The production of North Atlantic Deep Water: Sources, rates, and pathways

Updating an earlier account by Dickson et al., (1990), this paper reviews the initial development phase of North Atlantic Deep Water (NADW) production from the points where the dense inflows from Nordic seas cross the Greenland-Scotland Ridge to the point off south Greenland where the buildup of new production appears almost complete. In particular, three long-term current meter arrays totaling 91 instruments and set at ∼160 km intervals south from the Denmark Strait sill are used to validate earlier short-term arrays by others and, in combination with these earlier arrays, to describe the downstream evolution of mean speed, depth and entrainment, the variability of the overflow current in space and time, and the likely contribution of the other three main constituents of NADW production at densities greater than σ_θ = 27.8. From the points of overflow (5.6 Sv) the transport within this range increases by entrainment and confluence with other contributory streams to around 13.3 Sv at Cape Farewell. While recirculating elements prevent us from determining the net southgoing transport, a NADW transport of this order appears consistent with recent estimates of net abyssal flow passing south through the North and South Atlantic.