In December, Geotimes’ reporter Naomi Lubick spoke with Lonnie Thompson, a glaciologist at the Ohio State University in Columbus and a researcher at the Byrd Polar Research Center there, about what it means to hunt ice and about some of his current work.
NL: You’re an ice core hunter — what exactly does that mean?
LT: It means that we’re looking at the record of the Earth’s climate
and environmental history that is archived in glaciers around the world. I guess
what makes our group somewhat different is that we not only work in the polar
regions, but we also work in the high mountain regions around the world. If
you go high enough, even if you’re in the tropics, you encounter conditions
that are similar to those in the polar regions. Whether you are on tropical
or polar ice fields, you have an archive of the annual snow accumulation that
has built the glaciers over many years, and if you drill a core through the
ice, you can extract a climate history for that part of the world.
NL: You’ve told me a bit about why it is important to study the ice
record, but could you tell me more?
LT: For many parts of the world, we just don’t have the long time perspectives
that we need to assess the significance of the changes taking place today. One
way that we can get that perspective is to recover it from the paleoclimate
archives, and the archives that we study come from Earth’s glaciers, ice
caps and ice sheets.
We’re fortunate that some of these glaciers exist at low latitudes, in
the tropics. This is a very important region for understanding the climate of
Earth, as 50 percent of the planet’s surface lies in this region that receives
most of the sun’s heat, which drives Earth’s climate system.
The tropics are also dominated by some very large climate forcings, such as
the El Niño-Southern Oscillation and monsoons. These systems have exhibited
a large range of variability that affects the lives of over 2 billion people.
So to understand how those systems have worked in the past — that is, their
natural variability — provides a very important backdrop for assessing
the degree to which human activities are now inducing changes in the system.
NL: So what are some of the most important cores already sampled?
LT: Certainly at the top of the list have to be deep cores from Antarctica
that have provided the longest history of CO2 [carbon dioxide], methane and
other greenhouse gases that we worry so much about in today’s world. Understanding
what their natural variability has been is incredibly important.
I believe that in the tropics, for advancing our understanding of the longer
term variability of climate, we’ve been surprised at the length of some
of these records, and the ability to look at conditions during the last ice
age in the tropical Andes in Peru, just above the Amazon basin. These records
also contribute to our understanding of how the system works, as some of the
records from South America reach back 25,000 years. They also provide information
about the key drivers of climate in those parts of the world.
We currently have four ice core records from Tibet, and soon we will attempt
to recover our fifth record — from an extremely important part of the world.
Tibet is the highest plateau that we have on the planet, and some of the ice
fields are at least 750,000 years old. Our ultimate goal is to examine the chemical
and physical characteristics of a specific year — say, for example, A.D.
925 — over both the Andes of South America and the Tibetan plateau, and
then compare that information with similar information from the polar ice cores.
The goal would be to map out climate variability on a year-to-year basis.
NL: Where do you think is the most important place to go sample right now,
and why is it so important to go there right now?
LT: There are a number of areas. The problem and also the excitement in
science is that it’s what you discover that you didn’t expect that
really makes the breakthroughs. Based on our experience, I would suggest that
the most critical sites are those where the ice archives are disappearing.
And there are a number of sites. In 2000, we drilled Kilimanjaro in Africa and
we predicted that those ice fields are going to be gone in 15 years. We have
an ongoing program there, and in January we plan to take new aerial photographs
and document the rates of change in both the area of ice cover and the volume
of ice. This hasn’t been possible in the past.
The unfortunate part, of course, is that once the ice field is gone, you have
lost the archive or history of the past. A very important question right now
is what role humans are playing in the current climate changes. Assessing this
requires an archive that can reveal how the climate system has worked in the
past. This history is critical and we are rapidly losing it.
NL: Tell me more about your future planned trips.
LT: Our next big drilling project, after Kilimanjaro, is actually in the
southwestern Himalayas. It’s in a place called Naimona’nyi (Gurla
Mandhata), about a five-day journey west of Lhasa, at the top of the Himalayas.
It’s a site that’s about 10 kilometers from the western end of Nepal,
about 20 kilometers from the Indian border located in Tibet. It’s right
above a town called Burang. That city is over 1,500 years old; it used to be
on the old north-south silk road across the Tibetan plateau.
The glaciers on Naimona’nyi provide about 85 percent of the water for this
town, and all those glaciers are retreating. So one of the questions we want
to address is the possible impact of the loss of the glaciers on the people
who live in the region and who depend on these water resources provided by the
glaciers… (see story, this issue). We’re going
to be there between April 25 and June 10.
NL: Is there anything else
that you want to add?
LT: I would say that one
of the things that we didn’t discuss that I’m really interested in
right now is that as these glaciers retreat around the world, there are things
coming out of the ice. These provide compelling evidence about past climate
variability.
Three months ago, we were in the Andes down on the Quelccaya ice cap, the largest
tropical ice cap on Earth. We’ve been studying it since the mid-1970s,
and there are two things I find just incredible: One is how quickly the ice
is disappearing, I mean huge amounts of ice, and secondly, whether fascinating
things are being exposed as the ice disappears (see Geotimes,
April 2005). We’ve collected over 25 plants that are all radiocarbon-dated
to around 5,000 years ago; the oldest one in the group is about 6,500 years
old. The plants are perfectly preserved and they are soft-bodied plants, wetland
plants — there are no woody parts. So the only way they could be preserved
is if they have been under the ice for 5,000 to 6,000 years.
So the fact that all these plants are now being exposed by the retreating ice
means that the ice field has not been smaller than it is today for over 6,500
years. On a global scale, there are things coming out of the ice around the
world as glaciers retreat, and by dating those things, we can really put the
significance of the current ice retreat into an important time perspective.
Links:
"Global Water Supply Takes Some Heat,"
Geotimes, March 2006 Print
exclusive
"Melting glaciers reveal ancient bodies,"
Geotimes, April 2005
"Lonnie Thompson: Tracking ice in the
tropics," Geotimes, June 2005
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