[Vision2020] Report maps out rise of Pacific sea levels

[Art Deco]

   <http://www.spokesman.com/> June 23, 2012
Report maps out rise of Pacific sea levels More precise data allow
for planning
Jeff Barnard
Associated Press

In this Jan. 20, 2010 file photo, waves pound during a rainstorm in
Pacifica, Calif. A new federal report studies what to expect from rising
sea levels.
  By the numbers

*6 inches*: Predicted rise in sea levels for most of California by 2030

*3 feet*: Predicted rise in sea levels for most of California by 2100

*4 inches*: Predicted rise in sea levels for Northern California, Oregon
and Washington by 2030

*2 feet*: Predicted rise in sea levels for Northern California, Oregon and
Washington by 2100

Source: National Research Council

The West Coast will see an ocean several inches higher in coming decades,
with most of California expected to get sea levels half a foot higher by
2030, according a report released Friday.

The study by the National Research Council gives planners their best look
yet at how melting ice sheets and warming oceans associated with climate
change will raise sea levels along the country’s Pacific coast. It is
generally consistent with earlier global projections but takes a closer
look at California, Oregon and Washington.

Although the 6 inches expected for California by 2030 seem minor, the
report estimated that sea levels there will be an average of 3 feet higher
by 2100. About 72 percent of the state’s coast is covered by sandy cliffs,
and the rest includes beaches, sand dunes, bays and estuaries.

Seaside cliffs will be cut back about 30 yards over the next 100 years, and
sand dunes will be driven back even more, said Robert A. Dalrymple, a
professor of civil engineering at Johns Hopkins University and chairman of
the group that wrote the report. Coastal wetlands will be able to keep pace
for about 50 years, but will eventually be overwhelmed without new sources
of sand and room to move inland.

The report noted that dams hold back about a third of that sand, which once
washed into the sea from the Klamath River in Northern California.

Northern California, Oregon and Washington can expect a less dramatic
increase – about 4 inches by 2030 and 2 feet by 2100 – because seismic
activity is causing land to rise north of the San Andreas Fault, offsetting
increasing sea levels, and to drop south of it. The fault runs out to sea
at Cape Mendocino.

Oregon has the advantage of tough basalt formations on much of the coast,
but long stretches of Washington are low-lying sandy beaches.

“Anything close to the seas is vulnerable,” Dalrymple said.

The most immediate threat over the next few decades will come from periodic
ocean-warming El Niño events, said Gary Griggs, director of the Institute
for Marine Sciences at the University of California at Santa Cruz, who was
one of the scientists assembled by the council to produce the report.

“During those events, sea level is elevated as much as a foot above normal
and then we’ve got typically larger waves coming in with the high tides,”
particularly in the Northwest, he said.

The report noted that some computer models suggest storms will be stronger
as global warming progresses. But Dalrymple said there was no clear
consensus in scientific literature, and data from ocean buoys showing waves
getting bigger in the Northwest don’t go back far enough to conclude that
trend will continue.

If a major earthquake occurs beneath the Pacific Ocean off Oregon and
Washington, in what is known as the Cascadia subduction zone, that would
cause the land to drop, allowing sea level to rise another 3 to 6 feet
immediately, the report said. Such a major temblor occurred 300 years ago,
and another becomes more likely as time passes.

The report was commissioned by states and federal agencies looking for
detailed information so they can plan for an accelerated rate of erosion
along beaches, bluffs and sand dunes that are already crumbling into
the sea.

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Art Deco (Wayne A. Fox)
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