The seasonal cycle in the Atlantic transport to the Barents Sea during the years 1997–2001

Abstract

The seasonal cycle in the Atlantic inflow to the Barents Sea is investigated by using 4-year long records from moored current meters, additional moorings of shorter duration, and hydrographic measurements. A higher transport during winter than summer is most common, but in years where the Barents Sea climate changes from a climatically cold to a climatically warm period (and probably vice versa), it may differ substantially from this. The higher transport during winter is related to barotropic currents that are forced by sea-level changes within the section induced by a shear in the cross-section wind stress, although possibly enhanced by variations in the remotely forced Norwegian Atlantic Current. The seasonal variation within the section is not uniform, and the strongest seasonal signal is found in the middle and northern parts. In the area near 71°30′N the wind (both speed and direction) changes substantially from winter to summer, without changes of the net Ekman transport. The water-level gradient, and the associated barotropic current, therefore has no seasonal variation in this area. However, there is a seasonal signal in the front between the Atlantic and Coastal Waters near the Norwegian Coast. This is due to coastal downwelling during winter that is forced by strong southwesterly winds. The mean transport of Atlantic Water is estimated to 1.7 Sv (1 Sv=10^6 m3 s−1) during winter and 1.3 Sv during summer, but there is a pronounced minimum in Atlantic inflow (or even outflow) in spring due to an annual event of northerly winds.