The measure of the north's
By NED ROZELL
November 13, 2008
In 2007, Sandy Zirnheld flew the length of Hubbard Glacier with
pilot Paul Claus, using a laser altimetry system to see how much
the glacier had thinned in the last few years. After a successful
flight along Hubbard Glacier, Claus suggested they fly over Mt.
Logan on their way back to his landing strip in the Wrangell
As they flew over Canada's highest mountain, Zirnheld, a research
technician with UAF's Geophysical Institute, operated a laser-rangefinding
unit mounted in the belly of Claus's Super Otter. They flew over
the summit twice, recording the mountain's elevation as 19,574
Paul Claus flies over
the summit of Mt. St. Elias in his turbine Otter
in 2008 as Chris Larsen measures its elevation.
Photo by Chris Larsen.
Their measurement is 276 feet lower than the number appearing
on most maps, and 23 feet higher than the height of the mountain
determined by Michael Schmidt and a team of Canadian climbers
during a 1992 expedition.
Zirnheld's measurement was part of a campaign of opportunity
to measure high peaks by Chris Larsen of the Geophysical Institute.
Larsen has teamed with Claus, who helps him repeat elevation
measurements on Alaska and Canada glaciers pioneered by Keith
Echelmeyer. With a laser system in his Super Cub, Echelmeyer,
also of the Geophysical Institute, discovered that Alaska glaciers
had shrunk dramatically since the 1950s, when USGS mapmakers
drew Alaska maps.
When Larsen and Claus have the time and good weather, they fly
over high mountains to determine their elevations with the laser-rangefinding
system. They started last year by measuring Mt. Marcus Baker
in the Chugach Range (13,203 feet compared to the USGS map value
of 13,176 feet), and since then have measured Mt. Vancouver (15,763
feet compared the 15,979 feet on the map), Mt. Augusta (13,905
feet compared to the map's 14,070 feet), and the lovely sharp
summit of Mt. Saint Elias (18,029 feet compared to the 18,008
feet on maps).
The differences in measurements, sometimes hundreds of feet,
could be the result of errors in early surveying. Surveyors working
for the International Boundary Commission in the early 1900s
measured most of the mountains near the coast in the Wrangell-St.
Elias Range, and those readings are what remain on maps today.
The surveyors used the state of the art at the time, which began
with measurements at sea level and ended with surveyors aiming
a theodolite at the tops of peaks to measure angles and calculate
This method probably led to accurate measurements of mountains
close to the ocean, such as St. Elias, but led to greater errors
the farther a surveyor ventured inland, Larsen said.
Paul Claus, owner of
Ultima Thule Lodge in the Wrangell Mountains, sometimes flies
scientists in his turbine Otter aircraft.
Photo by Chris Larsen.
During the 1992 expedition to the summit of Mount Logan, a team
led by Michael Schmidt of the Geological Survey of Canada carried
two GPS receivers to the summit of the mountain and measured
it at 5,959 meters, or 19,551 feet. Their measurement corrected
the original boundary survey team's 1913 measurement of 6,050
meters, or 19,850 feet.
Larsen's team's 2007 measurement has Mount Logan 23 feet higher
than what Schmidt measured 15 years before, which Larsen said
could be due to accumulation of snow and ice since then.
"Right now, the summit is all snow and ice," Schmidt
said over the telephone from Victoria, B.C. "There could
have been that much snow accumulation since then, but there's
no way to tell. I'd be really surprised if there was seven meters
of snow accumulation in that time span, but you never say never."
Schmidt in 1992 established a few GPS survey markers on the mountain
for repeat measurements, but he hasn't been able to return. A
2008 climbing team had bad weather when they attempted to duplicate
his measurements, he said.
UAF's Larsen said he will pick off more peaks when the opportunities
arise, possibly even Mt. McKinley, but he's hoping to find some
funding that would enable a project devoted to elevation-truthing
of high peaks. A possible climate change scenario is warmer,
wetter weather, which would dump loads of snow on mountaintops.
"That could be what's going on with Alaska, and the high
peaks would be a perfect place to measure it," he said.
This column is provided
as a public service by the Geophysical
Institute, University of Alaska Fairbanks, in cooperation
with the UAF research community. Ned Rozell [email@example.com]
is a science writer at the institute.
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