Background Information

Southern Ocean science

Dr. Steve Rintoul

Dr. Steve Rintoul - The Great Australian Ocean


Author: Marine Climate Change 2012
Dr. Steve Rintoul Southern Ocean science New research by teams of Australian and US scientists has found there has been a massive reduction in the amount of Antarctic Bottom Water found off the coast of Antarctica. Comparing detailed measurements ta | Time: 18.73 min

New research by teams of Australian and US scientists has found there has been a massive reduction in the amount of Antarctic Bottom Water found off the coast of Antarctica.

Comparing detailed measurements taken during the Australian Antarctic program’s 2012 Southern Ocean marine science voyage to historical data dating back to 1970, scientists estimate there has been as much as a 60% reduction in the volume of Antarctic Bottom Water, the cold dense water that drives global ocean currents.

Dr Rintoul was Chief Scientist on the recent voyage and has made a dozen voyages to the Southern Ocean.

“When we speak of global warming, we really mean ocean warming: more than 90% of the extra heat energy stored by the earth over the last 50 years has gone into warming up the ocean. The Southern Ocean is particularly important because it stores more heat and carbon dioxide released by human activities than any other region, and so helps to slow the rate of climate change” Dr Rintoul said. “A key goal of our work is to determine if the Southern Ocean will continue to play this role in the future.”

The causes of the observed changes in the Southern Ocean are not yet fully understood. Changes in winds, sea ice, precipitation, or melt of floating glacial ice around the edge of Antarctica may be responsible. Data collected on the latest voyage will help unravel this mystery.

A major challenge is the lack of observations at high latitude, where much of the ocean is covered by sea ice in winter. During the voyage scientists deployed nine drifting profilers, called Argo floats, which will transmit profiles of temperature and salinity every 10 days for the next five years.

“The Argo floats have revolutionised our ability to measure the ocean, particularly in winter when ship observations are very rare,” said Dr Rintoul. “On this voyage, we deployed a new kind of float designed to survive encounters with the sea ice. These floats will allow us to see how dense water forms in winter for the first time.”

The Aurora Australis visited Commonwealth Bay as part of a celebration of the centenary of Sir Douglas Mawson’s Australian Antarctic Expedition. Dr Rintoul’s team had the opportunity to repeat oceanographic measurements made by Mawson’s team 100 years ago, obtaining one of the few century-long records obtained anywhere in the ocean.

“Our measurements collected in 2012 are quite different to those collected by Mawson in 1912,” Dr Rintoul said. “This is an indication of a change in the ocean currents that may be related to a reduction in the amount of dense water formed near Antarctica.”

“Mawson’s expedition really marked the transition from the “Heroic Age” of Antarctic exploration to a period where science was the primary motivation for Antarctic expeditions. I think he would have gotten a real kick out of the idea that measurements made by his team a century ago are still useful and that Australian scientists are continuing his legacy by studying Antarctica and its connection to the rest of the globe.”

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