Meltwater pulses in the northern North Atlantic: retrodiction and forecast by numerical modelling

Changes in sea surface salinity, especially by sudden meltwater pulses, are the most effective process to modify the circulation in the Greenland–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) reconstruction based on oxygen isotopes data from sediment cores and (b) the modern conditions of the GIN seas for their initial states. Meltwater inputs 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-estuarine mode. On the contrary, meltwater pulses originating from Greenland due to global warming mainly intensify the East Greenland Current without altering the overall circulation and temperature/salinity patterns significantly because they chiefly enhance the salinity minimum off the Greenland coast.