Freshwater Sources in the Subpolar Gyre from Isotopes of Sea Water
[26-Feb-2014] Benetti, M., Reverdin, G., Pierre, C., and Kathiwala, S.
Presented at the 2014 Ocean Sciences Meeting
The freshwater budget in the subpolar gyre contributes to controlling the meridional overturning circulation variability. The measurement of the isotopic composition of sea water allows to discriminate the origin of the freshwater sources flowing in the supbolar gyre. The transect Iceland-Newfoundland was sampled for isotopic measurements during two periods (1994-1996 and 2010s) in order to assess the recent changes. These two periods are very contrasted in terms of ocean circulation, Labrador Sea water formation. The recent one corresponds to a period of accelerated melting of Greenland ice sheets and of reduced subpolar and Arctic ice cover. Salinity measurements can be used with the isotopic composition to investigate the relative contributions of water from Greenland ice sheet and sea ice melt or Arctic freshwater. These sections also illustrate the seasonal variability of the freshwater input to the Labrador Current carrying freshwater from the higher latitudes. On the Newfoundland shelf, the salinity variability is dominated by the successive formation and melting of sea ice. We also observe significant decadal changes in the relation between salinity and isotopic composition in the interior subpolar gyre.