FREEDOM AND SAFETY
Antarctica’s ice sheet is melting far faster than previously thought, with more than 200 billion tonnes of ice flooding into oceans annually, according to new research published in Nature this week.
About three trillion tonnes of ice has disappeared since 1992. The rate of melting has accelerated threefold in the last five years, and may – a separate study suggests – lead to sea rises of 25cm by the year 2070, which would have a disastrous impact around the world.
"We can see where the ice melting is happening, and it's in West Antarctica – and that tells us why it's happening, because we know that the ocean in West Antarctica is too warm," says professor Andrew Shepherd from Leeds University, who led the latest research. "This is too much for the ice to resist, and the ice is melting away and causing this sea level rise... It tells us that the ice sheet isn't impervious to the effects of climate change as we once thought it might be, and that's a wake-up call."
Previous research suggested antarctic ice was melting faster over the last twenty years than the last 10,000 – we now know the prognosis is worse still. If melting continues at this pace, we could expect an extra 15cm of sea level rise by 2100 on top of present projections.
The study claims to be the most ambitious, comprehensive assessment of the Antarctic ice sheet to date, involving 84 scientists from 44 international organisations, pooling satellite assessments and techniques to produce as accurate a picture as possible.
There has been a sharp increase since 2012 in the rate of ice being lost: before 2012, Antarctica lost ice at a steady rate of 76 billion tonnes per year, which amounted to a 0.2mm yearly sea-level rise. Now, however, Antarctica is losing 219 billion tonnes of ice per year, amounting to a 0.6mm per year sea-level rise.
These aren't just perilous times for Pingu and co – Antarctica's health is intimately connected to the global ecosystem and the sustainability of human life.
A separate study, also published in Nature, envisaged the state of the climate in 2070 under two probable scenarios. In the first, urgent action on greenhouse gases and environmental protection had been taken, and in the second, emissions rose unabated and the Antarctic is exploited for its resources.
Were this to happen, we could see it contribute to global sea rises of more than a metre, in turn leading to the eventual collapse of the Antarctic ice sheet, and around 3.5m of sea-level rise. Scientists behind the study, including professor Martin Seigert from the Grantham Institute, say some of the changes taking hold in Antarctica are “already irreversible” – but there are effects we can still mitigate. "We can reduce emissions, and we'll slow down the rate at which the ice sheets'll melt," Shepherd says. "But unless we reverse the planet's temperature, we won't lower sea levels."