Identifying Sources of Fresh Water in the East Greenland Current

It has been speculated that climate change will increase the fresh water outflow of sea ice meltwater and river runoff from the Arctic Ocean to the deep-water formation regions of the Nordic and Labrador Seas. Fresh water flowing from the Arctic Ocean via the East Greenland Current influences deep water formation in the Nordic Seas as well as the salinity of the surface and deep waters flowing from there. Fresh water flowing from the Arctic Ocean has three sources: Pacific origin water (relatively fresh cf. Atlantic water), river runoff, and sea ice meltwater. Nutrient relationships distinguish Pacific source water from Atlantic source water and total alkalinity distinguishes river runoff from the other sources. We use these tracers, water samples collected in May 2002, to determine the relative amounts of the three sources of fresh water in sections along the East Greenland Current from 81.5 oN to the Irminger Sea south of Denmark Strait. In northern parts of the East Greenland Current near Greenland, Pacific source water dominated in the upper 100 m, comprising up to 70% in some regions, with river runoff contributing more than 7% of the total. River runoff contributed the largest part of the fresh water, up to the equivalent of 7 m of fresh water. It was also located closest to the deep-water formation areas of the Greenland and Iceland Seas, with the front extending over the continental slope. Pacific source water fresh water (taking Pacific source water S = 32.75 cf. Atlantic source water S = 34.85) typically provided about 1/3 of the river runoff contribution and was generally found closer to the coast. Sea ice meltwater was very nearly nonexistent in most parts of all sections, likely at least in part as a result of the samples being collected at the onset of the melt season.