Not all the CO 2 generated during the combustion of fossil fuels remains in the atmosphere and contributes to global warming. The ocean and land based ecosystems absorb considerable amounts of these CO 2 emissions from the atmosphere produced by man.
The ocean occupies CO 2 in two phases: first, the CO 2 dissolves in surface water. Subsequently, the upside-down circulation of the ocean distributes it: ocean currents and mixing processes transport dissolved CO 2 from the deep surface into the interior of the ocean, where it accumulates in the time.
Carbon sink in the ocean  This overturning circulation is the driving force behind the oceanic CO heat sink 2 . The size of this sink is very important for the atmospheric levels of CO 2 : without this sink, the concentration of CO 2 in our atmosphere and the extent of anthropogenic climate change would be considerably more high.
Determining which proportion of human CO 2 absorbed by man is absorbed has long been a priority for climate researchers. An international team of scientists led by Nicolas Gruber, professor of environmental physics at ETH Zurich, has now determined this ocean sink for a period of 1
The marine well is intact
This percentage of CO 2 occupied by the oceans has remained relatively stable compared to the previous 200 years, but the absolute quantity has increased considerably. This is because until the atmospheric concentration of CO 2 rises, the oceanic well strengthens more or less proportionally: more CO 2 is in the atmosphere, the more it is absorbed by the oceans – up to when it does not become saturated.
So far, that point has not been reached. "During the period examined, the global ocean has continued to deal with anthropogenic CO 2 at a congruent rate with the increase in atmospheric CO 2 ," explains Gruber .
The results of the research based on the data also confirm various previous estimates based on the models of the oceanic sink for CO produced by man 2 . "This is an important vision, which gives us the certainty that our approaches have been corrected," adds Gruber. The results also allow researchers to draw conclusions about the CO 2 field of ecosystems on earth, which are more difficult to determine.
Regional differences in absorption rate
While the overall results suggest an intact oceanic inlay for carbon dioxide produced by man 2 the researchers also discovered in the several ocean basins noticeable deviations from the absorption expected from the increase in atmospheric CO 2 . The North Atlantic Ocean, for example, absorbed 20% less CO 2 than expected between 1994 and 2007. "This is probably due to the slowing down of the North overturning Circulation Atlantic towards the end of the 1990s, which in turn is most likely a consequence of climate variability, "explains Gruber. But this lower sinking in the North Atlantic was offset by a considerably greater absorption in the southern Atlantic, such that the absorption by the whole of the Atlantic developed as expected.
The researchers documented similar fluctuations in the Antarctic Ocean, in the Pacific and in the Indian Ocean. Gruber points out: "We have learned that the marine heat sink is not only responding to the increase in atmospheric CO 2 . Its remarkable sensitivity to climatic variations suggests a significant potential for feedback with continuous climate change."  Results of two surveys
The results are based on a global survey on CO 2 and on other chemical and physical properties in the various oceans, measured from the surface to depth up to 6 kilometers. Scientists from 7 countries participated in the internationally coordinated program initiated in 2003. Globally they carried out over 50 research cruises until 2013, which were then synthesized into a global data product.
For their analyzes, the researchers used a new statistical method developed by Gruber and his former research doctorate. student, Dominic Clement. This method allowed them to distinguish between the changes in the artificial and natural components 2 that make up the changes in the total concentration of dissolved CO 2 in the water. Natural CO 2 refers to the amount of CO 2 that existed in the oceans before industrialization.
Gruber had already participated in a similar study around the turn of the millennium. Using the observations obtained from the very first global CO survey 2 conducted between the end of the 80s and the mid-90s, the study estimated that the ocean had absorbed about 118 gigatonnes of carbon from the beginning of the industrialization around 1800 until 1994. Its current team of researchers extended this analysis until 2007, allowing them not only to establish the budget for anthropization human 2 for the period from 1994 to 2007, but also to evaluate the entirety of the ocean carbon sink.
The increase in CO 2 content acidifies the marine habitats
By changing the global warming rate, the oceanic sink for industrial anthropization 2 provides an important service for humanity, but has its price: the CO 2 dissolved in the ocean acidifies the water. "Our data showed that this acidification reaches deep into the ocean, extending partly to depths of over 3000 m," says Gruber.
This can have serious consequences for many marine organisms. Calcium carbonate dissolves spontaneously in acidified environments, which represents a risk for mussels and corals whose shells and skeletons are made of calcium carbonate. The changing chemical composition of the ocean can also affect physiological processes such as fish breathing. Gruber is convinced: "Documenting the chemical changes imparted on the ocean as a result of human activity is crucial, not least to understand the impact of these changes on marine life."
Materials provided by ETH Zurich . Original written by Michael Keller. Note: the content can be changed by style and length.