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One-fourth of West Antarctic ice is now unstable

In a study that compared 25 years of satellite data from the European Space Agency (ESA), scientists have found that 24 percent of the glacier ice in West Antarctica is now unstable as a result of thinning caused by warming ocean water.

Experts at the UK Centre for Polar Observation and Modelling (CPOM) used over 800 million measurements of Antarctic ice sheet height from between 1992 and 2017. The data was recorded by radar altimeter instruments on the ERS-1, ERS-2, Envisat, and CryoSat satellite missions.

Along with simulations of snowfall over the same time period, the measurements made it possible to distinguish which changes in ice-sheet height had been caused by weather events that affect snow, and which were caused by longer-term climate changes that affect ice.

Some regions in the ice sheet had thinned by up to 122 meters, and the most rapid changes were discovered in areas where ocean melting has triggered glacier imbalance. “Parts of Antarctica have thinned by extraordinary amounts. So we set out to show how much was down to changes in climate and how much was instead due to weather,” said CPOM Director Andy Shepherd.

The team determined that fluctuations in snowfall drive small changes in ice height over large areas for a few years at a time, and the most extreme changes in ice thickness coincide with signs of glacier imbalance that have persisted for decades.

“Knowing how much snow has fallen has really helped us to isolate the glacier imbalance within the satellite record. We can see clearly now that a wave of thinning has spread rapidly across some of Antarctica’s most vulnerable glaciers, and their losses are driving up sea levels around the planet,” said Professor Shepard.

“After 25 years, the pattern of glacier thinning has spread across 24% of West Antarctica, and its largest ice streams – the Pine Island and Thwaites Glaciers – are now losing ice five times faster than they were in the 1990s. Altogether, ice losses from East and West Antarctica have added 4.6 mm of water to global sea level since 1992.”

“This is a fantastic demonstration of how satellite missions can help us to understand how our planet is changing,” said ESA engineer Marcus Engdahl. “The polar regions are hostile environments and are extremely difficult to access from the ground. Because of this, the view from space is an essential tool for tracking the effects of climate change.”

The study is published in the journal Geophysical Research Letters.

By Chrissy Sexton, Staff Writer

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Image Credit: Andrew Shepherd

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