Global warming may explain Arctic's green ice

Global warming may be responsible for massive blooms of phytoplankton growing under Arctic sea and more blooms in the future, potentially causing significant disruption in the Arctic food chain, suggests new research.

Phytoplankton should not be able to grow under the ice because ice reflects most sunlight back into space, blocking it from reaching the water below.

But over the past decades, Arctic ice has gotten darker and thinner due to warming temperatures, allowing more and more sunlight to penetrate to the water beneath, the study said.

Large, dark pools of water on the surface of the ice, known as melt ponds, have increased, lowering the reflectivity of the ice.

The research, detailed in the journal Science Advances, showed that thinning Arctic sea ice may be responsible for these blooms .

"Our big question was, how much sunlight gets transmitted through the sea ice, both as a function of thickness, which has been decreasing, and the melt pond percentage, which has been increasing," said first author Chris Horvat from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS).

"What we found was that we went from a state where there wasn't any potential for plankton blooms to massive regions of the Arctic being susceptible to these types of growth," Horvat said.

Twenty years ago, only about three to four per cent of Arctic sea ice was thin enough to allow large colonies of plankton to bloom underneath.

Today, the researchers found that nearly 30 per cent of the ice-covered Arctic Ocean permits sub-ice blooms in summer months.

The team's mathematical modelling found that while the melt ponds contribute to conditions friendly to blooms, the biggest culprit is ice thickness.

--IANS

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