West Antarctic melt rate has tripled: UC Irvine-NASA

A comprehensive, 21-year analysis of the fastest-melting region of Antarctica has found that the melt rate of glaciers there has tripled during the last decade.

The glaciers in the Amundsen Sea Embayment in West Antarctica are hemorrhaging ice faster than any other part of Antarctica and are the most significant Antarctic contributors to sea level rise. This study is the first to evaluate and reconcile observations from four different measurement techniques to produce an authoritative estimate of the amount and the rate of loss over the last two decades.

“The mass loss of these glaciers is increasing at an amazing rate,” said scientist Isabella Velicogna, jointly of the UC Irvine and NASA’s Jet Propulsion Laboratory. Velicogna is a coauthor of a paper on the results, which has been accepted for Dec. 5 publication in the journal Geophysical Research Letters.

Lead author Tyler Sutterley, a UCI doctoral candidate, and his team did the analysis to verify that the melting in this part of Antarctica is shifting into high gear. “Previous studies had suggested that this region is starting to change very dramatically since the 1990s, and we wanted to see how all the different techniques compared,” Sutterley said. “The remarkable agreement among the techniques gave us confidence that we are getting this right.”

The researchers 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 embayment lost mass throughout the entire period. The researchers 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 (91.5 billion U.S. tons). By comparison, Mt. Everest weighs about 161 gigatons, meaning the Antarctic glaciers lost a Mt.-Everest’s-worth amount of water weight every two years over the last 21 years.

The rate of loss accelerated an average of 6.1 gigatons (6.7 billion U.S. tons) per year since 1992.

From 2003 to 2009, when all 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 four sets of observations include NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, laser altimetry from NASA’s Operation IceBridge airborne campaign and earlier ICESat satellite, radar altimetry from the European Space Agency’s Envisat satellite, and mass budget analyses using radars and the University of Utrecht’s Regional Atmospheric Climate Model.

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,” Velicogna said, “because the changes are proceeding very fast.”


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Scientists find extensive glacial retreat in Mount Everest region

Researchers taking a new look at the snow and ice covering Mount Everest and the national park that surrounds it are finding abundant evidence that the world’s tallest peak is shedding its frozen cloak. The scientists have also been studying temperature and precipitation trends in the area and
found that the Everest region has been warming while snowfall has been declining since the early 1990s.

Members of the team conducting these studies will present their
findings on May 14 at the Meeting of the Americas in Cancun,
Mexico – a scientific conference organized and co-sponsored by
the American Geophysical Union.

Glaciers in the Mount Everest region have shrunk by 13 percent
in the last 50 years and the snowline has shifted upward by 180
meters (590 feet), according to Sudeep Thakuri, who is leading
the research as part of his PhD graduate studies at the University
of Milan in Italy.

Glaciers smaller than one square kilometer are
disappearing the fastest and have experienced a 43 percent
decrease in surface area since the 1960s. Because the glaciers are
melting faster than they are replenished by ice and snow, they are
revealing rocks and debris that were previously hidden deep
under the ice. These debris-covered sections of the glaciers have
increased by about 17 percent since the 1960s, according to
Thakuri. The ends of the glaciers have also retreated by an
average of 400 meters since 1962, his team found.

The researchers suspect that the decline of snow and ice in the
Everest region is from human-generated greenhouse gases
altering global climate. However, they have not yet established a
firm connection between the mountains’ changes and climate
change, Thakuri said.

He and his team determined the extent of glacial change on
Everest and the surrounding 1,148 square kilometer (713 square
mile) Sagarmatha National Park by compiling satellite imagery
and topographic maps and reconstructing the glacial history.
Their statistical analysis shows that the majority of the glaciers in
the national park are retreating at an increasing rate, Thakuri

To evaluate the temperature and precipitation patterns in the
area, Thakuri and his colleagues have been analyzing hydro-
meteorological data from the Nepal Climate Observatory stations
and Nepal’s Department of Hydrology and Meteorology. The
researchers found that the Everest region has undergone a 0.6
degree Celsius (1.08 degrees Fahrenheit) increase in temperature
and 100 millimeter (3.9 inches) decrease in precipitation during
the pre-monsoon and winter months since 1992.

In subsequent research, Thakuri plans on exploring the climate-
glacier relationship further with the aim of integrating the
glaciological, hydrological and climatic data to understand the
behavior of the hydrological cycle and future water availability.

“The Himalayan glaciers and ice caps are considered a water
tower for Asia since they store and supply water downstream
during the dry season,” said Thakuri. “Downstream populations
are dependent on the melt water for agriculture, drinking, and
power production.”