Did you know that the ocean acts as the world’s biggest carbon sink? That means that it stores a vast amount of carbon dioxide; in fact, as much as 30% of the CO2 emissions that humans produce is taken up by the ocean. So, we owe the ocean a big thank you. Yet, interestingly enough, new research indicates that some parts of the ocean are more effective in storing CO2 than others. Coastal waters, for instance, are taking a hit from acidification and rising sea temperatures because these waters over continental shelves are taking up more than their fair share of atmospheric CO2. A recent study published in Nature Communications explains the significance behind the phenomenon.
"This is [happening] because the coastal ocean is shallower than the open ocean and can quickly transfer sequestered carbon dioxide to the deep ocean; this process creates an additional and effective pathway for the ocean to take up and store anthropogenic carbon dioxide," said University of Delaware oceanographer Wei-Jun Cai.
The study, conducted by a collaboration of institutions, looked at data from the last 35 years to determine global trends of carbon dioxide concentrations in certain regions of the ocean. The team of scientists discovered a surprising finding: while CO2 levels in the open ocean are increasing at the same rate as in the atmosphere, they’re increasing slower in the coastal ocean. That means that coastal zones are holding more CO2.
"If this conclusion is confirmed by future observations, it would mean that the coastal ocean will become more and more efficient at removing carbon dioxide from the atmosphere," said Goulven Lurallue, the paper's lead author and a researcher from Université Libre de Bruxelles in Belgium.
Getting accurate data on coastal waters has been a challenge for studies like this one because coastal waters behave differently depending on multiple influences, such as location and topography. One example of the range that continental shelves can cover was explained by Science Daily: “In higher latitudes such as northern Canada and Greenland, coastal waters usually act as carbon sinks, absorbing excess carbon dioxide from the atmosphere. In tropical areas such as the South China Sea, coastal waters are generally considered a source of carbon dioxide.” Nevertheless, the findings from this study showcase how critical the role of coastal zones can be in global CO2 patterns, despite the relatively small fraction of the ocean they cover.
The scientists urge that this finding be considered when reassessing climate models in terms of atmospheric carbon dioxide. This new information, suggesting the impressive sink characteristics of coastal waters, is imperative to factor into the future of our changing climate in order to better understand what is to come.