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[strikingly informative photos on url - glacier in 1898, much smaller in 
2004]

Change in the air, part 2: Going, going, gone?

Front Range glaciers declining; researchers point to a warming world

By Jim Erickson, Rocky Mountain News
October 26, 2004
http://www.rockymountainnews.com/drmn/state/article/0,1299,DRMN_21_3281315,00.html

ARAPAHO GLACIER - "And Men shall fashion Glaciers into Greenness and 
harvest April rivers in the Autumn." - Inscription beneath a mural in 
the Colorado Capitol

The state's largest glacier is shrinking fast, and University of 
Colorado researchers suspect global warming is playing a role.

The surface of the 62-acre Arapaho Glacier along the Continental Divide 
west of Boulder has dropped 100 to 130 feet since 1960, according to 
recent CU reports.

A third CU analysis concludes that the surface of the 25-acre Arikaree 
Glacier, about five miles north of the Arapaho, has also sunk some 66 
feet since 1965.

The three reports are the first to document significant present-day 
declines in Colorado's pint-size Front Range glaciers, which are 
clustered along the Continental Divide from Rocky Mountain National Park 
south to Interstate 70.



"We can argue about the rate of decline, but I think we can say 
confidently that both of them are losing ice - and they've been losing 
it fairly seriously," said CU hydrologist Nel Caine, author of the 
Arikaree report.

CU researchers say there is no reason to believe that other Front Range 
glaciers aren't experiencing similar declines. Some of them could be 
gone in a few decades.

Just two years ago, at the height of Colorado's multiyear drought, two 
year-round ice patches along the Continental Divide disgorged ancient 
bison horns that have been radiocarbon dated between 2,090 and 2,280 
years old.

The animal remains suggest that, in some cases, ice along the divide has 
retreated to levels unseen since before the time of Christ.

"Over the last couple of decades, and especially over the last 10 years, 
we have entered a period of warming and retreat that is as great, or 
greater, than any we know of since the end of the last ice age" 10,000 
years ago, said glaciologist Tad Pfeffer, of CU's Institute of Arctic 
and Alpine Research, or INSTAAR.

"The Front Range glaciers and snowfields could be gone in a couple of 
decades," Pfeffer said.

"Are we directly responsible for this? Is this the smoking gun that says 
this is caused by fossil-fuel emissions? That's a harder question to 
answer," he said.

Change in the high country

Water managers say the loss of the state's 14 named mountain glaciers 
and the hundreds of unnamed year-round snow patches along the 
Continental Divide would have little effect on municipal water supplies, 
since their contribution is small.

But the loss of glaciers and the so-called perennial snowfields would 
redefine places such as Rocky Mountain National Park. It would reduce 
habitat for fish that rely on late-summer runoff from glacial sources. 
Some alpine plants and high-altitude forests also could suffer.

And the extinction of the alpine ice would cut deeper, beyond what can 
be measured in tourist dollars or acre-feet of water. Those scattered 
scraps of flowing mountaintop ice are remnants of the last ice age, the 
last links to a vanished time, when mammoths roamed the landscape.

"Compare these mountains to a really dry mountain range in New Mexico or 
Arizona or Nevada. They're very different places," Pfeffer said. "And to 
the extent that we care about the landscape that we live in, that matters."

"Aesthetically and emotionally, they're worth a lot," he said.

Diminishing glaciers

Mountain glaciers have been retreating worldwide for a century, and 
there's no end in sight.

The declines are viewed by many scientists as strong evidence that 
global warming - caused, in part, by the buildup of carbon dioxide and 
other heat-trapping greenhouse gases emitted when fossil fuels are 
burned - is reshaping the natural world.

During the past 40 years, the total volume of mountain glaciers around 
the globe has declined by about 10 percent, according to INSTAAR 
glaciologist Mark Dyurgerov.

The losses have been especially severe in Alaska, the Alps, the 
Himalayas and the Andes.

Western U.S. glaciers also have suffered, especially in places such as 
Glacier National Park.

U.S. Geological Survey maps show 1,700 glaciers or perennial mountain 
ice patches in the West. Most are in Washington, Montana and Wyoming, 
but 34 are listed in Colorado.

The only known growing glacier in the contiguous United States was, 
until recent weeks, inside Mount St. Helens, said Portland State 
University glaciologist Andrew Fountain. Now that one is shrinking, too, 
he said.




While glaciologists have flocked to remote mountain glaciers to document 
their decline, Colorado's glaciers have been largely overlooked. There 
have been few systematic, long-term monitoring studies here, in part 
because the puny Front Range ice slabs barely qualify as glaciers.

Surprisingly little work has been done on the status of the glaciers in 
Rocky Mountain National Park, home to about half the Colorado glaciers 
named on U.S. Geological Survey maps. Park officials blame tight 
research budgets.

