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Monday, August 26, 2013

Hudson shoreline faces threat from Greenland thaw and sea level rise

An icy warning for the Hudson Valley
An icy warning for the Hudson Valley: Greenland's ice sheets are melting at record paces, meaning higher sea-levels and higher tides and storm surges in the Hudson River Valley.

by John Ferro, Poughkeepsie Journal, August 25, 2013

After Tropical Storm Irene brought 4 feet of Hudson River water into the Beacon Sloop Club two years ago, its members made sure the damage would be less next time. 

The members of the club, which offers free sails on the sloop Woody Guthrie and sponsors annual strawberry and corn festivals, replaced ruined Sheetrock with exterior-grade siding.

“So when it flooded,” longtime club member Tom LaBarr said, “we wouldn’t have to replace it. And sure enough, last year it flooded again” during Superstorm Sandy.

Up and down the Hudson River, and along Long Island and the New Jersey shoreline, many communities are preparing for one of the most consistent trends reflecting the world’s changing climate: sea-level rise. The impacts range from higher tides that may inundate some riverfront areas of the Hudson, to more devastating storm surges.

More than 9,000 acres in the Hudson River Valley and as many as 3,600 households could be inundated by 2100 just at high tide, if global sea levels rise by as much as 6 feet, according to a recent report from Poughkeepsie-based nonprofit Scenic Hudson.

“Every waterfront community in the Hudson Valley has to be planning for sea-level rise and more violent storms,” Judith Enck, the Environmental Protection Agency’s local administrator, said during a visit to Poughkeepsie this month. “And that affects land-use decisions — where we put things, how close to the water and whether or not we want buffers.”

In Rockland County, scientists at Lamont-Doherty Earth Observatory returned recently from a trip to Greenland, where they continued testing the IcePod. The device contains infrared, laser, radar and photographic sensors that will provide greater insight into the biggest driver of sea-level rise: the melting of on-land ice.

“Any time we talk about the status of the ice sheets in Antarctica and Greenland, we talk about the concern of sea-level rise,” said Peter West, spokesman for the National Science Foundation’s Division of Polar Programs, which contributed $4.1 million to the five-year IcePod project.

When the National Oceanic and Atmospheric Administration issued its annual State of the Climate report Aug. 6, two facts were striking.

One, total sea level rose to a globally averaged record high last year at 1.4 inches above the 1993-2010 long-term average.

“That trend hasn’t ended at all,” Jessica Blunden, a scientist with NOAA’s National Climatic Data Center, said during a teleconference to announce the report’s findings. “We are still seeing continued increases in sea-level rise, and we are at record levels right now.”

And second, ice melt — primarily in Greenland and Antarctica — is contributing more than twice as much to global sea-level rise compared with warming waters, which expand as the temperature rises.

The potential impacts of ice melt are vast.

One-quarter of the world’s population resides within 60 miles distance and 300 feet elevation of the coastline, according to the Intergovernmental Panel on Climate Change.

More than 8 million people in the United States live in areas at risk of coastal flooding, according to NOAA.

More than 60% of New Yorkers live in homes that stand to be affected by future sea-level rise, according to a 2010 report prepared by the state Legislature’s Sea Level Rise Task Force.

The problem: Because conditions are changing so quickly, and so much about the complex interactions among weather, ice and ocean dynamics still need to be understood, scientists cannot say with certainty whether things will be better than expected – or much worse.

“Many of the planning models used in infrastructure planning rely on a set of assumptions that essentially count on the future being statistically a lot like the past,” NOAA Acting Administrator Kathryn Sullivan said during the agency’s teleconference. “Trends like the ones we have seen in the data certainly should lead one to question whether that will be so.”

Preliminary data suggest that 2012 will be the 22nd consecutive year the total mass of the world’s glaciers declined.

The Greenland ice sheet extends about 656,000 square miles, a little less than a quarter of the size of the continental United States. In some places it is more than two miles thick, its weight compressing the bedrock below.

Far larger is the Antarctic ice sheet, which is 5.4 million square miles, about 1.5 times the size of the lower 48 states.

Greenland’s ice sheet contains enough frozen freshwater that if it all melted — the chances of which are remote — sea levels would rise about 20 feet, according to the National Snow and Ice Data Center. Antarctica’s ice sheet has enough frozen water to raise sea levels by 200 feet.

The mass of Greenland’s ice sheet has been declining, NOAA’s records show. From 1979 to 2006, summer melt on the ice sheet increased 30 percent. In 2012, it reached a record, with 97 percent of the surface experiencing some melting for a two-day period in July. And though the glaciers recover ice in the winter months, the winter gains have not offset the losses in summer.

The ice’s behavior correlates with other changes. Drastic and persistent reduction in the extent of the summer sea-ice cover around the coasts of places like Greenland can be linked directly to the warming of ocean surface temperatures in those open areas, said Jackie Richter-Menge, a researcher with the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory.

In turn, the warmer oceans can be linked directly to increases in tundra vegetation and the productivity of aquatic life in the coastal regions.

The reason these linkages are important, Richter-Menge said, is they reflect the persistence in the changes scientists are observing in the Arctic.

“In the Arctic, the records or near-records being reported from year to year are no longer anomalies or exceptions,” Richter-Menge said. “Really, they have become the norm that we see in the Arctic and what we expect to see for the foreseeable future.”

Likewise, scientists think reduced ice levels are being driven by a number of factors, not just warmer temperatures.

Satellite data show the surface reflectivity of the Greenland ice sheet in the warm-weather months has decreased. In other words, the ice is getting darker and absorbing more sunlight.

One reason may be as simple as more meltwater absorbs more light. But some theories suggest small bits of ash from western wildfires are making their way to Greenland’s ice sheet. These dark flecks of material may contribute more directly to the loss of reflectivity.

Another force that may be accelerating ice loss lies underneath, unseen and largely unstudied. Glaciers emerging from the ice sheets appear to be flowing more quickly.

“We don’t know if that is because the ocean is warming the edges, or if there is water getting underneath and making the ice flow faster,” said Robin Bell, the lead scientist on Lamont-Doherty’s IcePod project.

Indeed, Bell admits much remains to be understood.

“We don’t really understand all the processes,” Bell said, “and that is why we have been working hard to put this instrumentation suite together. Satellites let us look from a long distance. But to understand the processes, we need to get up close and personal with the ice sheet.”

Asked whether she worries about the future, Bell said she does not. Nonetheless, challenges remain.

“Change is always scary,” she said. “Humans don’t like change. But change fosters innovation. A lot of the science we see happening is innovation. And there is going to be interesting, innovative engineering and social solutions. Really, it’s about us moving past being afraid and saying, ‘OK, what can we do?’ ”

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