What Is Eating Away at the Greenland Ice Sheet?

What Is Eating Away at the Greenland Ice Sheet?

SOURCE: Inside Climate News DATE: April 19, 2018 SNIP: [T]emperatures are rising in the Arctic at about twice the global average. That causes melting around the edges of the ice sheet each year and reaches across more of the surface during summer heat waves. In areas near the edge of the ice sheet, things get even more interesting: a carpet of microbes and algae mixed with dust and soot, a short-lived climate pollutant, is darkening the ice sheet, absorbing the sun’s rays and accelerating the melting of the ice. New research shows this dark zone is growing. The new research, published in the journal Nature Communications, describes a geological feedback loop on the ice that’s expanding the dark zone: Warming melts the western edge of the ice sheet, releasing mineral dust from rock crushed by the ice sheet thousands of years ago. That dust blows to the surface of the ice, nurturing the microbes and algae living there. Those organisms produce colored pigments as sunscreen, which contribute to the darkening of the surface, reducing reflectivity and increasing melting. “Just the little bit of extra heat from a tiny soot particle can start transforming feathery and highly reflective snow crystals into darker, rounded grains that absorb more heat,” said climate researcher Jason...
Ice cores show Greenland’s melting is unprecedented in at least four centuries

Ice cores show Greenland’s melting is unprecedented in at least four centuries

SOURCE: The Washington Post DATE: March 28, 2018 SNIP: Scientists who crossed western Greenland with a fleet of snowmobiles, pulling up long cylinders of ice at camps a little more than a mile above sea level, have found evidence that the vast sheet of ice is melting faster than at any time in the past 450 years at least — and possibly much longer than that. That’s worrisome, because the snow that has fallen on the island over millennia — now compacted into ice — could raise sea levels by 20 feet if it completely melted. The new study is further evidence that Greenland is seeing a lot of melt in the present, but what’s novel is the ability to put that in context, said Twila Moon, a research scientist at the National Snow and Ice Data Center who studies Greenland but was not involved in the current study. “It’s just another type or form of evidence to support the fact that we’re seeing really dramatic, rapid, and probably unprecedented changes,” Moon said. Based on such research, “I am personally fully confident that we haven’t seen melt like this for 5,000 years,” Osterberg...
Chain reaction of fast-draining lakes poses new risk for Greenland ice sheet

Chain reaction of fast-draining lakes poses new risk for Greenland ice sheet

SOURCE: University of Cambridge DATE: March 14, 2018 SNIP: Researchers from the UK, Norway, US and Sweden have used a combination of 3D computer modelling and real-world observations to show the previously unknown, yet profound dynamic consequences tied to a growing number of lakes forming on the Greenland ice sheet. Lakes form on the surface of the Greenland ice sheet each summer as the weather warms. Many exist for weeks or months, but drain in just a few hours through more than a kilometre of ice, transferring huge quantities of water and heat to the base of the ice sheet. The affected areas include sensitive regions of the ice sheet interior where the impact on ice flow is potentially large. Previously, it had been thought that these ‘drainage events’ were isolated incidents, but the new research, led by the University of Cambridge, shows that the lakes form a massive network and become increasingly interconnected as the weather warms. When one lake drains, the water quickly spreads under the ice sheet, which responds by flowing faster. The faster flow opens new fractures on the surface and these fractures act as conduits for the drainage of other lakes. This starts a chain reaction that can drain many other lakes, some as far as 80 kilometres away. These cascading events – including one case where 124 lakes drained in just five days – can temporarily accelerate ice flow by as much as 400%, which makes the ice sheet less stable, and increases the rate of associated sea level...
Earth’s Ice Is Melting Much Faster Than Forecast.

Earth’s Ice Is Melting Much Faster Than Forecast.

SOURCE: Garn Press DATE: February 5, 2018 SNIP: The key question, as I see it, is how to project what the sea level will soon be due to ice sheet melting. But this is confounded by us not really knowing what to expect. We keep being surprised by nature being more sensitive and complex. As the science develops, we see more interconnection, where multiplying feedbacks produce surprisingly fast responses. Will there be some saving self-regulation of human-induced climate warming and its melting land ice consequences? The enormous increase of heat in our oceans, from past decades of enhanced greenhouse effect, negates any hope that negative feedbacks or even solar output will prevent a much warmer world. The few negative feedbacks we have found for ice — like more snow as a result of a warming climate, more reflective frost, more efficient sub-glacial water transmission — are clearly being outdone. And at the global scale, despite some negative feedbacks like more clouds, clearly we are not seeing net cooling. Feedbacks, whether positive or negative, only do their thing after the initial effect. Negative feedbacks don’t reverse the perturbation. Seemingly the biggest issue with abrupt sea level rise comes from the now unstoppable loss of key sectors of west Antarctic ice and the discovery of more marine instability than we thought elsewhere. Like glaciers thinning rapidly in east Antarctica. Or in Greenland where improved bedrock maps reveal a marine connection an average of 40 kilometers further inland than previously thought. Or like how new fjord underwater mapping reveals greater fjord depths, increasing the odds that deep warm ocean water can communicate...

Glacial moulin formation triggered by rapid lake drainage

SOURCE: AGU DATE: January 17, 2018 SNIP: Scientists are uncovering the mystery of how, where and when important glacial features called moulins form on the Greenland Ice Sheet. Moulins, vertical conduits that penetrate through the half-mile-deep ice, efficiently funnel the majority of summer meltwater from the ice surface to the base of the ice sheet. The lubricating effects of the draining water can lead to faster sliding of the ice sheet. A new study published in Geophysical Research Letters, a journal of the American Geophysical Union, finds meltwater lakes that form on the ice surface can drain through moulins in a matter of hours. The new results indicate a potentially much broader importance for lake drainage events, because moulins control the locations where the majority of seasonal meltwater enters the ice sheet, accesses the bed, and accelerates the ice flow, according to Stephen Price, a researcher at Los Alamos and co-author of the new study. “These processes, which aren’t currently accounted for in computer simulations of ice sheet evolution and sea-level change, may need to be considered more carefully in future models,” he said. While previous studies identified a distinct possibility of a cascading effect from meltwater reaching the bed and modifying local stresses to cause nearby supraglacial lake drainage, the new results provide direct evidence that this effect is more widespread and can act over distances of many kilometers, said Matthew Hoffman, a glaciologist and computer scientist at Los Alamos National Laboratory in Los Alamos, New Mexico and lead author of the new study. This long-distance triggering mechanism could make new regions of the ice sheet vulnerable to...