UCSB oceanographer Timothy DeVries’ paper, “Decadal trends in the ocean carbon sink,” has been published in the Proceedings of the National Academy of Sciences, according to a UCSB news release.
The research found that the rate at “which CO2 was accumulating in the atmosphere doesn’t necessarily track emissions.”
“Up to 40% of the decadal variability of CO2 accumulation in the atmosphere can be attributed to how quickly the ocean takes up carbon; the rest can be attributed to activities in the terrestrial biosphere,” the news release stated.
The paper showed how “dynamic the ocean is” and how ocean circulation is a primary factor in carbon absorption. As carbon sinks, the current takes it to “cooler parts of the world, sequestering the greenhouse gas away from the atmosphere.”
“One would expect basically that if you’re increasing emissions at 10 percent, the accumulation rate in the atmosphere should increase at 10 percent, for example,” Dr. Devries said in the news-release. “But what we found is that the rate at which CO2 was accumulating in the atmosphere doesn’t necessarily track emissions.”
Grad student Michael Nowicki, who worked with Dr. Devries in the research, said in the news release: “It was interesting to see that the ocean models got the trend generally, but the magnitude was smaller (than what was noted in the observations).
“But that brings up the next question: Why is that?”
Said Dr. Devries: “We need to do more research to look at what’s driving this variability.” Capturing the ocean’s changing carbon sink in models, the researchers said, will lead to more accurate climate predictions.
The two partnered with a number of researchers, such as Lorinne Le Quéré and Oliver Andrews of the University of East Anglia, who ran a simulation of ocean models to see how much carbon the ocean was taking up. Mr. Devries and Mr. Novicki analyzed the output the other researchers provided for them.
“Myself and Michael Nowicki, the grad student, analyzed the output these groups provided for us. We did a comparison to see if the ocean models follow the other estimates we have,” he said. He said that the models mostly agreed with each other with a few minor variations.
“We learned that the amount of carbon taken up by the ocean varies quite a bit from one decade to the next. What we don’t understand as much are the drivers of this variability, why the amount of carbon taken up by the ocean is changing over time. If we can understand that better, we can build models that better predict how the ocean carbon sink will change in the future.”
Mr. Devries said the ocean will gradually start to absorb CO2 at a lower rate as the oceans and the Earth gets warmer.
“Generally speaking, we know pretty well that the ocean is taking up thirty percent of CO2,” Mr. Devries said. “However, this is variable from one year or decade to the next and we also know pretty well that as the Earth gets warmer and the oceans get warmer, they’re going to absorb this carbon dioxide at a slower rate.”