The findings are from a major climate assessment known as the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), and are published today in Nature. It is the most complete picture of Antarctic ice sheet change to date - 84 scientists from 44 international organisations combined 24 satellite surveys to produce the assessment.
Their findings show that, prior to 2012, Antarctica lost ice at a steady rate of 76 billion tonnes per year – a 0.2 mm per year contribution to sea level rise. However, since then there has been a sharp, threefold increase. Between 2012 and 2017 the continent lost 219 billion tonnes of ice per year – a 0.6 mm per year sea level contribution. Antarctica stores enough frozen water to raise global sea level by 58 metres, and knowing how much ice it is losing is key to understanding the impacts of climate change today and in the future.
The threefold increase in ice loss from the continent as a whole is a combination of glacier speedup in West Antarctica and at the Antarctic Peninsula, and reduced growth of the ice sheet in East Antarctica. West Antarctica experienced the largest change, with ice losses rising from 53 billion tonnes per year in the 1990s to 159 billion tonnes per year since 2012. Most of this came from the huge Pine Island and Thwaites Glaciers, which are retreating rapidly due to ocean melting. At the northern tip of the continent, ice shelf collapse at the Antarctic Peninsula has driven a 25 billion tonne per year increase in ice loss since the early 2000s. The East Antarctic ice sheet has remained close to a state of balance over the past 25 years, gaining just 5 billion tonnes of ice per year on average.
The assessment, led by Professor Andrew Shepherd at the University of Leeds and Dr Erik Ivins at NASA’s Jet Propulsion Laboratory in California, was supported by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA).
Professor Shepherd said: “According to our analysis, there has been a step increase in ice losses from Antarctica during the past decade, and the continent is causing sea levels to rise faster today than at any time in the past 25 years. This has to be a concern for the governments we trust to protect our coastal cities and communities.”
The comparative study assesses ice-sheet mass loss with an unprecedented degree of accuracy. On behalf of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), the climate researcher Dr Ingo Sasgen and the glaciologist Dr Veit Helm took part in the study. “We supplied content on land uplift and surface elevation change in the Antarctic,” reports Ingo Sasgen. One of three methods employed in the Nature publication involves assessing the mass balance of ice sheets using the Earth’s gravitational pull (satellite gravimetry). “Land uplift is produced by the retreat of ice since the last glacial period. The reduced weight of the ice sheets eventually leads to land uplift and mass changes within the Earth, which we need to quantify,” says Ingo Sasgen, explaining his own contribution, which is based e.g. on data from the GRACE satellites (see also AWI Press Release, dated 17 May 2018).
Data from the following satellite missions were used for the study:
- ENVISAT and CryoSat-2, European Space Agency (ESA)
- Japan Aerospace Exploration Agency Advanced Land Observatory System
- RADARSAT-1 and RADARSAT-2, Canadian Space Agency
- NASA Ice, Cloud, and land Elevation Satellite
- GRACE (NASA / German Aerospace Center Gravity Recovery and Climate Experiment)
- COSMO-SkyMed, Italian Space Agency
- TerraSAR-X, German Aerospace Center (DLR)
Original publication
IMBIE Team: „Mass balance of the Antarctic ice sheet from 1992 to 2017“, Nature, 14 June 2018. DOI: 10.1038/s41586-018-0179-y.
