September 10, 2008

Melting Ice Puts Cities at Greater Risk of Flooding

By Richard Sadler

New research by the Met Office has revealed that official predictions for sea level rise are out of date because they do not include the effects of melt water from the massive Greenland ice sheet.The situation is so serious that the Environment Agency is being forced to review its flood defence plans for London. Contingency plans for other major low-lying cities Hull, Newcastle, Glasgow and Norwich will also have to be re-evaluated.The extent of the problem was revealed for the first time yesterday by Dr Jason Lowe, a senior Met Office climate scientist who has just completed for the Environment Agency the most detailed study yet into the likely rates of sea level rise around Britain.Dr Lowe said that whereas the agency's current flood defences are based on predictions for a sea level rises of just under one metre this century, the average water levels around Britain could rise by as much as two or three metres. The effects of "storm surges" could push water levels up further to four or even five metres.If that happened the present Thames Flood Barrier designed to cope only with rises of just over a metre would be useless.Dr Lowe, speaking at the British Association for the Advancement of Science's conference in Liverpool, said other major conurbations on estuaries or in coastal areas as well nuclear power stations could now be vulnerable."Until we can rule out these larger rises or either rule them out or confirm them we think it is worthwhile planners looking at least at the vulnerability to these increases," he said.What is worrying scientists is new satellite evidence showing that the one million square mile Greenland ice cap is breaking up much more quickly than previously realised, shedding giant glaciers into the Arctic Ocean. The Antarctic ice sheet is also collapsing much faster than predicted."There has been an acceleration of some of the larger outflow group glaciers, in fact they've speeded out by a factor of two. Of course speeding up by a factor of two is a lot but in the present day they still make a minor contribution to sea level rise over say the last 10 years or the last 50 years."But it raises the possibility what if they go on accelerating?"To answer this question, Met Office scientists have studied historical evidence showing what happened when the polar ice caps last started melting 120,000 years ago. Their conclusion is that the rate of sea level rise this century could be two or three times previous estimates.For people in coastal areas of Britain as well as those living close to tidal estuaries like the Humber and the Thames the situation is made worse by increasing frequency of storms and heavy rainfall.Tim Reeder, the Environment Agency's climate programme manager for the Thames region, said plans to defend London and other parts of the country were being reviewed in the light of research. A formal announcement will be made next week.He accepted that if sea level rise accelerated in line with the Met Office's worst-case scenario, the Thames flood barrier would fail. However he pointed out the Environment Agency was already considering contingency plans including higher sea walls, flood water storage areas and proposals for a new, bigger flood barrier."The key thing is that the Environment Agency is doing the research to understand the consequences of accelerated ice cap melt," he said.Prof David Vaughan, principal investigator for the British Antarctic Survey, said: "A metre or two rise in sea water around the coast might not sound like much but when you add the effects of more frequent storms and flooding events it could be very serious."

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