Previous studies have shown that the ocean is one of the biggest absorbers of carbon dioxide emitted by way of human activity. However, previous studies have also revealed that the ocean's process for absorbing carbon has changed over time. Furthermore, this changing method might affect the ocean's ability to buffer climate change.
Timothy DeVries, an oceanographer from UC Santa Barbara, and Michael Nowicki, a graduate student, have stated that gaining a good understanding of the trends in the ocean's carbon cycle is the key to improving the current models of how the Earth's oceans absorb carbon. According to their study, this would result in better predictions for the climate.
DeVries explained that they started off looking at the rate at which carbon dioxide was accumulating in the atmosphere. They later compared the said data to that of the rate of emission. The scientist added that it was expected, for example, that if emissions were increasing at 10%, the accumulation rate in the atmosphere should increase at 10%.
The scientist continued that instead, they found out that the rate at which carbon dioxide was accumulating in the atmosphere does not really necessarily track emissions. To explain, he added that after looking at two decades' worth of carbon emissions and atmospheric carbon accumulation data, the output was a counterintuitive result.
DeVries further explained that in the 1990s they saw that the accumulation rate in the atmosphere was increasing at a high speed at a faster rate. However, the emissions did not increase very quickly at all. Whereas, in 2000, the opposite was true. The emissions increased sustainably, yet the accumulation rate in the atmosphere was steady.
According to the researchers, that variability is because of the ocean's carbon-absorbing activities. This entails a range of physical and biological processes that move carbon from the surface of the ocean to the depth. The duo further explained that a decadal variability at a rate of up to 40% of carbon accumulation in the atmosphere can be attributed to the speedy uptake of carbon by the ocean. The rest, they say, can be attributed to activities in the terrestrial biosphere.
The duo used a few different methods to estimate how quickly carbon dioxide has been accumulating in the ocean. The results have revealed that the ocean was absorbing carbon dioxide at a slower rate in the 1990s. This then resorted to a faster accumulation of carbon dioxide in the atmosphere.
The researchers concluded that the ocean's dynamic ability to act as a carbon sink is influenced by a number of factors. The duo added that one of the primary physical factors that affect oceanic carbon absorption is ocean circulation. This is when carbon dioxide is absorbed into the surface water which later sinks as the currents take it to cooler parts of the world. The circulation has been sequestering the greenhouse gas away from the atmosphere. However, present-day situations have changed.
The duo stated that warming could affect the deep ocean currents. In effect, this would slow down the current, which then decreases the rate at which carbon is absorbed.
DeVries noted that they still need to do more research on the causes of this variability.
