The annual cycle of the surface energy balance of Antarctic blue ice

Abstract

A 15‐month meteorological data set was obtained from an automatic weather station over a blue ice area in Dronning Maud Land, Antarctica. The meteorological measurements are used as input for a surface energy balance model in order to compute the hourly varying surface fluxes and the (sub)surface temperatures to a depth of 10 m. The model reproduces reasonably well the directly measured temperatures in the upper meter of ice. Model results show that the net shortwave radiation is the largest positive term in the annual mean energy budget (42.2 W m−2). Other positive fluxes are the downward sensible heat flux (12.1 W m−2) and the upward subsurface energy flux (0.2 W m−2). Energy is lost by net longwave radiation (−49.1 W m−2) and the upward directed latent heat flux (−5.0 W m−2). We analyze the annual cycle of the surface heat fluxes on the basis of daily, monthly, and seasonally mean values. In addition, we calculate the surface energy budget for two distinctly different weather regimes, which are typical for this region. Finally, we demonstrate that the annual cycle of the turbulent fluxes can be explained in terms of the limiting values of the Bowen ratio.