London: Scientists have shed light on how carbon is drawn down from the surface of the Southern Ocean to the deep waters beneath.
The Southern Ocean is an important carbon sink in the world – around 40 percent of the annual global CO2 emissions absorbed by the world’s oceans enter through this region.
Scientists from British Antarctic Survey (BAS) and Australia’s national research agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), revealed that rather than carbon being absorbed uniformly into the deep ocean in vast areas, it is drawn down and locked away from the atmosphere by plunging currents a thousand kilometres wide.
Winds, currents and massive whirlpools that carry warm and cold water around the ocean – known as eddies – create localised pathways or funnels for carbon to be stored.
“The Southern Ocean is a large window by which the atmosphere connects to the interior of the ocean below. 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,” said lead author, Dr Jean-Baptiste Sallee from British Antarctic Survey.
“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,” stated Dr Sallee.
CSIRO co-author, Dr Richard Matear said the rate-limiting step in the anthropogenic carbon uptake by the ocean is the physical transport from the surface into the ocean interior.
“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 Matear asserted.
The study was reported this week in the journal Nature Geoscience.