Could elevated atmospheric pCO2 levels reduce the strength of the biological carbon pump?

Hofmann, M.; Morales Maqueda, M.. 2006 Could elevated atmospheric pCO2 levels reduce the strength of the biological carbon pump? [Other] In: 2006 Ocean Sciences Meeting, Honolulu, Hawaii, 20-24 February 2006. OS45B-12 [Abstracts].

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The formation of calcareous skeletons by marine biota in the upper ocean causes a reduction in alkalinity and increases the partial pressure of CO2. Consequently, calcification by marine planktonic organisms and the subsequent export of calcite shells towards the deep ocean leave the sea surface enriched in CO2. Therefore, calcification was assumed to counteract the biological soft tissue carbon pump. However, by analyzing sediment trap data Klaas and Archer (2002) found a statistically significant correlation between the export fluxes of particulate organic carbon (POC) and mineral CaCO3 particles. They conclude that more than 80 % of the entire POC flux is accounted for fast sinking CaCO3 particles acting as mineral ballast. Hence, the existence of biogenic calcification is assumed to be a necessary precondition to sustain the biological carbon pump. Raising atmospheric pCO2 levels, however, will lead to a gradual acidification of most of the surface ocean. Since biogenic calcification rates will drop under lower pH conditions, the biological carbon pump will become less effective in future. This describes a positive feedback mechanism between atmospheric pCO2 levels and the biological carbon pump. Higher atmospheric pCO2 levels will tend to inhibit the biological carbon pump, reduce the oceanic uptake of atmospheric CO2, and lead to a higher growth rate of anthropogenic CO2 in the atmosphere. Employing the Earthsystem Model of Intermediate Complexity CLIMBER-3α, which was recently combined with the marine ecosystem/carbon cycle model by Six and Maier Reimer (1996), and the ballast model by Klaas and Archer (2002), we have quantitatively investigated the possible impacts of reduced calcification rates on the efficiency of the biological carbon pump under growing atmospheric pCO2 levels from preindustrial times up to 2100. Utilizing the IPCC IS92a CO2 emission scenario we will discuss the spatio temporal pattern of changing biogeochemical variables such as pH, calcification rates and biological export production. We also report on the simulated impacts of anthropogenic CO2 emissions on the large scale ocean circulation.

Item Type: Publication - Conference Item (Other)
Programmes: Oceans 2025 > Climate, ocean circulation and sea level
Additional Information. Not used in RCUK Gateway to Research.: CD-ROM, 4 3/4 in.
NORA Subject Terms: Marine Sciences
Date made live: 20 Oct 2008 11:09 +0 (UTC)

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