The summertime thermohaline evolution of an Arctic lead: Heat budget to the surface layer

Temperature and salinity profiles were measured in an Arctic lead for a two-month period during the summer of 1998 as part of the SHEBA field experiment. The measurements were made with a CTD deployed from a small boat. When the melt season began, a fresh layer with very low salinity (2 psu) and temperature well above freezing (2 C) formed on the surface of the lead. This layer persisted and grew to a depth of over 1 m until it was mixed into the upper ocean by the action of a passing storm in late July. The focus of this paper is on the heat budget of the fresh layer. Estimates were made of the total heat flux through the surface, which is composed of short- and long-wave radiation and sensible and latent heat fluxes. The shortwave flux through the base of the fresh layer was also estimated. Because of the exceptionally strong stratification, turbulent transfer at the base was neglected. The heat from the fresh layer used to melt ice was estimated as a residual.