The results of IMBIE 2016 were published in 2018 for Antarctica and in 2019 for Greenland. By combining the results of 50 different surveys produced by 89 participants from 50 international organisations, we produced reconciled time-series of ice sheet mass balance, showing that the Antarctic and Greenland Ice Sheets contributed 17.8 ± 1.8 mm to global sea level rise between 1992 and 2017.
The Antarctic Ice Sheet lost 2720 ± 1390 billion tonnes of ice between 1992 and 2017, with a 4-fold increase in the rate of mass loss between the first five years of our survey (1992-1997) and the last five years of our survey (2012-2017). West Antarctica experienced the largest change with the rate of mass loss rising from 53 ± 29 billion tonnes per year at the start of our survey to 159 ± 26 billion tonnes per year at the end of our survey due to increased ocean melting at Pine Island and Thwaites Glaciers causing glacier speedup. The Antarctic Peninsula also experienced increased ice losses following the collapse of Larsen B and Wilkins ice shelves with the rate of ice loss increasing from 7 ± 13 billion tonnes to 33 ± 16 billion tonnes per year. Finally, East Antarctica, where mass balance fluctuations are primarily driven by snowfall accumulation, has remained close to a state of balance with a small gain of 5 ± 46 billion tonnes of ice per year between 1992 and 2017.
The Greenland Ice Sheet lost 3902 ± 342 billion tonnes of ice between 1992 and 2018. Over half of Greenland’s ice losses comes from increased meltwater runoff driven by warmer atmospheric onditions, with the remainder originating from dynamical imbalance. The rate of ice loss has dramatically increased over the course of our survey, rising from 26 ± 27 billion tonnes per year in the early 1990s to 244 ± 28 billion tonnes per year between 2012 and 2017.
Time series of cumulative mass change and sea level contributions from the East, West and Antarctic Peninsula ice sheets and combined total (left), and cumulative mass change of the Greenland Ice Sheet, further partitioned into its surface mass balance and ice dynamics components (right)
These two assessments reveal that ice losses from the Greenland and Antarctic Ice Sheets are currently tracking the upper range of the IPCC Fifth Assessment Report (AR5) sea level rise projections, which predicts an additional contribution to sea level rise between 14.5 and 23 cm above the central predictions by the end of the century.