A gigatonne of ice here, a gigatonne of ice there... Soon enough we're talking about a meaningful quantity! A team of scientists from the UK Centre for Polar Observation and Modelling have compiled the first ever complete assessment of Antarctic ice sheet changes using data from the European Space Agency’s CryoSat-2 satellite.
What they found is rather alarming: On average, West Antarctica lost 134 gigatonnes of ice, East Antarctica three gigatonnes, and the Antarctic Peninsula 23 gigatonnes in each year between 2010 and 2013 – a total loss of about 159 gigatonnes each year (yes, we rounded it in the title, but all these numbers are rounded too, nobody can be sure to the tonne how much ice is lost).
“We find that ice losses continue to be most pronounced along the fast-flowing ice streams of the Amundsen Sea sector, with thinning rates of between 4 and 8 metres per year near to the grounding lines of the Pine Island, Thwaites and Smith Glaciers,” said lead author Dr Malcolm McMillan from the University of Leeds.To put this into context, this is a lot of ice, but the Earth's oceans are very big too, so this is only enough raise global sea levels by 0.45 millimetres each year. But combine this with other ice sheets and glaciers melting (ie. Greenland) and thermal expansion over long periods and it all adds up. Nobody is saying that sea levels will raise suddenly by large amounts, but when something is headed in the wrong direction, you better change course before things get really bad, not after.
“The increased thinning we have detected in West Antarctica is a worrying development. It adds concrete evidence that dramatic changes are underway in this part of our planet, which has enough ice to raise global sea levels by more than a metre,” said Professor Andrew Shepherd.
“The increasing contribution of Antarctica to sea-level rise is a global issue, and we need to use every technique available to understand where and how much ice is being lost,” said Professor David Vaughan of the British Antarctic Survey.