16 January 2016, Climate News Network, Giant boost for south polar waters. Massive icebergs more than 18km long are feeding vital nutrients into the Southern Ocean and helping to increase its carbon storage capacity. British scientists have identified the monsters that fertilise the Southern Ocean and help remove carbon dioxide from the atmosphere. Giant icebergs drifting northwards could be responsible for storing up to a fifth of all the carbon that sinks into the south polar waters. Geographers at the University of Sheffield report in Nature Geoscience journal that they analysed 175 satellite images of ocean colour – an indicator ofphytoplankton activity. They learned that each huge iceberg, as it breaks off the ice shelf and begins to float away, also begins to cascade iron and other vital mineral nutrients in its melting waters. This is enough to stimulate ferocious plankton productivity for up to a month in its wake. The icebergs are not small − the researchers define “giant” as at least 18 kilometres in length − and nor can they be very frequent. Area of influence “We detected substantially enhanced chlorophyll levels, typically over a radius of at least four to 10 times the iceberg’s length,” says Grant Bigg, Professor in Earth Systems Science, who led the research. “The evidence suggests that carbon export increases by a factor of five to 10 over the area of influence, and up to a fifth of the Southern Ocean’s downward carbon flux originates with giant iceberg fertilisation. “If giant iceberg calving increases this century, as expected, this negative feedback on the carbon cycle may become more important than we previously thought.” The guess is that the Southern Ocean accounts for perhaps 10% of the ocean’s absorption of carbon dioxide from the atmosphere. Research such as this is part of the global process of understanding all theintricacies of the carbon cycle − in turn, an important part of modelling future climate change as a consequence of rising levels of greenhouse gas in the atmosphere, driven by human combustion of fossil fuels. Read More here
Tag Archives: Antarctica
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
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