Melting ice-sheets rising Antarctic coastal waters, warns report

Melting ice-sheets

New research warns the Antarctic ice sheet is melting at unprecedented rates. Creative Commons: Christopher Michel, 2005

Melting ice sheets are fuelling sea-level rise around the coast of Antarctica, a new report from the University of Southampton.

Near-shore waters went up by about 2mm per year more than the general trend for the Southern Ocean as a whole in the period between 1992 and 2011.

Researchers used computer simulation and satellites and analysed data collected over the last 19 years to monitor the area, covering over a million square kilometeres of Antarctica.

The melting of the Antarctic land ice sheets and the thinning of floating ice shelves means that approximately 350 gigatonnes of fresh-water is flowing into the sea, causing a ‘freshening’ of the Antarctic seas- pushing up its surface.

Dr Rye, lead author of the report, said:

Freshwater is less dense than salt water and so in regions where an excess of freshwater has accumulated we expect a localised rise in sea level.

The White Continent is now losing an estimated 160 billion tonnes of ice annually.

Globally, sea levels are going up, in part because of the contribution of the world’s diminishing ice fields. This is well known.

But the Nature Geoscience report is the first to show the direct consequences to sea surface height around Antarctica itself, showing an additional 2mm per year can be attributed almost exclusively to freshwater runoff from Antarctica.

Recent satellite studies have underlined the increased mass losses occurring in Antarctica.

In one recent study, which examines data from CryoSat-2 – the European probe measuring the thickness of Earth’s ice sheets and glaciers since 2010 – found Antarctica is losing ice volume at around 30 cubic miles per year.

The data, which examined the planet’s two largest ice sheets – in Greenland and Antarctica – also found that the Greenland ice sheet across the other side of the planet is also being depleted at an astonishing rate of around 90 cubic miles each year.

The researchers found that since 2009 volume of loss in Greenland has increased by a factor of around two – with the whole sheet melting – while the West Antarctic ice sheet loss has increased by a factor of three.

By contrast East Antarctica is gaining volumes, thought the researchers warn the “moderate rate doesn’t compensate for the losses on the other side of the continent.”

The biggest elevation changes caused by ice loss were detected at the Jakobshavn glaciers in Greenland, which was recently found to be shifting ice into the oceans faster than any other glacier.

The Pine Island glacier, also in West Antarctica, has also been thinning rapidly in recent years.

According to a NASA study team, many of the key glaciers in the region are now in an ‘irreversible retreat’.

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