PerspectivePALEOCLIMATE

Northern Meltwater Pulses, CO2, and Changes in Atlantic Convection

Science  14 Jan 2011:
Vol. 331, Issue 6014, pp. 156-158
DOI: 10.1126/science.1201144

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Summary

Global climatic and oceanic conditions underwent fundamental transformations after the last ice age ended about 19,000 years ago. In the North Atlantic, for example, the deglaciation was marked by major changes in the Meridional Overturning Circulation (MOC), which carries warm and highly saline surface water north to cooler regions, where it sinks and creates “deep water” that eventually cycles back to the surface. This process plays a substantial role in regulating climate and levels of atmospheric carbon dioxide (CO2), and understanding how it operated in the past is important to understanding how it may influence climate in the future. On page 202 of this issue, Thornalley et al. (1) provide impressive and detailed evidence of how the North Atlantic MOC behaved after the Last Glacial Maximum (LGM), between 19,000 and 10,000 years ago. In particular, they show that the MOC experienced a series of abrupt changes that lasted from decades to centuries, and that some of the water masses involved were far older—and may have stored and released more carbon—than once believed.