Daily Mirror (Northern Ireland)
TIPPING POINT OF THE ICEBERG
Ice Flow
A HUGE glacier is at risk of crossing a tipping point which could cause a catastrophic 20in rise in global sea levels, scientists have warned.
Thwaites Glacier, in Antarctica, is heading towards an “instability” which, once reached, means it could all float out into the open ocean within just 150 years.
The resulting sealevel rise would be two-and-a-half times bigger than the 7.8in increase since preglobal warming levels of the late 19th century, a Nasafunded study found.
NASA scientist Dr Helene Seroussi said: “After reaching the tipping point, Thwaites Glacier could lose all of its ice in a period of 150 years. That would make for a sea-level rise of about half a metre.” Thwaites, measuring 70,000 square miles, is among five glaciers to double their rate of ice loss in six years, according to the National Science Foundation.
The dire prediction came after 500 ice-flow models of the glacier all predicted the instability would be triggered if the rate of ice melt due to ocean warming stays at current levels. Dr Seroussi said a glacier becomes unstable when warmer sea
NASA SCIENTIST
water reaches land which slopes downwards, adding: “The process becomes self-perpetuating.”
The point where the overhanging glacier, sea and bedrock meet is called the “grounding line”.
As the bedrock becomes deeper, undercutting seawater exerts more lift on the glacier – accelerating its flow into the sea.
Another climate expert, Dr Alex Robel, of Georgia Institute of Technology, said: “Once ice is past the grounding line and just over water, it’s contributing to sea level because buoyancy is holding it up more than it was.
“Ice flows out into the floating ice shelf and melts or breaks off as icebergs. If you trigger this instability, you don’t need to continue to force the ice sheet by cranking up temperatures.
“It will keep going by itself, and that’s
the worry.”