Centennial-scale changes in the global carbon cycle during the last deglaciation

TitleCentennial-scale changes in the global carbon cycle during the last deglaciation
Publication TypeJournal Article
Year of Publication2014
AuthorsMarcott S.A, Bauska T.K, Buizert C, Steig E.J, Rosen J.L, Cuffey K.M, Fudge T.J, Severinghaus JP, Ahn J., Kalk M.L, McConnell J.R, Sowers T., Taylor K.C, White J.WC, Brook E.J
JournalNature
Volume514
Pagination616-+
Date Published2014/10
Type of ArticleArticle
ISBN Number0028-0836
Accession NumberWOS:000343801500046
Keywordsair; antarctic ice; atmospheric co2; chronology aicc2012; circulation; climate; function regression; glacial; greenland ice cores; polar ice; termination
Abstract

Global climate and the concentration of atmospheric carbon dioxide (CO2) are correlated over recent glacial cycles(1,2). The combination of processes responsible for a rise in atmospheric CO2 at the last glacial termination(1,3) (23,000 to 9,000 years ago), however, remains uncertain(1-3). Establishing the timing and rate of CO2 changes in the past provides critical insight into the mechanisms that influence the carbon cycle and helps put present and future anthropogenic emissions in context. Here we present CO2 and methane (CH4) records of the last deglaciation from a new high-accumulation West Antarctic ice core with unprecedented temporal resolution and precise chronology. We show that although low-frequency CO2 variations parallel changes in Antarctic temperature, abrupt CO2 changes occur that have a clear relationship with abrupt climate changes in the Northern Hemisphere. A significant proportion of the direct radiative forcing associated with the rise in atmospheric CO2 occurred in three sudden steps, each of 10 to 15 parts per million. Every step took place in less than two centuries and was followed by no notable change in atmospheric CO2 for about 1,000 to 1,500 years. Slow, millennial-scale ventilation of Southern Ocean CO2-rich, deep-ocean water masses is thought to have been fundamental to the rise in atmospheric CO2 associated with the glacial termination(4), given the strong covariance of CO2 levels and Antarctic temperatures(5). Our data establish a contribution from an abrupt, centennial-scale mode of CO2 variability that is not directly related to Antarctic temperature. We suggest that processes operating on centennial timescales, probably involving the Atlantic meridional overturning circulation, seem to be influencing global carbon-cycle dynamics and are at present not widely considered in Earth system models.

DOI10.1038/nature13799
Impact: 

A new multi-institutional study including Scripps Institution of Oceanography, UC San Diego, shows that the rise of atmospheric carbon dioxide that contributed to the end of the last ice age more than 10,000 years ago did not occur gradually, but was characterized by three “pulses” in which CO2 rose abruptly.

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