"Such large changes are a tremendous surprise," said Dr Ute Schuster, who will publish the findings with professor Andrew Watson in the Journal of Geophysical Research next month.

"We expected that the uptake would change only slowly because of the ocean's great mass."

There is also evidence of a slowdown in the uptake of CO2 by the Southern ocean, although it is not as great or as sudden as in the North Atlantic.

The scientists based their findings on data collected by merchant ships fitted out with equipment to automatically measure the levels of carbon dioxide in the water.

One ship that sailed between Britain and the West Indies made more than 90,000 measurements in recent years.

The oceans are one of two major carbon "sinks" for CO2 emissions, the other being the land biosphere, which together absorb about half of all CO2 emitted into the atmosphere.

If the oceans soak up less CO2, it means CO2 levels in the atmosphere will rise much faster and the climate could warm more rapidly, the researchers said in a statement.

"The speed and size of the change show that we cannot take for granted the ocean sink for the carbon dioxide," said Watson.