<font color=Cyan>Too many GPRS handsets near (previously frozen solid) Arctic Ocean and North Pole (?)
August 29, 2000
Open Water at Pole Is Not Surprising, Experts Say
By JOHN NOBLE WILFORD
ecent eyewitness reports of open water from melting ice at the North
Pole have prompted climatologists and other scientists to make a
closer study of satellite imagery and other observations of northern sea
ice, past and present. Although striking and unusual, those reports are not as
surprising as suggested in a news article on Aug. 19 in The New York
Times, which was based on the descriptions and interpretations of two
scientists who had just visited there.
The data scientists are now studying reveal substantial evidence that on
average Arctic temperatures in the winter have risen 11 degrees over the past
30 years, and in the late 20th century were the warmest in four centuries.
Data also show that the ice pack over the entire Arctic Ocean has in recent
decades been shrinking in area and thickness.
But climatologists said they were still not sure if diminishing polar ice
reflected some short-term natural cycle or was a wake-up call of possibly
drastic climatic consequences of an industrial civilization's release of
heat-trapping gases.
"There seems to be a pretty coherent picture of change going on now in the
Arctic," said Dr. Mark Serreze, a climatologist at the National Snow and Ice
Data Center in Boulder, Colo. "But there's nothing to be necessarily alarmed
about. There's been open water at the pole before. We have no clear evidence
at this point that this is related to global climate change."
The ice covering most of the Arctic Ocean, several researchers said, is
broken by long, wide cracks and gaping holes in many places, sometimes
even at the pole, and especially in the summer. During a typical summer, 90
percent of the high Arctic region is covered with ice, with the remaining 10
percent open water. This has probably been true for centuries, they said, the
result of motions in the ice sheet caused by winds and the force of ocean
currents, as well as warming temperatures.
Dr. Serreze said an examination of satellite images from July 15 showed what
looked like a large body of ice-free water about 10 miles long and 3 miles
wide near the pole. On Friday, the ice data center made available two images
taken by NASA's Terra satellite on July 26, about the time visitors on the
Russian icebreaker Yamal were in the polar region. Although the pole was
obscured by clouds, the images show how fractured the ice was near the
pole and the many large patches of open water over much of the area.
"The fact of having no ice at the pole is not so stunning," said Dr. Claire L.
Parkinson, a climatologist at the Goddard Space Flight Center in Greenbelt,
Md. "But the report said the ship encountered an unusual amount of open
water all the way up. That is reason for concern."
Dr. Parkinson said that her examination of satellite data since the 1970's
revealed that the Arctic ice cover had been retreating on an average of
one-quarter of a percent a year. But there are fluctuations up and down; the
retreat was striking in the 1980's, then rebounded somewhat in the 90's. "So
we are very reluctant," she said, "to make projections into the future" based
on only two or three decades of observations.
In a February report, Dr. Parkinson said, "If trends toward shortened sea ice
seasons and lesser sea ice coverage continue, this could entail major
consequences to the polar and perhaps global climate, and to the lifestyles
and survivability of selected Arctic plant and animal species."
Dr. James J. McCarthy, a Harvard oceanographer who was quoted in the
article in The Times, said he would not argue with critics who said that open
water at the pole was not unprecedented.
"What was really unusual was that over a period of two weeks we never had
a day of what would be considered normal ice," Dr. McCarthy said. "When
we reached the pole and found open water, that simply punctuated what we
were seeing everywhere. These were conditions that did not seem
representative of a transient phenomenon."
Dr. McCarthy, director of the Harvard Museum of Comparative Zoology, is
the co-leader of a group preparing reports for the Intergovernmental Panel on
Climate Change, which the United Nations is sponsoring for the study of the
possible consequence of a warmer climate. Dr. Malcolm C. McKenna, a
paleontologist at the American Museum of Natural History in Manhattan, also
was a passenger on the Yamal and joined Dr. McCarthy in describing their
surprise at finding thin ice and intermittent open seas.
Even while cautioning against reading too much into such anecdotal evidence,
Dr. Parkinson said, "It did get into the public consciousness that, hey, there
are changes going on that might be really important."
Scientists said the descriptions by Dr. McCarthy and Dr. McKenna focused
new attention on the collection and analysis of more data about polar ice
conditions.
The end of the cold war, for instance, has brought to light important sonar
measurements of Arctic ice collected by United States Navy submarines.
They are being analyzed by Dr. Drew Rothrock at the Applied Physics
Laboratory of the University of Washington in Seattle. By comparing
measurements of ice thickness between 1958 and 1976 with data from 1993
and 1997, he determined that the thickness had decreased from 10.2 feet in
the early period to 5.9 feet in the 1990's.
"This is not a case of thicker ice appearing in one region simultaneously with
thinner ice appearing in another, induced perhaps by a change in surface
winds or other transient conditions," Dr. Rothrock said, noting that the
decrease was widespread in the central Arctic Ocean, and most pronounced
in the eastern Arctic.
Researchers at the Jet Propulsion Laboratory are analyzing images from the
Canadian Radarsat spacecraft, which has made the most detailed satellite
observations of the expanse of the Arctic Ocean. Passing over at an altitude
of about 400 miles, the spacecraft bounces mapping radar signals off the
polar region to produce a complete image every three days. This permits
researchers to track the short-term dynamics of the sea ice, watching cracks
open up and grow wider, sometimes more than 1,200 miles long, and seeing
thin ice eventually covering some of the openings.
"If the ice is thinning due to warming, we'll expect to see more of these long
cracks over the Arctic Ocean," said Dr. Ronald Kwok, a senior research
scientist at the Pasadena laboratory. But Radarsat has been returning data for
only four years, not long enough for researchers to recognize any meaningful
patterns in Arctic climate.
While cautioning against jumping to dire conclusions based on the sighting of
open polar water, Dr. Serreze of the ice data center is the principal author of
a review article, published this summer in the Dutch journal Climate Change,
on Arctic environmental change over decades and centuries. Many of the
changes, he said, appeared to be partly a result of human activity.
In reporting that parts of Alaska and northern Eurasia had warmed by nearly
11 degrees in winter months the past 30 years, Dr. Serreze observed, "We
have climate evidence from the past four centuries gleaned from ice cores,
lake cores and tree rings that don't show nearly as dramatic warming, putting
the modern record into context."
But Dr. Serreze said that an examination of recent research "validates
climate-model results that predict the Arctic will be among the first regions
on Earth to respond to a global warming trend." The issue in the reaction to
the report of open water at the North Pole is whether it is time to start
reading a trend into the disappearing and thinning ice encountered by an
icebreaker in the summer of 2000.
Copyright 2000 The New York Times Company |
