Link: http://www.newsobserver.com/content/print/front_pdf/1-A-Sat-July-25-09.pdf
Weather experts are contemplating a new mystery of the deep blue sea:
why it's been deeper than usual at high tide all along the East Coast
for the past several weeks.
Since June, tides have been running from 6 inches to 2 feet above what
would normally be expected, even considering seasonal and lunar
fluctuations. While local tidal changes are not uncommon, researchers
for the National Oceanic and Atmospheric Administration aren't sure they
have ever recorded an event like this one, which is showing up all the
way from Maine to Florida. In North Carolina, tides have been about a
foot above normal predictions.
"Right now we're trying to get a better understanding of what's the
cause," said Mike Szabados, director of NOAA's tide and current program
in Silver Spring, Md.
Global warming isn't to blame, scientists say, as the rise was too
sudden. Possibly, Szabados said, the explanation lies in something
called the North Atlantic oscillation, a disturbance in the atmospheric
pressure in the area of the North Atlantic Ocean between the Icelandic
Low and the Azores High.
A change in the atmospheric pressure can change wind velocities and
directions, which can affect ocean circulation, Szabados said.
NOAA monitors sea level at more than 200 stations along U.S. coastlines.
Remote sensors mounted on piers and other structures measure water depth
acoustically, sending a signal to the bottom and calculating the time it
takes to bounce back. NOAA gets the readings in real time.
Using less scientific methods, boat captains may have noticed they're
coming in to dock higher than usual or that it's been easier to navigate
shallows behind barrier islands.
The higher tides have also flooded the nests of shore birds and sea
turtles close to the water line. The higher water brings an increased
risk of rip tides. And if a tropical storm or hurricane strikes before
the phenomenon subsides, damage near the shore could be magnified.
North Carolina has more than 300 miles of ocean shoreline, with more
than 250,000 insured properties in 18 coastal counties.
The surge peaked in the third week of June, at the same time the coast
was experiencing a high spring tide, and ocean water pushed into places
it isn't usually seen in the absence of a tropical storm. It washed over
a bulkhead at the end of Harbor Island, something Joe Abbate, a wildlife
biologist who runs Wrightsville Beach Scenic Tours and Taxi Service, had
never seen before.
"It was weird," said Abbate, who goes by Cap'n Joe.
One evening, he said, he took a group out for a nature tour on his beach
catamaran, the Shamrock, and was surprised to see the water over the top
of marsh grasses.
It had swept out a bunch of trash, he said, and lifted a pair of baby
clapper rails with their mother on a mat of dead spartina grass.
"Rails are not very good fliers," Abbate said. "They're kind of limited
in what they can do."
Not nice for turtle nests
Some of the thousands of volunteers who patrol North Carolina beaches
for sea turtle nests during the summer have noticed the higher tides
because they've had to relocate nests higher on the beach to keep the
eggs from being repeatedly submerged.
In a normal year, Nancy Busovne, coordinator for the Pleasure Island Sea
Turtle Project, said she and her volunteers would have to relocate about
half the turtle nests they find to save the eggs. This year, they've
moved five of the seven nests laid so far.
And during that week in June when the surge combined with a high spring
tide, Busovne said, friends who live on the canal side of the island had
several inches of water in their house when the tide came in.
"That's very unusual," Busovne said.
Szabados said that while the surge has diminished, it hasn't
disappeared, and researchers don't know when it will.
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