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Why Are Rising Sea Levels a Threat?
Coastlines, Islands and Arctic Ice Are Threatened by
Rising Sea Levels
By Larry West, About.com
Dear EarthTalk: Recent NASA photos showed the opening of
the Northwest Passage and that a third of the Arctic’s sea
ice has melted in recent decades. Are sea levels already
starting to rise accordingly, and if so what effects is
this having?
-- Dudley Robinson, Ireland
Researchers were astounded when, in the fall of 2007, they
discovered that the year-round ice pack in the Arctic Ocean
had lost some 20 percent of its mass in just two years,
setting a new record low since satellite imagery began
documenting the terrain in 1978. Without action to stave
off climate change, some scientists believe that, at that
rate, all of the year-round ice in the Arctic could be gone
by as early as 2030.
This massive reduction has allowed an ice-free shipping
lane to open through the fabled Northwest Passage along
northern Canada, Alaska and Greenland. While the shipping
industry—which now has easy northern access between the
Atlantic and Pacific oceans—may be cheering this “natural”
development, scientists worry about the impact of the
resulting rise in sea levels around the world.
The Impact of Rising Sea Levels
According to the Intergovernmental Panel on Climate Change,
made up of leading climate scientists, sea levels have
risen some 3.1 millimeters per year since 1993. And the
United Nations Environment Program predicts that, by 2010,
some 80 percent of people will live within 62 miles of the
coast, with about 40 percent living within 37 miles of a
coastline.
The World Wildlife Fund (WWF) reports that low-lying island
nations, especially in equatorial regions, have been
hardest hit by this phenomenon, and some are threatened
with total disappearance. Rising seas have already
swallowed up two uninhabited islands in the Central
Pacific. On Samoa, thousands of residents have moved to
higher ground as shorelines have retreated by as much as
160 feet. And islanders on Tuvalu are scrambling to find
new homes as salt water intrusion has made their
groundwater undrinkable while increasingly strong
hurricanes and ocean swells have devastated shoreline
structures.
WWF says that rising sea levels throughout tropical and
sub-tropical regions of the world have inundated coastal
ecosystems, decimating local plant and wildlife
populations. In Bangladesh and Thailand, coastal mangrove
forests—important buffers against storms and tidal waves—
are giving way to ocean water.
Unfortunately, even if we curb global warming emissions
today, these problems are likely to get worse before they
get better. According to marine geophysicist Robin Bell of
Columbia University’s Earth Institute, sea levels rise by
about 1/16” for every 150 cubic miles of ice that melts off
one of the poles.
“That may not sound like a lot, but consider the volume of
ice now locked up in the planet’s three greatest ice
sheets,” she writes in a recent issue of Scientific
American. “If the West Antarctic ice sheet were to
disappear, sea level would rise almost 19 feet; the ice in
the Greenland ice sheet could add 24 feet to that; and the
East Antarctic ice sheet could add yet another 170 feet to
the level of the world’s oceans: more than 213 feet in
all.” Bell underscores the severity of the situation by
pointing out that the 150-foot tall Statue of Liberty could
be completely submerged within a matter of decades.