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Antarctic ice loss has accelerated: Study

Crevasses near the grounding line of Pine island in West Antarctica that is experiencing huge ice losses. (Credit: Ian Joughin, University of Washington)

New Delhi: Ice loss from Antarctica has increased global sea levels by nearly 8 mm over the past 25 years and unchecked climate change could accelerate this process, threatening coastal populations around the world, scientists cautioned on Wednesday.

Their study, described as the most comprehensive analysis to date of past changes in Antarctic ice sheets, has shown that the continent lost ice at a steady rate of about 76 billion tonnes per year from 1992 to 2012, corresponding to a 0.2 mm per year rise in sea level.

But the ice loss rose to 219 billion tonnes per year between 2012 and 2017, contributing to a 0.6 mm per year increase in global sea level, an international team of scientists from 16 countries said in the study published in the journal Nature. The continent has lost nearly three trillion tonnes of ice between 1992 and 2017, the study found.

"The continent is causing sea levels to rise faster today than at any time in the past 25 years," said Andrew Shepherd, professor of earth observation at the University of Leeds who led the study in a media release. "This has to be a concern for governments we trust to protect our coastal cities and communities."

The scientists said tracking Antarctic ice loss is important to understand future impacts of climate change as the continent's ice sheets hold enough frozen water to increase the global sea level by 58 metres.

Shepherd and his colleagues used 24 sets of satellite surveys to assess annual heat-driven loss of ice and ice growth through winter snowfall between 1992 and 2017, using satellite imagery and gravity measurements that revealed ice and glacier changes on the continent.

Another group of scientists has used the latest available observations to speculate on the future of Antarctica, warning that some anticipated changes are already irreversible - but there is still opportunity and time to prevent the worst case scenarios.

Antarctic ice sheets do not respond immediately to global temperature changes. If global warming were to magically stop today, researchers say, the continent will continue to lose ice for a few decades.

"We're already locked in to see some sea level rise," Martin Siegert, professor of geosciences at the Imperial College London and co-author of a paper on the future of Antarctica in the same issue of Nature, told The Telegraph over the phone.

"In the best case scenarios where the world adequately curbs global warming, we could still expect the Antarctic contribution to global sea level to rise by 6 to 7 cm over the next 50 years, Siegert said.

"What we must do is to avoid the worst case scenarios under which Antarctica may lose enough ice to raise sea level by 30 cm over the next 50 years, leading to more than a metre in the decades after that."

The net ice loss study suggests the world is at present not on the path of the base case scenarios.

"We're somewhere in between the best case and the worst case scenarios and our actions to check global warming in the coming decades will determine the future of Antarctica, which will have wide implications for other ecosystems and people around the world," Siegert said.

Siegert and his colleagues have speculated that unabated global warming could lead to an expansion of ice-free areas on Antarctica by 2070 which could make the continent - if current regulations on human activities are weakened - more vulnerable to mining, tourism, and even permanent hotels.

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