They say warmer conditions are encouraging algae to grow and darken the surface.
Dark ice absorbs more solar radiation than clean white ice so warms up and melts more rapidly.
Currently the Greenland ice sheet is adding up to 1mm a year to the rise in the global average level of the oceans.
It is the largest mass of ice in the northern hemisphere covering an area about seven times the size of the United Kingdom and reaching up to 3km (2 miles) in thickness.
This means that the average sea level would rise around the world by about seven meters, more than 20ft, if it all melted.
That is why Greenland, though remote, is a focus of research which has direct relevance to major coastal cities as far apart as Miami, London, and Shanghai and low-lying areas in Bangladesh and parts of Britain.
Algae were first observed on the Greenland ice sheet more than a century ago but until recently its potential impact was ignored. Only in the last few years have researchers started to explore how the microscopically small plants could affect future melting.
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The possibility of biologically inspired melting was not included in the estimates for sea level rise published by the UN's climate panel, the IPCC, in its latest report in 2013.
That study said the worst-case scenario was a rise of 98cm (3.2ft) by the end of the century.
One concern now is that rising temperatures will allow algae to flourish not only on the slopes of the narrow margins of the ice-sheet but also on the flat areas in the far larger interior where melting could happen on a much bigger scale.
Read more at Sea Level Fears as Greenland Darkens
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