Temporal Variability of the Energy Balance of Thick Arctic Pack Ice

Abstract

The temporal variability of the six terms of the energy balance equation for a slab of ice 3 m thick is calculated based on 45 yr of surface meteorological observations from the drifting ice stations of the former Soviet Union. The equation includes net radiation, sensible heat flux, latent heat flux, bottom heat flux, heat storage, and energy available for melting. The energy balance is determined with a time-dependent 10-layer thermodynamic model of the ice slab that determines the surface temperature and the ice temperature profile using 3-h forcing values. The observations used for the forcing values are the 2-m air temperature, relative humidity and wind speed, the cloud fraction, the snow depth and density, and the albedo of the nonponded ice. The downwelling radiative fluxes are estimated with parameterizations based on the cloud cover, the air temperature and humidity, and the solar angle. The linear relationship between the air temperature and both the cloud fraction and the wind speed is also determined for each month of the year. The annual cycles of the mean values of the terms of the energy balance equation are all nearly equal to those calculated by others based on mean climatological forcing values. The short-term variability, from 3 h to 16 days, of both the forcings and the fluxes, is investigated on a seasonal basis with the discreet wavelet transform. Significant diurnal cycles are found in the net radiation, storage, and melt, but not in the sensible or latent heat fluxes. The total annual ice-melt averages 0.67 m, ranges between 0.29 and 1.09 m, and exhibits large variations from year to year. It is closely correlated with the albedo and, to a lesser extent, with the latitude and the length of the melt season.