Upper ocean T-S variations in the Greenland Sea and their association to climatic conditions

Abstract

Hydrography from the Nordic seas from 1951 to 2003 was analyzed focusing on the upper ocean conditions during known periods of deep mixing. The analysis used data from NOAA National Oceanographic Data Center and from International Council for the Exploration of the Sea Oceanographic Database. Because of the sparseness of the wintertime data, only summertime data are analyzed, primarily at 200 m, which retains memory of previous winter's effects below summer mixed layer. It is found that the salinity variability in the central Greenland Gyre follows closely the sea level pressure (SLP) fluctuations found along the Greenland Coast, e.g., at Angmagssalik. Corresponding large-scale SLP field resembles North Atlantic Oscillation (NAO) in its negative index phase. The dissimilarity between the central gyre salinity fluctuations and the incoming Atlantic water salinity fluctuations suggests that mixing with other water masses (Arctic origin waters and recirculating Atlantic waters) present in the central gyre is important in modifying the incoming Atlantic water salinity at interannual timescales. However, the largest freshwater addition to the Atlantic waters takes place in the Norwegian Sea or even further upstream in the North Atlantic. The variability of this freshwater intake resembles the NAO index on multidecadal timescales.