The paper doesn't say just how much of the Earth's carbon budget is stored in the deep ocean now. But this research suggests that if Climate Destabilization shuts down the North Atlantic thermohaline circulation, we'd be in for a new release of that stored carbon in the Southern Ocean. What I don't understand is how this would differ from the current release of deep ocean CO2 in the Pacific. Would it happen thousands of years sooner, due to the shortened journey? The paper doesn't apply the new understanding to our current situation.
... the ocean is the place where most of the carbon dioxide that was not in the atmosphere during ice ages was stored ...
At each ice age's end, massive ice melting triggered an enormous release of fresh water in the northern ocean, "basically forming a freshwater lid on the north Atlantic."
That lid of low-density water shut off the formation of deep water in the Atlantic. Deep water is cold, dense water that sinks to the ocean depths.
This basically stopped the normal north-to-south ocean circulation,...
... around Antarctica, where even the surface ocean water is already quite cold and dense, some of that water in the ocean depths, which is also carbon rich, eventually warmed enough so that it became less dense than the water above it.
... that then would release the CO2 to the atmosphere in the Southern Ocean."
Kevin Trenberth from the National Center for Atmospheric Research figured out why global average temperature seemed to slow for a decade. The irony is that paying attention to only the surface mislead us. The planet was actually warming up faster than we expected. In a sense our perception was too shallow, too superficial for a water planet.
The finding may help explain why the pace of global warming at the surface has slowed in recent years compared to the 1990s, a phenomenon that has left members of the climate science community scratching their heads.
... found that about 30 percent of the extra heat has been absorbed by the oceans and mixed by winds and currents to a depth below about 2,300 feet. Oceans are well-known to absorb more than 90 percent of the excess heat, but its presence in the deep ocean "is fairly new, it is not there throughout the record," Trenberth said ...
... some of this heat ... is probably contributing to the warming of the overall planet, the warming of the oceans. … It means that the planet is really warming up faster than we might have otherwise expected," he said. [emphasis mine]