Public Release: 

Past spikes in carbon dioxide levels accompanied by high ocean circulation

American Association for the Advancement of Science

This news release is available in Japanese.

Two abrupt rises in carbon dioxide and Northern Hemispheric warming occurred during the last glacial ice melt, and new evidence confirms that these spikes were accompanied by deep ocean "flushing" events. Atlantic Meridional Overturning Circulation (AMOC) circulates surface and deep water between the Northern and Southern hemispheres, which plays a critical role in heat transport, which in turn affects climate. To analyze Atlantic circulation over the past 20,000 years, Tianyu Chen et al. collected numerous samples of differently aged deep sea coral, which serve as proxies for carbon storage in the ocean over time, in the Equatorial Atlantic and Drake Passage. The researchers used radiocarbon measurements to trace the isolation of deep ocean waters over the millennia. They found that the dramatic increases of atmospheric carbon dioxide that occurred at the ends of Heinrich Stadial 1 and the Younger Dryas, two major climate events, occurred at the same time that deep ocean radiocarbon inventories decreased, suggesting that carbon dioxide was released into the atmosphere when excess carbon in the deep ocean was being flushed out due to an increase in the AMOC. Furthermore, the authors note a relatively rapid return to modern-like carbon levels after both flushing events, suggesting that the timing of decline in peak AMOC strength occurred within less than 500 years, which is consistent with AMOC predictions from modeling studies. These insights into the relationship between rising carbon dioxide levels and ocean circulation in the past could provide valuable clues about what to expect during modern climate change.

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Article #20: "Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation," by T. Chen; L.F. Robinson; P. Spooner; P.J. Morris; H.C. Ng at University of Bristol in Bristol, UK; A. Burke at University of St. Andrews in St. Andrews, UK; J. Southon at University of California, Irvine in Irvine, CA; P.J. Morris at International Atomic Energy Agency in Monaco.

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