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Tag: sea level
Greenland Ice Loss More ‘Local’ Than Thought, Climate Study Says

Greenland Ice Loss More ‘Local’ Than Thought, Climate Study Says

By Geoffrey Mohan, Los Angeles Times (TNS)

When it comes to melting ice on Greenland, climate change experts got everything right but the present.

That means Greenland’s contribution to sea level rise this century remains roughly the same — three inches — but where it comes from and how it gets to the ocean are now more clear, according to a new study that crunched 20 years of NASA data.

The findings will make climate models far more precise, according to the researchers.

Until now, the United Nation’s Intergovernmental Panel on Climate Change based its estimation of ice loss from Greenland on the four largest of an estimated 242 major outlet glaciers on that land mass, and admitted its modeling was at a “fairly early stage,” according to the study.

The new study, published online this week in the journal Proceedings of the National Academy of Sciences, reconstructs ice thickness at about 100,000 sites, at a scale of single glaciers or drainage basins.

“These are billions of measurements, so the actual number of observations is really huge,” said the study’s lead author, Beata Csatho, a geophysicist at the University at Buffalo, N.Y.

There are about 656,000 square miles of ice on Greenland, or roughly three times the acreage of Texas. If all of that ice melted, it would raise average sea levels about 20 feet, according to the National Snow and Ice Data Center.

Several factors are important to figuring out how much fresh water could be dumped into the world’s oceans, where it could potentially alter water cycles that drive Earth’s climate. The large-scale fluctuation of melt versus precipitation is relatively well known, but how ice changes locally as it grinds against underlying bedrock “is not well understood at all,” said Csatho.

Those local-level dynamics are responsible for nearly half of the ice loss — 48 percent — according to Monday’s study.

The researchers used 20 years of NASA’s laser-based measurements of elevation changes, which are accurate to about a centimeter. They found that Greenland shed 243 billion tons of ice annually from 2003-2009, but in fits and starts, and hardly uniformly.

Southeastern Greenland, for example, was responsible for nearly half of the overall ice loss — its glaciers thinned rapidly, reaching a peak discharge of 166 billion tons in 2005, according to the study. Two of the four glaciers used in the IPCC model are from that region, Csatho said.

The region’s accelerated loss eased, however, as several glaciers and some high-elevation ice masses actually thickened, the study found. By 2009, however, losses accelerated again, while the northwest region experienced an uninterrupted thinning during the six-year time period, according to the study.

Overall, said Csatho, the newly calculated ice losses are close to range projected by the existing IPCC model, which “is more likely underestimating” ice loss, Csatho said.

“IPCC got everything right, but the present,” she said.

“The thing to understand is that these models have relied on data sets that are poorly known,” said Eric Larour, a NASA-JPL cryosphere scientist who manages the agency’s Ice Sheet System Model.

Larour, Csatho and others at Argonne National Lab and the University of California, Irvine, did a bit of mathematical reverse-engineering of climate models and came up with estimates of surface mass gains and losses as well as the small-scale effects of friction between the ice and bedrock.

“Those are very difficult to observe from space, but if you have a model and surface elevations that are observed from space, you can infer those unknowns,” Larour said.

“We now can infer the state of the ice,” he added. “Now the model matches the observations better, so it’s more reliable.”

Photo via Wikimedia Commons

Report: Climate Change Imperils Nation’s Historical, Cultural Landmarks

Report: Climate Change Imperils Nation’s Historical, Cultural Landmarks

By Chris Adams, McClatchy Washington Bureau

WASHINGTON — Saying there’s a “race against time,” an advocacy group reported this week that climate change — leading to sea level rise and worsening wildfires — is putting some of the nation’s most significant historical sites at risk.

Highlighting archaeological and other historical sites in several states, a report released Tuesday by the Union of Concerned Scientists said that rising waters and raging flames could endanger some of the nation’s most-cherished locations.

“You can almost trace the history of the United States through these sites,” Adam Markham, director of climate impacts at the Union of Concerned Scientists and a co-author of the report, said in a statement. “The imminent risks to these sites and the artifacts they contain threaten to pull apart the quilt that tells the story of the nation’s heritage and history.”

Among the 30 sites at risk, according to the report:

—The huge prehistoric mounds of oyster and clam shells that dot Florida’s Gulf and Atlantic coasts. The report says Florida is one of the only places on Earth where coastal hunter-gatherers built shell structures as large and complicated as they are along Florida’s southwest coast. Across the state in Canaveral National Seashore, Turtle Mound is a massive shell structure that dates back at least 1,200 years. In both places, rising seas and worsening storm surge are endangering the shell structures.

—In St. Augustine, Fla., sea level rise, erosion and worsening storm surge threaten landmarks in the oldest city in the nation. The city, on the Atlantic coast, was the seat of Spanish rule in North America for 200 years. Without major engineering feats, the Castillo de San Marcos fort likely will become inaccessible if sea levels rise 3 feet; a major report earlier this month about climate change projected that sea levels could rise 1 to 4 feet by 2100.

—In California, Groveland and other Gold Rush-era towns are imperiled by wildfires. Citing a marked increase in giant wildfires, the report says climate change has driven up temperatures, caused earlier melting of winter snowpack and made forests drier for longer periods — making them ripe for fire. The report singles out Groveland, a town near Yosemite National Park that was imperiled by the devastating Rim fire in 2013.

Other locations highlighted by the group include the Cape Hatteras Lighthouse in North Carolina; the Statue of Liberty in New York; and the Old and Historic District of Charleston, S.C. At Cape Hatteras and the Statue of Liberty, steps already have been taken to make the sites more resilient to climate change.

Headquartered in Cambridge, Mass., the Union of Concerned Scientists is a nonprofit research and advocacy organization that seeks to “create innovative, practical solutions for a healthy, safe, and sustainable future,” according to its website.

The report in many ways echoes the U.S. National Climate Assessment, a major assessment released to a blizzard of attention earlier this month. That report was overseen by federal officials and represented the views of more than 300 experts and top Obama administration officials; it was instantly attacked by climate change skeptics, who accused the report of overreach.

In it, scientists detailed how climate change already has affected many parts of the country. The new report this week zeroed in on the current or potential impact on historical sites.

AFP Photo/Ted Aljibe