Heat and Freshwater Fluxes through the Nordic Seas

Abstract

The major exchanges of volume, heat, and freshwater between the Arctic Ocean and the World Ocean occur through the Nordic seas. Here is presented the northernmost estimate for the oceanic transport of these properties that is derived from a set of hydrographic and direct current measurements, using a lowered acoustic Doppler current profiler, between the Greenland and European coasts. By applying box inverse methods to a synoptic section from the summer of 1999, a heat transport of 0.20 ± 0.08 PW toward the Arctic and a freshwater transport of 0.10 ± 0.05 Sv (1 Sv ≡ 106 m3 s?1) away from the Arctic are calculated, with a likely additional freshwater transport on the order of 0.05 Sv near the Greenland coast. Uncertainties associated with how representative the section is of the seasonal mean are included in the error analysis. Large depth-independent components in the currents throughout the section, including the Atlantic inflow, are observed. The increase (decrease) in the heat transport resulting from an increase (decrease) in the transport of this inflow is 0.033 PW Sv?1, and this is the dominant source of uncertainty in the solution. Therefore, determining only depth-dependent transports is unlikely to be sufficient when measuring heat transport in the region. The overturning components of the section heat and freshwater transport are 0.15 ± 0.07 PW and 0.04 ± 0.02 Sv, respectively. From the horizontal transport of layers within the section, a densification of 4.3 ± 2.5 Sv of waters north of the section is predicted, to densities greater than the boundary between inflow and outflow waters between the Atlantic Ocean and the Nordic seas.