On the move
by Guest Blogger
July 5, 2005
We are getting ready to head out after a successful three days of
research and documentation in this area. Gordon and Leigh, our guest
scientists from the University of Maine, seem well satisfied with the
data they collected. After analysis they should have a clearer picture
of how these glaciers are reacting to warming temperatures. Getting
this data wasn’t easy though, or without risk.
To understand the danger involved in glacier work, you need to first
know a few things about the nature of glaciers – mainly that they move,
or rather, flow. That is, the ice of a glacier flows downhill somewhat
like water, only much more slowly. Being ice, it doesn’t act just like
liquid water. Deep cracks and ridges form – especially towards the
front (terminus) of the glacier where both of the ones they studied here
flow the fastest.
As the Australian Antarctic Division’s Field Manual
puts it, “Crevasses are caused by the inelasticity of ice and snow. As
the ice flows over obstructions or changes in the underlying terrain, it
splits and cracks.”
Think of water flowing over a rock in a fast
stream. Now imagine if that water froze in an instant, but by the sheer
mass of it still kept slowly moving.
Some details of the work
Different glaciers flow at different speeds. The interesting question
is whether these glaciers are moving faster now than they have historically.
cases, glacier speed can be measured by satellite (this is part of
Leigh’s work), but in this instance the front of the glaciers are moving
too quickly (roughly 10 meters per day) to be measured with periodic
satellite overpasses – so on the ground data is needed.
To get this data, the science team use Global Positioning System (GPS)
receivers, which get positioning information from between four and
twelve satellites at a once – allowing for precision of up to one
centimeter (.39 inches) after processing the data.
First the team deploys a static receiver on stable rock, to be used as a
stationary reference point. Then five more receivers, with mushroom
like antennas mounted on copper pipes drilled into the ice, are placed
across the glacier.
To do this the team is brought on site by
helicopter because ice this close to its front, the glacier is so
riddled with crevasses, some hundreds of feet deep, it would be
impossible (or nearly suicidal anyway) to cross by foot.
How and where
“Landing” might not be the exact right word for what Hughie (pilot) has
to do on such uneven and potentially unstable ice. Perching maybe, or
“hovering exactly at ground level” is a more accurate description.
Hughie picks the location itself carefully with input from John
(logistics) or Gordon, who both have extensive professional experience
in glacier work. The site needs to be big enough to set up the
equipment at least a short distance from the helicopter, to minimize
blow down from the propellers. It also has to be at least somewhat
flat, and ideally will be slightly bowl shaped to keep people from
slipping over an edge. One fortunate thing is that there is little
snow in this wind swept part of the glacier since it’s summer – so at
least the cracks and crevasses are visible. No one goes any closer to
the edge than is absolutely necessary, or stays on the ice one minute
longer than they need to. In reality, the area they have to work with
is often smaller than the hold of our ship, say 50 feet (15m) by 30 feet
(10m), and the team usually gets their work done in under 15 minutes.
The entire deployment process has to be done twice for each glacier.
Each unit stays out for an hour or two, gathering positioning data,
before being retrieved. Twelve hours later the units are re-deployed in
the exact same locations on the ice (marked by pink flagging tape,
yellow leftover banner material and the antenna poles).
The ice in
this part of the glacier is too unstable to risk leaving the equipment
out there for too long. After the second set of data is collected,
everything is removed from the site.
Why it’s safe
It isn’t safe, not really. However, a combination of experience,
training, proper equipment, and careful planning reduces the amount of
risk to a small and reasonable level.
That said, there still is a certain element of danger that each member
of the team has made a personal decision to accept because they believe
in the importance of the work.
We are all driven to expand the base of
knowledge about global warming – a base of knowledge that scientists
world wide now agree indicates human induced global warming. The more
we know about how fast our planet is heating up, and the impacts this
will have, the better our chances of getting business and political
leaders to take real action.
This is an urgent matter, and time is not
on our side. Help is needed around the world, but because the U.S. is the
world’s largest per capita global warming emitter, we are making an
extra effort to mobilize people there. If you are a U.S. citizen, join the
Thin Ice Contest.