Global carbon burial in deep-sea sediment across the last glacial cycle based on a comprehensive sediment proxy database.

English Abstract:

The ultimate fate of most carbon released from the solid Earth through volcanoes (and now human activity) is as organic carbon and carbonate minerals in marine sediments. As such, the marine burial of carbon exerts a strong control on long-term climate, via its impact on CO2, and modulated by the silicate weathering feedback. But the sensitivity of these fluxes and feedbacks to climate remains uncertain.

Here, we sought to evaluate and quantify past changes in the organic carbon and carbonate burial in deep-sea sediment over the last glacial cycle, taking advantage of a comprehensive global marine sediment proxy database we have built. Our strategy consists of three consecutive steps. First, to produce a global map of modern burial in the sediment. Second, to subdivide the ocean into provinces with consistent biogeochemical properties. Third, to modulate the modern burial in each province over time, according to the mean changes in burial rates calculated using sediment cores from the same province.

Our results suggest a significant change in global deep-sea organic carbon burial over glacial interglacial timescales, with a peak in organic carbon burial during glacial maxima, that represent 150-175% of interglacial burial rates (±25%). In contrast, despite regional heterogeneity, preliminary results do not suggest consistent and significant variations of the global burial of carbonates in the deep-sea over glacial/interglacial timescales and during glacial termination. Rather, the increase of carbonate burial in the Atlantic during the deglaciation was compensated by a decrease in the Pacific and Indian Ocean. Considering the large burial flux of carbonate on continental shelves that has existed throughout the Holocene, which was essentially absent during glacial maxima, implies that the total carbonate burial has been substantially greater in the Holocene. Given the relatively short timescale of carbonate compensation (a few thousand years) this suggests that silicate weathering rates were also substantially larger during the Holocene.