MELTWATER PULSES IN THE NORTHERN NORTH-ATLANTIC - RETRODICTION AND FORECAST BY NUMERICAL MODELING

Changes in sea surface salinity, especially by sudden meltwater pulses , are the most effective process to modify the circulation in the Gree nland-Iceland-Norwegian (GIN) seas. With ''Sensitivity and Circulation of the Northern North Atlantic'' (SCINNA), a three-dimensional ocean general circulation model, several experiments addressing the possible effects of meltwater inputs of different intensities were carried out . The experiments used (a) the last glacial maximum (LGM) reconstructi on based on oxygen isotopes data from sediment cores and (b) the moder n conditions of the GIN seas for their initial states. Meltwater input s from Europe as recorded during the last deglaciation succeeding the LGM change the circulation pattern drastically. These pulses can push the high-salinity inflow from the northeast Atlantic away from Europe over to the southern coast of Iceland, thus allowing the low-salinity meltwater to spread all over the GIN seas. As a result, the deepwater formation in this region can be turned off and the circulation system shifts from the normal cyclonal-antiestuarine into an anticyclonal-est uarine mode. On the contrary, meltwater pulses originating from Greenl and due to global warming mainly intensify the East Greenland Current without altering the overall circulation and temperature/salinity patt erns significantly because they chiefly enhance the salinity minimum o ff the Greenland coast.