The Jan Mayen Current and the deep waters of the Greenland Basin

Abstract

During Sep 1989 the USNS BARTLETT occupied a dense array of 48 high- quality CTD stations in the Greenland Basin to characterize the Jan Mayen Current (JMC) system as part of the Greenland Current (EGC) waters in the form of a surface Polar Water (PW) tongue, a near-surface (approx 50m) core of modified PW, and an intermediate (approx 100m) core of Atlantic Water displaced approx 75 km northward of the PW core. In contrast, the Greenland Sea Gyre is very weakly stratified aside from a thin surface gradient. Historical data demonstrate the JMC axis to move approx 100 km north and south of its 1989 observed position near 74 deg and show that upper water column temperatures and salinities were significantly lower in 1989 and 1982 than in 1958. The dynamic height pattern (0-1000 dbar) supplemented with Lagrangian ice drift rates reveal the JMC as partly an anticyclonic meander in the EGC; drifters indicate a significant barotropic component. Baroclinic transport estimates yield a 2 Sv initial eastward transport by the JMC. This transport results in an annual freshwater excess of 1.4m over the survey area which equates to roughly 14 of the annually available fresh water in the EGC. Deep water analyses show that isopycnal mixing of Eurasian Basin Deep Water and Greenland Sea Deep Water to yield Norwegian Sea Deep Water occurs within the Greenland Basin. Historical data indicate no appreciable inter-annual fluctuation in deep water properties occurs between 1958 and 1989.