Antarctica's climate clues

The ship is strengthened to get through ice

By Christine McGourty, science correspondent, in the Antarctic

If humans really are interfering with the Earth's climate and pushing up world temperatures, some of the best evidence could come from Antarctica.

Changes in the environment on and around the White Continent can have far-reaching effects.

I joined scientists on one of the world's most advanced research vessels, the James Clark Ross, as it sailed through the Drake Passage, the notoriously rough stretch of water that separates the Antarctic and the southern tip of South America.

The researchers on board were engaged in their annual survey of the currents here. They want to know how the temperature and movement of the water is changing.

Giant thermometer

The Antarctic Ocean has the world's largest ocean current, carrying water clockwise around the continent and interacting with the Atlantic, the Pacific and the Indian oceans.

We have to understand the oceans as well as the atmosphere

Brian King, Southampton Oceanography Centre

Mike Meredith of the British Antarctic Survey explained: "The waters that form around the Antarctic spread out and move northwards into the Atlantic, reaching the latitudes of the UK, so any changes in temperature for example will have a long-term effect on global climate.

"Exactly how that works is something that nobody really knows, which is why the measurements we're making at the moment are so important."

The team is using a CTD (conductivity - which relates to the amount of salt in the water- temperature and depth) instrument to monitor the current. The instrument is like a giant thermometer and has to be lowered overboard using a crane-like device.

Long-term records

Of course, the equipment looks nothing like a real thermometer - it is a giant metal frame about three times the size of a large fridge, with 11 black cylinders attached to it to sample water at various depths. Data is sent back to the surface via a cable.

The CTD instrument will descend over two miles down, almost to the seabed.

The CTD equipment samples water at different depths

The whole process is repeated 30 times over the course of five days. Every year, the scientists come back and repeat the exercise in exactly the same locations.

Brian King, of the UK's Southampton Oceanography Centre, says long-term ocean records are essential if we are to understand the effects any global warming might have on the planet.

"Meteorological records go back hundreds of years, but ocean records go back only a couple of decades," he told the BBC.

"The work we're doing now will be collecting data that in future will be used to understand and perhaps even predict climate change far better than we can now."

Personal view

The closer the James Clark Ross moves to Antarctica, the more difficult it can be for the vessel to get to the locations it needs to visit.

The water turns to slush and then freezes. Although the ship is strengthened to get through the ice, it can be difficult sometimes to make headway.

Frequently, a plane is sent out from the British Antarctic Survey's base at Rothera to survey the ice and offer some advice to the ship's captain on where to steer.

Captain Chris Elliott has been sailing these waters for more than 30 years and knows them better than anyone. As parts of the continent have warmed up he has noticed a reduction in annual ice cover. And he feels this is not all that is changing.

"The weather is even more volatile than it was," he said. "We're getting a greater frequency of very deep depressions, causing very strong winds. I'm not saying we didn't get them before, but it seems to me the frequency is greater."

This is only the personal view of one very experienced sailor, but it echoes the growing feeling that things are changing in Antarctica.

The scientists on the James Clark Ross hope they can understand exactly how and why. If we can predict global changes, perhaps we may be better able to adapt to them.