Thwaites Glacier, West Antarctica

Given Texas’ long coastline and low-lying, flood-prone coastal terrain, scientists have warned for years that cities and industries near the Gulf of Mexico are vulnerable both to the direct threat of sea-level rise and to its magnification of tropical storm-surge hazards.

A pair of scientific studies documenting the apparently “unstoppable” collapse of the melting West Antarctic ice sheet dramatically underscore the risks faced by the state and other coastal areas as manmade global warming accelerates.

The Science Now website of the American Academy for the Advancement of Science reported the research results, which suggest the warming trend will bring more sea-level rise than some scientists have projected until now:

A disaster may be unfolding—in slow motion. Earlier this week, two teams of scientists [one from NASA and the University of California and the other from the University of Washington] reported that the Thwaites Glacier, a keystone holding the massive West Antarctic Ice Sheet together, is starting to collapse. In the long run, they say, the entire ice sheet is doomed, which would release enough meltwater to raise sea levels by more than three meters [about 10 feet].

The New York Times summarized the news this way:

The finding [that the collapse of the West Antarctic ice sheet is now “almost certainly unstoppable”], which had been feared by some scientists for decades, means that a rise in global sea level of at least 10 feet may now be inevitable. The rise may continue to be relatively slow for at least the next century or so, the scientists said, but sometime after that it will probably speed up so sharply as to become a crisis.

A study by other researchers, published in 2009, projected that sea-level rise from a collapse of the Antarctic ice sheet would not be globally uniform and that North America would be at higher risk, with sea level rising as much as 21 feet in places like the Washington, D.C., area.

Texas Climate News asked Larry McKinney, executive director of the Harte Research Center for Gulf of Mexico Studies at Texas A&M University-Corpus Christi, to comment on the ramifications of the two new studies about Antarctica that were published this week.

His emailed reply:

The recent reports of an accelerated disintegration of the West Antarctic ice sheet have implications for the Gulf of Mexico and especially Texas where sea level rise is a significant issue, especially along the Upper Coast.

Regardless of the cause, we may have reached a tipping point where we will see a rise in sea level more quickly than anticipated. It adds urgency to the need for the long-range planning to adapt to a changing world-scape and in our case, Gulf-scape.

The Harte Research Institute announced last year that it had received a $790,000 grant from the Houston Endowment foundation (previously a financial supporter of Texas Climate News) to undertake “a ground-breaking project to map and evaluate the effects of sea level rise on the upper Texas coast and develop tools to address this critical issue.”

The institute, which has done sea-level-rise modeling and research along the Texas coast, “will assess the impacts of sea-level rise on the greater Houston area in order to acquire the knowledge necessary to mitigate and adapt to higher sea level during the next 50 to 100 years,” it said at the time.

Writing before the two new studies’ release, Rice University oceanography professor John Anderson, a widely recognized expert on sea-level rise, outlined his appraisal of risks for Texas in the current issue of Cite magazine, a publication of the Rice Design Alliance:

The acceleration of sea-level rise, coupled with minimal sediment supply to the coast, has resulted in increased rates of coastal erosion, both along the Gulf Coast and within bays, and loss of wetlands. Thus, the first line of defense against storm surge in more inland areas is being removed. At the same time, the population of the greater Houston area continues to push south and into areas that are highly vulnerable to storm surge. The highly vulnerable Port of Houston and petrochemical industry at the head of Galveston Bay continues to expand. The City of Galveston refuses to adopt a setback policy for new construction along the Gulf shoreline. We are truly living in a “state of denial.”

Last year, a World Bank study projected financial losses from sea-level rise for Houston and the world’s other 135 largest coastal cities.

TCN reported at the time:

The … study, led by a senior economist at the institution and published in the scientific journal Nature Climate Change, projected that among the world’s 136 biggest coastal cities, Houston will have the seventh-largest percentage increase in average annual losses from sea-level rise by 2050. It’s the only U.S. city on a list of the 20 with the largest percentage increases worldwide.

