The contribution of Greenland to global sea level change and the mapping of previously unknown basins and mountains beneath the Antarctic Ice Sheet are highlighted in a new film released by Cambridge University this morning.
The work of glaciologist Professor Julian Dowdeswell, Director of Cambridge University's Scott Polar Research Institute, is the focus of This Icy World, the latest film in the University's Cambridge Ideas series.
A frequent visitor to both the Arctic and Antarctic, Dowdeswell's research has found that the glaciers around Greenland are the fastest flowing in the world.
He said: "There is evidence that some parts of the ice sheet have doubled in speed up to 10 km per year in the last decade. That means the contribution of Greenland to global sea level change is increasing."
"The numbers of icebergs released into the seas around Greenland is also increasing. We need to know just how fast these changes are taking place.
"Things are changing very rapidly here because the Arctic is the most sensitive part of the global climate system. Over the coming century, temperatures are likely to rise at double the global average here."
Professor Dowdeswell, who has spent a total of more than three years in the polar regions, also reveals that his work in Antarctica as part of an team of international scientists, using radar systems pioneered in Cambridge, has mapped sub-glacial mountains hidden beneath the ice sheet that scientists were not aware of before.
The Scott Polar Research Institute, a research centre within Cambridge University, has about 40 scientists and post-graduate students working on various aspects of polar research. Professor Dowdeswell's next polar trip, funded by a large grant from the UK's Natural Environment Research Council, will be in March and April to the Greenland Ice Sheet.
Airborne radar systems will be used to measure ice thickness and the presence of lubricating water at the ice-sheet bed. This should yield key information relating to the recent speed-up of the ice.
He said: The ice in Antarctica is an average of 2-3 km in thickness, with the deepest ice almost 5 km thick. It's changes in the volume of the ice sheet that will affect global sea level.
"Glacier and ice-sheet change is a reality at both poles. The ice is thinning and retreating and that means water is flowing back into the global ocean. Today,
sea level is rising 3mm per year; over the coming century, sea level is likely to rise by up to about 1m and it's actually that rise - with the worst storm waves you can imagine - that could cause real damage.
"In those circumstances, sea defences can be breached and low lying areas of the world can be flooded. That has serious implications for humankind." Resources www.cam.ac.uk
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der, Colorado. The increases coincide closely with rises in sea surface temperatures in the eastern Atlantic tropics. Previous studies have attributed these rises to human emissions of greenhouse gases. "That [correlation] implies there is a substantial contribution by greenhouse warming to the current crop of tropical cyclones," Holland said. The study also shows that the proportion of major hurricanes to less intense hurricanes has sharply increased in recent years, which agrees with earlier studies showing an increase in stronger storms. However, the new study found the proportion of major hurricanes has fluctuated with a "remarkably constant period of oscillation" over the past century, Holland said. The oscillation appears to be a natural variability not associated with warming. So while the storms' severity seems to fluctuate in a natural cycle, their frequency is on the rise, he explained. "What we're seeing [now] is a high point of major storms, which has been a very, very stable oscillation, combined with a sharp increase in the frequency of all storms, which has been a trend," Holland said. Holland and Peter Webster of the Georgia Institute of Technology in Atlanta published their findings online today in the research journal Philosophical Transactions of the Royal Society of London. He is a leading critic of studies that link increased storm intensity to global warming, saying historical data are too crude to determine long-term trends. The same, he argues, is true for storm frequency. "The doubling in the number of storms that they find in their paper is just an artifact of technology, not climate change," he wrote. Airplanes and satellites outfitted with sensitive instruments to monitor tropical storms did not exist a hundred years ago. Aircraft began monitoring hurricanes in 1944, satellites about 1970. Recent research by Landsea finds three to four tropical storms were missed before the mid-1960s. And one storm a year was missed from the 1970s to the 1990s. "When one takes into account these missing storms, the upward trend disappears and large multiyear variations remain," he said. According to Holland, however, the technological improvements cannot account for all the observed increase in tropical storms. His new study accounts for three missed storms per year in the pre-satellite era, and a statistically significant increase is still present, he said. "So, yes there's uncertainty, there's no doubt about that," Holland said. "But it doesn't change our conclusions." Frequency Transitions According to the study, the period from 1900 to 1930 saw an average of six Atlantic tropical storms a year, with four of those storms growing into hurricanes. From 1930 to 1940, the annual average increased to ten, with five hurricanes and five tropical storms. Then, from 1995 to 2005, the average number of storms increased to 15, with 8 hurricanes and 7 tropical storms. Even 2006, which seemed mild in the wake of the record-breaking 2005 season, saw ten tropical storms, the authors note. Holland likened the transition phases to a thunderstorm in the Rocky Mountains—the sun rises and warms up the clear blue skies for hours, and then suddenly a thunderstorm develops. "That's a very good example, but what we're looking at is happening on the global scale," he said. The most recent period has yet to stabilize, leading the authors to conclude there may be even more active hurricane seasons in the future, though other factors may dampen the storm activity. "What I will say is there is no evidence that I'm aware of and nothing I can think of which indicates they are going to go back down," Holland said. Increase your knowledge and be aware about global warming and its impact, for more knowdlage visit (Courtesy:nationalgeographic.com)
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