14 January 2016, Science Daily, Study finds high melt rates on Antarctica’s most stable ice shelf. Melting rates found to be 25 times higher than expected. A new Scripps Institution of Oceanography at UC San Diego-led study measured a melt rate that is 25 times higher than expected on one part of the Ross Ice Shelf. The study suggests that high, localized melt rates such as this one on Antarctica’s largest and most stable ice shelf are normal and keep Antarctica’s ice sheets in balance. The Ross Ice Shelf, a floating body of land ice the size of France jutting out from the Antarctic mainland, continuously melts and grows in response to changes to both the ice sheet feeding it and the warmer Southern Ocean waters beneath it. For six weeks the researchers collected radar data to map changes in ice shelf thickness to understand the processes that contribute to melting at its base. The findings revealed dramatic changes in melt rate within less than a mile. The highest melting rates of more than 20 meters (66 feet) per year are thought to contribute to the rapid formation of channels at the base of the ice shelf, which can result from fresh water flowing out from lakes under the West Antarctica ice sheet. Shifts in subglacial drainage patterns change the location of these basal channels, which could impact the ice shelf’s stability by unevenly distributing the melting at the base. “The highest melt rates are all clustered at the start of a developing ice shelf channel,” said Scripps alumnus Oliver Marsh, a postdoctoral researcher at the University of Canterbury and lead author of the study. “The location of the melting strengthens the idea that freshwater from the local subglacial drainage system is responsible for the evolving ice shelf features.” Read more here
Category Archives: Antarctica
9 January 2016, Climate News Network, Ice melt speeds up sea level rise. Scientists have found evidence suggesting that melting icecap water from the interior of Greenland is adding to sea level rise faster than previously realised. Water may be flowing from the Greenland icecapand into the sea more quickly than anybody expected. It doesn’t mean that global warming has got conspicuously worse: rather, researchers have had to revise their understanding of the intricate physiology of the northern hemisphere’s biggest icecap. There is enough ice and snow packed deep over 1.7 million square kilometres of Greenland that, were it all to melt, would cause a rise in global sea levels of about six metres. Climate calculations Since the icecap is melting as the atmospheric levels of the greenhouse gas carbon dioxide rise, and global temperatures rise with them, as a consequence of the human combustion of fossil fuels, the rate at which summer meltwater gets into the oceans becomes vital to climate calculations. The latest rethink begins not with the pools of water that collect on the surface each summer, or the acceleration of the glaciers as they make their way to the ocean, but with a granular layer of snow just below the surface, called firn. This is old snow in the process of being compacted into glacier ice, and covers the island in a layer up to 80 metres thick. Until now, researchers have understood this firn layer as a kind of sponge that absorbs meltwater and holds it, thus limiting the flow of melting ice into the sea. Read More here
29 December 2015, New York Times, Countries Rush for Upper Hand in Antarctica. On a glacier-filled island with fjords and elephant seals, Russia has built Antarctica’s first Orthodox church on a hill overlooking its research base, transporting the logs all the way from Siberia. Less than an hour away by snowmobile, Chinese laborers have updated the Great Wall Station, a linchpin in China’s plan to operate five bases on Antarctica, complete with an indoor badminton court, domes to protect satellite stations and sleeping quarters for 150 people. Not to be outdone, India’s futuristic new Bharathi base, built on stilts using 134 interlocking shipping containers, resembles a spaceship. Turkey and Iran have announced plans to build bases, too. More than a century has passed since explorers raced to plant their flags at the bottom of the world, and for decades to come this continent is supposed to be protected as a scientific preserve, shielded from intrusions like military activities and mining. But an array of countries are rushing to assert greater influence here, with an eye not just toward the day those protective treaties expire, but also for the strategic and commercial opportunities that exist right now. “The newer players are stepping into what they view as a treasure house of resources,” said Anne-Marie Brady, a scholar at New Zealand’s University of Canterbury who specializes in Antarctic politics. Read More here
18 November 2015, Science Daily, Sea level rise from Antarctic collapse may be slower than suggested. A new study by scientists in the UK and France has found that Antarctic ice sheet collapse will have serious consequences for sea level rise over the next two hundred years, though not as much as some have suggested. This study, published today in the journal Nature, uses an ice-sheet model to predict the consequences of unstable retreat of the ice, which recent studies suggest has begun in West Antarctica. Scientists, led by Catherine Ritz from Université Grenoble Alpes in France and Tamsin Edwards from The Open University, predict that the contribution is most likely to be 10 cm of sea-level rise this century under a mid to high climate scenario, but is extremely unlikely to be higher than 30 cm. When combined with other contributions, that’s a significant challenge for adapting to future sea level rise. But it’s also far lower than some previous estimates, which were as high as one metre from Antarctica alone. The study’s central estimate raises the Intergovernmental Panel on Climate Change (IPCC) central prediction of 60 cm global sea-level rise by just a few centimetres under the mid to high scenario they used. But the UK and France team’s method allowed them to assess the likelihood of sea-level rise from substantial parts of the ice sheet collapsing, which the IPCC could not due to a lack of evidence. They predict there is a one in twenty chance that Antarctic collapse could contribute more than 30 cm sea-level rise by the end of the century and more than 72 cm by 2200. This does not rule out larger contributions on longer time scales. Read More here