Warming of subsurface waters of the subtropical North Atlantic Ocean

Sirpa Hakkinen (NASA Goddard Space Flight Center, United States)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Science Results from Satellite Altimetry: Regional and basin-scale processes and sea level rise

Presentation type: Type Poster

Warming of the North Atlantic Ocean is investigated using SODA ocean reanalysis, altimetry, and observed ocean heat content (OHC) data for 1955-2011. The observed OHC and reanalysis subsurface temperature are dominated by two modes accounting about 50-60% of all variability. The dominant mode is a trend, with a strong positive center over the Gulf Stream-North Atlantic Current (GS-NAC) region, and a weaker negative signal in the subpolar gyre. The second mode of variability is associated with the Atlantic Multi-decadal Variability (AMV), exhibiting a negative center over the GS-NAC, and strong positive anomalies over the subpolar gyre and in the eastern basin extending to the tropics. These modes can be found also at deeper density levels, but their spatial appearance is quite different. By dividing the upper ocean into density layers between the surface and permanent thermocline we find that the subducting subtropical mode waters (σθ = 26.0 to 27.0) have gained the most heat over the 57 years, with an abrupt downturn after 2008. A significant portion of this heat gain has come from northward migration of the density surfaces. The geography of recent deep heat gain is discussed, with emphasis on activity near 30N latitude. We will also discuss the OHC variability due to heaving and water mass change and the correspondence of altimetric SSH and subsurface OHC.
Sirpa Hakkinen
NASA Goddard Space Flight Center
United States