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Buoyancy Budget of the North Atlantic

OCCI Project Funded: 2004

Proposed Research

Both temperature and salinity affect the density of seawater, so the separate fluxes of heat and freshwater are important when trying to determine whether upper-ocean waters can become dense enough to sink below the surface. In the North Atlantic, significant sinking occurs because of a loss of buoyancy due to the large heat fluxes from ocean to atmosphere. This sinking of dense waters allows significantly larger flows of warm southern waters into the region than would otherwise occur, with a large impact on northern hemisphere climate.

However, there has been much speculation that the present trend of global warming will cause a decrease in North Atlantic sinking if too much freshwater is added at the surface. Global warming is predicted to accelerate the water cycle, and good evidence that this is occurring can be seen in oceanic salinity trends. In this project we are evaluating the magnitudes of the buoyancy changes due to heat and freshwater fluxes at the surface of the North Atlantic. A new flux climatology produced by colleagues Lisan Yu and Robert Weller is being combined with new rainfall estimates from satellites. Calculation of Evaporation – Precipitation (E-P) for the Atlantic is a step in the process of obtaining the buoyancy fluxes due to heat and freshwater. A map of the annual average E-P for 1988-1999 is shown in the figure below. When our buoyancy flux computations are completed, we will have a better understanding of the potential for decreased sinking rates of high latitude waters.

Originally published: January 1, 2004