Southern Ocean: Eddies transport carbon into deep water

August 09, 2015

Southern Ocean (Bernd F. Laeschke – July 2012): Carbon is not absorbed into the deep ocean uniformly in vast areas; it is drawn down and locked away from the atmosphere by plunging currents a thousand kilometers wide. Winds, currents and massive whirlpools that carry warm and cold water around the ocean, known as eddies, create localized pathways or funnels for carbon to be stored, scientists from British Antarctic Survey (BAS) and Australia’s national research agency, the Commonwealth Scientific and Industrial Research Organization (CSIRO), discovered after studying the Southern Ocean. The southernmost waters of the World's Oceans is an important carbon sink – around 40 percent of the annual global Carbon Dioxide (CO2) emissions absorbed enter through this region.

“The Southern Ocean is a large window by which the atmosphere connects to the interior of the ocean below,” says Lead author, Dr. Jean-Baptiste Sallée, a scientist with the British Antarctic Survey and lead author of the study. “Until now we didn’t know exactly the physical processes of how carbon ends up being stored deep in the ocean. It’s the combination of winds, currents and eddies that create these carbon-capturing pathways drawing waters down into the deep ocean from the ocean surface. Now that we have an improved understanding of the mechanisms for carbon draw-down we are better placed to understand the effects of changing climate and future carbon absorption by the ocean.”

“Our study identifies these pathways for the first time and this matches well with observationally - derived estimates of carbon storage in the ocean interior,” Dr. Richard Matear, a scientist with CSIRO and co-author of the paper, says. The rate-limiting step in the anthropogenic carbon uptake by the ocean is the physical transport from the surface into the ocean interior, according to Matear.

Due to the size and remote location of the Southern Ocean, scientists have only recently been able to explore the workings of the ocean with the help of small robotic probes, also known as Argo floats. In 2002, 80 floats were deployed in the Southern Ocean to collect information on the temperature and salinity. This unique set of observations spanning 10 years has enabled scientists to investigate this remote region of the world for the first time. The floats are just over a meter in length and dive to depths of 1.24 miles (2 kilometers). Today, there are over 3,000 floats in the oceans worldwide providing detailed information used in oceanic climate models.