Mechanisms of Heat Content and Thermocline Change in the Subtropical and Subpolar North Atlantic

  • Richard G. Williams, Vassil Roussenov, M. Susan Lozier, Doug Smith
  • Journal of Climate, December 2015, American Meteorological Society
  • DOI: 10.1175/jcli-d-15-0097.1

How does ocean heat content change over the North Atlantic Ocean?

What is it about?

There has been a pronounced warming of the North Atlantic Ocean over the last 60 years, which are associated with changes in both sea surface temperature and the thickness of the thermocline (the warm layer of the upper ocean). In this study, we explore whether these decadal changes in ocean heat storage and thermocline thickness are controlled by changes in how the ocean redistributes heat, rather than by the direct effect of air–sea heat fluxes. We reconstruct the changes in ocean heat content from 1962to 2011. We find that the subtropical changes in heat content are mainly controlled by stronger Trade winds giving a greater northward transport of heat. The subpolar changes in heat content are mainly controlled by the heat redistribution involving the ocean overturning. Hence, the heat content anomalies are formed in a different manner over the North Atlantic, the anomalies at low latitudes are controlled mainly by the wind, while those at mid and high latitudes are affected mainly by the ocean overturning.

Why is it important?

It is important to understand the reason for different ocean warming patterns. While the global ocean is warming from the increased radiative forcing from the increase in atmospheric CO2, there are regional patterns of warming that can reverse in sign and are a much larger magnitude than the global-mean response. The North Atlantic Ocean is a particular region of rapid heat gain, but the response is not uniform with latitude. Instead we find that there are different regional warming responses, connected to the direct effect of the winds in redistributing heat and the effect of changes in the ocean overturning.


Professor Richard G Williams
University of Liverpool Department of Earth Ocean and Ecological Sciences

This collaboration involved scientists based in Liverpool University, the Hadley Centre in the UK Met Office and Duke University, North Carolina, USA.

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The following have contributed to this page: Professor Richard G Williams