The open water nearest to the sea ice surrounding Antarctica releases significantly more carbon dioxide in winter than previously believed, showed a study conducted using an array of robotic floats. The robotic floats diving and drifting in the Southern Ocean around the southernmost continent made it possible to gather data during the peak of the Southern Hemisphere’s winter from a place that remains poorly studied, despite its role in regulating the global climate.
“These results came as a really big surprise, because previous studies found that the Southern Ocean was absorbing a lot of carbon dioxide,” said lead author Alison Gray, Assistant Professor at the University of Washington.
In the Southern Ocean region, carbon atoms move between rocks, rivers, plants, oceans and other sources in a planet-scale life cycle. It is also among the world’s most turbulent bodies of water, which makes obtaining data extremely difficult. According to the study published in the journal Geophysical Research Letters, the floating instruments collected the new observations. The instruments dive down to 1 km and float with the currents for nine days.
Next, they drop even farther, to 2 km, and then rise back to the surface while measuring water properties. After surfacing they beam their observations back to shore via satellite. Unlike more common Argo floats, which only measure ocean temperature and salinity, the robotic floats also monitor dissolved oxygen, nitrogen and pH — the relative acidity of water.
The study analysed data collected by 35 floats between 2014 and 2017. The team used the pH measurements to calculate the amount of dissolved carbon dioxide, and then uses that to figure out how strongly the water is absorbing or emitting carbon dioxide to the atmosphere.