Antarctica Is Thawing Faster, Tripling Its Effect on Rising Seas

June 13, 2018, 5:12 PM

Policy makers and planners should start anticipating an extra 20 percent increase in global sea levels by the end of the century if the faster pace of Antarctic melting continues, scientists working on new research say.

The Antarctic ice sheet can’t endure the current pace of global warming, leading to a threefold increase since 2012 in its effect on rising seas worldwide, new research from a team of American and European scientists finds.

The study should be a cause for concern for policy makers and coastal planners, who should expect scenarios of even greater sea level rise, the scientists told Bloomberg Environment.

How quickly the Antarctic ice sheet thaws—and how much that contributes to rising seas—remains one of the biggest questions about future ocean levels, and the research finds that recent changes in the region’s ice loss are surprisingly large.

Until 2012, the Antarctic’s contribution to sea level rise had been consistent with lower-end estimates by the Intergovernmental Panel on Climate Change, driving only minimal sea level change over the next century, according to Andrew Shepherd, a professor of Earth observation at the University of Leeds in the U.K. and the co-leader of the joint research project.

The research, known as the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), was published June 13 in Nature.

It shows there is a realistic possibility that the Antarctic’s contribution to sea level rise will reach the upper end of global projections. That scenario projects an extra 15 centimeters (about 6 inches) of sea level rise on top of the IPCC’s central estimate of 60 cm (about 2 feet) of global sea level rise by the end of the century, Shepherd said.

NASA, European Space Mission

The research examined satellite data from several NASA and European Space Agency missions to determine how ice levels in Antarctica have changed over time due to a warming world.

The assessment finds that before 2012, annual Antarctic ice loss was roughly 76 billion tons and contributed to an average 0.2 millimeter per year rise in global sea level. Between 2012 and 2017, however, those rates roughly tripled to an annual ice loss of 219 billion tons and an average 0.6 millimeter contribution to sea level rise.

Those millimeter increases in sea level may seem like tiny numbers, but small changes compound over time, Shepherd said.

The bulk of the ice loss in the region occurred in West Antarctica, where the ice sheet rests directly on the sea bed, the research finds. That ice sheet is extremely sensitive to even small changes in the ocean temperature.

Scientists think the rate of change could accelerate further. The West Antarctica ice sheet is “the largest, most vulnerable piece of ice on our planet,” Robin Bell, a research professor at Columbia University’s Palisades Geophysical Institute who reviewed the research report, told Bloomberg Environment. “If I was a policy maker, I might think more carefully about my coasts and my investments along the coast.”

Satellite Research

The IMBIE research assessed the Antarctic ice sheet’s response to a changing climate through satellite measurements.

Using space satellites is invaluable to understand changes to the ice sheets, particularly in Antarctica where the losses aren’t readily visible, the scientists said.

Shepherd said it is vital to continue satellite missions led by NASA and the European Space Agency. The research now is based on single missions, but long-term, continuous monitoring of changes to the ice sheets are also needed, he said.

“We were surprised at how fast ice sheets could change. We used to think they changed very slowly,” Bell said. It is critical for climate models to use the most up-to-date information on ice sheet loss for sea level rise projections, she said.

Funding Concerns

Concerns have persisted, however, that the Trump administration will seek to sharply cut funding for climate science research.

The Trump administration sees climate change research as a waste of taxpayer money, White House budget director Mick Mulvaney said in a March 2017 news conference. “We’re not spending money on that anymore.”

NASA, along with the German Research Center for Geosciences, launched the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) satellite mission May 21, which Shepherd said could help provide further measurements needed to continue assessment of ice sheet loss and sea level rise.

That satellite was the first climate mission launched after Jim Bridenstine, a former Oklahoma Republican congressman, was confirmed as NASA’s head.

Bridenstine previously declined to say definitively whether humans are the major driver of global climate change. But in remarks to NASA employees shortly after his confirmation, he said he doesn’t deny consensus climate science.

“We’re putting [carbon dioxide] into the atmosphere in volumes that we haven’t seen, and that greenhouse gas is warming the planet,” Bridenstine said May 17. “That is absolutely happening, and we are responsible for it.”

Isabella Velicogna, an earth science professor at the University of California, Irvine and scientist with NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said she has so far seen continued support for research efforts like IMBIE and the GRACE-FO satellite.

“We are observing some very significant changes, changes that will affect the coastline,” she said, adding sea level rise also affects national security and population planning. “It’s not just about climate. It’s about the impact it has on people.”

Sea levels also don’t rise uniformly, meaning some areas of the globe could see a quicker rise due to loss in the ice sheets, Velicogna, a member of the research team, added. Areas such as Florida, South America, Bangladesh, and Africa that are nearer the Equator will experience sea level rise faster than the rest of the world, she added.

To contact the reporter on this story: Abby Smith in Washington at asmith@bloombergenvironment.com

To contact the editor responsible for this story: Rachael Daigle at rdaigle@bloombergenvironment.com

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