Climate Science

Melting triggers more melting

    The whole of Greenland's ice sheet is likely to experience some degree of melting over the next decade.

    Credit: A. COOPER/R. HARDING

    Jason Box at the Ohio State University in Columbus and his team combined satellite measurements of surface albedo — how much sunlight the ground reflects — with models of surface air temperature and solar radiation hitting the surface for the past 12 summers. The researchers found that positive albedo feedback — whereby melting ice reduces surface reflectivity, leading to faster melting — has doubled the ice sheet's surface melt rate since 2000.

    The authors identified three ways in which recent warm summers could have contributed to the reduced albedo: surface heating due to unusually warm air currents creates larger snow grains that reflect less sunlight; less cloudy skies increase direct heating from sunlight; and reduced summer snowfall results in a darker surface.

    Another warm decade could mean that Greenland will absorb instead of resist the heat from 24-hour sunlight, leading to expansion of the melt area to encompass the entire ice sheet. This process has already begun, with an estimated 97% of Greenland's ice sheet having shown surface melting by mid-July of this year.

    Cryosphere 6, 821–839 (2012)

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    Melting triggers more melting. Nature 488, 433 (2012).

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