Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions

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Science  21 Aug 2020:
Vol. 369, Issue 6506, pp. 1000-1005
DOI: 10.1126/science.aay8178

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Pulses of the past

Bursts of carbon dioxide, released into the atmosphere and occurring on centennial time scales, were seen during the cold periods of the last glacial cycle but not in older or warmer conditions. Nehrbass-Ahles et al. present a record of atmospheric carbon dioxide concentrations retrieved from the European Project for Ice Coring in Antarctica Dome C ice core showing that these carbon dioxide jumps occurred during both cold and warm periods between 330,000 and 450,000 years ago. They relate these pulses to disruptions of the Atlantic meridional overturning circulation caused by freshwater discharge from ice sheets. Such rapid carbon dioxide increases could occur in the future if global warming also disrupts this ocean circulation pattern.

Science, this issue p. 1000


Pulse-like carbon dioxide release to the atmosphere on centennial time scales has only been identified for the most recent glacial and deglacial periods and is thought to be absent during warmer climate conditions. Here, we present a high-resolution carbon dioxide record from 330,000 to 450,000 years before present, revealing pronounced carbon dioxide jumps (CDJ) under cold and warm climate conditions. CDJ come in two varieties that we attribute to invigoration or weakening of the Atlantic meridional overturning circulation (AMOC) and associated northward and southward shifts of the intertropical convergence zone, respectively. We find that CDJ are pervasive features of the carbon cycle that can occur during interglacial climate conditions if land ice masses are sufficiently extended to be able to disturb the AMOC by freshwater input.

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