Atlantic Ocean getting warmer: Temperature rise linked to global warming

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The Independent Online
THE ATLANTIC Ocean is getting warmer in what could be a sign of global warming due to increasing carbon dioxide in the atmosphere.

But the findings of an international team of oceanographers are unlikely, as yet, to turn St Ives into St Tropez. The total rise in temperature measured is about 0.32 degrees over the past 35 years.

Although the difference might seem modest, according to Dr Harry Bryden, of the James Rennell Centre for Ocean Circulation at Southampton, 'this change is not subtle, it comes right out and hits you'.

The increase, which works out at roughly one degree per century, is broadly consistent with predictions of the rise in ocean temperatures due to increasing carbon dioxide in the atmosphere.

But some of the details, reported in today's issue of Nature, conflict. The warmer water is present right across the Atlantic, and is present down to depths of 3,000m (9,840ft) - much deeper than would have been predicted from most models of global warming, which tend to suggest that the upper surface layers of the oceans should warm up first.

Dr Bryden fears that the temperature rise indicates that a major change is under way in the pattern of ocean currents. There is a 'conveyor belt' at work in the ocean: warm surface water flows north from the tropics and subtropics - the best known example is the Gulf Stream - but the water cools and sinks as it reaches polar regions, before flowing south again at depths greater than 1,000m (3,280ft).

Dr Bryden said yesterday: 'The region where we see warming is in the depth range of water masses formed in the subpolar Atlantic - changes in the Laborador Sea that have been brought south.'

The water now sinking in the Labrador Sea is warmer than it used to be. However, Dr Bryden warned against jumping to the conclusion that the cause is increased carbon dioxide levels - the ocean-atmosphere interaction is too complicated to make simple connections.

Last year, another group of researchers reported that they had found cooling in some subpolar regions of the Atlantic, which appears to conflict with the idea of global warming.

Dr Bryden looks forward to an international systematic study of the Atlantic planned for 1997. If the scope of that survey is big enough, 'I think the ocean offers us an opportunity to understand the changes in the atmosphere and climate', he said.