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: Impacts Observed & Projected
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
20 December 2015, Climate News Network, Rapid warming brings Arctic changes. Tundra plants that bloom fresh and green in the short Arctic summer are declining or turning brown as rising temperatures increasingly affect the region. Scientists in the US who have been checking on the health of the Arctic over the last year are worried by what they’ve learned: it’s warmer, has less ice, and some of its animals and fish are facing new stresses. And in a surprise finding , which they cannot yet explain, the scientists discovered that green vegetation over much of the Arctic began a few years ago to turn an uncharacteristic brown. Plenty of what they detail in the Arctic Report Card − published annually to document the sometimes rapidly changing conditions in the region − comes as no great surprise. The latest Report Card, sponsored by the US National Oceanic and Atmospheric Administration (NOAA), shows the air temperature continuing its warming trend. In 2015, it was well above average across the Arctic, with temperature anomalies over land more than -0.16°C above average − the highest since records began in 1900. The report reveals increases not only in air but also in sea surface temperatures, decreasing sea ice extent and Greenland ice sheet mass, and changes to the behaviour of fish and walruses. Read More here
17 December 2015, The Hindu, Climate change warming world’s lakes at alarming rate. The study spanned six continents. A total of 236 lakes, representing more than half of the world’s freshwater supply, were monitored for at least 25 years. Climate change is warming lakes around the world at an alarming rate, threatening freshwater supplies and ecosystems, says the largest study of its kind led by an Indian-origin researcher. For the study spanning six continents, a total of 236 lakes, representing more than half of the world’s freshwater supply, were monitored for at least 25 years. “We found that lakes are warming at an average of 0.34 degrees Celsius each decade all around the world, threatening freshwater supplies and ecosystems,” said study lead author Sapna Sharma from York University in Toronto, Canada. “This can have profound effects on drinking water and the habitat of fish and other animals,” Sharma said. At the current rate, algal blooms, which can ultimately rob water of oxygen, will increase 20 per cent in lakes over the next century, the study said. Algal blooms that are toxic to fish and animals would increase by five per cent. These rates also imply that emissions of methane, a greenhouse gas 25 times more powerful than carbon dioxide, will increase four per cent over the next decade. “We found that ice-covered lakes, including Canadian lakes, are warming twice as fast as air temperatures and the North American Great Lakes are among the fastest warming lakes in the world,” Sharma noted. Read More here