Image Credit: Christopher Harig, Department of Geosciences

Researchers at Princeton University have confirmed accelerating rates of loss in the Antarctic ice sheet.  If this continues, significant rises in sea level are predicted.

This may not seem like news.  After all, prior studies have indicated that the Antarctic ice sheet is melting.  However, these former studies primarily measured the volume of the ice sheet, or how much space it takes up.  That approach has problems, because the volume can be impacted by other variables.  For example, as snow gets compacted under its own weight, the volume will decrease, in spite of the fact that there is still the same amount of snow.

In a new study published in Earth and Planetary Science Letters, researchers from Princeton University used gravity measurements from satellite data to assess the mass or weight of the Antarctic ice sheet.  The satellite data was provided by GRACE, the Gravity Recovery and Climate Experiment, a joint satellite mission between NASA and the German Aerospace Center.  By “weighing” the ice, the researchers were able to more accurately assess melting, because a reduction in the mass or weight of the ice indicates that ice has been lost. 

According to Frederick Simons, co-author of the paper and a Princeton Associate Professor of Geosciences, “You shouldn’t only look at the ice volume — you should also weigh it to find the mass changes.”  In other words, you wouldn’t weigh yourself by looking in a mirror, you would need to stand on a scale.

Utilizing this new technique, the researchers found that overall, the Antarctic ice sheet lost 92 billions tons of ice per year in the past 11 years.  That’s enough to dump a mile-high pile of ice on the island of Manhattan.  And alarmingly, the ice is melting at a larger rate than was previously known.  Overall, the melting rate of the Antarctic ice sheet grew by 6 billion tons per year.

As indicated by the red area in the map, most of the loss was found to be occurring in West Antarctica’s Amundsen Sea region.  Indeed, the ice-loss rate in West Antarctica increased by 18 billion tons per year throughout the study period, making that area particularly unstable.

Christopher Harig, first author of the study and a Princeton Postodoctoral Research Associate in Geosciences, expressed concern that the loss of ice in West Antarctica is accelerating.  “If we continue losing mass in those areas, the loss can generate a self-reinforcing feedback whereby we will be losing more and more ice, ultimately raising sea levels by tens of feet,” said Harig.

Previously, Harig and Simons also demonstrated ice loss in Greenland.  In that 2012 study, they reported that Greenland lost about 200 billion tons of ice per year over the seven-year study period.  Assuming that rate continues, they estimated that it would take 13,000 years to melt the Greenland ice sheet, resulting in at least a 21-foot rise in global sea levels.

“We have a solution that is very solid, very detailed and unambiguous,” said Simons.  According to Simons, this study conclusively shows that the Antarctica ice sheet is melting, and while the study can’t prove the cause, global warming is certainly suspect.  “With the rapidly accelerating rates at which the ice is melting, and in the light of all the other, well-publicized lines of evidence, most scientists would be hard pressed to find mechanisms that do not include human-made climate change.”

Image Credit: Ben Holt (NASA)

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