Rain may be causing a worrying amount of ice to melt in Greenland

Rain may be causing a worrying amount of ice to melt in Greenland

SOURCE: New Scientist DATE: March 7, 2019 DATE: Rain is becoming more common across Greenland’s ice sheet and it may be playing an important role in rising sea levels. Greenland’s 660,000-square mile ice sheet contains enough fresh water to flood coastal cities around the world. Warm air over the sheet is causing it to melt, but new work reveals that rainfall is also causing more melting than previously thought. An analysis of satellite and weather station records suggests that around 300 melt events in Greenland between 1979 and 2012 were linked to rainfall. Over this time, rain-associated melting became twice as frequent in summer, and three times as frequent in winter. Rain now appears to account for 28 per cent of the ice sheet’s melt. When precipitation falls as rain, it causes some of Greenland’s ice sheet to be covered in ice rather than snow. Come the summer, this ice reflects less of the sun’s energy, exacerbating summer melting. Historically, Greenland’s melt season has run between May and August, but rainfall means melting is now happening in winter too. “The rain events are extremely important because they are one of the only triggers for melting in winter,” says Marco Tedesco, of Columbia University in New York, who was involved in the...
Are we headed toward the worst-case climate change scenario?

Are we headed toward the worst-case climate change scenario?

SOURCE: Pacific Standard and New York Times DATE: January 25, 2019 SNIP: This week, researchers warned that Greenland’s ice sheet has reached a tipping point. Looking at more than a decade’s worth of ice loss, an international team of scientists found that the rate of Greenland’s ice loss in early 2013 was four times higher than in 2003. [I]n this new study, Michael Bevis, a professor at Ohio State University, and his colleagues were surprised to see that most of the ice loss occurred in the southwest corner of Greenland, a region with very few glaciers. In other words, most of the ice loss was in the form of meltwater runoff, draining from land-based ice sheets into the sea. What Bevis and his colleagues found was that the melting was being controlled by something called the North Atlantic Oscillation—an irregular fluctuation in atmospheric pressure over the Atlantic Ocean that influences the weather on several continents. “Global warming brought summertime temperatures just shy of the critical temperature at which massive melting would occur, and the NAO pushed it over this critical threshold,” he says. It means that the ice sheet is now sensitive to small fluctuations in summer temperatures, and if global temperatures continue to rise as predicted, soon Greenland’s summers will be warm enough to cause massive melting regardless of the NAO’s phase. The new research dovetails with other recent papers on the accelerating melting. Last month a team of researchers published a paper in Nature that used satellite observations, analysis of ice cores and models to show that losses from the Greenland ice sheet have reached their fastest...
Greenland ice melting rapidly

Greenland ice melting rapidly

SOURCE: Ohio State News and National Geographic DATE: January 21, 2019 SNIP: Greenland is melting faster than scientists previously thought—and will likely lead to faster sea level rise—thanks to the continued, accelerating warming of the Earth’s atmosphere, a new study has found. Scientists concerned about sea level rise have long focused on Greenland’s southeast and northwest regions, where large glaciers stream iceberg-sized chunks of ice into the Atlantic Ocean. Those chunks float away, eventually melting. But a new study published Jan. 21 in the Proceedings of the National Academy of Sciences found that the largest sustained ice loss from early 2003 to mid-2013 came from Greenland’s southwest region, which is mostly devoid of large glaciers. “Whatever this was, it couldn’t be explained by glaciers, because there aren’t many there,” said Michael Bevis, lead author of the paper, Ohio Eminent Scholar and a professor of geodynamics at The Ohio State University. “It had to be the surface mass—the ice was melting inland from the coastline.” That melting, which Bevis and his co-authors believe is largely caused by global warming, means that in the southwestern part of Greenland, growing rivers of water are streaming into the ocean during summer. The key finding from their study: Southwest Greenland, which previously had not been considered a serious threat, will likely become a major future contributor to sea level rise. “We knew we had one big problem with increasing rates of ice discharge by some large outlet glaciers,” he said. “But now we recognize a second serious problem: Increasingly, large amounts of ice mass are going to leave as meltwater, as rivers that flow...
Greenland is melting much faster than we thought

Greenland is melting much faster than we thought

SOURCE: Popular Science DATE: December 6, 2018 SNIP: Greenland is losing its cool. That’s not much of a surprise—its mile-thick sheet of ice was not made for this epoch of climate change. But that cool is getting shredded faster than we think. According to new findings published Wednesday in Nature, climate change has accelerated the melting of Greenland’s ice sheet to unparalleled levels, unseen in at least 350 years and likely in the past 7,800. The rate of melt and the resulting runoff falling into the ocean (and adding to a rising sea level) is speeding up over time, thanks to a motley of factors acting as a feedback loop. “By using ice cores, we can literally ‘drill back in time,’ and we are able to extend the observational period back in time ten-fold,” says Sarah Das, a glaciologist at Woods Hole Oceanographic Institution and a coauthor of the new study. In all, the team’s analysis suggests melt intensity in Greenland increased by a whopping 250 to 575 percent over just the last 20 years, relative to pre-industrial levels. In those same two decades, total ice sheet runoff has increased by 50 percent since the industrial age began, spiking up by 33 percent since the 20th century alone. Multiple factors are coalescing to create multiple feedback loops, all exacerbating the ice and snow melt. One of these is the melt-albedo feedback, in which melting creates a more granular consistency of snow that absorbs more sunlight and melts faster. Melting also exposes darker ice to sunlight, which warms up and melts faster than lighter shades of ice. And when melting...
Modest warming risks ‘irreversible’ ice sheet loss, study warns

Modest warming risks ‘irreversible’ ice sheet loss, study warns

SOURCE: NewsAsia DATE: November 13, 2018 SNIP: Even modest temperature rises agreed under an international plan to limit climate disaster could see the ice caps melt enough this century for their loss to be “irreversible”, experts warned on Monday (Nov 12). Scientists have known for decades that the ice sheets of Greenland and Antarctica are shrinking, but it had been assumed that they would survive a 1.5-2°C temperature rise relatively intact. However, according to a new analysis published in the journal Nature Climate Change, even modest global warming could cause irreversible damage to the polar ice, contributing to catastrophic sea level rises. “We say that 1.5-2°C is close to the limit for which more dramatic effects may be expected from the ice sheets,” Frank Pattyn, head of the department of geosciences, Free University of Brussels and lead study author, told AFP. His team crunched data on annual temperature rises, ice sheet coverage and known melt levels and found that both Greenland and Antarctic ice sheets would reach a “tipping point” at around 2°C. “The existence of a tipping point implies that ice-sheet changes are potentially irreversible – returning to a pre-industrial climate may not stabilise the ice sheet once the tipping point has been crossed,” said Pattyn. Many models of the 1.5-2°C scenario allow for the threshold to be breached in the short term, potentially heating the planet several degrees higher, before using carbon capture and other technologies to bring temperatures back into line by 2100. The study warned against this approach, however, saying that a feedback loop set off by higher temperatures would “lead to self-sustained melting of...