Formation of dense water dome over the Central Bank under conditions of reduced ice cover in the Barents Sea

Abstract

In this study on the basis of various data sets we traced formation of a ‘dome’- shaped density structure over the Central Bank - an important morphological element of the Barents Sea bottom topography. The major conclusion, which follows from the performed analysis, is that under changed conditions at the sea surface, transformation of thermohaline structure during the cold season principally differs from that under the mean climate conditions in the 20th century. Transition from the stratified vertical structure (in summer) to the homogeneous one (in winter) is governed by thermal convection. Additional input of warm and salty water with inflowing Atlantic origin water is crucial to allow vertical mixing to reach the seabed before the temperature drops to the freezing point. Cascading of dense water from the bank commences as soon as the convection goes down to the level of seabed. The influence of cascading on the Barents Sea hydrographic structure extends several hundreds of kilometers off the bank. In the absence of advective influx of salt and warm water vertical convection can also reach the seabed. However, under this condition formation of sea ice and haline convection is required. In this case water temperature in the homogeneous water column over the bank is close to the freezing point. Obtained results suggest that in the warmer climate the role of sea ice in winter transformation of thermohaline conditions over the bank is opposite to what it was in the 20th century: imported sea ice blocks convection, thus making the water in the dense ‘dome’ warmer than it typically was in colder climate.