10:00 AM - 10:15 AM
[MIS21-15] Global oxygenation by enhanced deep convection in the Southern Ocean under millennial-scale global warming
Keywords:dissolved oxygen, global warming, open ocean convection, thermohaline circulation
Here we use a coupled AOGCM and offline biogeochemical model to simulate multi-millennial oxygen change under atmospheric carbon dioxide doubling and quadrupling. At the first 500 model years in the warming simulation, dissolved oxygen is decreased globally, which is consistent with the previous studies. Thereafter, however, O2 concentration in the Southern Ocean between subsurface and deep ocean increases and overshoot rapidly, and that in the other deep ocean except the North Atlantic recovery gradually. Consequently, global mean O2 concentration recovers and overshoots by the end of warming experiment, in spite of surface oxygen reduction due to lower oxygen saturation and weaker Atlantic meridional overturning circulation. Recovery of deep ocean convection in the Weddell Sea after initial cessation enhances ventilation and supplies the oxygen into each of the three major basins through strengthened Antarctic Bottom Water, resulting in the oxygen overshoot in the deep ocean. Our results suggest that enhanced deep convection and ventilation in the Southern Ocean have global impact on millennial-scale oxygen change. The mechanisms of cessation and recovery of deep convection in the Weddell Sea will be discussed.