A regional coupled ice-ocean model for the Kara Sea, forced with boundaryconditions from a large-scale North Atlantic/Arctic Ocean Model, is used to studydispersion and export of freshwater from Ob and Yenisei rivers toward the Arctic Oceanand the Laptev Sea, for the period 19962001. The years 1998 and 1999 werecharacterized by a strong positive sea level pressure (SLP) anomaly in the Siberian part ofthe Arctic Ocean. Owing to prevailing northeasterly winds, the SLP anomaly caused ablocking situation, which suppressed the otherwise eastward freshwater export to theArctic Ocean and Laptev Sea. This reversal of the prevailing circulation scheme led to adramatic freshening of the Kara Sea through accumulation of low-saline river water in thecentral and western parts. Additionally, the Kara Strait inflow from the Barents Sea,which presents the main source for saline Atlantic derived water, was reduced and partlyeven reversed. The suppressed freshwater export during winter 1998/1999 recovered inthe following winter 1999/2000 when a significant pulse of low-saline surface waterleft toward the Laptev Sea. The variability of the river discharge plays a minor role forthe investigated period because the interannual variability of runoff rates is generallytoo low to explain the observed hydrographic changes. The results underline theimportance of local shelf sea processes for the variability of the freshwater export from theArctic Shelves to the central Arctic Ocean.