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| Last Updated:17/03/2020

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Sea levels across the world to rise faster than imagined

LONDON: Sea levels across the world are all set to rise much faster than imagined, thanks to the Greenland ice sheet, known to be stable till now, having started to melt. 

Regional warming has triggered a sudden and sustained mass loss in Northeast Greenland ice sheet. 

The scientists found that the northeast Greenland ice sheet lost about 10 billion tons of ice per year from April 2003 to April 2012. 

The Greenland ice sheet is thought to be one of the largest contributors to global sea level rise over the past 20 years, accounting for 0.5 millimetres of the current total of 3.2 millimetres of sea level rise per year. 

According to previous measurements and aerial photographs, the northeast Greenland ice sheet margin appeared to be stable for 25 years — until 2003. 

Around that time, a string of especially warm summers triggered increased melting and calving events, which have continued to the present day. 

Northeast Greenland, where the glacier is found, is of particular interest as numerical model predictions have suggested there is no significant mass loss for this sector, leading to a probable underestimation of future global sea-level rise from the region. 

An international team of scientists, including Professor Jonathan Bamber from the University of Bristol, studied the Northeast Greenland Ice Stream which extends more than 600 km into the interior of the ice sheet: much further than any other in Greenland. 

Professor Bamber said "The Greenland ice sheet has contributed more than any other ice mass to sea level rise over the last two decades and has the potential, if it were completely melted, to raise global sea level by more than seven metres. About half of the increased contribution of the ice sheet is due to the speed up of glaciers in the south and northwest. Until recently, Northeast Greenland has been relatively stable. This new study shows that is no longer the case". 

The international team of scientists discovered that the last remaining stable portion of the Greenland ice sheet is stable no more. 

The new result focuses on ice loss due to a major retreat of an outlet glacier connected to a long river of ice - known as an ice stream - that drains ice from the interior of the ice sheet. 

The Zachariae ice stream retreated about 20 kilometers (12.4 miles) over the last decade, the researchers concluded. 

For comparison, one of the fastest moving glaciers, the Jakobshavn ice stream in southwest Greenland, has retreated 35 kilometers (21.7 miles) over the last 150 years. 

Ice streams drain ice basins, the same way the Amazon River drains the very large Amazon water basin. 

Zachariae is the largest ice stream in a drainage basin that covers 16% of the Greenland ice sheet — an area twice as large as the one drained by Jakobshavn. 

"Northeast Greenland is very cold. It used to be considered the last stable part of the Greenland ice sheet," explained lead investigator Michael Bevis of The Ohio State University. "This study shows that ice loss in the northeast is now accelerating. So, now it seems that all of the margins of the Greenland ice sheet are unstable". 

Study leader Shfaqat Abbas Khan, a senior researcher at the National Space Institute at the Technical University of Denmark, said that the finding is cause for concern. 

"The fact that the mass loss of the Greenland Ice Sheet has generally increased over the last decades is well known but the increasing contribution from the north-eastern part of the ice sheet is new and very surprising," Khan said.

The Times of India (17-03-2014)