Carbonate ion concentrations, ocean carbon storage, and atmospheric CO2. Issue 3 (30th August 2013)

• Record Type: Journal Article
• Authors: Goodwin, Philip; Lauderdale, Jonathan Maitland
• Is Part Of: Global biogeochemical cycles. Volume 27:Issue 3(2013)
• Page Start: 882
• Page End: 893
• Publication Date: 2013-08-30
• Subjects: Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/gbc.20078
• Languages: English
• ISSNs: 0886-6236

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>[1] Reconstructing past ocean [CO<sub>3</sub><sup>2−</sup>] allows the paleodepth of the chemical lysocline to be constrained, an important control on past atmospheric CO<sub>2</sub>. However, the causal mechanisms responsible for observed spatial and temporal variations in [CO<sub>3</sub><sup>2−</sup>] are difficult to quantify because of the complicated carbonate chemistry system. Here spatial and temporal variations in [CO<sub>3</sub><sup>2−</sup>] are quantitatively and concisely related to variations in ocean carbon storage due to different processes. The spatial variation in [CO<sub>3</sub><sup>2−</sup>] is given by Δ[CO<sub>3</sub><sup>2−</sup>] = <italic>γ</italic>(Δ<italic>C</italic><sub>soft</sub> + Δ<italic>C</italic><sub>dis</sub> <italic>+</italic> (∂<italic>C</italic><sub>sat</sub>/∂<italic>T</italic>)Δ<italic>T</italic> − Δ<italic>C</italic><sub>carb</sub>), where <italic>C</italic><sub>soft</sub> and <italic>C</italic><sub>carb</sub> are the dissolved inorganic carbon (DIC) from remineralization of marine soft tissue and CaCO<sub>3</sub>, respectively, <italic>T</italic> is seawater temperature, (∂<italic>C</italic><sub>sat</sub>/∂<italic>T</italic>) is the temperature‐solubility sensitivity of DIC, <italic>C</italic><sub>dis</sub> is the DIC from air‐sea disequilibrium, and <italic>γ</italic> is a carbonate chemistry coefficient. A similar quantitative function for temporal variation in global mean ocean [CO<sub>3</sub><sup>2−</sup>] is derived in terms of atmospheric CO<sub>2</sub>, CaCO<sub>3</sub> precipitation and dissolution, and carbon exchanges of terrestrial or fossil fuel origin. Comparing published [CO<sub>3</sub><sup>2−</sup>] reconstructions at the Last Glacial Maximum (LGM) and the late Holocene, the quantitative relationships reveal how the spatial distribution of ocean carbon storage was altered. Relative to the Intermediate North Atlantic, the rest of the ocean saw <italic>C</italic><sub>soft</sub> + <italic>C</italic><sub>dis</sub> + (∂<italic>C</italic><sub>sat</sub>/∂<italic>T</italic>)<italic>T</italic> − <italic>C</italic><sub>carb</sub> increase by an extra 570–970 Pg C during the LGM. Assuming that the Intermediate North Atlantic <italic>C</italic><sub>soft</sub> + <italic>C</italic><sub>dis</sub> + (∂<italic>C</italic><sub>sat</sub>/∂<italic>T</italic>)<italic>T</italic> − <italic>C</italic><sub>carb</sub> did not decrease during the LGM, this 570–970 Pg C increase in the rest of the ocean is enough to explain 40%–70% of the observed glacial decrease in atmospheric CO<sub>2</sub>.</p> </abstract>