Sea Ice Simulations Performed with Forcing Fields Specified from a General Circulation Model as a Step Toward Modeling the Climate System in Total

摘要

As a first step in the development of a fully coupled atmospheric ice model including ice dynamics, an Interannual simulation of the Arctic ice cover with GCM simulated surface fluxes and winds is compared to a Control equilibrium simulation using observed atmospheric forcing. For the simulated forcing results form a coarse resolution GCM with specified sea surface temperatures and ice extents, but simulated cloud cover, are used. For the observed data, climatological temperatures and winds (with daily fluctuations added) are employed. Results from a thermodynamic sea ice model subjected to the simulated forcing are also reported for comparison. Main fields as ice thickness, compactness, and drift was well as radiative and wind forcing are analyzed, both in terms of the seasonal cycle and in terms of interannual variability. An analysis of regional mass budget and longitudinal variability of key variables is presented in addition to results covering the full spatial domain. Amplitude and phase of simulated annual cycles of total ice mass and extent are in good agreement with those of the Control cycles; the annual mean thickness being about 2.5m and ice extent in summer being about 50% of the extent in winter. The simulated spatial distribution of ice is however considerably distorted. Large portions of the Arctic Ocean become ice free each summer while marginal seas stay ice covered. This is caused by a wind forcing that is generally simulated too stationary and too strong on account of the GCM's low resolution.