World’s water cooling system concern
‘Our preliminary results from the voyage suggest the dense water sinking near Antarctica is continuing to become less salty and less dense,’ said Dr Steve Rintoul of the Antarctic Climate and Ecosystems Cooperative Research Centre, who led an international team of scientists on a month-long voyage to investigate changes in the ocean.
Water needs to sink in the Southern Ocean in order to drive a huge ‘conveyor belt’ of ocean currents around the globe. ‘This circulation pattern controls global climate by transporting vast amounts of heat and carbon dioxide around the Earth,’ said Rintoul. ‘We know that in some past periods of the Earth’s history, climate underwent large and rapid changes when this circulation slowed down or stopped in response to changes in salinity in the polar regions.’
In order to see if this ‘switch’ might be flicked again in the future, Rintoul and his team are now trying to work out why the water is freshening. The three possibilities are more rain, less sea ice production, or an increased flow of glacial melt off the Antarctic continent. ‘The freshening is an indication that the climate in the Indian and Pacific sectors of the Southern Ocean is changing, due to either natural variability or human activities,’ said Rintoul. However, he added that ‘the changes in salinity we have observed in the Southern Ocean are more subtle than those that occurred in the past, and may not have the same impact’.
Meanwhile, researchers modelling the climate of Europe and North America have found that a major ocean current bringing warm water into the North Atlantic is weakening, to the point where it may temporarily counteract global warming.
The current, known as the meridional overturning current, weakens and strengthens on a natural 70–80-year cycle. When it’s strong, it brings warmer water and a warmer climate to the Northern Hemisphere.
‘Our results show that global mean temperatures may plateau or cool weakly over the next ten years because of natural fluctuations, but in the long term, temperatures will continue to rise,’ said Dr Noel Keenlyside, who led the team from the Leibniz Institute for Marine Scientists, who published their results in the journal Nature.
July 2008
Water needs to sink in the Southern Ocean in order to drive a huge ‘conveyor belt’ of ocean currents around the globe. ‘This circulation pattern controls global climate by transporting vast amounts of heat and carbon dioxide around the Earth,’ said Rintoul. ‘We know that in some past periods of the Earth’s history, climate underwent large and rapid changes when this circulation slowed down or stopped in response to changes in salinity in the polar regions.’
In order to see if this ‘switch’ might be flicked again in the future, Rintoul and his team are now trying to work out why the water is freshening. The three possibilities are more rain, less sea ice production, or an increased flow of glacial melt off the Antarctic continent. ‘The freshening is an indication that the climate in the Indian and Pacific sectors of the Southern Ocean is changing, due to either natural variability or human activities,’ said Rintoul. However, he added that ‘the changes in salinity we have observed in the Southern Ocean are more subtle than those that occurred in the past, and may not have the same impact’.
Meanwhile, researchers modelling the climate of Europe and North America have found that a major ocean current bringing warm water into the North Atlantic is weakening, to the point where it may temporarily counteract global warming.
The current, known as the meridional overturning current, weakens and strengthens on a natural 70–80-year cycle. When it’s strong, it brings warmer water and a warmer climate to the Northern Hemisphere.
‘Our results show that global mean temperatures may plateau or cool weakly over the next ten years because of natural fluctuations, but in the long term, temperatures will continue to rise,’ said Dr Noel Keenlyside, who led the team from the Leibniz Institute for Marine Scientists, who published their results in the journal Nature.
July 2008
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