Ice loss spreads up Antarctic glaciers

Ice loss spreads up Antarctic glaciers

12 December, 15:24 197

The scale and pace of change now taking place in West Antarctica is captured in a new, long-term satellite record, the BBC reported.

Scientists have combined nearly a quarter of a century of observations to show how the region's great glaciers are losing height by up to 7m per year.

The satellite data also traces the way this thinning behaviour has spread up the length of the ice streams.

The glaciers concerned all terminate in the Amundsen Sea and are significant contributors to global ocean rise.

Their names are Pine Island, Thwaites, Pope, Smith, and Kohler.

Right now, they are dumping some 120 to 140 billion tonnes of ice a year into the ocean, which is sufficient to push up global waters by between 0.34mm and 0.40mm per annum - more than 10% of the total worldwide trend.

The glaciers' reduction in height is likely the result of the warm seawater recorded around Antarctica in recent decades.

This attacks the underside of the ice streams at the point where they cease to push out along bedrock and begin to float. Eroding this "grounding line" back towards the land makes the glaciers move faster.

"As the glaciers accelerate, they have to take ever more ice from the interior to compensate for the speed-up. This means they thin; they lose height, which we can detect from space," explained Dr Hannes Konrad from the UK's Centre for Polar Observation and Monitoring (CPOM).

"And if there is no increase in snow and ice in the interior then this thinning will just migrate further and further upstream," the Leeds University researcher told BBC News.

Dr Konrad is presenting his team's work here at the Fall Meeting of American Geophysical Union (AGU) - the world's largest annual gathering of Earth scientists.

His study has also just been accepted for publication in the journal Geophysical Research Letters.

It seamlessly ties together for the first time the altimetry observations from five different satellites operated by the European and American space agencies from 1992 to the present day.

What is interesting in the data is the individual responses of the glaciers to the melting assault.

They all show thinning over the period, but the behaviours are far from uniform.

Pine Island Glacier (PIG), which currently contributes more to sea level rise than any other ice stream on the planet, thins fairly steadily and relentlessly.

The lowering of its surface is already in play by the start of the satellite measurements, and now spreads back from its grounding line, along its main trunk for hundreds of km inland.

At maximum, the glacier is losing 5m in height every year and the thinning spreads inland at up to 15km per year at times.

Thwaites, on the other hand, started dropping its elevation later than the PIG and did so in two broad periods. Its delayed and episodic response means thinning on Thwaites has not spread so far inland.

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