The researchers gauged CO2 absorption through more than 90,000 measurements from merchant ships equipped with automatic instruments. The result of their 10-year study in the North Atlantic showed that CO2 uptake had halved between the mid-90s and 2000 to 2005.
The findings assume significance as the ocean's ability to soak up less of the greenhouse could worsen the global warming scenario. The study authors said the findings were worrying, as there were grounds to believe, that in time, the ocean might become saturated with emissions.
Environment analyst Roger Harrabin said: "The researchers don't know if the change is due to climate change or to natural variations". "But they say it is a tremendous surprise and very worrying because there were grounds for believing that in time the ocean might become 'saturated' with our emissions - unable to soak up any more," the BBC quoted him as saying.
Harrabin said the saturation of the oceans would "leave all our emissions to warm the atmosphere". Of all the CO2 emitted into the atmosphere, only half of it stays there; the rest goes into carbon sinks.
There are two major natural carbon sinks: the oceans and the land "biosphere". They are equivalent in size and absorb a quarter of all CO2 emissions each.