Water mass transformation in the Barents Sea - Application of the Hamburg Shelf Ocean Model (HamSOM)

Abstract

The bottom water formation in the Barents Sea plays an important role in the maintenance of the Arctic halocline. Deep water is partly formed by haline convection caused by brine release during ice growth. To investigate this process, the HAMburg Shelf Ocean Model (HAMSOM) was coupled to a dynamic and thermodynamic ice model and applied to the Barents and Kara Seas. The coupled model is initialised with climatological temperature and salinity data and forced with realistic wind stresses and air temperatures. The results of simulated winter scenarios show that the role of the thermo-haline convection is two fold. First, convection in the upper layers erodes the locally pronounced haline stratification while ice is formed in major portions of the area. Second, local and small-scale openings in the ice cover (polynyas) provide the necessary brine release for dense bottom waters. The polynyas open frequently near Franz Josef Land and Novaya Zemlya due to off-shore winds. Tidal currents, however, may also play a role in opening the closed ice sheet. Tracer studies reveal that most of the bottom water leaves the Barents Sea through the Svyataya Anna Trough towards the Arctic Ocean. Outflow rates of the deep water as well as the temporal and spatial evolution of stratification and ice cover are presented.