摘要：Waters of the Atlantic and Pacific tropical oxygen minimum zones (OMZs), located in the
poorly ventilated shadow zones of their respective ocean basins, reach the sea surface
mostly in the eastern boundary and equatorial upwelling regions, thereby providing
nutrients sustaining elevated biological productivity. Associated export of sinking organic
matter leads to oxygen consumption at depth, and thereby helps to maintain the tropical
OMZs. Biogeochemical feedback processes between nutrient-rich OMZ waters and
biological production in the upwelling regions and their net impact on the evolution of
the OMZs depend on the strengths of the flow pathways connecting OMZs and
the upper ocean, because even though water has to be isolated below the mixed
layer for some time in order for OMZs to develop, it has to be brought up to the
surface mixed layer eventually in order to exchange properties with the atmosphere. Here, we investigate the connections between OMZs and the surface mixed layer, and their
sensitivity to global warming with a coupled ocean–atmosphere general circulation model
by analyzing the fate of simulated floats released in the OMZs. We find that under
present-day climate conditions, on decadal time scales a much larger portion of the model's
OMZ waters reaches the surface ocean in the Pacific than in the Atlantic Ocean:
within 20 years, 75% in the Pacific and 38% in the Atlantic. When atmospheric
CO2 is doubled, the fraction of modeled OMZ waters reaching the upwelling in the same time
decreases by about 25% in both oceans. As a consequence, feedback between
biogeochemical processes in OMZs and in the surface ocean is likely to be weakened in the
future.
