Ventilation of the deep Greenland and Norwegian seas: evidence from krypton-85, tritium, carbon-14 and argon-39

Abstract

On leg 5 of the TTO expedition, the distributions of 85Kr, tritium, 14C, 39Ar, temperature, salinity, oxygen, carbon dioxide and nutrients were measured in the Greenland and Norwegian seas. These observations support previous observations that Greenland Sea Deep Water is formed by a deep convective process within the Greenland gyre. They also support Aagaard et al.'s (1985, Journal of Geophysical Research, 90, 4833–4846) new hypothesis that Norwegian Sea Deep Water forms from a mixture of Greenland Sea Deep Water and Eurasian Basin Deep Water. Volume transports estimated from the distributions of 85Kr, tritium, 14C and 39Ar range from 0.53 to 0.74 Sv for exchange between the surface and deep Greenland Sea and from 0.9 to 1.47 Sv for exchange between the deep Greenland and deep Norwegian seas. The residence time of water in the deep Greenland Sea with respect to exchange with surface water ranges from 24 to 34 years compared to 26–31 years reported by Peterson and Rooth (1976, Deep-Sea Research, 23, 273–283) and 35–42 years reported by Bullister and Weisss (1983, Science, 221, 265–268). The residence time of water in the deep Norwegian Sea with respect to exchange with the deep Greenland Sea ranges from 19 to 30 years compared to 97–107 years reported by Peterson and Rooth (1976) and 10–28 years reported by Bullister and Weiss (1983). The oxygen consumption rate was estimated to be at most 1.04 μM kg −1 y −1 for the deep Greenland Sea and to be between 0.47 and 0.79 μM kg −1 y −1 for the deep Norwegian Sea.