A Comparison of Radiation Budgets in the Fram Strait Summer Marginal Ice Zone

Abstract

Measurements of surface radiation fluxes and meteorological conditions collected in the Fram Strait during the summer 1984 Marginal Ice Zone Experiment (MIZEX) are presented and analyzed. These data were combined with calculations from a radiative transfer model to estimate surface and atmospheric moan radiation budgets on a daily basis and for the early summer season over both sea ice and open water in the marginal ice zone (MIZ). Intensities of solar and infrared fluxes within the atmospheric column, radiative properties of Arctic stratus, and atmospheric cooling rates due to the net loss of radiation were computed by the model. Results show significant differences between the radiation budgets of sea-ice and open-water regimes in the MIZ. Fluxes averaged over the experimental period (16 June to 10 July) indicate that the atmosphere-open water system gained approximately 60 W m?2, while the atmosphere-ice regime was nearly in equilibrium. The open water absorbed twice as much radiation as did the ice, and the mean cooling rate of the over-water atmosphere was approximately 15% larger than that over ice. Observations and model calculations agree that the effect of varying surface albedo on flux intensities is significantly reduced in overcast conditions as compared to under clear skies. Fluxes and atmospheric cooling rates were compared to values computed by other investigators. Few studies of Arctic radiation exist due to the dearth of observations from polar regions, but available values compare well with those derived from MIZEX data. Cooling rates calculated for the Farm Strait MIZ are twice as large as estimates for the central Arctic in summer. Evidence suggests that this cooling may be offset by a relatively strong poleward atmospheric advection of sensible and latent heat from the Norwegian Sea area.