Climate change: Earth’s deepest ice canyon vulnerable to melting

Climate change: Earth’s deepest ice canyon vulnerable to melting

SOURCE: BBC DATE: March 23, 2020 SNIP: East Antarctic’s Denman Canyon is the deepest land gorge on Earth, reaching 3,500m below sea-level. It’s also filled top to bottom with ice, which US space agency (Nasa) scientists reveal in a new report has a significant vulnerability to melting. Retreating and thinning sections of the glacier suggest it is being eroded by encroaching warm ocean water. Denman is one to watch for the future. If its ice were hollowed out, it would raise the global sea surface by 1.5m. Most people recognise the shores around the Dead Sea in the Middle East to have the lowest visible land surface elevation on Earth, at some 430m below sea level. But the base of the gorge occupied by Denman Glacier on the edge of the East Antarctic Ice Sheet (EAIS) actually reaches eight times as deep. Dr Brancato and colleagues used satellite radar data from 1996 to 2018 to show there’s been a marked retreat in the glacier’s grounding line. This is the point where the ice stream lifts up and floats as it flows off the land and enters the ocean. The line has reversed 5-6km in 22 years. What’s interesting about this reversal, however, is that it’s asymmetric; it’s occurring pretty much all on the western side of the glacier. The reason, the scientists can now determine, is a buried ridge under the eastern flank which is pinning and protecting that side of the glacier. In contrast, the western flank features a narrow but sizeable trough that would allow warm ocean water to erode the grounding line and push it backwards....
Antarctic temperature rises above 20C for first time on record

Antarctic temperature rises above 20C for first time on record

SOURCE: The Guardian DATE: February 13, 2020 SNIP: The Antarctic has registered a temperature of more than 20C (68F) for the first time on record, prompting fears of climate instability in the world’s greatest repository of ice. The 20.75C logged by Brazilian scientists at Seymour Island on 9 February was almost a full degree higher than the previous record of 19.8C, taken on Signy Island in January 1982. It follows another recent temperature record: on 6 February an Argentinian research station at Esperanza measured 18.3C, which was the highest reading on the continental Antarctic peninsula. These records will need to be confirmed by the World Meteorological Organization, but they are consistent with a broader trend on the peninsula and nearby islands, which have warmed by almost 3C since the pre-industrial era – one of the fastest rates on the planet. Scientists, who collect the data from remote monitoring stations every three days, described the new record as “incredible and abnormal”. Schaefer said the temperature of the peninsula, the South Shetland Islands and the James Ross archipelago, which Seymour is part of, has been erratic over the past 20 years. After cooling in the first decade of this century, it has warmed rapidly. While temperatures in eastern and central Antarctica are relatively stable, there are growing concerns about west Antarctica, where warming oceans are undermining the huge Thwaites and Pine Island glaciers. Until now, this has led to a relatively low amount of sea-level rise, but this could change rapidly if there is a sustained jump in temperature. On a recent trip with Greenpeace, the Guardian saw glaciers that have...
Antarctica logs hottest temperature on record with a reading of 18.3C

Antarctica logs hottest temperature on record with a reading of 18.3C

SOURCE: The Guardian DATE: February 7, 2020 SNIP: Antarctica has logged its hottest temperature on record, with an Argentinian research station thermometer reading 18.3C (65F), beating the previous record by 0.8C. The reading, taken at Esperanza on the northern tip of the continent’s peninsula, beats Antarctica’s previous record of 17.5C, set in March 2015. A tweet from Argentina’s meteorological agency on Friday revealed the record. The station’s data goes back to 1961. Antarctica’s peninsula – the area that points towards South America – is one of the fastest warming places on earth, heating by almost 3C over the past 50 years, according to the World Meteorological Organization. Almost all the region’s glaciers are melting. The Esperanza reading breaks the record for the Antarctic continent. The record for the Antarctic region – that is, everywhere south of 60 degrees latitude – is 19.8C, taken on Signy Island in January 1982. Prof James Renwick, a climate scientist at Victoria University of Wellington, was a member of an ad-hoc World Meteorological Organization committee that has verified previous records in Antarctica. “The reading is impressive as it’s only five years since the previous record was set and this is almost one degree centigrade higher. It’s a sign of the warming that has been happening there that’s much faster than the global average. “To have a new record set that quickly is surprising but who knows how long that will last? Possibly not that long at all.” He said the temperature record at Esperanza was one of the longest-running on the whole continent. Previous research from 2012 found the current rate of warming in...
Scientists Find Record Warm Water in Antarctica, Pointing to Cause Behind Troubling Glacier Melt

Scientists Find Record Warm Water in Antarctica, Pointing to Cause Behind Troubling Glacier Melt

SOURCE: NYU DATE: January 29,2020 SNIP: A team of scientists has observed, for the first time, the presence of warm water at a vital point underneath a glacier in Antarctica—an alarming discovery that points to the cause behind the gradual melting of this ice shelf while also raising concerns about sea-level rise around the globe. The recorded warm waters—more than two degrees above freezing—flow beneath the Thwaites Glacier, which is part of the Western Antarctic Ice Sheet. The discovery was made at the glacier’s grounding zone—the place at which the ice transitions between resting fully on bedrock and floating on the ocean as an ice shelf and which is key to the overall rate of retreat of a glacier. Thwaites’ demise alone could have significant impact globally. It would drain a mass of water that is roughly the size of Great Britain or the state of Florida and currently accounts for approximately 4 percent of global sea-level rise. Some scientists see Thwaites as the most vulnerable and most significant glacier in the world in terms of future global sea-level rise—its collapse would raise global sea levels by nearly one meter, perhaps overwhelming existing populated areas. While the glacier’s recession has been observed over the past decade, the causes behind this change had previously not been determined. The scientists’ measurements were made in early January, after the research team created a 600-meter deep and 35-centimeter wide access hole and deployed an ocean-sensing device to measure the waters moving below the glacier’s surface. This device gauges the turbulence of the water as well as other properties such as temperature. The result...
Antarctic Waters: Warmer with More Acidity and Less Oxygen

Antarctic Waters: Warmer with More Acidity and Less Oxygen

SOURCE: University of Arizona News DATE: January 6, 2020 SNIP: The increased freshwater from melting Antarctic ice sheets plus increased wind has reduced the amount of oxygen in the Southern Ocean and made it more acidic and warmer, according to new research led by University of Arizona geoscientists. The researchers found Southern Ocean waters had changed by comparing shipboard measurements taken from 1990 to 2004 with measurements taken by a fleet of microsensor-equipped robot floats from 2012 to 2019. The observed oxygen loss and warming around the Antarctic coast is much larger than predicted by a climate model, which could have implications for predictions of ice melt. “It’s the first time we’ve been able to reproduce the new changes in the Southern Ocean with an Earth system model,” said co-author Joellen Russell, a professor of geosciences. The research is the first to incorporate the Southern Ocean’s increased freshwater plus additional wind into a climate change model, she said. The team used the National Oceanic and Atmospheric Administration’s ESM2M model. Previously, global climate change models did not predict the current physical and chemical changes in the Southern Ocean, said Russell, who holds the Thomas R. Brown Distinguished Chair in Integrative Science. “We underestimated how much influence that added freshwater and wind would have. When we add these two components to the model, we can directly and beautifully reproduce what has happened over the last 30 years,” she said. Now, models will be able to do a better job of predicting future environmental changes in and around Antarctica, she said, adding that the Southern Ocean takes up most of the heat...