Changes in freshwater content in the North Atlantic Ocean 1955–2006

Freshwater content changes (FW) for the North Atlantic Ocean (NA) are calculated from in situ salinity profiles for the period 1955–2006 from the surface to 2,000 meters. Heat content (HC) is also calculated from in situ temperature profiles for comparison. A decrease in FW between 1955 and 2006 of ~30,000 km3 is found for the NA, despite an increase in FW of ~16,000 km3 in the subpolar North Atlantic (SNA) and Nordic Seas between the late 1960s and the early 1990s. Over the last two decades there is a pattern of decreasing FW in the upper 400 meters and increasing FW below 1,300 meters for the NA. FW and HC are strongly negatively correlated for both the SNA (r = −0.93) and the NA (r = −0.79). Net precipitation, from NCEP/NCAR, is found to have a strong influence on FW changes in the SNA but this relation is weaker elsewhere.