30 January 2018, The Conversation, Climate scientists explore hidden ocean beneath Antarctica’s largest ice shelf. Antarctica’s Ross Ice Shelf is the world’s largest floating slab of ice: it’s about the size of Spain, and nearly a kilometre thick. The ocean beneath, roughly the volume of the North Sea, is one of the most important but least understood parts of the climate system. We are part of the multi-disciplinary Aotearoa New Zealand Ross Ice Shelf programme team, and have melted a hole through hundreds of metres of ice to explore this ocean and the ice shelf’s vulnerability to climate change. Our measurements show that this hidden ocean is warming and freshening – but in ways we weren’t expecting. A hidden conveyor belt All major ice shelves are found around the coast of Antarctica. These massive pieces of ice hold back the land-locked ice sheets that, if freed to melt into the ocean, would raise sea levels and change the face of our world. An ice shelf is a massive lid of ice that forms when glaciers flow off the land and merge as they float out over the coastal ocean. Shelves lose ice by either breaking off icebergs or by melting from below. We can see big icebergs from satellites – it is the melting that is hidden. Because the water flowing underneath the Ross Ice Shelf is cold (minus 1.9C), it is called a “cold cavity”. If it warms, the future of the shelf and the ice upstream could change dramatically. Yet this hidden ocean is excluded from all present models of future climate. All major ice shelves are found around the coast of Antarctica. These massive pieces of ice hold back the land-locked ice sheets that, if freed to melt into the ocean, would raise sea levels and change the face of our world. An ice shelf is a massive lid of ice that forms when glaciers flow off the land and merge as they float out over the coastal ocean. Shelves lose ice by either breaking off icebergs or by melting from below. We can see big icebergs from satellites – it is the melting that is hidden. Because the water flowing underneath the Ross Ice Shelf is cold (minus 1.9C), it is called a “cold cavity”. If it warms, the future of the shelf and the ice upstream could change dramatically. Yet this hidden ocean is excluded from all present models of future climate. Read More here
Tag Archives: Antarctica
10 January 2018, CSIRO-ECOS, Scientist’s 30-year search for Southern Ocean climate secrets. After more than 24 hours the ice breaker still hadn’t managed to break through the heavy sea ice and Chief Scientist Dr Steve Rintoul had secretly given up hope. All that would change in seconds though, leading to the senior scientist’s greatest but most disturbing discovery of his 30 year career. It was January 2015 when Rintoul and his team aboard the RSV Aurora Australis achieved what no others had managed – reaching the front of the Totten Glacier. They found that warm water was flooding into the cavity beneath the floating ice, melting what was thought to be a stable area of East Antarctica. The sea level rise problem had just got worse. wo years on, Rintoul will return to the Southern Ocean aboard CSIRO’s research vessel Investigator, this time further east towards the Mertz Glacier, on an expedition to piece together some of the remaining unknowns of the climate-critical region. With a physics degree from Harvard, post-graduate qualifications from MIT and Woods Hole, a post-doctorate from Princeton, and decades of experience in Southern Ocean research, Rintoul is more than qualified to lead the voyage. Read More here
4 January 2018, Geophysical Research Letters, Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations. The Antarctic ozone hole is healing slowly because levels of the man-made chemicals causing the hole have long lifetimes. We use Microwave Limb Sounder (MLS) satellite data to measure O3 over Antarctica at the beginning of winter and then compare it to O3 near the end of winter to calculate depletion. During this period, nearly all O3 change is due to depletion. MLS also measures HCl, and when ozone levels are very low, nearly all the reactive chlorine species (Cly) are converted to HCl. Clyvaries a lot from year to year from atmospheric motions. Fortunately, MLS measures nitrous oxide (N2O), a long-lived gas that also varies with the motions. Using the ratio of Cly to N2O, we find that there is less chlorine now than 9 years ago and that Cly has decreased on average about 25 parts per trillion/yr (0.8%/yr). The O3 depletion we calculate from MLS data responds to changes in the Clylevels, and the ratio of the change in ozone loss to the change in Cly matches model calculations. All of this is evidence that the Montreal Protocol is working—the Cly is decreasing in the Antarctic stratosphere and the ozone destruction is decreasing along with it. Read More here
12 October 2017, BBC News, Ozone layer recovery could be delayed by 30 years. Rising global emissions of some chlorine-containing chemicals could slow the progress made in healing the ozone layer.A study found the substances, widely used for paint stripping and in the manufacture of PVC, are increasing much faster than previously thought. Mainly produced in China, these compounds are not currently regulated. Experts say their continued use could set back the closing of the ozone hole by up to 30 years. Scientists reported last year that they had detected the first clear evidence that the thinning of the protective ozone layer was diminishing. The Montreal Protocol, which was signed 30 years ago, was the key to this progress. It has progressively helped governments phase out the chlorofluorocarbons and the hydrochlorofluorocarbons that were causing the problem. However, concern has been growing over the past few years about a number of chemicals, dubbed “very short-lived substances”. Antarctic ozone hole starts to ‘heal’ How Arctic ozone hole was avoided Weather ‘behind ozone hole changes’ Dichloromethane is one of these chemicals, and is used as an industrial solvent and a paint remover. Levels in the atmosphere have increased by 60% over the past decade. Read More here