Abstract
The supply of freshwater to fjord systems in Greenland is increasing as a result of climate change-induced acceleration in ice sheet melt. However, insight into the marine implications of the melt water is impaired by lack of observations demonstrating the fate of freshwater along the Greenland coast and providing evaluation basis for ocean models. Here we present 13 years of summer measurements along a 120 km transect in Young Sound, Northeast Greenland and show that sub-surface coastal waters are decreasing in salinity with an average rate of 0.12 ± 0.05 per year. This is the first observational evidence of a significant freshening on decadal scale of the waters surrounding the ice sheet and comes from a region where ice sheet melt has been less significant. It implies that ice sheet dynamics in Northeast Greenland could be of key importance as freshwater is retained in southward flowing coastal currents thus reducing density of water masses influencing major deep water formation areas in the Subarctic Atlantic Ocean. Ultimately, the observed freshening could have implications for the Atlantic meridional overturning circulation.
Highlights
The Arctic Ocean has increased its freshwater content significantly the past decade[1] and is freshening at a rate of approximately 600 km[3] per year[2]
The fjord system is divided into an inner shallow basin (Tyroler Fjord, to the west) and an outer deep basin (Young Sound) separated from the shelf by a shallow (45 m depth) sill (Fig. 1b)
To visualize the inter-annual change we averaged all profiles for fjord and coastal water for each year to produce a contour plot of changes in average salinity profiles from 2003 to 2015
Summary
The Arctic Ocean has increased its freshwater content significantly the past decade[1] and is freshening at a rate of approximately 600 km[3] per year[2]. At 30–50 m in the coastal water, the significant linear decrease in salinity observed in the time series was 0.12 ± 0.05 per year This is a significant freshening, of a magnitude similar to that found in the Beaufort Gyre[23] To better assess the trend in freshening we calculated the integrated freshwater content (FWC) of the surface waters (0–50) in the fjord. As there is no significant change in FWC_S over the time series this calculation indicates that the freshening of the incoming water is driving the observed trends in FWC (Fig 3d) This supports the findings of no significant change in local river discharge, snow depth and degree days. Year Degree days Discharge 106 m3 Discharge % Snow depth m Date of CTD Ice free days Wind stress m s−1
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