Study finds rapid ice melt is ‘overtaking the climate models’

The global alarm over rising sea levels and the colossal loss of Earth’s ice sheets continues with new results that one scientist calls “mind-blowing” in their implications for the climate change future.

“The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise,” says Dr. Tom Slater of the Centre for Polar Observation and Modelling at the University of Leeds in the United Kingdom.

Slater, fellow Leeds colleague Dr. Anna Hogg and a climate scientist from the Danish Meteorological Institute, Dr. Ruth Mottram, collaborated on research that shows melt rates so far are tracking with the worst-case scenarios predicted by the Intergovernmental Panel on Climate Change (IPCC). Their work was published Monday in the journal Nature Climate Change, and it is the latest to warn of sea-level projections that may be worse than previously thought.

Since satellite monitoring of ice sheets began in the 1990s, melting from Antarctica has pushed global sea levels up by 7.2mm, with another 10.6mm from Greenland. The latest measurements show that the world’s oceans are now rising by 4mm each year; if these rates continue, the ice sheets are expected to raise sea levels to a height that threatens an additional 16 million people with annual coastal flooding by 2100.

If the melting does continue at the same rate, it will double the frequency of storm-surge flooding in many of the world’s largest coastal cities, says Hogg.

The new research is based on a comparison of satellite surveys from the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE) with climate model calculations. It comes as global ice melt caused by warming temperatures has overtaken thermal expansion, the process by which the volume of seawater expands as it gets warmer, as the main driver of sea level rise.

“It is not only Antarctica and Greenland that are causing the water to rise,” warns Mottram. “In recent years, thousands of smaller glaciers have begun to melt or disappear altogether. … This means that melting of ice has now taken over as the main contributor of sea level rise.”

Greenland alone lost a record 532 billion tons last year, according to another team of scientists who just published their work 10 days ago. That translates into 3 million tons of extra water every day, or six Olympic-sized swimming pools every second. Even a partial melting of Greenland’s ice would inundate islands and low-lying coastal areas, and this latest study suggests it is not slowing down.

“Although we anticipated the ice sheets would lose increasing amounts of ice in response to the warming of the oceans and atmosphere, the rate at which they are melting has accelerated faster than we could have imagined,” said Slater.