The Norwegian Atlantic Current in the Lofoten basin inferred from hydrological and tracer data (129I) and its interaction with the Norwegian Coastal Current

Abstract

From three hydrological sections taken across the Lofoten Basin in May 2000, we estimated geostrophic transports of 7.2 Sv (Sverdrup = 106 m³ s-¹) for the Norwegian Atlantic Current (NAC) and its division between northern (4.8 Sv) and eastern (2.4 Sv) branches. From 129I/127I concentration ratio measurements and transport estimations, we calculated 129I mass flux across the three sections. It appears that in the Lofoten Basin (a) 129I tracerladen Norwegian Coastal Current (NCC) is transporting northward 55 kg/y of 129I assuming a volume flux of 0.7 Sv, (b) the estimated mass fluxes of 129I by the NAC and theNCC are comparable, (c) the total mass flux of 129I by the NAC and NCC, accounts only for about 1/3 of the 129I annual discharge (350 kg/y) from two reprocessing plants based in France and UK. If these measurements are representative of annual mean, it suggests an important transfer of 129I outside the NAC/NCC system.