Scientists find far higher than expected rate of underwater glacial melting

Scientists find far higher than expected rate of underwater glacial melting

SOURCE: Phys.org DATE: January 29, 2020 SNIP: Tidewater glaciers, the massive rivers of ice that end in the ocean, may be melting underwater much faster than previously thought, according to a Rutgers co-authored study that used robotic kayaks. The findings, which challenge current frameworks for analyzing ocean-glacier interactions, have implications for the rest of the world’s tidewater glaciers, whose rapid retreat is contributing to sea-level rise. The study, published in the journal Geophysical Research Letters, surveyed the ocean in front of 20-mile-long LeConte Glacier in Alaska. The seaborne robots made it possible for the first time to analyze plumes of meltwater, the water released when snow or ice melts, where glaciers meet the ocean. It is a dangerous area for ships because of ice calving—when falling slabs of ice that break from glaciers crash into the water and spawn huge waves. “With the kayaks, we found a surprising signal of melting: Layers of concentrated meltwater intruding into the ocean that reveal the critical importance of a process typically neglected when modeling or estimating melt rates,” said lead author Rebecca Jackson, a physical oceanographer and assistant professor in the Department of Marine and Coastal Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. Two kinds of underwater melting occur near glaciers. Where freshwater discharge drains at the base of a glacier (from upstream melt on the glacier’s surface), vigorous plumes result in discharge-driven melting. Away from these discharge outlets, the glacier melts directly into the ocean waters in a regime called ambient melting. The study follows one published last year in the journal Science that measured...
Dwindling Arctic Sea Ice May Affect Tropical Weather Patterns

Dwindling Arctic Sea Ice May Affect Tropical Weather Patterns

SOURCE: Inside Climate News DATE: January 27, 2020 SNIP: The rapid decline of Arctic sea ice during the last couple of decades has spurred climate scientists to study how that meltdown influences the rest of the planet, and a new study suggests that the effects may extend deep into the tropics. The study, published Monday in the journal Proceedings of the National Academy of Sciences, detected a pattern that links sea ice decline since the late 1990s with more frequent warm cycles in the Central Pacific Ocean. The surges of ocean heating in that region can disrupt the climate, affecting drought, flood and hurricane patterns around the world. Winds are the link between the melting ice and the tropics. The researchers posit that the Arctic Ocean has warmed up so much in the last 20 years that warm, late-summer sea surface air forms powerful convective towers, rising to the stratosphere. When the air falls back toward the equatorial Pacific, it intensifies prevailing east-to-west trade winds that push warm water toward Asia and Oceana, giving birth to a Central Pacific El Niño, a geographically specific variation of the well-documented Pacific warming and cooling cycle that is a key driver of the global climate. The study found a secondary effect. The atmospheric roller coaster rebounds back north, and may weaken a weather pattern near Alaska that steers Pacific storms toward the West Coast. The new research shows that El Niños forming in the Central Pacific started becoming more frequent at the same time that Arctic sea ice extent started its precipitous decline. Jennifer Francis, a climate researcher with the Woods Hole...
The Arctic’s grand reveal

The Arctic’s grand reveal

SOURCE: University of Alaska Fairbanks DATE: December 12, 2019 SNIP: “This green line looks like the death of permafrost — it’s flatlining,” Louise Farquharson said to an audience of a few dozen scientists. Her reserved tone hid a bombshell message — by 2035 permafrost thaw may continue on its own, disregarding the processes that have kept it frozen for thousands of years. Farquharson is a research associate at the University of Alaska Fairbanks Geophysical Institute. She is an expert on permafrost, the parts of the ground that stay frozen for at least two consecutive years. Permafrost thaw causes the ground surface to sink, which leads to infrastructure damage, accelerates microbial activity and releases carbon and other gases into the atmosphere, accelerating global warming even more. Most experts suggest permafrost thaw will continue and even speed up as we go into the next century. However, calculated rates of thaw may be far lower than what will really happen. According to Farquharson, a key accelerating factor in permafrost thaw has been dramatically underestimated. “It’s the Arctic’s ‘grand reveal,’” Farquarson said. “We thought we saw what was happening, then it really stepped out from behind the curtain.” This factor is called talik, thawed zones in permafrost areas. The mixture of wet, frigid dirt is commonly associated with Arctic thermokarst lakes that form when enough ice-rich permafrost thaws to create a body of water. The talik beneath these lakes significantly contributes to the thawing process. Just as icewater melts faster than a lone cube of ice, the waterlogged ground accelerates thawing of the permafrost around it. Normally talik has been thought of as...
Climate change: Greenland ice melt ‘is accelerating’

Climate change: Greenland ice melt ‘is accelerating’

SOURCE: BBC DATE: December 10, 2019 SNIP: Greenland is losing ice seven times faster than it was in the 1990s. The assessment comes from an international team of polar scientists who’ve reviewed all the satellite observations over a 26-year period. They say Greenland’s contribution to sea-level rise is currently tracking what had been regarded as a pessimistic projection of the future. It means an additional 7cm of ocean rise could now be expected by the end of the century from Greenland alone. This threatens to put many millions more people in low-lying coastal regions at risk of flooding. It’s estimated roughly a billion live today less than 10m above current high-tide lines, including 250 million below 1m. “Storms, if they happen against a baseline of higher seas – they will break flood defences,” said Prof Andy Shepherd, of Leeds University. “The simple formula is that around the planet, six million people are brought into a flooding situation for every centimetre of sea-level rise. So, when you hear about a centimetre rise, it does have impacts,” he told BBC News. Whereas in the early 90s, the rate of loss was equivalent to about 1mm per decade, it is now running at roughly 7mm per decade. Imbie team-member Dr Ruth Mottram is affiliated to the Danish Meteorological Institute. She said: “Greenland is losing ice in two main ways – one is by surface melting and that water runs off into the ocean; and the other is by the calving of icebergs and then melting where the ice is in contact with the ocean. The long-term contribution from these two processes is...
Greenland ice losses rising faster than expected

Greenland ice losses rising faster than expected

SOURCE: Phys.org DATE: December 10, 2019 SNIP: Greenland is losing ice seven times faster than in the 1990s and is tracking the Intergovernmental Panel on Climate Change’s high-end climate warming scenario, which would see 400 million more people exposed to coastal flooding by 2100. A team of 96 polar scientists from 50 international organisations have produced the most complete picture of Greenland ice loss to date. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) Team combined 26 separate surveys to compute changes in the mass of Greenland’s ice sheet between 1992 and 2018. Altogether, data from 11 different satellite missions were used, including measurements of the ice sheet’s changing volume, flow and gravity. The findings, published today in Nature today, show that Greenland has lost 3.8 trillion tonnes of ice since 1992—enough to push global sea levels up by 10.6 millimetres. The rate of ice loss has risen from 33 billion tonnes per year in the 1990s to 254 billion tonnes per year in the last decade—a seven-fold increase within three decades. The assessment, led by Professor Andrew Shepherd at the University of Leeds and Dr. Erik Ivins at NASA’s Jet Propulsion Laboratory in California, was supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA). Professor Shepherd said: “As a rule of thumb, for every centimetre rise in global sea level another six million people are exposed to coastal flooding around the planet.” “On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to...