Controls on CO2 storage in the glacial ocean
The cause of glacial-interglacial CO2 cycles is a first order, unsolved question in climate science. Although a number of viable mechanisms for glacial CO2 change have been proposed, suitable data to provide robust tests of these have been lacking. A major missing piece of this puzzle is the nature of CO2 storage in the deep ocean during glacial periods (Rae et al., 2018).
This project will quantify the extent and nature of deep ocean CO2 storage during the last glacial cycle, constraining the roles of changes in respired carbon, carbonate compensation, sea ice, and ocean circulation (MacGilchrist et al., 2019).
Deep ocean CO2 reconstructions will be based on the boron concentration (B/Ca) and isotope composition (11B) of benthic foraminifera (Rae et al., 2011), which record ΔCO32- and pH respectively.
To quantify CO2 storage by the biological pump, we will reconstruct deep ocean oxygen using a suite of novel trace elements in foraminifera and bulk sediments, including iodine, uranium, manganese, and cerium (e.g. Zhou et al., 2016; Gottschalk et al., 2016). This will be complemented by carbon isotope gradients between different species of benthic foraminifera (e.g. Hoogakker et al., 2015), and preserved alkenone fluxes (Anderson et al., 2019). Interpretation will be guided by a suite of experiments with simple models of the ocean carbon cycle.
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The Southern Ocean plays a critical role in CO2 and climate change, both past and present