Pulse-like jumps in atmospheric carbon dioxide occurred in glacial and early interglacial periods

Once only associated with colder climate conditions of the last glacial period, a new study finds that rapid, pulse-like increases in atmospheric carbon dioxide (CO₂) also occurred during earlier, warmer interglacial periods. Using a new record of atmospheric CO₂ concentrations retrieved from the EPICA Dome C Antarctic ice core, Christoph Nehrbass-Ahles and colleagues show that these abrupt CO₂ releases are a pervasive phenomenon of Earth’s coupled climate-carbon system, perhaps linked to changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC). The results suggest that similar jumps in atmospheric carbon could also occur in the future should global warming similarly impact circulation in the Atlantic Ocean.  Abrupt bursts of CO₂ released to the atmosphere on centennial time scales are known to have occurred during the colder periods of the last glacial cycle. While these carbon dioxide jumps are thought to have been absent during the warmer climate conditions of previous interglacial periods, submillenial-scale records of atmospheric CO₂ variability needed to evaluate this only exist for roughly the last 60,000 years, and not beyond the last glacial. Previously locked in ancient Antarctic ice, Nehrbass-Ahles et al. present a high-resolution CO₂ record from 330,000 to 450,000 years ago, which reveals pronounced CO₂ releases under both cold and warm climate periods. Based on the findings, the authors suggest these events are a pervasive feature of the natural carbon cycle that may go undetected in CO₂ records of insufficient temporal resolution and precision, and also that the pulse-like release events relate to disruptions in the AMOC caused by melting ice sheets. Future rapid increases in atmospheric CO₂ could occur if similar human climate change-driven ice melt disrupts the AMOC, they say.

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