Antarctica’s Ice Loss Is Speeding Up, with Sharp Acceleration in Past 5 Years

Antarctica’s Ice Loss Is Speeding Up, with Sharp Acceleration in Past 5 Years

SOURCE: Inside Climate News and Nature DATE: June 13, 2018 SNIP: The most complete assessment to date of Antarctica’s ice sheets confirms that the meltdown accelerated sharply in the past five years, and there is no sign of a slowdown. That means sea level is expected to rise at a rate that will catch some coastal communities unprepared despite persistent warnings, according to the international team of scientists publishing a series of related studies this week in the journal Nature. The scientists found that the rate of ice loss over the past five years had tripled compared to the previous two decades, suggesting an additional 6 inches of sea level rise from Antarctica alone by 2100, on top of the 2 feet already projected from all sources, including Greenland. Between 1992, when detailed satellite measurements started, and 2012, Antarctica lost about 76 billion tons of ice per year. But since 2012, that rate has tripled to about 219 billion tons of ice loss per year, the scientists found. Another study, published June 13 in the journal Science Advances, raises even more concerns about the vulnerability of Antarctic ice to global warming. Data from radar and laser readings of the ice enabled scientists with the University of Texas at Austin and the University of Waterloo to map a vast network of channels in the base of many ice sheets formed by intrusions of warm water. Some are several kilometers wide, said University of Texas at Austin researcher Jamin Greenbaum. They found the channels everywhere they looked, including beneath the ice shelf of the Totten Glacier, in East Antarctica, as well...
Stanford researcher: Interacting Antarctic glaciers may cause faster melt and sea level contributions

Stanford researcher: Interacting Antarctic glaciers may cause faster melt and sea level contributions

SOURCE: Stanford University DATE: January 23, 2018 SNIP: A new study shows that a large and potentially unstable Antarctic glacier may be melting farther inland than previously thought and that this melting could affect the stability of another large glacier nearby – an important finding for understanding and projecting ice sheet contributions to sea-level rise. The findings, by a Stanford-led team of radar engineers and geophysical glaciologists, came from radar data collected at the same locations in 2004, 2012 and 2014, each revealing details of the glaciers miles below the surface. The surveys show that ocean water is reaching beneath the edge of the Pine Island Glacier about 7.5 miles further inland than indicated by previous observations from space. The team also found that the Southwest Tributary of Pine Island Glacier, a deep ice channel between the two glaciers, could trigger or accelerate ice loss in Thwaites Glacier if the observed melting of Pine Island Glacier by warm ocean water continues down the ice channel. This new perspective on the Southwest Tributary shows melting beneath Pine Island may be currently or imminently causing the melting of Thwaites and speeding the rate of sea-level...
Shrinking Mountain Glaciers Are Affecting People Downstream

Shrinking Mountain Glaciers Are Affecting People Downstream

SOURCE: Scientific American DATE: January 23, 2018 SNIP: Mountain glaciers around the world, from the Himalayas to the Andes, are shrinking in the face of climate change—and that could pose a major threat to water resources for nearby communities. These mountain glaciers are important resources for human settlements. Glacial runoff, especially during the spring and summer, can provide a critical source of fresh water downstream. But in a new modeling study of 56 glacier drainage basins worldwide, roughly half the studied sites have already reached a kind of tipping point—after which the amount of fresh water that runs off each year begins to decline. “As glaciers recede, water is released from long-term glacial storage,” the researchers note in the paper, which was published yesterday in the journal Nature Climate Change. “Thus, annual glacier runoff volume typically increases until a maximum is reached, often referred to as ‘peak water.'” After this point is reached, they note, the amount of annual runoff begins to decline again. Now, scientists are increasingly aware that mountain glaciers—like mountain snowpack—are growing more vulnerable to the influence of climate change. Yesterday’s study suggests that total glacier volume across all the investigated basins will decrease by about 43 percent by the year 2100, even if the world takes serious steps to mitigate climate change. Under a more severe “business-as-usual” trajectory, in which greenhouse gas emissions continue unabated into the future, these total declines could be as high as 74...

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...
East Antarctic Ice Has a Wild Past. It May Be a Harbinger

East Antarctic Ice Has a Wild Past. It May Be a Harbinger

SOURCE: National Geographic DATE: December 13, 2017 SNIP: Scientists sounding the seabed off Antarctica have uncovered some surprising episodes from the continent’s history: The East Antarctic Ice Sheet, they say, experienced a series of dramatic retreats in the distant past—retreats that were often punctuated by catastrophic floods of meltwater that erupted from beneath the ice sheet and left deep scars in the seafloor. The ice covering East Antarctica, more than 12,000 feet thick in many places, has long been considered more stable and permanent than the West Antarctic Ice Sheet —and thus more likely to weather global warming unscathed. But the new research, published this week in Nature by Sean Gulick of the University of Texas and his colleagues, reinforces a growing concern that large swaths of East Antarctica are more vulnerable than once thought. In recent years scientists have mapped the East Antarctic bedrock with ice-penetrating radar and found that, like West Antarctica, it includes large regions that plunge thousands of feet below sea level. Because they sit on such low ground, those areas of the ice sheet are susceptible to melting by deep, warm ocean currents. One of the biggest is the Aurora Subglacial Basin. Much of the ice there flows to the sea through the Totten Glacier, which has been found to be thinning...