V: IN WHICH GEORGE SEES INTO THE PAST
The farther north you travel in this hemisphere, the
more you hear conversations about the climate
getting conducted not in the future, but in the present
tense. In Whitehorse, the capital of Canada's Yukon
Territory, officials now hold an annual exposition
showcasing products to help residents mitigate and adapt
to an already warmer climate. In Barrow, the Alaska
Eskimo Whaling Commission spent a large part of its
annual convention last year discussing, among other
things, the perils of hunting bowhead whales from
increasingly thinner ice. Some Alaskan natives, mindful
that ''traditional knowledge'' is often considered merely
anecdotal and lacking in scientific rigor, have set up a
Web site (nativeknowledge.org), on which you can see two
thousand people sharing much the same anecdotes:
turtles appearing for the first time on Kodiak Island, birds
starving on St. Lawrence Island, thunder first heard on
Little Diomede Island, coastal storms undercutting houses
at Shishmaref, snowmobiles falling through the ice in
Nenana. . . . Already the central Arctic is warming 10
times as fast as the rest of the planet, outpacing even our
attempts to describe it. In Canada's Northwest Territories,
Inuit Eskimos saw their first robin last summer, though
there's no word in Inuit for ''robin.''
Those who remain skeptical that the Arctic is undergoing
a period of rapid climate change point out that the region
has always gone through cycles of warming and cooling,
sometimes in just decades or even years. Perhaps,
according to this argument, natural fluctuations cause the
water to warm and cool, and the ice to thin and thicken as
atmospheric pressures, water currents and wind patterns
change. But the latest findings coming out of the Arctic
suggesting a longer-term trend are hard to dismiss, even if
their ramifications may not be felt elsewhere for many
years. Recently unclassified submarine data, for example,
show that the ocean's covering of snow and ice has
thinned in some places by up to four feet, or 40 percent,
since the 1960's. And satellite data indicate that the ice's
reach has receded at a rate of 3 percent per decade since
the 1970's. Recently, warmer, saltier water from the North
Atlantic has crept farther into the Arctic basin than ever
seen before. And that water is about 2.7 degrees
Fahrenheit warmer than it was only a decade ago, causing
further melting. Current models predict that global
temperatures will rise by between 0.9 and 3.6 degrees
Fahrenheit by 2050. And the rate of increase could be
three to five times higher in the Arctic.
For their part, the black guillemots of Cooper Island
cannot foretell the future. But just this past year George
did devise an ingenious way for his birds to narrate the
past. In the feathers of any guillemot are a host of
chemical compounds that reveal aspects of its physiology,
and one such compound -- a naturally occurring carbon
isotope called delta 13C -- gives, in effect, a snapshot of
what that bird has eaten from the carbon-based food
chain in the past six months, just as a human autopsy
can reveal the deceased's last meal. Since each region of
the Arctic also has a different carbon signature -- the
sub-Arctic Bering Sea, for example, is biologically highly
productive and therefore possesses more of the isotope
than the more northerly Beaufort and Chukchi Seas -- a
particular feather's delta 13C content can identify not just
what that bird may have eaten, but also where.
Knowing that delta 13C is permanently preserved in
feathers; knowing, too, that many Barrow-area guillemots
going back as far as the 1880's had been shot, stuffed and
housed in museum collections throughout the country,
George sought permission to analyze those birds' feathers
in order to compare them with feathers taken from his
Cooper Island colony. Permission was granted, and
guillemot feathers going back 120 years arrived at his
Seattle home from collections in Philadelphia, Fairbanks
and several points in between. George immediately sent
them off to a lab, and when he plotted his data on a map,
the results were startling. While the delta 13C content of
the 19th-century birds was quite high, suggesting they'd
had to fly as far south as the Bering Sea in winter to find
ice cracks in order to fish, the more recent feathers
possessed far less of the isotope, indicating that the birds
had been able to winter some 500 miles to the north, in
the Beaufort and Chukchi Seas. It suggested that over the
past 120 years increasingly warmer temperatures were
causing the pack ice to recede, causing cracks to open up
farther and farther north. In effect, George had taken his
27-year study and back-cast it to show that guillemots
were tracking more than a century of warming.
''Skeptics can always find fault with the instrumentation
used to take temperatures back in the 1880's,'' he says.
''But with the carbon isotope, it shows a huge decrease in
delta 13C from 1880 to the present, which only makes
sense if the birds were wintering farther and farther to the
north. It's incredibly powerful. It's more than a hundred
years. And it is,'' he says in a moment of gravity, ''the only
interpretation of this data.''
nytimes.com |