One unfinished U.S. Geological Survey study of the park's Andrews 
Glacier, however, suggests it has retreated a bit since 1991.

And Fountain recently embarked - with funding from NASA and the National 
Science Foundation - on a multiyear study of Western glaciers, including 
some in Rocky Mountain National Park.

He said the park's glaciers appear to be "holding steady," but that 
early assessment is based mainly on a review of archival glacier 
photographs.

Warming's effects disputed

INSTAAR researchers Caine, Pfeffer and Dyurgerov are among the few who 
have made an effort to study the local glaciers in detail.

Pfeffer compared the Arapaho Glacier's current surface elevation with 
measurements made in 1960 and determined that the ice surface has 
dropped 100 feet.

Caine has measured May-through-October runoff at Arikaree Glacier weekly 
since 1981. Combining his runoff records with data from two nearby 
weather stations, he calculated that the Arikaree has lost up to 66 feet 
in depth since 1965.

Dyurgerov used 2003 Arapaho Glacier measurements, weather records and 
some of Caine's Arikaree data to calculate a loss of about 130 feet at 
Arapaho Glacier since 1960.

Though the INSTAAR researchers are convinced the losses are real, they 
can't say for sure why the changes are happening.

But given the condition of mountain glaciers worldwide, it seems likely 
that global climate change is playing some role, Pfeffer and Dyurgerov 
said.

"We know the temperature is rising globally, and we know that glacial 
volumes are shrinking globally," Pfeffer said.

"My feeling is that global warming is probably involved.

"But I can't point at Arapaho - by itself, in isolation - and say this 
is evidence of global warming. You just can't do that.

"You have to look at these things in aggregate."

Boulder geologist and archaeologist Jim Benedict says it would be "bad 
science" to blame global warming for any of the Arapaho decline.

Benedict began photographing Arapaho Glacier annually in 1980. When he 
compares his pictures with an 1898 archival photograph taken by CU's 
R.S. Brackett, it's clear to him that "this poor thing has taken a 
beating, no question."

Archival photos reveal that the Arapaho lost a tremendous amount of ice 
between 1898 and 1960. The losses since then are less obvious in the 
photos, although the CU reports suggest declines are continuing.

Dyurgerov's "mass balance study" concludes that the Arapaho actually 
gained ice and snow from 1969 to 1975, but has been declining since 
1976, with sharp drops during the current multiyear drought.

"We're losing this glacier," Benedict said as he mounted his Hasselblad 
camera on a tripod at the Arapaho Col overlook during an early September 
hike to the glacier. "It used to be big and convex. Now it's little, 
shrinking and sad."

Due to local peculiarities of weather and topography, however, the Front 
Range glaciers don't behave like typical mountain glaciers. So 
assumptions about the effects of global climate change simply don't 
apply here, he said.

"It's more difficult to interpret the effects of climate change here 
than it is in other places, because things are complex here, not 
straightforward," Benedict said.

State's temperature up

So why then are the Arapaho and Arikaree glaciers shrinking?

Are the declines simply a reaction to local and regional conditions, or 
is global climate change involved?

In general, mountain glaciers are considered sensitive indicators of 
temperature change: They advance when it gets colder and they retreat 
when it warms.

During the 20th century, the global average surface temperature 
increased by about 1 degree, according to the Intergovernmental Panel on 
Climate Change.

The IPCC was established by the World Meteorological Organization and 
the United Nations in 1988 and includes hundreds of climate researchers 
from around the world.

Some of that warming is likely due to natural climate variability.

But most of the observed warming during the past 50 years is probably 
the result of human activities, the IPCC concluded in 2001.

And Colorado has not escaped the warming trend.

The state's average annual temperature has increased 1.5 degrees during 
the past century, according to research meteorologist Martin Hoerling, 
of the U.S. Climate Diagnostics Center in Boulder.

Six of Colorado's 10 warmest years have occurred since 1981, according 
to temperature records from the National Climate Data Center.

"It's hard to pooh-pooh it and say that it doesn't look like a trend," 
said Assistant State Climatologist Nolan Doesken. "One can argue why 
it's there, but it's hard to deny that it's there."

Colorado contradiction

In some mountainous regions, including the Himalayas, Andes and Alps, 
the warming of recent decades is more pronounced at higher altitudes. 
But for reasons that remain unclear, that does not appear to be the case 
- at least not yet - along Colorado's Front Range, said Henry Diaz, 
another Climate Diagnostics Center meteorologist.


"In Colorado, there isn't any clear signal as far as (warming) 
differences between the elevations," Diaz said.

Weather data from CU's Mountain Research Station on Niwot Ridge, several 
miles northwest of Nederland, demonstrate that the warming picture is a 
bit muddled along the Front Range.

In 1951, CU biologist John Marr established weather stations at various 
elevations on the ridge to help clarify the Front Range ecology. 
Conditions at four of the stations - known as A-1, B-1, C-1 and D-1 - 
have been continuously monitored since 1953.

