Abstract:

Comparisons of repeated hydrographic sections between the 1990s and 2000s revealed a global pattern of deep and abyssal ocean warming.  However, the mechanisms driving the deep warming are still poorly understood.   I will use new data to present updated deep ocean warming rates and examine how the distribution of Southern Ocean Water masses has shifted over the last three centuries.  Second, I show how transient tracers can be used to explore deep circulation and detect decreases in ventilation rates of Antarctic Bottom Water (AABW) in the Pacific sector of the Southern Ocean.  Together, these observations provide strong evidence that there has been a significant slowdown in the bottom limb of the meridional overturning circulation.