Mean full-depth summer circulation and transports at the northern periphery of the Atlantic Ocean in the 2000s

Abstract

A mean state of the full-depth summer circulation in the Atlantic Ocean in the region in between Cape Farewell (Greenland), Scotland and the Greenland-Scotland Ridge (GSR) is assessed by combining 2002-2008 yearly hydrographic measurements at 59.5N, mean dynamic topography, satellite altimetry data and available estimates of the Atlantic-Nordic Seas exchange. The mean absolute transports by the upper-ocean, mid-depth and deep currents and the Meridional Overturning Circulation (MOC σ= 16.5±2.2Sv, at σ0 = 27.55) at 59.5°N are quantified in the density space. Inter-basin and diapycnal volume fluxes in between the 59.5°N section and the GSR are then estimated from a box model. The dominant components of the meridional exchange across 59.5°N are the North Atlantic Current (NAC, 15.5 ± 0.8Sv, σ0 < 27.55) east of the Reykjanes Ridge, the northward Irminger Current (IC, 12.0±3.0Sv) and southward Western Boundary Current (WBC, 32.1±5.9Sv) in the Irminger Sea and the deep water export from the northern Iceland Basin (3.7±0.8Sv, σ0 > 27.80). About 60% (12.7±1.4Sv) of waters carried in the MOC upper limb σ(0 < 27.55) by the NAC/IC across 59.5°N (21.1±1.0Sv) recirculates westward south of the GSR and feeds the WBC. 80% (10.2±1.7Sv) of the recirculating NAC/IC-derived upper-ocean waters gains density of σ0 > 27.55 and contributes to the MOCσ lower limb. Accordingly, the contribution of light-to-dense water conversion south of the GSR (∼10 Sv) to the MOCσ lower limb at 59.5°N is one and a half times larger than the contribution of dense water production in the Nordic Seas (∼6 Sv). Copyright 2012 by the American Geophysical Union.