According to a new NASA-led study published in the journal Geophysical Research Letters, the melt rate of glaciers in the Amundsen Sea Embayment, West Antarctica, has tripled during the past decade, causing the loss of a Mt. Everest-sized amount of ice every two years.
An iceberg is seen out the window of a research aircraft as it flies above the Amundsen Sea in West Antarctica on October 21, 2009. Image credit: NASA / Jane Peterson.
The 21-year study is the first to evaluate and reconcile observations from four different measurement techniques – NASA’s Gravity Recovery and Climate Experiment satellites, laser altimetry from NASA’s Operation IceBridge airborne campaign and the earlier ICESat satellite, radar altimetry from the ESA’s Envisat satellite, and mass budget analyses using radars and the University of Utrecht’s Regional Atmospheric Climate Model – to produce an authoritative estimate of the amount and the rate of loss over the last two decades.
“Previous studies had suggested that the Amundsen Sea Embayment is starting to change very dramatically since the 1990s, and we wanted to see how all the different techniques compared. The remarkable agreement among the techniques gave us confidence that we are getting this right,” said study lead author Dr Tyler Sutterley of the University of California, Irvine.
Dr Sutterley and his co-authors reconciled measurements of the mass balance of glaciers flowing into the Amundsen Sea Embayment. Mass balance is a measure of how much ice the glaciers gain and lose over time from accumulating or melting snow, discharges of ice as icebergs, and other causes.
Measurements from all four techniques were available from 2003 to 2009. Combined, the four data sets span the years 1992 to 2013.
The glaciers in the Amundsen Sea Embayment lost mass throughout the entire period.
The scientists calculated two separate quantities: the total amount of loss, and the changes in the rate of loss.
The total amount of loss averaged 83 gigatons per year. By comparison, Mt. Everest weighs about 161 gigatons, meaning the Antarctic glaciers lost an amount of ice weight equivalent to Mt. Everest every two years over the last 21 years.
The rate of loss accelerated an average of 6.1 gigatons per year since 1992.
During the period when the four observational techniques overlapped, the melt rate increased an average of 16.3 gigatons per year – almost three times the rate of increase for the full 21-year period. The total amount of loss was close to the average at 84 gigatons.
The scientists noted that glacier and ice sheet behavior worldwide is by far the greatest uncertainty in predicting future sea level.
“We have an excellent observing network now. It’s critical that we maintain this network to continue monitoring the changes, because the changes are proceeding very fast,” said co-author Dr Isabella Velicogna from NASA’s Jet Propulsion Laboratory in Pasadena and the University of California, Irvine.
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Tyler C. Sutterley et al. Mass loss of the Amundsen Sea Embayment of West Antarctica from four independent techniques. Geophysical Research Letters, published online November 15, 2014; doi: 10.1002/2014GL061940
