British and Australian researchers working on data collected over a ten-year period from robotic probes wandering around the Southern Ocean have discovered an important method of how carbon is drawn from the surface of the Southern Ocean to the deeper waters below.
The research shows that carbon is not drawn down uniformly by the ocean in vast areas, rather, it is drawn down and stored by plunging currents that are at times a thousand kilometres wide. These eddies span the entire world, and through wind, currents and massive whirlpools carry warm and cold water around the ocean.
These eddies create localised pathways or funnels by which carbon is drawn from the atmosphere and into the deep ocean to be stored and locked away.
“The Southern Ocean is a large window by which the atmosphere connects to the interior of the ocean below, explains lead author, Dr Jean-Baptiste Sallée from British Antarctic Survey. “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.”
CSIRO co-author, Dr Richard Matear says 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 says.
Unsurprisingly, access to this information has been locked away due to the story and at times sheer-fatal nature of the Southern Ocean. Only in the last decades have we been able to traverse the region with any surety and even more recently allow ourselves to conduct scientific research.
One such tool for research in the Southern Ocean is the Argo float – a small robotic probe that can dive to depths of 2 kilometres and measure only a metre in length. There are currently over 3,000 Argo floats wandering around our plant’s oceans, providing detailed information that is used in oceanic climate models the world over.
Back in 2002, 80 floats were deployed in the Southern Ocean specifically to collect information on the temperature and salinity of the region. This data – in concert with temperature, salinity and pressure data collected from ship-based observations since the 1990s – has enabled the scientists to investigate this remote region of the world and reach these most recent conclusions.
Source: British Antarctica Survey