Rising seas threaten the coast's future
Updated 11:11 pm, Tuesday, January 29, 2013
Turn back the clock 10,000 years or so -- not a long time in the grand scheme of things -- and you would find human settlements many miles beyond today's shoreline. This was during the last ice age, when sea levels were about 200 feet below where they are now.
When the planet warmed and the sea began to rise, moving to higher ground wasn't difficult for these stone-age clans. They had few possessions, and building new shelter didn't entail construction permits, flood insurance, mortgages and all of the other baggage that comes with shoreline housing today.
"Sea levels have been rising for a long time, but there's evidence now that the rate of rise is accelerating," said James O'Donnell, professor of marine sciences at the University of Connecticut's Avery Point campus in Groton. "A half-meter in the next 50 to 100 years," he said. "That doesn't sound like a lot, but what it means is that very destructive storms would be occurring much more frequently."
O'Donnell said he performed an analysis after Tropical Storm Irene in 2011.
"And what I found was that instead of getting a storm like Irene once every 20 years, it would be an annual event, more or less," he said.
Staying put along the shoreline will be possible for some time to come, but the cost will be increasingly prohibitive.
"We can build wherever we want -- it's a matter of money and environmental impact," he said. "You'll have to weigh these costs and the benefits."
Then there are the tides. Compare the tides of New London with those of Greenwich, for example.
In New London harbor, the difference between low and high tide is a mere 30 inches or so. In Greenwich, 80 miles to the west, the tidal amplitude is about 8 feet.
This phenomenon is magnified, O'Donnell said, when there's a storm and the easterly prevailing winds pile up even more water in western Long Island Sound.
Experts say that as bad as Sandy was, the region caught something of a break because the 10-foot storm surge rolled through not long after low tide. If Sandy hit five hours later, another 4 feet or so could have been added to the water height totals from Milford to Greenwich.
What to do about this increasingly soggy landscape will almost certainly lead to discord between denizens of the shoreline and those on higher ground. Should the shoreline be "hardened" or should there be a gradual retreat?
Michael Tetreau, first selectman of Fairfield, heavily damaged in Superstorm Sandy, noted that the United States is a nation of laws, so ordering families to give up their beachfront homes isn't an option.
"We have to work within zoning laws," he said. We can't unilaterally take someone's property away. The ocean might do it, but we can't do it."
He said cities and towns have an obligation to their citizens to rebuild infrastructure, and the question is better posed to the federal government, which at some point must decide whether it is going to provide flood insurance to build in dangerous areas.
It's not just homes and streets, it's infrastructure, too.
"Somebody pointed out that things like Interstate 95 and the railroad tracks are not that high above sea level right now," Tetreau said.
Then there are the waste-treatment plants. Along the state's coastline, all are built at very low elevations.
"It's ... because things flow downhill," he said. "That's the lowest point. You've got to put it there. At some point if the lowest point is underwater, you have to back it up."
George Wisker, the coastal geologist for the state Departmental of Energy and Environmental Protection, said that the tons of carbon dioxide that humans are pumping into the atmosphere every second "isn't helping matters any," but he notes that when the seas rise -- and they will -- it will be silly arguing about the cause when the water is rising "up around your knees."
Speaking as a geologist, he said the beach is about the worst place to build a house.
"The last place I'd ever want to be," he said. "As one colleague asked me: `Why is it that the land that's the least likely to be there tomorrow carries such a huge price tag?' It's lovely in the summer, but..."
He said that the tides in the Sound slosh from one end to the other, not unlike a dinner plate filled with water that's tipped just a little bit. He agrees with O'Donnell -- the slosh effect is much worse when there's a storm surge.
"Like in Sandy, you had a high tide that never really went out, and then you had another high tide that came in on top of it," Wisker said.
As for hardening the shoreline with concrete and beach replenishment, Wisker said that those solutions can backfire.
"Let's say you pump sand from offshore onto a beach," he said. "Well, that's going to change your wave dynamics, which will make things worse in the long run."
Even finding sand to replenish beaches can become a knotty problem for local authorities, experts say. Coastal scientists said there may not be enough sand on the continental shelf to continue rebuilding beaches.
"People built palatial houses and we are now trying to protect the houses by making the sandbar stay in one place," said Nicole Heller, an ecologist at Duke University. "That's not what a sandbar does."
The rate of sea level rise has doubled since 1990; it is expected to accelerate But there could be events, unlikely but not out of the question, that would cause a mass exodus from the coast.
"Rapid melting in the Antarctic and in Greenland would be catastrophic," O'Donnell said. "Over a decade, seas would rise several meters, (leading to a) huge dislocation of people."
But a more likely scenario, he said, would be more like "boiling a frog," in which people make gradual adjustments to increasingly difficult conditions.
These would include a greater likelihood of severe storm damage, particularly in the western reaches of Long Island Sound. This is because of what tidal researches call resonance -- and that "slosh effect."
"The geometry of the Sound causes that effect," O'Donnell said, referring to the greater tide differential in the western reaches on Long Island Sound, as opposed to what's seen in New London. "And during a storm, these two effects cooperate with one another."
The rate of sea level rise has doubled since 1990; it is expected to accelerate with the rapid melting of the Greenland and West Antarctica ice sheets. Greenland set a record for melting last July. Arctic sea ice reached a record low in September. Carbon dioxide concentrations are the highest they've been in 15 million years, according to a World Bank report, "Turn Down the Heat," that last month summarized current research. At today's emissions rate, the planet could warm by four degrees Celsius by the end of the century, a realm "unknown in human experience," the report said. The coolest months of the year will be "much warmer" than the warmest months now.
Last year broke U.S. records with 10 severe weather events costing more than $1 billion. As the oceans warm, storms become more intense. The report warned of increasing heat waves, droughts, floods, extinctions and sea level rise, citing heat waves in Russia and Europe and floods in Pakistan in 2010, the Plains heat wave last year and the U.S. drought this year.
Greenhouse gas emissions are already "above the absolute highest scenario" that was projected by the Intergovernmental Affairs Panel on Climate Change in its latest report in 2007, said S. Jeffress Williams, a scientist emeritus at the U.S. Geological Survey at the Woods Hole Science Center in Massachusetts. Most coastal cities are "built within a couple of meters of sea level, and they're all extremely vulnerable."
Under current high-emissions scenarios, seas are expected to rise from 3 to 4 feet this century. Gradual coastal inundation is feared less than destructive storm surges, such as Sandy's, that launch from a higher sea platform, in storms made more intense by the warming air.
Sandy is the future, climate scientists say.
As carbon dioxide emissions blast past worst-case scenarios, rising sea levels and storm surges will reshape every U.S. coastline, from San Francisco to Houston to New York. It is only beginning to dawn on Americans, half of whom live on the coast, that their future is a battle against the sea.
email@example.com; 203-330-6403; http://twitter.com/johnburgeson; Carolyn Lochhead is the San Francisco Chronicle's Washington correspondent. firstname.lastname@example.org