A study based on aircraft observations of carbon dioxide reveals that the Southern Ocean is still absorbing huge amounts of the carbon dioxide released by human fossil fuel combustion. According to the new findings, the seas around Antarctica may not be absorbing as much CO2 as previously assumed, and in certain areas may even be releasing it back into the sky.

While the seas, which are already getting more acidic and storing unprecedented quantities of heat as a result of climate change, may be able to take on some of the extra weight, the news is far from comforting. A researcher at the National Center for Atmospheric Research in Boulder said the conclusion was “reassuring” to him.

That is because the Southern Ocean is believed to absorb roughly half of all the CO2 emitted by humans every year.. As a result, it has a significant impact on reducing the short-term consequences of these pollutants. A year’s worth of float-based estimations had previously revealed that the Southern Ocean was more of a source than a sink of carbon dioxide, with an annual emissions rate approaching 0.3 billion metric tons.

From 2009 to 2018, the Southern Ocean was still a net carbon dioxide sink, absorbing around 0.55 billion metric tons of CO2 year, according to new research published in Science on Dec. 3.

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Deep-diving ocean floats recently deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project were employed in the 2018 study. It was found that, during the winter months, a significant amount of carbon dioxide was being released back into the atmosphere, according to calculations based on data gathered by 35 floats between 2014 and 2017. That raised the possibility that the Southern Ocean’s role in protecting the Earth from the effects of climate change may not be as strong as previously imagined.

Long, along with other academics, had some doubts about this finding. Scientists use the data from the floats to compute the carbon dioxide concentration in the water at depths of up to 2,000 meters. There are a number of assumptions that must be made regarding ocean water qualities in order for these calculations to work. Long speculates that this could be distorting the data and leading to overestimations of water-borne carbon dioxide emissions.

Airborne data can also be used to determine how much carbon dioxide is circulating between the atmosphere and the ocean. To conduct the new research, the team gathered previously recorded carbon dioxide data over vast regions of the Southern Ocean from three independent aircraft flights that took place between 2009 and 2011. Using these data, the scientists then ran computer simulations to estimate how much carbon dioxide is transported annually between the ocean and the atmosphere.

A seasonal trend of less carbon dioxide absorption by the ocean was found by both float-based and aircraft-based investigations, but the overall amount emitted from the ocean was different. Both forms of data are picking up on genuine trends, according to Ken Johnson, an ocean scientist at the Monterey Bay Aquarium Research Institute, in Moss Landing, California. “We are all going up and down.”

SOCCOM data may or may not have been inaccurate. Direct measurements of water carbon dioxide from ships must be compared with pH-based estimates at the same place in order to better understand biases that could effect pH predictions. Johnson believes that these kinds of research are currently being place off the coast of California.

According to Johnson, both databases and the few and far between direct shipboard observations in the Southern Ocean are going to be vital for understanding the function that these waters play in the planet’s carbon cycle in the future. In spite of the fact that aerial studies can assist constrain the overall picture of carbon dioxide emissions data from Southern Ocean, the floats are considerably more widely spread, and so are able to identify local and regional variations in carbon dioxide, which the atmosphere data cannot do.

To paraphrase Dr. Johnson, the Southern Ocean “is the flywheel of the climate system,” meaning it keeps everything running smoothly. Our comprehension of the Southern Ocean is critical to our ability to comprehend the rest of the planet.