Ocean Circulation and Carbon Cycle in the Last Glacial Maximum

MUGLIA, JUAN; SCHMITTNER, ANDREAS

Workshop; Second IPODS Workshop: Ocean Circulation and Carbon Cycling; 2016

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In this work we study changes in the ocean circulation and carbon cycle that could explain reconstructed concentrations of atmospheric CO2 and nitrogen and carbon isotope distributions for the Last Glacial Maximum (LGM). We evaluate the effect of preindustrial-to-LGM changes in iron solubility, ligand concentration, dust flux into the ocean,and sedimentary iron flux on the ocean component of an isotope enabled biogeochemical model, coupled with a global ocean circulation model. These changes are then combined with sedimentary reconstructions or nitrogen and carbon isotopes to evaluate effects on the carbon cycle of the LGM. We find that higher dust fluxes into the ocean in the LGM increase productivity and enhance the biological pump, trapping carbon in deep waters. However, the effect is countered by changes in sedimentary release of iron due to lower sealevel, and its significance depends on the assumed solubility of ironin dust.Effects of circulation changes are also evaluated. We produce LGM simulations with different ocean circulation states. An ocean with shallow North Atlantic Deep Water and high penetration of Antarctic Bottom Water into the northern hemisphere preserves more deep dissolved carbon, and has isotope distributions more similar to reconstructions than an ocean with deep and fast Atlantic Meridional Overturning Circulation. p { margin-bottom: 0.08in; }a:link { }