'Grim future' on the horizon as Antarctic ice melt triples

Wednesday, 13 June 2018

Scientists believe Antarctic ice melt is causing sea levels to rise faster today than at any time in the past 25 years.

Antarctica has lost three trillion tonnes of ice over the last 25 years – roughly the volume of Wellington Harbour each day – with almost half of the melting happening in the last five years.

A major analysis of the frozen continent's ice sheets and glaciers found the loss has caused an 8 millimetre rise in global sea levels since the early 1990s.

Sea level contribution due to the Antarctic ice sheet between 1992 and 2017, from data gathered by international scientists working on the Ice Sheet Mass Balance Inter-comparison Exercise.

The rate of melting has tripled since 2012, with the 219 billion tonnes of ice being lost every year since then contributing to a 3mm rise in sea levels.

Scientists are uncertain whether this acceleration will continue at the same rate but fear unless political decisions are made to protect Antarctica the results could be catastrophic.

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Better understanding in recent years about ice loss means they now also believe that if greenhouse gas emissions continue to increase as they have done in the past, sea levels could rise by up to two metres by the end of the century – double the previous estimates – putting half a billion lives at risk.

Professor Tim Naish, of the Victoria University of Wellington, who contributed to the study, said the scenario had 'sent shockwaves around the world' and painted a 'grim future'.

But he said there is still hope if there is concerted global collaboration to tackle global warming.

'There is still time to prevent major meltdown of the ice sheets, and other far-reaching dangerous impacts if nations collectively reduce their emissions in line with the Paris Climate Agreement target of 2C warming above pre-industrial levels,' he said.

Analysis of satellite data by a team of international scientists – research published on Thursday in the journal Nature – found melting of ice by warm ocean water had tripled the rate of ice loss in West Antarctica, from 53 billion tonnes a year in 1992 to 159 billion tonnes annually in 2017.

The rate of melting for Antarctica as a whole has gone up threefold in the last five years, what Naish described as a 'massive acceleration'.

'The atmosphere has been warming by a degree since the industrial revolution, and a lot of that heat has gone into the ocean.

'I think the acceleration from Antarctica represents the beginning of the effect on the ocean, which we haven't seen until about a decade ago.

'But there is still a very valid question as to how we predict that into the future, and whether we can keep that acceleration going for 100 years or whether that part of Antarctica will stabilise a little bit and things will slow down.'

Nick Golledge, an associate professor at the Antarctic Research Centre, said the acceleration of ice loss and melting of ice shelves suggested a 'runaway retreat' of the West Antarctic ice sheet, something that may be irreversible.

'As individuals, we need to acknowledge the impact that our lifestyle choices have on the environment. As a society we need to rapidly transition to a low-carbon footprint, and the easiest way to do that is to adopt an entirely plant-based diet.'

Naish acknowledged the future is 'grim', saying: 'We are not on target for Paris [agreement obligations], we're on target for a climate that might not be as bad as our worst-case scenario.

'But not only do we cause massive change to Antarctica, we cause massive hardship to humanity through sea levels rising, large coastal cities being drowned, climate change refugees and extreme climate events.'

In a separate study published in Nature, Australian scientists have found storm-driven ocean swells have triggered catastrophic disintegration of Antarctic ice shelves in recent decades.

Reduced sea ice coverage since the late 1980s has led to increased exposure of ice shelves on the Antarctic Peninsula to ocean swells, causing them to flex and break.