An expedition of adventurers and researchers will investigate how the global rise in carbon dioxide is increasing acidity in waters close to the North Pole.

Polar explorer Pen Hadow will lead an expedition to a purpose-built ice base 750 miles from the pole in March, where scientists will study the environmental impacts of the changing acidity of some of the coldest waters on the planet.

Carbon dioxide's leading role as a greenhouse gas driving climate change is well known, but the effect it is having on the pH of the world's oceans gets less air time.

Some scientists believe that by 2050 oceans will reach a level of acidity not seen for over 20 million years - which will undoubtedly have a significant impact on marine life around the globe.

French scientist Prof Jean-Pierre Gattuso who is among those heading for the ice base, said: "Ocean acidification is the 'other carbon dioxide problem'.

"The oceans absorb about a quarter of human-made CO2. This has been limiting the amount of greenhouse gas in the atmosphere and mitigating climate change.

"However, the massive amounts of CO2 absorbed considerably upsets the ocean chemistry by increasing the acidity of sea water.

"It is certain that it will impact marine ecosystems, although we do not fully understand how all marine species will cope at the levels of acidity projected later in this century."

The study will be carried out as part of the Catlin Arctic Survey 2010, which will also see experienced polar explorers trek up to 500 kilometres across the floating Arctic sea ice to collect scientific data in a region in which it would be unsafe for scientists to work.

Both teams will face the extreme conditions of the Arcticat his time of year which, with a wind-chill factor, could reach minus 75 degrees Celsius.

Pen Hadow described the Survey as an example of modern exploration:"Our aim at the Catlin Arctic Survey is to make it possible for science work to be undertaken that would otherwise be exceptionally difficult to do.

"The scientists will be able to work safely thanks to the skills of our polar support team, who will be guiding them out onto the floating sea ice.

"Our ice base will have all the facilities they need to conduct research and to survive in the extreme conditions of an Arctic winter and spring."

Sam Bond