The melting of the Greenland ice sheet could accelerate and raise sea levels faster than expected, and scientists are “very worried.”
Warmer conditions are encouraging algae to grow and darken the surface. Dark ice absorbs more solar radiation, escalating heating and melting times.
Today, the Greenland ice sheet, the largest mass of ice in the northern hemisphere, adds up to 1 mm a year to the rise in the global average level of the oceans. At the size of the United Kingdom and up to 2 miles thick, it has the potential to raise the sea level by more than 20 feet if it melted entirely. So it’s not surprising it is a focus of research—it has direct relevance to major coastal cities from Miami to London and Shanghai.
Though algae was first observed on the Greenland ice sheet more than a century ago, its impact was largely ignored until recently. In the past few years, researchers have continued exploring how the small plants could affect future melting. Black and Bloom, a UK research project, is under way to investigate the different species of algae and how they could spread.
A current concern is that rising temperatures will allow algae to flourish on the flat areas in the interior of the ice sheet, where melting could occur on a much larger scale. While white snow reflects 90% of solar radiation, dark patches of algae only reflect about 35% percent—or even 1% in the most extreme cases.
In the past two decades, Greenland has been losing more ice than it gains through snowfall in the winter. Over that same period of time, images from the MODIS satellite showed a darkening trend, Dr. Andrew Tedstone, a glaciologist from Bristol University notes.
Earlier research revealed that the ice sheet is covered with a range of contaminants carried on winds, but studies over the past five years have shown that the majority of the dark material may be biological.
“This is a living landscape,” according to Dr. Joe Cook, a glacial microbiologist at Sheffield University. “This is an extremely difficult place for anything to live but, as we look around us, all this darkness we can see on the ice surface is living – algae, microbes, living and reproducing in the ice sheet and changing its color. We know they’re very widespread and we know that they’re very dark and we know that that’s accelerating melt but that’s not something that’s built into any of our climate projections – and that’s something that needs to change.”
The final phase of the Black and Bloom project will involve weaving the new factor of biological darkening into climate models and coming up with revised estimates for future sea level rise.