Transport of newly ventilated deep water from the Iceland Basin to the Westeuropean Basin

Abstract

Increased values of trichlorofluoromethane (CFC-11), tritium and stable tritium in the depth range from 2500 to 3500 m at the eastern flank of the Mid-Atlantic Ridge at 48°N (WHP section A2) indicate an influence of newly ventilated water. Water with similar Θ, S and tracer properties is found on the WHP section A1 (55°N) situated north of the Gibbs Fracture Zone in the Iceland Basin. The high tracer concentrations are due to the influence of Iceland Scotland Overflow Water (ISOW). The ISOW-influenced water found in the Iceland Basin partially passes by the Gibbs Fracture Zone (52°N) and flows southward along the topography of the Mid-Atlantic Ridge. A quantitative analysis of the transport from the Iceland Basin to the Westeuropean Basin is carried out based on the assumption that the water with enhanced tracer values is a two-component mixture of recirculating North East Atlantic Deep Water from the eastern part of the Westeuropean Basin and ISOW-influenced water as found on A1 in the Iceland Basin (NEADW IB). The composition of the mixture and the transport time for the NEADW IB are deduced from the temporal evolution of the tracer values. From the distance between the two sections and the area with enhanced tracer values, a transport of NEADW IB from the Iceland Basin to the Westeuropean Basin of 1.63±0.32 Sv 1 1 1Sv=10 6m 3/s. is calculated for the density range 41.37< σ 3<41.475. Transports between 2.4 and 3.5 Sv result if the transport in the former density range is extrapolated to 41.35< σ 3<41.52 (corresponding to σ Θ >27.8) in different ways.