A simple time-dependent coupled ice-ocean model with application to the Greenland-Norwegian Sea

Abstract

A time-dependent single active layer reduced gravity thermodynamic upper ocean model is coupled to a thermodynamic dynamic sea-ice model and is used to investigate sea-ice cover in the Greenland-Norwegian Sea on the seasonal to interannual time scales. The model is driven by prescribed wind stress, air temperature and salinity and temperature distributions across the open zonal boundaries located at 60°N and 80°N. Two spin-up experiments which employ steady forcing fields, but differ in the magnitude of the shear stress between air and ice, demonstrate that regions of high salinity can become convectively unstable leading to vertical mixing and hence reduced ice cover. In particular, increasing the magnitude of the air-ice shear stress leads to an enhanced stress acting on the surface of the ocean, and this in turn leads to a northwards extension of the region which is preconditioned for convective overturning. When the model is forced by time-dependent air temperatures, the predicted seasonal behaviour of the 10%, 50% and 90% ice concentration contours agrees well with observations. The increased sea-ice cover associated with the Great Salinity Anomaly during the late 1960s is also successfully simulated by the model.