The Transformations of Atlantic Water in the Arctic Ocean and Their Significance for the Freshwater Budget

Abstract

The Arctic Ocean comprises the inner part of the Arctic Mediterranean Sea, which also includes the Nordic Seas. The Arctic Ocean constitutes the northernmost extension of the North Atlantic, and --- through the shallow and narrow Bering Strait --- it is connected to the North Pacific. The Arctic Ocean thus forms a direct link between the two ``opposite poles'' of the world ocean --- the main pool of low salinity water (Pacific) and the main pool of high salinity water (Atlantic). The transport through the Bering Strait is predominantly northward and brings Pacific water into the Arctic Ocean and ultimately to the North Atlantic. Because of its lower salinity and density the Bering Strait inflow is confined to the upper 150-200m and is mainly restricted to the North American side of the Arctic Ocean. Most of the Pacific water enters the North Atlantic through the Canadian Arctic Archipelago, where it constitutes the bulk of the outflow. Analysis of nutrient data shows that some Pacific water is also present in Fram Strait; in the low salinity outflow of the East Greenland Current [1] as well as in the deep waters [2]. Here, however, its contribution is small and, to the first order, the Arctic Ocean can be viewed as the inner part of an extensive North Atlantic bay which --- because of the strong river run-off --- acts as a large estuary of truly global scale. The great rivers enter the Arctic Ocean at the wide shelf seas which comprise more than 1/3 of the 9 1012m2 large surface area of the Arctic Ocean.