Carbon benthic release

Injection of compressed CO2 into the deep ocean has already been tested. The goal of this approach is to emplace the CO2 into waters with low temperatures, ensuring the formation of relatively immobile gas hydrates. This strategy has the potential to sequester thousands of gigatonnes of carbon, but likely environmental impacts include (1) a change in the pH in the seawater near the emplaced gas hydrates, (2) benthic kills, (3) other ecosystem impacts, and (4) release back to the atmosphere as an eventual consequence of meridional overturning circulation. 

The transient impact of methane release on surface ocean values is undoubtedly greater than predicted by Equation (22). Equation (22) is based on two assumptions that the ocean carbon cycle is at steady state, and that the oceans are well-mixed. Methane release can occur at a rate that violates both of those assumptions. Kennett et al (2000) correlated millenial-scale negative excursions in foraminiferal values with massive releases of methane from basinal sediments. Oscillations of up to 6%o were identified in benthic foraminiferal species, and up to 3%o in planktonic species. The temporal scale of the variations—and therefore, the inferred maximum rate of methane release—is... 

One of the best-characterized links between marine and terrestrial paleoclimate concerns the Paleocene-Eocene thermal maximum (PETM). High-resolution marine cores delineated a rapid drop in benthic foraminifera 5 C and 5 0 at 55 Ma. The drop corresponds to a deep-sea temperature rise of 5-6°C in ten thousand years or less (Kennett and Stott 1991, Bralower et al. 1995, Thomas and Shackleton 1996). The cause is now inferred to be catastrophic methane release from clathrates on the continental margins (Dickens et al. 1995, 1997 Dickens 1999). Because methane is a greenhouse gas and has an extremely low value (—60%o), a large release would affect both temperature (oxygen isotopes) and carbon isotopes. 

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