Darkening Greenland Ice Cap Absorbing 7% More Solar Energy/Decade - New Positive Feedback Loop
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The snowy surface of Greenland started becoming significantly less reflective of solar radiation from around 1996, the analysis found, with the ice absorbing 2% more solar energy per decade from this point. At the same time, summer near-surface temperatures in Greenland have increased at a rate of around 0.74C per decade, causing the ice to melt.
This winnowing away of the ice, exacerbated by soot blown on to the ice from wildfires, means that Greenland’s ice is stuck in what is known as a “feedback loop” that will make it ever more vulnerable to warming global temperatures. The study predicts that the ice surface reflectivity, or albedo, will drop by 10% or more by the end of the century, which will trigger further melting.
“It’s melting cannibalism, basically – it’s melting that’s feeding itself,” said lead author Marco Tedesco, of Columbia University’s Lamont-Doherty Earth Observatory. “Rising temperatures are promoting more melting, and that melting is reducing albedo, which in turn is increasing melting.
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Tedesco’s research shows that as the surface of Greenland’s ice melts, old impurities, such as dust from erosion or soot that has been entombed for years, start to appear, darkening the surface. If the summer is warm enough to remove all the snow, these dark impurities begin to spread across the surface, providing a far more heat-absorbent environment. At the same time, as this snow melts and then refreezes, the grains of snow get larger. These larger grains, invisible to the eye but detected by satellite’s infrared instruments, also create a less reflective surface. These two processes are turning Greenland into a store, rather than a reflector, of solar energy, with consequences far beyond the icy wilderness. Water from the melting flows into the sea, contributing to rising oceans around the world. This process is unlikely to reverse given the increasing concentrations of greenhouse gases in the atmosphere.
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http://www.theguardian.com/environment/2016/mar/03/greenland-ice-sheet-melting-global-warming-feedback-loop
