Speaker: Emily Newsom (Caltech)
Reassessing the Role of the Indo-Pacific in the Global Meridional Overturning Circulation.
Surface buoyancy fluxes in the North Atlantic and Southern and Oceans are expected to exert a strong control on the ocean's residual Global Overturning Circulation (GOC). In contrast, surface fluxes and shallow ocean processes in the low-latitude Indo-Pacific are commonly expected to adjust passively to higher latitude forcing. Here, this assumption is explored through an assessment of global buoyancy transport in the Community Earth System Model 1.0. We show that in a preindustrial-like steady-state, the GOC exports a large surplus in surface-sourced buoyancy out of the Indo-Pacific and into the high latitudes of the Atlantic and Southern Oceans, a surplus incurred in the Indo-Pacific due to its vast equatorial surface area. This transport requires interactions between shallow equatorial dynamics and the deeper circulation, zonal structure in the GOC, and inter-basin coupling between Atlantic and Indo-Pacific mediated by the Southern Ocean, all processes absent from many conceptual descriptions of overturning dynamics. Further, this suggests that a geometrically-enforced Indo-Pacific surplus in buoyancy may constrain global overturning dynamics across a range of climate states. We examine this possibility within an ensemble of 24 mean state climate simulations, ranging from glacial-like conditions (180 ppm CO2) to very warm climates (905 ppm).