Antarctica ice loss has tripled in 5 years, threatening coastlines

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An analysis of satellite data collected since 1992 suggests that ocean-driven melting has led to a tripling in the rate of ice loss from West Antarctica, from 53 billion to 159 billion metric tons per year.

The frozen continent lost nearly three trillion tonnes of ice between 1992 and 2017, the 84 scientists said in what they called the most complete overview of Antarctic ice to date.

And the ice losses quickened to 219 billion tonnes a year since 2012, from 76 billion previously.

In the last quarter century, the Antarctic ice sheet, which is often used as a key indicator of climate change, has melted into enough water to cover Texas to a depth of almost 13 feet, according to researchers calculations.

Each of these plays an important environmental role: the ice sheet holds enormous freshwater reserves, the ice shelves feed freshwater into the ocean, and the sea ice is more reflective of sunlight than the water it floats in, which reduces the amount of heat the planet absorbs.

A separate study warns that unless urgent action is taken in the next decade the melting ice could contribute more than 25cm to a total global sea level rise of more than a metre by 2070.

Scientists were able to produce a more complete picture of Antarctic ice loss by compiling data from a wide array of monitoring efforts.

Co-author Professor Martin Siegert, from the Grantham Institute, said: "Some of the changes Antarctica will face are already irreversible, such as the loss of some ice shelves, but there is a lot we can prevent or reverse".

As the ice sheet loses ice, its gravitational pull is reduced, so the local sea level near Antarctica is diminished. Altogether, 34,000 square kilometers (more than 13,000 square miles) of ice shelf area has been lost since the 1950s. According to nine award-winning scientists if the ice keeps melting at the same rate the sea level will rise and all the coastal countries will be threatened by flooding.

This significant increase in the rate of melting is caused, first of all, the influence of ocean currents that bring warmer water flows and accelerate the melting of the ice shelf.

ESA's Director of Earth Observation Programmes, Josef Aschbacher, added, "CryoSat and Sentinel-1 are clearly making an essential contribution to understanding how ice sheets are responding to climate change and affecting sea level, which is a major concern".

The researchers relied on samples taken as part of the global ANtarctic geological DRILLing (ANDRILL) project. In 2014 the intergovernmental panel on climate change (IPCC) published its fifth assessment report, which includes modelled projections of Antarctica's contribution to sea level rise over the century. There are large glaciers, pine island and Thwaites Glacier, plunging into the open ocean.

In the Greenland study, levels of beryllium-10 found in sandy deposits brought out to sea in icebergs suggested the ice sheet has been a "persistent and dynamic" presence that melted and re-formed periodically in response to temperature fluctuations.

The Antarctic Ice Sheet covers an area of about 14 million square kilometres; by comparison, the area of Australia is about 7.7 million square kilometres, and that of the US is about 9.8 million square kilometres.

The study found more than 10 percent of Antarctica's coastal glaciers are now retreating more than 25m per year. The researchers also found that three millimeters of this sea level rise has occurred in the last five years alone.

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