River runoff into the Arctic Ocean: Results from a high-resolution ocean general circulation model and model-data comparisons

A relatively high-resolution ice-ocean General Circulation Model is used to study the distribution of river runoff and Bering Strait Inflow (BSI) to the Arctic Ocean. The model is driven by winds from the 1979–1997 ECMWF Re-Analysis outputs and by relaxation to Levitus temperature and salinity fields at the surface. 9 large rivers and the freshwater content of the BSI are added to the model as passive (dye) tracers and as dynamically active changes to the salinity and temperature fields. The behavior of the model is critiqued in detail. It is found that the relaxation terms defeat attempts to simulate the role of freshwater influx in the density-driven circulation. Thus, interannual changes in the model behavior are interpreted as primarily adjustments to wind changes. A mechanism is displayed through which changes in the winds are linked to basin-scale changes in the surface currents, which redistribute freshwater horizontally. It is shown that the sense of the model changes, if not exactly their amplitude, match observations. Thus, it is argued that much of the recent change in location of density fronts in the Arctic is a barotropic response to changes in the large-scale wind, which are linked to the Arctic currents by systematic changes in the convergence of Ekman transport. The model-data comparisons include some data analysis that is new, and confirms earlier speculation that the observed frontal shifts might be caused by a shift in the location of cross-shelf outflow of buoyant plumes. Proposals are made for improving the model simulations, and for further data analysis, based on analysis of the model output.