From The Guardian:
Ice losses are rapidly spreading deep into the interior of the Antarctic, new analysis of satellite data shows.
The warming of the Southern Ocean is resulting in glaciers sliding into the sea increasingly rapidly, with ice now being lost five times faster than in the 1990s. The West Antarctic ice sheet was stable in 1992 but up to a quarter of its expanse is now thinning. More than 100 metres of ice thickness has been lost in the worst-hit places.
A complete loss of the West Antarctic ice sheet would drive global sea levels up by about five metres, drowning coastal cities around the world. The current losses are doubling every decade, the scientists said, and sea level rise are now running at the extreme end of projections made just a few years ago.
The research, published in the journal Geophysical Research Letters, compared 800m satellite measurements of ice sheet height from 1992 to 2017 with weather information. This distinguished short-term changes owing to varying snowfall from long-term changes owing to climate.
“From a standing start in the 1990s, thinning has spread inland progressively over the past 25 years – that is rapid in glaciological terms,” said Prof Andy Shepherd, of Leeds University in the UK, who led the study. “The speed of drawing down ice from an ice sheet used to be spoken of in geological timescales, but that has now been replaced by people’s lifetimes.”
He said the thinning of some ice streams had extended 300 miles inland along their 600-mile length. “More than 50% of the Pine Island and Thwaites glacier basins have been affected by thinning in the past 25 years. We are past halfway and that is a worry.”
“From a standing start in the 1990s, thinning has spread inland progressively over the past 25 years – that is rapid in glaciological terms,” said Prof Andy Shepherd, of Leeds University in the UK, who led the study. “The speed of drawing down ice from an ice sheet used to be spoken of in geological timescales, but that has now been replaced by people’s lifetimes.”
He said the thinning of some ice streams had extended 300 miles inland along their 600-mile length. “More than 50% of the Pine Island and Thwaites glacier basins have been affected by thinning in the past 25 years. We are past halfway and that is a worry.”
“Along a 3,000km [1,850-mile] stretch of West Antarctica, the water in front of the glaciers is too hot,” he said. This causes melting of the underside of the glaciers where they grind against the seabed. The melting lessens the friction and allows the glaciers then to slide more quickly into the ocean and therefore become thinner.
“In parts of Antarctica, the ice sheet has thinned by extraordinary amounts,” Shepherd said.
From the BBC:
Scientists believe that global sea levels could rise far more than predicted, due to accelerating melting in Greenland and Antarctica.
The long-held view has been that the world's seas would rise by a maximum of just under a metre by 2100.
This new study, based on expert opinions, projects that the real level may be around double that figure.
This could lead to the displacement of hundreds of millions of people, the authors say.
The question of sea-level rise was one of the most controversial issues raised by the Intergovernmental Panel on Climate Change (IPCC), when it published its fifth assessment report in 2013.
It said the continued warming of the planet, without major reductions in emissions, would see global waters rising by between 52cm and 98cm by 2100.
Many experts believe this was a very conservative estimate.
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