Ocean currents predict climate change

Scientists at the University of East Anglia, England, have by tracing the path of helium from underwater volcanoes, discovered how ocean circulation is working in the current that is flowing around Antarctica.

The team, led by Alberto Naveira Garabato of the National Oceanography Centre, Southampton, has discovered a ‘short-circuit’ in the circulation of the world’s oceans, which they say could aid predictions about future climate change.

This process in the Southern Ocean allows cold waters that sink to the depths to return to the surface more rapidly than previously thought, consequently affecting the Southern Ocean circulation, which links all the other oceans.

According to the research team, this process is also relevant to the uptake and release of carbon dioxide by the sea, as transport between the deep and surface waters in the Southern Ocean is particularly important for this process.

Also understanding oceanic circulation is particularly important since it distributes heat, carbon and nutrients around the globe and therefore plays a central role in regulating Earth’s climate.

According to co-author Prof Andrew Watson from the University of East Anglia’s School of Environmental Sciences, the findings are fundamental, as they show that much of the overturning circulation – how water moves and mixes vertically – around Antarctica takes place just around the tip of South America and in the small region in the Atlantic south of the Falklands, called the Scotia Sea.

The helium dissolves in the deep sea and a plume of this marked water travels down the coast of Chile. It is injected at depth into the Antarctic current on the Pacific side of Cape Horn. It then streams through into the Atlantic with the current, but in the process is spread, shifted and diffused by the circulation. Measurements of this spreading of the helium were used to deduce the ‘short-circuit’.

“The Southern Ocean is the least well understood part of the world ocean, but one of the most important parts. We are going to have to understand its circulation before we can make really confident predictions about how the climate is going to change over the next 100 years. This is a piece of knowledge that will help us do that. This tells us how an important part of it works,” said Prof. Watson.

“The research shows that a combination of rapid mixing across and rapid movement along density surfaces creates a ‘short-circuit’ in the overturning circulation, meaning it is more concentrated in this part of the Southern Ocean,” he said.

The study appears in the journal Nature.