Heat balance of supraglacial lakes in the western Dronning Maud Land

Abstract

Thermodynamics of a seasonal supraglacial lake were examined based on field data from three summers. At maximum, the lake body consisted of an upper layer with thin ice on top, and a lower layer with slush, hard ice and sediment at the bottom. Sublimation from the upper ice surface averaged to 0.7 mm d(-1), and melting in the ice interior averaged to 9.1 mm d(-1) during summer. Albedo was on average 0.6 and light attenuation coefficient was similar to 1 m(-1). Averaged over December and January, and over 3 different years, we found that the net solar heating was 137 W m(-2), while the losses averaged to 62 W m(-2) for the longwave radiation, 16 Wm(-2) for the sensible heat flux, 24 W m(-2) for the latent heat flux and 3 W m(-2) for the bottom flux. The depth scale is determined by the light attenuation distance and thermal diffusion coefficient, and the net liquid water volume ranged from 0.5 to 1.0 m in different years. The potential winter growth is more than summer melting, and thus the lake freezes up completely in winter in the present climate.