London, September 11 : A new research has suggested that as the northern polar cap melts, it could lift the lid off a new carbon sink capable of soaking up carbon dioxide (CO2).
According to a report in New Scientist, the findings, from two separate research groups, raise the possibility - albeit a remote one - of weakening the greenhouse effect.
The researchers said that the process of carbon sequestration is already underway.
Even so, the new carbon sink is unlikely to make a significant dent in the huge amounts of CO2 pumped into the atmosphere by industrial activities.
Kevin Arrigo and colleagues at Stanford University studied satellite data collected between 1998 and 2007 to see how sea surface temperatures and the quantities of sea ice and phytoplankton had changed during that time.
Phytoplankton produce chlorophyll to obtain energy from CO2, and so increased phytoplankton productivity would remove carbon from the atmosphere.
"We found that as sea ice diminishes, annual productivity goes up," said Arrigo.
Satellite remote sensing measures the amount of chlorophyll in surface waters, and so provides an estimate of ocean productivity.
From one year to the next, the phytoplankton grew more in areas where the ice had disappeared: less ice meant more open water for longer, allowing the plankton to soak up more energy from the Sun.
In some areas, production was boosted more than three-fold.
But, Ken Denman of the Canadian Centre for Climate Modelling and Analysis warns that the Arctic sink as it stands is likely to have only a very small impact on human emissions.
Typically between half and a quarter of the carbon soaked up by phytoplankton ends up stored at the bottom of the ocean.
If the Arctic became completely ice-free and phytoplankton productivity levels were maintained, Arrigo and his colleagues calculated that the new carbon sink could in theory absorb an extra 160 million tonnes of carbon each year.
"Given the current rate of human emissions, that would only account for 0.7 per cent of total annual emissions," said Arrigo.