Antarctica lost 3 trillion tonnes of ice in just 25 years

Christopher Davidson
June 15, 2018

But that has changed.

Overall between 1992 and 2017, Antarctica's ice sheet lost 3 trillion tons of ice - enough water to cover Texas to a depth of almost 13 feet, scientists calculated.

Shepherd said Antarctica alone is now on track to raise world sea levels by about 12 inches by 2100, above most past estimates.

"Satellites have given us an incredible, continent-wide picture of how Antarctica is changing", said Dr. Pippa Whitehouse, a member of the IMBIE team from Durham University, according to a University of Leeds press release.

"Unfortunately, we appear to be on a pathway to substantial ice-sheet loss in the decades ahead, with longer-term consequences for enhanced sea-level rise; something that has been predicted in models for some time".

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While the current ice loss measured is literally a drop in the ocean compared to Antartica's catastrophic potential to raise global sea level by as much as 58 metres (190 ft) if the ice sheets were to completely melt, the apparent acceleration in the latest satellite observations is enough to have scientists duly anxious. Warming of the southern ocean is connected to shifting winds, which are connected to global warming from the burning of coal, oil and natural gas, Shepherd said. That's causing glaciers to flow more quickly into the sea. That's "an important distinction, because it means it's insulated from changes in the ocean's temperature".

Even under ordinary conditions, Antarctica's landscape is perpetually changing as icebergs calve, snow falls and ice melts on the surface, forming glacial sinkholes known as moulins. "They show no indication of being exposed to cosmic rays", said Marc Caffee, a co-author of the paper and professor of physics and atronomy at Purdue University.

"Continued ice loss in Antarctica is of great concern for humanity, affecting coastal communities, people, and infrastructure", she said in a statement. "So that was the motivation for originally setting up the project".

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The assessment is an analysis of 24 different satellite-based measurements of ice loss on the continent, making it one of the most comprehensive studies of Antarctic melting to date.

To gauge the ice sheet's stability, researchers took ultra-sensitive analytical measurements of chemical signatures in sediment samples taken from the ice sheet's sea bed. Satellites launched by the European Space Agency and NASA allow scientists to monitor changes in ice height, ice velocity and ice mass through changes in Earth's gravity field.

"The good news is that measures to reduce emissions (eg. adoption of renewable energy) are also growing exponentially.

The general consensus in glaciology was that ice sheets couldn't change rapidly - but that's not the case", Shepherd said.

So what accounts for the apparent three-fold speed up in Antarctica's melting in the last five years? However, ice retreat today is about more than 20 times that rate - more than 3,200 feet (1 kilometer) per year.

Shepherd said the ice on West Antarctica can be melted by very small changes in ocean temperature.

Shepherd says until 2010, the data had been tracking a lower scenario which estimated that Antarctica "wouldn't make much of a contribution to sea level rise at all" because of the effects of higher snowfall. This uncertainty persists because global sea level estimates for the Pliocene have large uncertainties and can not be used to rule out substantial terrestrial ice loss, and also because direct geological evidence bearing on past ice retreat on land is lacking.

"It just so happens that offshore from those ice shelves, it's a hotspot of sea-ice loss", Dr Massom said.

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