The Spatial Pattern and Mechanisms of Heat-Content Change in the North Atlantic
M. Susan Lozier,1*
Susan Leadbetter,2
Richard G. Williams,2*
Vassil Roussenov,2
Mark S. C. Reed,1
Nathan J. Moore1
The total heat gained by the North Atlantic Ocean over the past 50 years is equivalent to a basinwide increase in the flux of heat across the ocean surface of 0.4 ± 0.05 watts per square meter. We show, however, that this basin has not warmed uniformly: Although the tropics and subtropics have warmed, the subpolar ocean has cooled. These regional differences require local surface heat flux changes (±4 watts per square meter) much larger than the basinwide average. Model investigations show that these regional differences can be explained by large-scale, decadal variability in wind and buoyancy forcing as measured by the North Atlantic Oscillation index. Whether the overall heat gain is due to anthropogenic warming is difficult to confirm because strong natural variability in this ocean basin is potentially masking such input at the present time.
1 Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Science, Duke University, Durham, NC 27708, USA.
2 Department of Earth and Ocean Sciences, Liverpool University, Liverpool L69 3GP, UK.
Present address: Department of Geography, Michigan State University, East Lansing, MI 48823, USA.
* To whom correspondence should be addressed. E-mail: mslozier{at}duke.edu (M.S.L.); ric{at}liverpool.ac.uk (R.G.W.)
