Antarctica has lost a staggering three trillion tonnes of ice since 1992, according to a landmark study published Wednesday that suggests the frozen continent could redraw Earth’s coastlines if global warming continues unchecked.
Two-fifths of that ice loss occurred in the last five years, a three-fold increase in the pace at which Antarctica is shedding its kilometres-thick casing, a consortium of 84 scientists reported in the journal Nature.
The findings should dispel any lingering doubts that the continent’s ice mass is shrinking, the authors said.
They also highlight the existential threat facing low-lying coastal cities and communities home to hundreds of millions of people.
"We now have an unequivocal picture of what’s happening in Antarctica," said co-lead author Eric Rignot, a scientist at NASA’s Jet propulsion Laboratory who has been tracking Earth’s ice sheets for two decades.
"We view these results as another ringing alarm for action to slow the warming of our planet."
Up to now, scientists have struggled in determining whether Antarctica has accumulated more mass through snowfall than it loses in meltwater run-off and ice flows into the ocean.
But more than two decades of satellite data – the new findings draw from 24 separate space-based surveys – have finally yielded a more complete picture.
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Covering twice the area of the continental United States, Antarctica is blanketed by enough ice pack to lift global oceans by nearly 210 feet.
More than 90 percent of that frozen water sits atop East Antarctica, which has remained mostly stable even as climate change has driven up Earth’s average surface temperature by a full degree Celsius.
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Some studies had suggested a net gain in mass over recent decades.
West Antarctica, however, has proven far more vulnerable to global warming, especially the Antarctic Peninsula, where more than 2,500 square miles of ice shelves have sheared off into the sea since 1995.
Already floating, ice shelves breaking off into icebergs do not add to sea level. But massive glaciers on West Antarctica slowly gliding seaward hold enough water to push oceans up by 11 feet.
Two of these glaciers – Pine Island and Thwaites – have accelerated and are today seen as unstable. Together, they act as corks holding back ice mass further inland from falling into the ocean.
Nearly all of the mass shed over the last quarter century has come from West Antarctica, the study found.
Ice loss of 2.7 trillion tonnes since 1992 added about eight millimetres to sea level.