If sea-level-rise adaptation measures (such as dikes, pumps and movable storm-surge barriers) are implemented that maintain flooding probability at the current level, Houston will experience average annual losses of $190 million as a result by 2050 – about a 60 percent increase, the researchers calculated.

If new protective structures are above the elevated sea level, they could keep average annual losses at their current level, the researchers said. But one storm surge in 2050 that exceeds those new defenses would bring flood losses in Houston exceeding $9 billion, they added. (Cost estimates of Ike’s Texas impact are around $20 billion.)

That scenario combines a higher sea level dubbed “optimistic” (meaning it’s toward the lower end of scientists’ current expectations), coastal subsidence and population and economic growth. In this case, “optimistic” meant a sea-level rise of 20 centimeters, or about 7.9 inches, by 2050.

In a major summary of scientific research from the previous six years, the U.N.’s Intergovernmental Panel on Climate Change reported last fall that about 75 percent of the recorded global mean rise in sea level in recent decades was attributable to glacier changes and thermal expansion of oceans from atmospheric warming, with about 9 percent due to changes in the West Antarctic ice sheet.

The IPCC reported a global mean sea-level rise of about 2.8 millimeters (0.1 inch) per year from 1993-2010. It estimated that if heat-trapping gases continue to be emitted at a high rate, sea level would rise between a half-meter and a meter (about 20 inches to 38 inches) by 2100, threatening some coastal cities and island nations.

The IPCC also said, regarding the West Antarctic ice sheet, that “the short period of observations does not allow one to either dismiss or confirm that [accelerating ice losses] are associated with destabilization” of the ice shelf itself.

Science Now provided these details about the two new studies’ more definitive conclusions on that subject:

One team [at the University of Washington] combined data on the recent retreat of the 182,000-square-kilometer Thwaites Glacier with a model of the glacier’s dynamics to forecast its future. In a paper published online today in Science, they report that in as few as two centuries Thwaites Glacier’s outermost edge will recede past an underwater ridge now stalling its retreat. Their modeling suggests that the glacier will then cascade into rapid collapse. The second team [at NASA and the University of California, Irvine], writing in Geophysical Research Letters, describes recent radar mapping of West Antarctica’s glaciers and confirms that the 600-meter-deep ridge is the final obstacle before the bedrock underlying the glacier dips into a deep basin.

Because inland basins connect Thwaites Glacier to other major glaciers in the region, both research teams say its collapse would flood West Antarctica with seawater, prompting a near-complete loss of ice in the area. “The next stable state for the West Antarctic Ice Sheet might be no ice sheet at all,” says the Science paper’s lead author, glaciologist Ian Joughin….

“Very crudely, we are now committed to global sea level rise equivalent to a permanent Hurricane Sandy storm surge,” says glaciologist Richard Alley of Pennsylvania State University, University Park, referring to the storm that ravaged the Caribbean and the U.S. East Coast in 2012. Alley was not involved in either study.

A NASA announcement of the other research project quoted Eric Rignot, glaciologist at UC Irvine and NASA’s Jet Propulsion Laboratory, who was lead author of that study:

“The collapse of this sector of West Antarctica appears to be unstoppable. The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.”


[Disclosure: Larry McKinney recently agreed to be a member of an advisory committee for Texas Climate News. The panel, to comprise scientists, journalists and others distinguished in their fields, is in the process of being assembled. The volunteer members will have no authority over TCN’s editorial decisions, which will continue to be made solely by our independent editors and writers. On occasion, we may report on TCN’s advisors, their work and their publicly stated views. If so, we will strive to do it impartially and in keeping with the same standard we announced when Texas Climate News was introduced in 2008: “We publish public-interest journalism, based on traditional principles of independent-mindedness, accuracy and fairness.” We will disclose advisors’ membership on the committee in articles that report on them.]

– Bill Dawson

Image credit: NASA