NYT article about that huge Antarctic ice sheet that is melting.
(By the way, almost all of South Florida is between 0 and about 12 feet above sea level, so these articles always catch my attention).
October 12, 1999
Global Warming Not to Blame for Melting of
Huge Ice Sheet
By THE ASSOCIATED PRESS
WASHINGTON -- The huge West Antarctic Ice Sheet may be headed
for a complete meltdown in a process that a new study indicates
was started thousands of years ago, and not as a result of global
warming or other changes brought on by humans.
The study, however, did not address the possibility that actions of people --
like the burning of coal, oil and natural gas -- could help accelerate the
process.
As scientists have been increasingly able to document melting and the
discovery of icebergs breaking off from Antarctica in recent years, concerns
have risen that a change in climate could be damaging the Antarctic ice sheet.
But the future of the West Antarctic Ice Sheet "may have been predetermined
when the grounding line retreat was triggered in early Holocene time," which
was about 10,000 years ago, according to a team of scientists that was led
by Dr. Howard Conway of the University of Washington in Seattle. They
reported their findings on Friday in the journal Science.
The grounding line is the boundary between floating ice and ice thick enough
to reach the sea floor, and the scientists found that line has receded about
800 miles since the last ice age, withdrawing at an average of about 400 feet
per year for the last 7,600 years.
Referring to the melting, Dr. Conway said, "It seems like the rate that been
going on since the early Holocene is similar to the rate right now." Dr.
Conway said.
"Collapse appears to be part of an ongoing natural cycle, probably caused by
rising sea level initiated by the melting of the Northern Hemisphere ice sheets
at the end of the last ice age." Dr. Conway added in a telephone interview.
Continued shrinking of the ice sheet, perhaps even complete disintegration,
"could well be inevitable," the report concluded.
According to estimates, the ice sheet's complete melting could raise the global
sea level by 15 to 20 feet, swamping low-lying coastal communities
worldwide.
But, at the current rate of melting, that would take about 7,000 years, the
researchers estimated.
Dr. Conway said the melting annually contributed about one twenty-fifth of
an inch to sea-level rise.
Although the study indicates that global warming is not the cause of the
melting, changes in climate remain a problem, Dr. Conway said.
"Global warming could well speed the process," Dr. Conway said.
"Our study," he added, "doesn't address that problem."
Some environmentalists have grown concerned that industrial chemicals
added to the atmosphere are trapping heat like a greenhouse, causing the
temperature of the earth to rise.
But there is disagreement about just what is causing any rise in temperature
and how great a hazard is being posed.
Dr. Conway's report is one of three in this issue of Science, which focuses
on the Antarctic ice sheet.
In the another, scientists studying satellite-based measurements found a
complex system of tributaries feeding major rivers of ice on the West
Antarctic Ice Sheet.
The web of tributaries forms a transition zone between the sluggish inland ice
and the swiftly moving ice streams closer to the margins.
Still other researchers, using the ages of volcanic debris that erupted onto the
West Antarctic Ice Sheet, reconstructed the past elevation of the ice sheet as
it began to melt just after the end of the last ice age. They concluded that the
sheet was not the source of a huge flow of meltwater into the oceans 10,000
years ago.
West Antarctica, a section of the continent south of the tip of South America,
is covered by an ice sheet that extends over about 360,000 square miles --
about the combined areas of Texas and Colorado.
Dr. Conway's team calculated the movement of the grounding line using
evidence gathered from raised beaches and radar imaging of subsurface ice
structures.
The timing of start of the melting was determined by carbon-14 dating of
samples that were found on raised beaches.
Copyright 1999 The New York Times Company |
