Climate Change

Antarctic Ocean also emits CO2

Print edition : January 18, 2019

Icy southern waters help blunt climate change by pulling carbon dioxide from the atmosphere. Photo: Nature/Graeme Snow

The Southern Ocean is believed to slow down global warming by absorbing heat and carbon dioxide from the atmosphere. In a recently published paper in “Nature”, researchers have reported that the ocean waters around Antarctica are also emitting massive quantities of CO2 during the dark and windy winter, thus reducing the ocean’s positive contributions to climate change.

According to the scientists, the winter emissions reduce the Southern Ocean’s net uptake of CO2 by 34 per cent, or more than 1.4 billion tonnes a year. That amount is roughly equal to Japan’s annual carbon emissions. “The Southern Ocean is still going to be important in the global carbon cycle,” said Seth Bushinsky, an oceanographer at Princeton University in New Jersey who is leading the study. “We’re just trying to understand exactly how and why.” Winter CO2 emissions from the Antarctic Ocean, which were tracked by a fleet of robotic floats, occur when deep waters rise to the surface and release centuries-old carbon. This is understood as part of a larger process of ocean circulation that moves heat and nutrients around the earth. Until now, the uptake of carbon in the Southern Ocean had been estimated on the basis of measurements made by ships sailing to and around Antarctica, but the data are sparse, particularly during the winter months.

The new research gathered data over 3.5 years from 65 floats deployed as part of the $21-million Southern Ocean Carbon and Climate Observations and Modelling project. The floats traverse up and down in the upper 2,000 m of the ocean, measuring temperature, salinity, oxygen, carbon and nutrients. This information can be used to infer how much carbon is moving into and out of the ocean.