The earth is performing an enormous disposal service for the human race. About half of the carbon we are dumping into the atmosphere does not stay there and is instead taken up by the oceans and land. Were this not the case, scientists say, the earth would probably be warming far more rapidly.
One of the biggest questions in climate science is: How long will that disposal service last?
Remarkably, the earth’s ability to keep socking away carbon has for decades kept up with human activity, with the proportion that disappears from the atmosphere remaining close to 50 percent even as our emissions soared. Computer analyses of the climate have long predicted that the uptake would become less efficient sometime in this century. If that happened, the level of carbon dioxide in the air would begin rising faster, trapping more of the sun’s heat.
Two new scientific papers shed some light on this issue. One of them is reassuring, at least in the short run, while the other offers new reasons to worry about the long-term stability of the “carbon sink,” as scientists call it.
"A second paper, published earlier in the week by the journal Nature Geoscience, provides insight into how the disposal service in the ocean is actually working. The surprising finding is that a handful of relatively concentrated spots in the Southern Ocean account for a high proportion, roughly 20 percent, of the entire oceanic carbon uptake.
The reason is that while carbon dioxide can easily dissolve out of the air into ocean water, it tends to stay in a surface layer that does not mix well with the colder, denser water below. It can even escape that surface layer to re-enter the atmosphere. The scientists found that certain combinations of winds and currents are required to overcome the barrier and pump carbon dioxide into the deep ocean, where much of it stays locked away for thousands of years."
The scientists used measurements from the new Argo network of floating robots to make the most complete analysis yet of the role of currents.