The world's glaciers are shrinking at alarming rates, and many scientists believe it is due to changes in climate. Dr. Lonnie Thompson of Ohio State University and Dr. Douglas Hardy of UMass-Amherst discuss glaciers and how they melt, and pay special attention to Africa's tallest mountain, Mt. Kilimanjaro. "Changing Planet" is produced in partnership with the National Science Foundation.
Melting Mountain Glaciers
ANNE THOMPSON, anchor:
It is the highest mountain in all of Africa, and one of the most iconic mountains in the world. For decades, Mount Kilimanjaro has attracted hikers, adventurers, and romantics alike. Popular in books and movies, Ernest Hemingway described it as "wide as all the world, great, high, and unbelievably white in the sun."
GREGORY PECK (Film Clip: Snows of Kilimanjaro, 1952): Kilimanjaro is a snow-covered mountain, 19,710 feet high.
A. THOMPSON: When people talk about the snow on Kilimanjaro, they're talking about its glaciers: immense sheets of slowly moving ice are formed from layer upon layer of compacted snow accumulating for hundreds, or even thousands, of years.
Dr. LONNIE THOMPSON (Ohio State University): To be a glacier ice has to move. Ice and motion, to have them move you have to have pressure from accumulating snow on top.
A. THOMPSON: And like other glaciers on Earth, the ones on Kilimanjaro are in serious trouble.
L. THOMPSON: We're losing glaciers around the planet. It doesn't matter whether you’re in the tropics or the Andes in South America or Kilimanjaro or any other glaciers in Africa, or over in Papua, Indonesia, the ice is disappearing.
A. THOMPSON: For the past thirty years Dr. Lonnie Thompson of Ohio State University has been collecting ice core samples from glaciers all over the globe. His ice core collection, stored in a freezer kept at 30 degrees below zero, is one of the largest in the world.
L. THOMPSON: The oldest records we have to date are from the Guliya ice cap in Western Kunlun Mountains in China. That record goes back over 750,000 years, from a mountain range.
One of our best records is what's recorded in the ice as far as getting us a perspective on many of variables that cause climate change.
Off-Screen Voice: And this is the second core to bedrock on Kilimanjaro.
L. THOMPSON: We can look at the composition of the world's atmosphere in the past looking at the air trapped in the bubbles, so you have little capsules of the air of the past.
A. THOMPSON: Analyzing the ice cores can reveal many things about Earth's climate from the past thousands of years.
L. THOMPSON: So you can measure CO2, methane, nitrous oxide. Everything we're concerned about in today's world, only you can get these long-term histories of these-- how they varied in the past.
A. THOMPSON: Through the many layers in the ice cores, no layer has shown more impact from climate change than the most recent years.
L. THOMPSON: There's really no analog in this long archive of where we are today. And of course, we're really concerned about where we're going to be in less than a hundred years, if we continue on our current path.
A. THOMPSON: If the ice and snow on Kilimanjaro were to disappear, the economy of Tanzanian communities that rely on the mountain for tourism and natural resources could be in serious jeopardy. Elsewhere in the world, the disappearance of glaciers could have serious impacts on communities that rely on them for drinking water, hydroelectric power, irrigation, and many other needs. Scientists also worry that the vanishing of glaciers worldwide is a signal of other more drastic climate changes to come.
L. THOMPSON: They are the canaries and the coal mine for-- for ice and-- and I think the fact that they are all telling us the same story to me is what's really, uh, of concern.
A. THOMPSON: To better understand how climate change is impacting the mechanics of glaciers, it's important to look at how glaciers melt.
L. THOMPSON: Most glaciers around the world today are-- experience a negative mass balance of the glacier as a whole.
A. THOMPSON: Dr. Douglas Hardy of UMass-Amherst has been to Mt. Kilimanjaro a total of 13 times and continues to go once a year, measuring the decline of its glaciers. From his camp near the summit, Hardy sets up weather stations at different points along the glaciers that measure everything from air temperature to solar reflection.
Dr. DOUGLAS HARDY (UMass-Amherst): Working at 6,000 meters is very difficult. It's very unpleasant much of the time. And it's exhausting to spend an entire day-- chipping into the ice or walking and drilling holes into the glacier to reposition stakes on the glacier and climbing the tower, it's exhausting.
A. THOMPSON: At the summit, air temperatures stay below freezing. But because the air is so thin, the sun's solar radiation is more intense, and that has a huge impact on the ice.
HARDY: We've got a tremendous amount of radiation coming from the sun, energy coming from the sun because we're at high altitude. We're above much of the atmosphere.
A. THOMPSON: As the solar radiation penetrates the glaciers, it causes the ice to melt, thus turning the solid ice into a liquid. In some cases the radiation is so intense that the ice is vaporized--a process called sublimation.
HARDY: Sublimation is nothing more than evaporation going in the case where we go from a solid to a vapor.
A. THOMPSON: Precipitation is one of the keys to preventing these glaciers from melting and sublimating. The more snow that falls on the mountain, the more the glaciers are protected from solar radiation, which reflects off the white surface of the snow.
HARDY: Kilimanjaro precipitation is always in the form of snow and every time it snows it brightens the surface of the glacier.
A. THOMPSON: If there is less snow cover, the glaciers are more exposed to solar radiation, and thus, more subject to melting and sublimation. Tanzania has been seeing a lack of precipitation, in the form of a drought--resulting in less snow cover on Kilimanjaro. The drought, some scientists believe, could be a result of climate change over a much larger area: the Indian Ocean.
HARDY: We know that the heat content of the Indian Ocean has been increasing-- as a result of warming of the atmosphere. We know that the sea surface temperatures have been changing. And we know that precipitation over much of Tanzania, East Africa, has been decreasing.
L. THOMPSON: Climate is everything-- I mean it's temperatures, it's precipitation, it's radiation, it's cloudiness. I mean all of those variables are out there.
A. THOMPSON: All of which are driving the glaciers of Kilimanjaro and others around the world to disappear, sometimes into thin air.
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