The carbon dioxide that enters the atmosphere doesn’t necessarily stay there. As part of the natural carbon cycle, much of it goes into plants, soil and, very significantly, the ocean. In fact, the world’s oceans are a sink for human-generated carbon dioxide without which the extent of global climate change would be far worse.
Oceans takes up CO2 in two steps: first the CO2 dissolves in the surface water. Then, the ocean’s overturning circulation distributes it. Currents and mixing processes transport the dissolved CO2 from the surface deep into the ocean’s interior, where it accumulates over time.
A long-standing priority for climate researchers is to determine how much of the CO2 we produce is being absorbed by the oceans and, ultimately, how much can they hold?
An international team of scientists has recently provided some answers. As reported in Science, the researchers have determined that the oceans have taken up from the atmosphere as much as 37 billion tons of human-made carbon between 1994 and 2007. This figure corresponds to nearly a third of all the anthropogenic CO2 emitted during that time.
Furthermore, they found that the percentage of CO2 taken up by the oceans has remained relatively stable compared to the preceding 200 years even as the absolute quantity has increased. So, evidently, the oceans’ capacity for carbon dioxide has not yet been saturated.
That’s the good news. The bad news is that putting all that CO2 into the oceans has a steep price: the dissolved CO2 acidifies the water. The consequences for a wide range of marine life including coral reefs are serious and getting worse. We need to drastically reduce carbon emissions.
Photo, posted November 5, 2018, courtesy of Flickr.