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A change in the freshwater balance of the Atlantic Ocean over the past four decades


The oceans are a global reservoir and redistribution agent for several important constituents of the Earth's climate system, among them heat, fresh water and carbon dioxide. Whereas these constituents are actively exchanged with the atmosphere, salt is a component that is approximately conserved in the ocean. The distribution of salinity in the ocean is widely measured, and can therefore be used to diagnose rates of surface freshwater fluxes1, freshwater transport2 and local ocean mixing3—important components of climate dynamics. Here we present a comparison of salinities on a long transect (50° S to 60° N) through the western basins of the Atlantic Ocean between the 1950s and the 1990s. We find systematic freshening at both poleward ends contrasted with large increases of salinity pervading the upper water column at low latitudes. Our results extend a growing body of evidence indicating that shifts in the oceanic distribution of fresh and saline waters are occurring worldwide in ways that suggest links to global warming and possible changes in the hydrologic cycle of the Earth.

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Figure 1: Western Atlantic meridional property sections and surface climatologies.
Figure 2: Western basin meridional property sections versus depth.
Figure 3: Time series of upper ocean salinity anomalies and estimated EP anomalies.

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We are grateful to J. Toole and R. Schmitt for their encouragement and discussions. This work was supported by an NSF grant and the WHOI Ocean and Climate Change Institute. It has also formed part of the data synthesis phase of the WOCE Program, of the ASOF Project of the US NSF and the Framework V Programme of the European Community, and of the NOAA Consortium on the Ocean's Role in Climate of the Scripps Institution of Oceanography and the Lamont-Doherty Earth Observatory.

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Correspondence to Ruth Curry.

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Curry, R., Dickson, B. & Yashayaev, I. A change in the freshwater balance of the Atlantic Ocean over the past four decades. Nature 426, 826–829 (2003).

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