The C-1 station is in subalpine forest at an elevation of 9,973 feet.

Between 1976 and 2000, the average annual air temperature there 
increased by about 3 degrees, according to Mark Losleben, manager of the 
Mountain Climate Program at Niwot Ridge.

But the weather records from the highest station, D-1, tell a different 
story.

D-1 is in alpine tundra at 12,339 feet, roughly the same elevation as 
Arapaho Glacier.

The D-1 station has the longest unbroken high-altitude weather record in 
North America.

At D-1, which is about five miles north of Arapaho Glacier, near 
Arikaree Glacier, there's been no statistically significant temperature 
change since 1953, Losleben said.

During that span, annual precipitation has increased by nearly half an 
inch a year at D-1.

State Climatologist Roger Pielke Sr. and colleagues at Colorado State 
University have suggested that increased cropland irrigation and 
irrigated landscaping along the Front Range has boosted the amount of 
cool, wet air flowing into the mountains in recent decades.

Moister air and an accompanying increase in mountain cloudiness could be 
holding temperatures in check at places such as Niwot Ridge, Pielke and 
his colleagues have suggested.

So, if the average annual temperature at D-1 hasn't changed and 
precipitation is up, why are the Arapaho and Arikaree glaciers retreating?

Pfeffer suspects it's because the summer melting season is starting 
earlier and lasting longer.

Caine wonders if more and more dust is being blown into the high 
country, darkening the glacial ice and causing increased melting.

But no one knows for sure why it's happening.

"That's a puzzle," Caine said. "And it will probably remain a puzzle."

The long age of ice

During the Pleistocene Epoch, from 1.8 million to 10,000 years ago, the 
Front Range was lined with rivers of ice that flowed down mountain 
valleys as far east as present-day Nederland, Georgetown, Allenspark, 
Fairplay and nearly to Estes Park.

The Cache la Poudre Glacier, northwest of present-day Fort Collins, was 
the region's largest.

It sprawled nearly 30 miles from its source in the southern Medicine Bow 
Mountains and was up to 2,000 feet thick, according to Richard Madole, 
of the U.S. Geological Survey.

Scattered scraps of glacial ice persist today because west winds blow 
snow over the Continental Divide. In many cases, the snow collects in 
high, sheltered, bowl-shaped rock basins called cirques.

Over time, the snow is compressed into granules called firn, then 
pressure welds the granules into glacial ice.

The Arapaho is Colorado's largest survivor and the southernmost active 
glacier in the Rockies, according to INSTAAR researchers.

It is a cirque glacier, a tongue of ice and snow that creeps down the 
Silver Lake Valley at 3 to 6 feet a year.

But if the melting continues at its current rate, when will Arapaho 
Glacier disappear?

That depends on the thickness of the remaining ice slab, which has never 
been precisely measured.

To probe the depths of the Arapaho ice, seven researchers from INSTAAR 
and the National Snow and Ice Data Center in Boulder recently backpacked 
into the glacier - a six-mile round-trip hike - lugging a 170-pound 
portable radar system.

Affectionately known as the Wright Flyer, the radar contraption looks 
like a cross between the famous Kitty Hawk biplane and a high-tech dog 
sled.

Like a giant Lego toy, the Flyer's wobbly 12-foot framework is pieced 
together from segments of plastic PVC tubing. The frame rests on two 
cross-country skis, so it can be hauled back and forth across the glacier.

A radar transmitter, receiver and batteries are strapped to the frame, 
and fiber-optic cables send a digitized signal to a laptop computer.

The transmitter sends radar pulses through the ice to bedrock.

The time it takes for that signal to bounce back to the receiver - 
measured in milliseconds - tells researchers the depth of the ice.

Boulder geophysicist Ted Scambos supervised the effort, as several 
graduate student "Sherpas" lugged the Flyer across slushy snow, beneath 
towering walls and spires of ancient gray gneiss and granite.

The radar reflection appeared to show an ice/rock boundary at a depth of 
about 150 feet.

But the result was deemed inconclusive, and Pfeffer suspects the true 
depth is less. A previous attempt to probe the glacier with radar, 
conducted by the same group in 2002, yielded a depth of 73 feet.

"I'm not happy with either one of those numbers," Pfeffer said after the 
trip.

The Boulder researchers are planning a return visit, possibly next month.

If 150 feet is in the ballpark, then Arapaho Glacier has lost at least 
40 percent of its thickness since 1960. It would last another 60 years 
or so if melting continues at its current rate.

But if the slab is just 73 feet thick, the glacier could be gone in half 
that time.

If the latter measure is accurate, Arapaho Glacier, a final vestige of 
the last ice age, could be gone from the face of Colorado within 30 years.
For updates and info, contact scott at planttrees dot org.