Abyssal Ocean Warming Around Antarctica Strengthens the Atlantic Overturning Circulation

Thursday, 18 December 2014
Claus W Boning and Lavinia Patara, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
The abyssal warming around Antarctica is one of the most prominent multi-decadal signals of change in the global ocean. Here we investigate its dynamical impacts on the large-scale circulation and heat transport in the Atlantic Ocean by performing a set of experiments with a global ocean-sea ice model. The simulations suggest that the ongoing warming of AABW, already affecting much of the Southern Hemisphere with a rate of up to 0.05 °C per decade, has important implications for the Atlantic Meridional Overturning Circulation (AMOC). While the abyssal northward flow of AABW is weakening, we find the upper cell of the AMOC to progressively strengthen by 5-10% in response to deep density changes in the South Atlantic. The simulations suggest that the AABW-induced strengthening of the AMOC is already extending into the subtropical North Atlantic, implying that the process may counteract the projected decrease of the AMOC in the next decades.