Ocean Science

A Drop in the Ocean

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Science  28 Sep 2012:
Vol. 337, Issue 6102, pp. 1585
DOI: 10.1126/science.337.6102.1585-a

Observations from over the past 130 years show that global mean sea level has been rising by an average of about 1.7 mm/year and by about 3 mm/year over the past 20 years. Projections of future global mean sea level essentially all agree that this rise will continue as climate warms, mostly because of increasing ocean volume caused by the melting of glaciers and ice sheets, as well as the volume increase due to the thermal expansion of the global ocean. Superimposed on these trends are other variations, both positive and negative, caused by large-scale ocean-atmosphere processes such as the El Niño—Southern Oscillation. Boening et al. report that global mean sea level dropped by 5 mm during 2010 and 2011 because of an increase in terrestrial water storage caused by changes in global precipitation patterns accompanying the transition from El Niño conditions in 2009–2010 to a strong La Niña in 2010–2011. The increase in terrestrial water storage occurred mostly in Australia, northern South America, and Southeast Asia. This drop will probably be temporary, though, as runoff to the ocean moves that water back from where it came.

Geophys. Res. Lett. 10.1029/2012GL053055 (2012).

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