Ocean currents near the Antarctic coast appear to be a critical means by which the Earth controls levels of atmospheric CO2, according to new research from Princeton University. The precise causes that underlie the well documented variation in CO2 that is found in the Geological record, derived from ice-core samples, have provided a long and fraught debate. In a new paper, published (22 June) in the prestigious scientific journal "Nature", the Princeton researchers conclude that the waters in the "Southern Ocean" at a latitude below 60 degrees play a far more prominent role in regulating atmospheric CO2 globally, while those north of this line of demarcation have relatively little influence.
As the study's corresponding author, Irina Marinov, put it: "Cold water that wells up regularly from the depths of the Southern Ocean spreads out on the ocean's surface along both sides of this dividing line, and we have found that the water performs two very different functions depending on which side of the line it flows toward. While the water north of the line generally spreads nutrients throughout the world's oceans, the second, southward-flowing stream soaks up carbon dioxide, a greenhouse gas, from the air. Such a sharply defined difference in function has surprised us. It could mean that a change to one side of the cycle might not affect the other as much as we once suspected."
It has long been recognised that the (Antarctic) Southern Ocean influences the planet overall in a number of different ways. However, only two years ago the Princeton team discovered that the world's ocean nutrient distribution depended on the circulation pattern in the Southern Ocean, but did not realise then that the pattern also affected carbon dioxide levels. The real advance made by these workers is that they have been able to draw a distinct line between the two effects, regarding nutrients and CO2.
At the Antarctic sea-air interface, CO2 dissolves in the water, which is then drawn down deep into the ocean depths by the particular circulation pattern there. The team suggest that focus should be shifted from the Atlantic to the Antarctic in reference to CO2 uptake and regulation. They speculate that their research may have implications for future "iron fertilisation" studies, where the growth of certain microorganisms is stimulated by iron, which consequently take-up more CO2, as an antidote to human-induced (CO2) greenhouse gas emissions. When the organisms die, they fall to the ocean floor, taking down the CO2 that they have absorbed with them, so lowering its concentration in the surface waters and allowing more atmospheric CO2 to be absorbed.
There is one caveat, however: namely that these conclusions are based on computer models, which necessarily have limitations according to the precise nature of the algorithm that is employed to do the calculations. In conclusion, this interesting finding reveals yet another element of the complex interplay between the various global components that will altogether conspire to bring about the outcome of the "Global Climate Change Experiment" that we are each and all of us involved in, whether we like it or not!