5 January 2011

Antarctic expedition seeks climate clues in ocean

An expedition departs from Australia today (6th January 2011) for the Mertz Glacier in east Antarctica to measure the impacts of a major iceberg calving event, and also to measure how much CO2 is stored by the ocean.

An array of underwater cameras, moorings and sensors will be deployed at the Mertz Glacier this summer for the first time since 78 kilometres of the glacier's tongue broke off after being hit by another 97 kilometre long iceberg in January of last year.

A team of nearly 40 Australian and international scientists will depart from Hobart on the Aurora Australis ship for a month-long voyage to carry out the investigations.

Voyage Leader and Oceanographer with the Antarctic Climate and Ecosystems Cooperative Research Centre, Dr Steve Rintoul, said the Mertz Glacier region is one of the few places in the ocean where dense, salty water forms at the surface and sinks four or five kilometres to the sea floor.

"This sinking of dense water near Antarctica is a key link in a network of ocean currents that influences global climate patterns," said Dr Rintoul.

"One goal of the expedition is to see how the calving of the large ice tongue has affected the formation of dense bottom water in the region," he added.

Another important study to be carried out by the team is the measurement of how much CO2 is held by the ocean.

"The ocean slows the rate of climate change by soaking up some of the carbon dioxide emitted by human activities, but this is gradually making the ocean more acidic affecting the ability of some organisms to form shells or other hard structures like reefs to develop," Dr Rintoul said.

The effect of CO2 on the ecosystem could be substantial. The Australian Antarctic Division's Acting Chief Scientist, Dr Martin Riddle, said the area around the glacier is one of the biological hotspots of the Antarctic and Southern Ocean ecosystem.

"Biological productivity is high in the region, attracting whales, penguins and seals to feed on plankton in one of the few areas not covered by ice in the Antarctic winter," said Dr Riddle.

According to Dr Riddle, scientists on board will measure the impact of ocean acidification on phytoplankton, the base of the Southern Ocean food chain, to get a full picture of the potential effects to biodiversity.

Underwater cameras will be deployed to explore the ocean floor in the area previously covered by the Mertz Glacier tongue. The expedition is the latest in a series than began in 1991 to assess how and why the Southern Ocean is changing.

"I expect to see new and unusual animals on the sea-floor as the area has been covered by ice hundreds of metres thick for about 80 years – this is a once in a life-time opportunity to discover what lives in these inaccessible places under the ice," said Dr. Rintoul.

The Aurora Australis will return to Hobart in February.

By comparing new measurements to earlier observations, the expedition hopes to determine how the temperature, salinity and circulation of the Southern Ocean is changing, and this information will be used to help track how rapidly the climate is changing. It is also hoped to provide improved strategies for future action.

Author: Marianna Keen | Climate Action

Image: NASA Goddard Photo and Video | Flickr

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