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...
Greenland’s ice sheet is driving global sea level rise. One section is melting 80% faster.

Greenland’s ice sheet is driving global sea level rise. One section is melting 80% faster.

SOURCE: Vox DATE: December 14, 2017 SNIP: Average temperatures around the world may be slowly ticking upward, but their effects on the environment can be sharp and quick. Earlier this week, we learned that Arctic sea ice extent is declining at its fastest rate in 1,500 years. On Wednesday, scientists reported that in 2003, the ice sheet on Greenland suddenly began melting at a much faster rate. Greenland’s ice is hugely important for the planet. The sheet of ice that covers 660,000 square miles is more than a mile thick and has a volume of 684,000 cubic miles. If it all melts, it would raise global sea levels by 25 feet. On Thursday, scientists published a new map of the land mass beneath Greenland’s ice, showing that the ice is deeper than previously thought, so losing it all would lead to an additional 2.7 inches of sea level rise above past estimates. In a paper published Wednesday in the journal Science Advances, scientists reported that in one catchment in Southwestern Greenland, the melt rate surged 80 percent between 2003 and 2014 compared to the 26-year period beforehand, hinting at changes in the overall melt rate of the ice...
New Maps Show How Greenland’s Ice Sheet Is Melting from the Bottom Up

New Maps Show How Greenland’s Ice Sheet Is Melting from the Bottom Up

SOURCE: Scientific American DATE: November 6, 2017 SNIP: Significantly more ice in Greenland’s glaciers may be exposed to warming ocean waters than previously thought, new research suggests. Indeed, more than half the ice sheet may be subject to the melting influence of the sea. These are the latest conclusions of a detailed mapping project exploring the topography of the seafloor and bedrock around and beneath Greenland’s glaciers. Published in their final form last week in the journal Geophysical Research Letters, the maps draw on a variety of data sources, including satellite radar and aerial imagery, as well as special sonar data collected on ship expeditions to the front of the ice sheet. Included in the new paper are some of the most detailed data yet on the depths of the canyons and fjords scarring the Greenland coast, which carry water in from the sea to lap against the ice. The results suggest that the western and northern regions of Greenland are most exposed to the influence of ocean water. Out of 139 ocean-touching glaciers the team identified, they also found that 67 rest in waters 200 meters (about 650 feet) or more below sea level, where warm water is typically found—at least twice as many as previously...
New Greenland Maps Show More Glaciers at Risk

New Greenland Maps Show More Glaciers at Risk

SOURCE: NASA DATE: November 1, 2017 SNIP: New maps of Greenland’s coastal seafloor and bedrock beneath its massive ice sheet show that two to four times as many coastal glaciers are at risk of accelerated melting as previously thought. Researchers at the University of California at Irvine (UCI), NASA and 30 other institutions have published the most comprehensive, accurate and high-resolution relief maps ever made of Greenland’s bedrock and coastal seafloor. The new maps reveal that two to four times more oceanfront glaciers extend deeper than 600 feet (200 meters) below sea level than earlier maps showed. That’s bad news, because the top 600 feet of water around Greenland comes from the Arctic and is relatively cold. The water below it comes from farther south and is 6 to 8 degrees Fahrenheit (3 to 4 degrees Celsius) warmer than the water above. Deeper-seated glaciers are exposed to this warmer water, which melts them more rapidly. OMG Principal Investigator Josh Willis of JPL, who was not involved in producing the maps, said, “These results suggest that Greenland’s ice is more threatened by changing climate than we had...