Analysis of "Antarctic ice loss has tripled in a decade. If that continues, we are in serious trouble." Published in The Washington Post , by Chris Mooney on

Four scientists analyzed the article and estimate its overall scientific credibility to be 'high'. more about the credibility rating

A majority of reviewers tagged the article as: Accurate, Insightful.

SCIENTISTS’ FEEDBACK

SUMMARY

This article in The Washington Post describes an important study from a project called the Ice sheet Mass Balance Intercomparison Exercise (or IMBIE), which synthesized many existing records of Antarctic ice based on different types of measurements. The resulting estimate shows that Antarctica alone lost enough ice between 1992 and 2017 to raise global sea level by around 7.6 millimeters—almost 10% of the total sea level change over that time period.

Scientists who reviewed the article found that it accurately summarized this result, while explaining some of the processes behind this mass loss and the sea level rise it produces. However, they note that future trends depend partly on complex natural variability, which the article could have made clear.

See all the scientists’ annotations in context

REVIEWERS’ OVERALL FEEDBACK

These comments are the overall opinion of scientists on the article, they are substantiated by their knowledge in the field and by the content of the analysis in the annotations on the article.

Thomas Frederikse, Postdoctoral researcher, Jet Propulsion Laboratory/California Institute of Technology:

The article accurately summarises the main conclusions of the discussed study, and multiple experts give a clear overview of the current knowledge of the fate of the Antarctic ice sheet and associated sea level rise under global warming.

Peter Neff, Postdoctoral research associate, University of Washington:

Chris Mooney’s article on recent Antarctic ice mass loss results faithfully reports on the new data, providing a wealth of useful information to the reader. However, a lack of exploration of the causes of this Antarctic ice mass loss leaves the article vulnerable to being wrongly filed under “one more depressing impact of human-caused climate change” when the true story is more complex. From the article’s title, Mooney would have done well to address what processes, in addition to continued atmospheric warming, may cause continued Antarctic ice mass loss.

Anna Hughes, Lecturer, University of Manchester:

The article presents the results of the study accurately, and uses multiple comments from scientists both involved and not-involved in the study to highlight the key findings. Some of the explanations are simplified, and there is a slight attempt at the end to downplay the results by suggesting scientists can’t predict the future. It is correct that the study presented is not making predictions, rather documenting past changes, but the positive trend is what we would expect based on the longer record of change we have for glaciers and ice caps.

Aimée Slangen, Researcher, Royal Netherlands Institute for Sea Research (NIOZ):

An informative article citing relevant experts, and a good explainer of the findings of the IMBIE study.

Notes:

[1] See the rating guidelines used for article evaluations.

[2] Each evaluation is independent. Scientists’ comments are all published at the same time.

KEY TAKE-AWAYS

The statements quoted below are from the article; comments and replies are from the reviewers.

1. The loss of Antarctic ice has accelerated over the last 25 years. The future outlook is complicated, depending on both natural processes and human activity, but could result in large contributions to global sea level rise.



“Antarctica’s ice sheet is melting at a rapidly increasing rate, now pouring more than 200 billion tons of ice into the ocean annually and raising sea levels a half millimeter every year, a team of 80 scientists reported Wednesday.” Peter Neff, Postdoctoral research associate, University of Washington:

If these numbers seem abstract, consider this: Much of the ice mass loss is focused along the Amundsen Sea coast of West Antarctica. This is essentially the Pacific Coast of West Antarctica, which is roughly the same length as the Pacific Coast of the United States (~1200 miles, 1900 kilometers). The two Pacific Coasts—of the USA and the Antarctic—are overlain in this NASA image: Basically, this entire Pacific coast of West Antarctica is where Antarctic ice mass loss comes from, as can be seen in this animation of GRACE satellite gravity measurements from 2002-2016 which were part of the IMBIE study. In this illustration you can also see a “hot-spot” of mass loss on the left side of the Antarctic map, where Totten Glacier drains a portion of the East Antarctic ice sheet that is also increasingly losing mass.

“Antarctica, the planet’s largest ice sheet, lost 219 billion tons of ice annually from 2012 through 2017 — approximately triple the 73 billion ton melt rate of a decade ago, the scientists concluded. From 1992 through 1997, Antarctica lost 49 billion tons of ice annually.” Thomas Frederikse, Postdoctoral researcher, Jet Propulsion Laboratory/California Institute of Technology:

This is a correct summary of the results from the study. Aimée Slangen, Researcher, Royal Netherlands Institute for Sea Research (NIOZ):

This translates to about 0.6 mm/yr in 2012-2017, while the 1992-1997 rates were 0.14 mm/yr. This may not sound like much, but the current total rate of sea-level rise is around 3.2 mm/yr, so Antarctica is responsible for an increasingly large portion of the observed sea-level rise.

“The study is the product of a large group of Antarctic experts who collectively reviewed 24 recent measurements of Antarctic ice loss, reconciling their differences to produce the most definitive figures yet on changes in Antarctica.” Aimée Slangen, Researcher, Royal Netherlands Institute for Sea Research (NIOZ):

This sounds like there are only 24 data points, but the data going into the analysis is much more extensive than this, encompassing 24 types of measurements and analysis methodologies for the period from 1992 through to 2017.

2. Recent ice loss has primarily come from the West Antarctic Ice Sheet, making regional processes important to understanding the trend.



“[The West Antarctic Ice Sheet] is known to be losing ice rapidly because it is being melted from below by warm ocean waters, a process that is rendering its largest glaciers unstable.” Peter Neff, Postdoctoral research associate, University of Washington:

This is accurate but doesn’t fully explain that the warm ocean water is not a result of human-caused climate change and it is not a linear warming of Southern Ocean waters that causes melt beneath West Antarctic ice shelves. Rather, it is variability in the delivery of this relatively warm water (called Circumpolar Deep Water) that can directly affect how much melt is happening. Delivery of this water is altered by the direction and strength of winds over the Amundsen Sea, a subset of the Pacific sector of the Southern Ocean. If winds blow from west to east across the Amundsen Sea, they promote upwelling of this deep water under ice shelves, promoting melt and hence increasing ice loss*. Steig et al (2012) Tropical forcing of Circumpolar Deep Water Inflow and outlet glacier thinning in the Amundsen Sea Embayment, West Antarctica, Annals of Glaciology

“The growth is largely attributable to just two huge glaciers — Pine Island and Thwaites. The latter is increasingly being viewed as posing a potential planetary emergency, because of its enormous size and its role as a gateway that could allow the ocean to someday access the entirety of West Antarctica, turning the marine-based ice sheet into a new sea.” Aimée Slangen, Researcher, Royal Netherlands Institute for Sea Research (NIOZ):

This is known as the Marine Ice Sheet Instability hypothesis (MISI), see Box 13.2 in the latest IPCC report (Working Group 1).

3. The loss of Antarctic ice produces greater sea level in the Northern Hemisphere than it does near Antarctica.

