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Geophysical Monograph Series

 

Keywords

  • greenhouse gases
  • global warming
  • hydrothermal flux
  • CO2 hydrate

Index Terms

  • 4901 Paleoceanography: Abrupt/rapid climate change
  • 4930 Paleoceanography: Greenhouse gases
  • 1616 Global Change: Climate variability
  • 4938 Paleoceanography: Interhemispheric phasing

Article

GEOPHYSICAL MONOGRAPH SERIES, VOL. 193, PP. 123-138, 2011

Hypothesized Link Between Glacial/Interglacial Atmospheric CO2 Cycles and Storage/Release of CO2-Rich Fluids From Deep-Sea Sediments

Lowell Stott

Department of Earth Sciences, University of Southern California, Los Angeles, California, USA


Axel Timmermann

International Pacific Research Center, SOEST, University of Hawai'i at Mānoa, Honolulu, Hawaii, USA


During the last glacial termination, the rise in atmospheric pCO2 was accompanied by a precipitous drop in surface ocean Δ14C that cannot be explained by changes in 14C production alone and therefore appears to require a flux of 14C-depleted carbon into the surface ocean. The magnitude of this Δ14C excursion is hard to reconcile with an ocean-only mechanism of CO2 regulation. Here we explore the possibility that hydrothermal sources of CO2 contributed to glacial/interglacial CO2 variability and to the Δ14C variations during the last deglaciation. We hypothesize that as the ocean cooled during glaciations CO2-hydrate stability expanded upward to shallower depths and over a broader region of the seafloor, reducing the flux of 14C-depleted CO2 into the ocean from sediment reservoirs that blanket active vents throughout the ocean. Conversely, as the oceans warmed during deglaciation, the CO2-hydrate stability horizon deepened and caused a transient release of 14C-depleted CO2 from the sediment reservoirs. Using a transient glacial-interglacial simulation conducted with the Earth system model of LOVECLIM, we estimate that ∼3°C temperature increase at intermediate water depths in the Pacific during the last deglaciation would have been large enough to lower the hydrate stability horizon by several hundred meters and significantly reduce the areal extent of seafloor where hydrate was stable. This hypothesis would explain why 14C ages of abyssal water masses were not anomalously old during the last glacial and why there was a large radiocarbon activity (Δ14C) anomaly during the last deglaciation at intermediate (500–700 m) water depths.

Citation: Stott, L., and A. Timmermann (2011), Hypothesized link between glacial/interglacial atmospheric CO2 cycles and storage/release of CO2-rich fluids from deep-sea sediments, in Abrupt Climate Change: Mechanisms, Patterns, and Impacts, Geophys. Monogr. Ser., vol. 193, edited by H. Rashid, L. Polyak and E. Mosley-Thompson, pp. 123–138, AGU, Washington, D. C., doi:10.1029/2010GM001052.

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