Climate Science

Change in the Water

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Science  31 Aug 2007:
Vol. 317, Issue 5842, pp. 1149
DOI: 10.1126/science.317.5842.1149c

The rapid, millennial-scale cooling episodes (called Dansgaard-Oeschger events) that occurred repeatedly throughout the last glacial period are normally associated with climate change in the North Atlantic region. However, research over the past decade has also implicated their expression in the Pacific and Indian Oceans, leading to two competing explanations for the connection: atmospheric or oceanic transmission of the signal. Schmittner et al. used an ocean-atmosphere climate model to show that changes in buoyancy-forced ocean circulation can cause large variations in subsurface oxygen levels by changing oxygen demand. This result suggests that the climate signal of Dansgaard-Oeschger events originating in the North Atlantic was transmitted by oceanic, rather than atmospheric, teleconnections; further, it is consistent with the association of Dansgaard-Oeschger events with changes in the Meridional Overturning Circulation of the Atlantic Ocean. The influence of changes in wind stress and North Pacific Intermediate Water formation was also notable, though somewhat weaker than that of thermohaline circulation. Thus, ocean ecosystems and biogeochemical cycles appear to respond sensitively to ocean circulation changes. — HJS

Paleoceanography 22, 10.1029/2006PA001384 (2007).

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