Sack Lunch Seminar (SLS)

Abstract:
Uncertainty about the causes of natural atmospheric carbon dioxide variations in the past demonstrates our incomplete grasp of fundamental processes that govern the climate. The Southern Ocean residual overturning circulation is thought to play an important role in the global carbon cycle. Using a coarse resolution configuration of MITgcm and it’s coupled biogeochemistry code, an ensemble of idealized perturbations to external forcing and internal physics of the Southern Ocean is examined revealing a striking positive correlation between atmospheric carbon dioxide levels and the rate of Southern Ocean overturning: stronger or northward-shifted westerly winds in the Southern Hemisphere result in increased residual circulation, greater upwelling of carbon-rich deep waters and oceanic outgassing, which increases atmospheric pCO2 by ~20 uatm; weaker or southward-shifted winds lead to the opposing result. The ocean carbon inventory in our model studies varies through contrasting changes in the diagnosed saturated, disequilibrium, soft-tissue and carbonate reservoirs, each varying by O(10–100) PgC, all of which contribute to the net anomaly in atmospheric CO2, elucidating the processes that link circulation, nutrient distributions and biological productivity.