CHANGES IN SEA ICE THICKNESS IN THE ARCTIC OCEAN IN WINTER 1970—1990

A. P. Nagurnyi, G. V. Alekseev, and V. G. Korostelev

With a method for determining sea ice thickness based on measuring sea ice surface vibrations, the effect of the reduction in the integral sea ice thickness over the entire Arctic Ocean area in wintertime (February) was determined. The existence of this minimum is attributed to changes in mechanical properties of sea ice with its consolidation as a result of freshening and low air temperature rise. The ice rheology changes sharply in February from viscous-plastic to prevailing elastic forms characteristic of the strongly freshened ice, which results in changes in ice deformation properties and decreases in its concentration, respectively. The fact that the ice thickness minimum is connected with ice concentration decrease can be confirmed by a sharp increase in salinity of the water beneath the ice in February and a coincidence of the ice thickness minimum with the CO2 concentration minimum in the layer above the ice, directly connected with intense CO2 absorption in the open-water areas in wintertime.