alt.energy.renewable

Caps Shrink By 50 Percent Since 1950s, Expected To Disappear by Middle of
Century

ScienceDaily (Feb. 2, 2008) - A new University of Colorado at Boulder study
has
shown that ice caps on the northern plateau of Baffin Island in the Canadian
Arctic have shrunk by more than 50 percent in the last half century as a
result
of warming, and are expected to disappear by the middle of the century.

Radiocarbon dating of dead plant material emerging from beneath the receding
ice
margins show the Baffin Island ice caps are now smaller in area than at any
time
in at least the last 1,600 years, said geological sciences Professor Gifford
Miller of CU-Boulder's Institute of Arctic and Alpine Research. "Even with
no
additional warming, our study indicates these ice caps will be gone in 50
years
or less," he said.

The study also showed two distinct bursts of Baffin Island ice-cap growth
commencing about 1280 A.D. and 1450 A.D., each coinciding with ice-core
records
of increases in stratospheric aerosols tied to major tropical volcanic
eruptions, Miller said. The unexpected findings "provide tantalizing
evidence
that the eruptions were the trigger for the Little Ice Age," a period of
Northern Hemisphere cooling that lasted from roughly 1250 to 1850, he said.
A paper on the subject was published online in Geophysical Research Letters
and
featured in the Jan. 28 edition of the American Geophysical Union journal
highlights. Authors on the study included Miller, graduate students Rebecca
Anderson and Stephen DeVogel of INSTAAR, Jason Briner of the State
University of
New York at Buffalo and Nathaniel Lifton of the University of Arizona.

Located just east of Greenland, the 196,000 square-mile Baffin Island is the
fifth largest island in the world. Most of it lies above the Arctic Circle.
The researchers also used satellite data and aerial photos beginning in 1949
to
document the shrinkage of more than 20 ice caps on the northern plateau of
Baffin Island, which are up to 4 miles long, generally less than 100 yards
thick
and frozen to their beds. "The ice is so cold and thin that it doesn't flow,
so
the ancient landscape on which they formed is preserved pretty much intact,"
said Miller.

In addition to carbon-dating plant material from the ice edges, the
researchers
extracted and analyzed carbon 14 that formed inside the Baffin Island rocks
as a
result of ongoing cosmic radiation bombardment, revealing the amount of time
the
rocks have been exposed, he said. The analysis of carbon 14 in quartz
crystals
indicated that for several thousand years prior to the last century, there
had
been more ice cover on Baffin Island, Miller said.

The increase of ice extent across the Arctic in recent millennia is thought
to
be due in large part to decreasing summer solar radiation there as a result
of a
long-term, cyclic wobble in Earth's axis, said Miller. "This makes the
recent
ice-cap reduction on Baffin Island even more striking," he said.

Funded primarily by the National Science Foundation, the study is among the
first to use radiocarbon samples from rocks for dating purposes, Miller
said.
The radiocarbon portion of the study was conducted at INSTAAR and the
University
of Arizona.

Temperatures across the Arctic have been rising substantially in recent
decades
as a result of the build up of greenhouse gases in Earth's atmosphere.
Studies
by CU-Boulder researchers in Greenland indicate temperatures on the ice
sheet
have climbed 7 degrees Fahrenheit since 1991.