Constraints on Estimating Mass, Heat and Freshwater Transports in the Arctic Ocean: An Exercise

Abstract

The ASOF programme, with its study of the transports between the Arctic Ocean and the North Atlantic via the subarctic seas – the Nordic Seas, Baffin Bay and the Labrador Sea –, also provides an opportunity to examine the mass (volume), freshwater and heat budgets of the Arctic Ocean. The exchanges between the two passages between the Arctic Ocean and the Nordic Seas, Fram Strait and the Barents Sea opening between Norway and Bear Island, have been measured continuously since 1997, first in the VEINS programme (Variability of Exchanges in the Northern Seas) and then in ASOF and the observations are presently continued within the DAMOCLES (Developing Arctic Modelling and Observing Capabilities for Longterm Environmental Studies) programme. The transports through two of the three main channels in the Canadian Arctic Archipelago, the Lancaster Sound and the Jones Sound, have been directly measured for a couple of years now (Prinsenberg and Hamilton 2005), and the instruments from the first year-long measurements in Nares Strait have been brought in. The fluxes through Bering Strait have also been studied intensely the last 10–15 years (e.g. Woodgate and Aagaard 2005). The work within ASOF has shown that the transports through Fram Strait and through the Canadian Arctic Archipelago are those most difficult to determine. The Archipelago because of the severe climate, the remoteness of the area and the nearby location of the magnetic North Pole, Fram Strait because of its depth, the transports in both directions, and the presence of baroclinic and barotropic eddies leading to high spatial and temporal variability. The estimates of the mean transport through Bering Strait obtained since the mid-1980s have ranged around 0.8 Sv (1 × 10 m s), but large seasonal variations have been reported, 1.2 Sv in summer and 0.4 Sv in winter (Coachman and Aagaard 1988; Woodgate and Aagaard 2005). The mean transport of Atlantic water to the Arctic Ocean through the Barents Sea opening has been estimated to 1.5 Sv from