IPCC author: Antarctica’s abrupt glacial melting ‘greatly overestimated’
Written by Thomas Richard, examiner.com
Researchers from the University of Bristol (UOB) announced Thursday that glaciers in the Antarctic peninsula are starting to thaw much faster than expected, dumping millions of gallons of freshwater into the oceans, which they blame on global warming. But according to an expert in the field of polar observations, those conclusions appear to be “greatly overestimated.”
Dr. Andrew Shepherd, an IPCC author who works at the Centre for Polar Observation and Modelling, said the UOB study used calculations that appeared to have overlooked shifts insnowfall, noting that the “new estimates of ice loss computed (from the thinning of the ice) are far too high, because the glaciers in this sector just haven’t speeded up that much.”
By using “suite of satellites, the [UOB] researchers found that the Southern Antarctic Peninsula showed no signs of change up to 2009.” But in 2009, according to the study’s authors, glaciers in that area began shedding ice into the ocean at a rate of 55 trillion litres (14.5 trillion gallons) each year. The research team doesn’t believe the sudden change can be explained away by snowfall or air temperatures, but rather by rapid loss from “warming oceans” pushing up against the coast.
Dr. Bert Wouters, who led the study, said that stronger westerly winds encircling the continent are pushing warmer waters “from the Southern Ocean poleward.” They believe these westerly winds have become stronger due to global warming and ozone depletion, even though atmospheric temperatures across Antarctica haven’t moved up or down since satellite record keeping began. It also overlooks how snowfall contributes to the size and mass of any glacier, as well as geologic forces not seen from above.
The region showing the greatest ice loss in the UOB study is “home to continental arcs, oceanic arcs, and the anomalous Marie Byrd Seamount region. The only subduction-related volcanic activity related to the plate forms the South Sandwich Islands and the South Shetland Islands. The continent is divided by large rift structures, which have created one of the world’s largest alkalic volcanic provinces.” In other words, it’s one of the most active tectonic areas on Earth.
Antarctica as a whole is home to 25 known active volcanoes, the majority of which are in West Antarctica. With the continent entirely enshrouded in ice, except for brief peeks of coastline bedrock during summer, these volcanoes melt the glaciers from below, creating canals, lakes, and freshwater streams that eventually empty out into the ocean, warming the currents that slowly chip away at the massive ice shelves abutting the coastal regions.
Another study based on radar analysis has also shown that a vast subglacial water system lies under one of West Antarctica’s largest glaciers. These subglacial water systems act like a conveyor belt, moving the glacier closer to the ocean where the “tug of war” begins with the ocean and sea ice. Unfortunately for researchers, radar analysis is a manual, time-consuming job that requires vast amounts of super-computing power to accurately model these subglacial freshwater formations.
Dr. Shepherd, who expressed doubt about the results of the UOB study, was a contributing author of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, and he is currently investigating the stability of the Larsen B Ice Shelf in Antarctica.
The University of Bristol study, lead by Dr. Bert Wouters, was published in the journal Science.
read more from Thomas Richard at www.examiner.com