Antarctic abyss also affected by global warming

March 12th, 2009 - 2:08 pm ICT by ANI  

London, March 12 (ANI): A new research has shown that even the deepest, darkest reaches of the Antarctic abyss have been affected by global warming.

The research, conducted by Gregory Johnson, of the US National Oceanic and Atmospheric Agency, and a team of international colleagues, suggests the changes could be responsible for up to 20 percent of the observed global sea-level rise.

As part of the CLIVAR (Climate Variability and Predictability) project, Johnson and his team have been spending weeks at a time at sea, tracing straight lines across all of the worlds oceans.

As they make these traverses, they measure the temperatures of the water from the very bottom right up to the surface.

The team takes its measurements along the same routes as expeditions carried out in the 1990s, which provides a picture of how things have changed in roughly one decade.

The researchers are particularly interested in the masses of cold water that sink down to the abyss along the shores of Antarctica before moving north along the ocean floor into the Atlantic, Pacific and Indian Oceans.

These three flows of Antarctic abyssal water overwhelmingly influence the deep waters of the world, says Johnson.

Water sinks off the coast of Greenland too, but the Antarctic abyssal water volume is twice that of the north Atlantic.

Early results from CLIVAR show that abyssal water is warmer now than it was in the 1990s.

The water that travels from Antarctica into the south-eastern Indian basin is roughly 0.1 degree Celsisus warmer. The deep ocean current travelling from Antarctica into the Pacific is 0.03 degree C warmer.

In the northern hemisphere, the deep abyssal Atlantic water, which sits between the ocean floor and the layer of deep water that sinks off the coast of Greenland and travels south, is 0.04 degree C warmer.

The researchers have also looked at the salinity of the deep Antarctic waters, which is important because it affects water buoyancy.

They found that here, too, there is change: in both the southeast Indian Ocean and in the Pacific, the water is less salty today than it was in the 1990s.

Most likely, this is a direct result of dilution from the melting Antarctic ice, said Johnson.

According to Johnson, the warming and consequent expansion of the deep water flows may be responsible for between 10 percent and 20 percent of the global sea-level rise seen during that time. (ANI)

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