently rising after a decade of decreasing. Precipitation falls as snow, so lake hydrology is dominated by energy available to melt glacier ice and to sublimate lake ice. To understand the energy and hydrologic controls on lake level changes and to explain the variability between neighboring lakes, only a few kilometers apart, we model the hydrology for the three largest lakes in Taylor Valley. We apply a physically based hydrological model that includes a surface energy balance model to estimate glacial melt and lake sublimation to constrain mass fluxes to and from the lakes. Results show that lake levels are very sensitive to small changes in glacier albedo, air temperature, and wind speed. We were able to balance the hydrologic budget in two watersheds using meltwater inflow and sublimation loss from the ice-covered lake alone. A third watershed, closest to the coast, required additional inflow beyond model uncertainties. We hypothesize a shallow groundwater system within the active layer, fed by dispersed snow patches, contributes 23% of the inflow to this watershed. The lakes are out of equilibrium with the current climate. If the climate of our study period (1996-2013) persists into the future, the lakes will reach equilibrium starting in 2300, with levels 2-17 m higher, depending on the lake, relative to the 2020 level. Plain Language Summary The McMurdo Dry Valleys (MDV) in Antarctica are a polar desert, characterized by a cold and dry climate. A number of permanently ice-covered lakes occupy the MDV. These lake are fed by melt from nearby glaciers, and many lakes occupy watersheds with no outlet. Lake levels have changed dramatically in the past. Precipitation in the MDV falls as snow, contributing very little water directly to the lakes. Lake hydrology is controlled by the energy available to melt glacier ice and to sublimate ice from the frozen lake surface. To understand the energy and water balance controls on lake level changes, we model the hydrology for the three largest lakes in Taylor Valley. We use a numerical model, based on real world hydrological processes, to estimate the water balance of these lakes. The model results show that lake levels are highly responsive to small changes in glacier albedo, summer air temperature, and wind speed. The lakes in Taylor Valley are out of balance with the current climate. If the climate of our study period (1996-2013) continues into the future the lakes will reach levels 2-17 m higher, depending on the lake, relative to the 2020 level.

Automated summary

The McMurdo Dry Valleys in Antarctica are home to a number of permanently ice-covered lakes that are fed by nearby glaciers. These lakes have experienced significant changes in water levels, and current trends show an increase after a period of decrease. The hydrology of these lakes is influenced by the energy available for melting glacier ice and sublimation of ice from the lake surface. A study was conducted on the three largest lakes in Taylor Valley to understand the factors affecting their water levels. The results showed that small changes in glacier albedo, air temperature, and wind speed can have a significant impact on lake levels. Additionally, a shallow groundwater system was hypothesized to contribute to the water inflow in one of the watersheds. The lakes in this region are currently out of balance with the climate, and if current climate trends continue, the water levels could rise by 2-17 meters by 2300.