As
Alaska Glaciers Melt, It’s Land That’s Rising
JUNEAU, Alaska
— Global warming conjures
images of rising seas that threaten coastal areas. But in Juneau,
as almost nowhere else in the world, climate change is having the
opposite effect: As the glaciers here melt, the land is rising,
causing the sea to retreat.
Morgan DeBoer, a property owner,
opened a nine-hole golf course at the mouth of Glacier Bay in 1998,
on land that was underwater when his family first settled here 50
years ago.
“The highest tides of the year would
come into what is now my driving range area,” Mr. DeBoer
said.
Now, with the high-tide line receding
even farther, he is contemplating adding another nine
holes.
“It just keeps rising,” he
said.
The geology is complex, but it boils
down to this: Relieved of billions of tons of glacial weight, the
land has risen much as a cushion regains its shape after someone
gets up from a couch. The land is ascending so fast that the rising
seas — a ubiquitous byproduct of global warming — cannot keep pace.
As a result, the relative sea level is falling, at a rate “among
the highest ever recorded,” according to a 2007 report by a panel
of experts convened by Mayor Bruce Botelho of Juneau.
Greenland and a few other places have
experienced similar effects from widespread glacial melting that
began more than 200 years ago, geologists say. But, they say, the
effects are more noticeable in and near Juneau, where most glaciers
are retreating 30 feet a year or more.
As a result, the region faces unusual
environmental challenges. As the sea level falls relative to the
land, water tables fall, too, and streams and wetlands dry out.
Land is emerging from the water to replace the lost wetlands,
shifting property boundaries and causing people to argue about who
owns the acreage and how it should be used. And meltwater carries
the sediment scoured long ago by the glaciers to the coast, where
it clouds the water and silts up once-navigable
channels.
A few decades ago, large boats could
sail regularly along Gastineau Channel between Downtown Juneau and
Douglas Island, to Auke Bay, a port about 10 miles to the
northwest. Today, much of the channel is exposed mudflat at low
tide. “There is so much sediment coming in from the Mendenhall
Glacier and the rivers — it has basically silted in,” said Bruce
Molnia, a geologist at the United States Geological Survey who
studies Alaskan glaciers.
Already, people can wade across the
channel at low tide — or race across it, as they do in the
Mendenhall Mud Run. At low tide, the navigation buoys rest on
mud.
Eventually, as the land rises and the
channel silts up, Douglas Island will be linked to the mainland by
dry land, said Eran Hood, a hydrologist at the University of Alaska
Southeast and an author of the 2007 report, “Climate Change:
Predicted Impacts on Juneau.”
When that happens, Dr. Hood said, the
Mendenhall Wetlands State Game Refuge, 4,000 acres of boggy
habitat, will be lost. “That wetland will have nowhere else to go,”
he said.
In some places along the coast, the
change has been so rapid that kayakers whose charts are not
up-to-the-minute can find themselves carrying their boats over
shoals that are now so high and dry they now support grass or even
small trees.
In and around Juneau, “you can walk
around and see what was underwater is turning into grassland and
eventually into forest,” Dr. Hood said.
The topographical changes have
threatened crucial ecosystems and even locally vital species like
salmon.
“The lifeblood of our region has been
salmon species and their return — and what is the impact when they
return and the streams are dry?” said Mayor Botelho, who was born
and raised in Juneau. “The salmon is bound to our identity as a
region, who we are.”
He said he did not think that any
species were in imminent danger, but added, “Anyone who is
following climate change has to see that there are risks, perhaps
great ones.”
Dr. Hood said many people in Juneau
had hoped to maintain a waterway called Duck Creek as a salmon
stream. But small streams like that “appear to be drying out,” he
said. “There are a lot of people in town saying, Let’s just let it
return to a greenway.”
Relative to the sea, land here has
risen as much as 10 feet in little more than 200 years, according
to the 2007 report. As global warming accelerates, the land will
continue to rise, perhaps three more feet by 2100, scientists
say.
The rise is further fueled by the
movement of the tectonic plates that form the earth’s crust. As the
Pacific plate pushes under the North American plate, Juneau
and its hilly Tongass National Forest environs rise still
more.
“When you combine tectonics and
glacial readjustment, you get rates that are incomprehensible,” Dr.
Molnia said.
In Gustavus, where Mr. DeBoer’s
property is, the land is rising almost three inches a year, Dr.
Molnia said, making it “the fastest-rising place in North
America.”
In addition to expanding the golf
course, Mr. DeBoer is negotiating with the Nature Conservancy to
preserve some of the newly emergent land. He can do both, he said,
because the high tide line has pushed almost a mile out to sea
since his family first homesteaded on the property.
Where the shoreline is relatively
flat, “it doesn’t take much uplift to make quite a bit of
difference,” Mr. DeBoer said.
Kristin White, a 28-year-old
schoolteacher who grew up in Haines, a town north of here, is from
another family in the area whose real estate grew as land rose.
When her father tried to sell some property in Haines, she said,
“he had to have it resurveyed.”
But for Ms. White, who has vivid
memories of visiting the Mendenhall glacier as a child, the gain in
acreage has been bittersweet. Seeing the glacier retreat, she said,
is “as if you lived in the Smoky Mountains and you were used to
seeing certain peaks — and they disappeared. It’s just totally,
totally sad.”
