Massif meltdown: why is the ice on Africa’s Mount Kilimanjaro disappearing?
Emma Davy
Kilimanjaro, the highest peak in Africa, is a world in miniature. The base and lower slopes of the massif (very large mountain or rock structure) in northeastern Tanzania are swaddled in fertile farmlands that give way, higher up, to steaming rain forests. Higher still, upland slopes of shrubs and grasses merge into an alpine desert. Topping it all off are the mountain’s polar ice caps–pieces of arctic-like terrain just a few hundred kilometers south of the equator!
Kilimanjaro’s glaciers have crowned the mountain since the last ice age ended, nearly 12,000 years ago. But they might not for much longer. More than 80 percent of Kilimanjaro’s ice cover has disappeared in the last century. Scientists are trying to explain the disappearance before the glaciers are gone.
GREAT RECESSION
What might be melting the glaciers? Lonnie Thompson, a glaciologist from The Ohio State University, suggests that global warming–the gradual rise in the globally averaged temperature of Earth’s atmosphere–over the last century may be a major culprit. Thompson and his research team have extracted six ice cores from the glaciers on Kilimanjaro’s summit. The long cylinders of ice are composed of thousands of years of snowfall that has piled up and compressed under its own weight into compact layers of ice. Each ice layer contains a year’s buildup of compressed snow. By analyzing the frozen layers, scientists can tell how snowfall and climate have changed over time.
Thompson’s ice cores provide a glimpse of Africa’s climate history dating back nearly 11,700 years and are the continent’s only record of this kind. By studying deposits within the cores, such as the concentrations of various chemicals and dust layers, Thompson and his team have found evidence of abrupt climate changes that resulted in three huge droughts 8,300; 5,200; and 4,000 years ago.
Even during the worst dry spells, when there was no snow to accumulate on Kilimanjaro’s peaks, the glaciers did not disappear. The ice core layers showed no telltale signs of meltwater until the 20th century.
In the 88 years preceding 2000, Kilimanjaro’s ice cover shrank in area from about 12 square kilometers (4.6 square miles) to 2 square kilometers (0.8 square miles), with one-third of it disappearing in the last dozen years.
How is global warming melting the glaciers? One theory is that the gradually warming surface of the tropical oceans is releasing more water vapor into the atmosphere. Water vapor is a greenhouse gas, like carbon dioxide, that traps heat and contributes to global warming. Moreover, when water vapor rises into the atmosphere and condenses into rain or snow, heat is released. (That type of heat release explains wily the air feels warmer in the winter during a snowfall.)
More water vapor behaving as a greenhouse gas, and releasing more heat into the atmosphere through condensation, is increasing the air temperature over eastern Africa. That increase may be one key driver that is melting Kilimanjaro’s ice, says Thompson.
LOWER PRECIPITATION
Some scientists disagree with Thompson. They believe that the mater culprit is eastern Africa”, dry weather–a natural climate shift that began abruptly more than a century ago. Georg Kaser, an Austrian glaciologist, and Douglas Hardy, a U.S. geologist, propose that dry weather is affecting Kilimanjaro in two ways:
One, it limits the precipitation, such as snow, needed to sustain Kilimanjaro’s glaciers. Two, less water vapor in the air means that fewer clouds are blocking out solar radiation from the sun. More exposure to scalar radiation is melting the glaciers.
Deforestation due to farming on Kilimanjaro’s slopes may also be accelerating the drying effect. Dwindling rain forests have released less warm, moist air into the atmosphere to fall as snow on the mountain’s summit. Without a fresh, while snow cover to reflect the sun’s rays, the existing dirty snow absorbs more solar radiation and melts.
HOT ROCKS
Kilimanjaro itself could also be melting the ice. Kilimanjaro is a massif that formed from three volcanoes–Kibo. Mawenzi, and Shira. Scientists exploring Kilimanjaro’s craters have found fumaroles, or vents, from which hot volcanic gases can escape into the atmosphere. Heat from Kibo, a still-active volcano, may be melting the glaciers.
Whether the shrinkage of Kilimanjaro’s glaciers is due to one factor or several, the fact remains: The mountain’s shimmering white peaks could soon be nothing more than a tropical mirage.
ALL OVER THE WORLD–ICE IS ON THE RUN
Kilimanjaro’s glaciers are not the only ones most of the world’s glaciers are melting. The photos at right show the extent of that melting in Glacier National Park in Montana. The top photo was taken in 1932. The bottom photo was taken in the same spot in 1988. If the glaciers in the park continue to recede at their current rate, they’ll be gone by 2050–and the park will need a new name. In the Himalaya Mountains in Asia, glaciers are “wasting at alarming and accelerating rates,” said Jeff Kargel, a scientist with the United States Geological Survey. The aerial photo below shows glacial lakes that have been created by the meltwater from retreating Himalayan glaciers.
Critical Thinking
* Should something be done to halt the shrinking of Kilimanjaro’s ice? If so, what?
* How might people and wildlife be affected if glaciers around the world continue to melt?
National Science Education Standards
* Structure of the Earth system: water and the atmosphere
* Environmental quality: air pollution
Internet Links
* National Geographic News: Mount Kilimanjaro’s Glacier Is Crumbling: news.nationalgeogra phic.com/news/2003/09/0923_03 0923_kilimanjaroglaciers.html
* NASA Earth Observatory: Melting Snows of Kilimanjaro: earthobservatory.nasa.gov /Newsroom/NewImages/images .php3?img_id=10856
Massif Meltdown (Page 4)
Multiple Choice
Choose the response that best completes each statement or answers each question. Write the letter of the response in the space provided.
— 1. Mount Kilimanjaro is located in (A) Kenya. (B) Tanzania. (C) Uganda.
— 2. Kilimanjaro has been capped by glaciers since the last ice age ended, about (A) 2,000 years ago. (B) 6,000 years ago. (C) 12,000 years ago.
— 3. A large mountain or rock structure, such as Kilimanjaro, is known as a (A) glacier. (B) massif. (c) summit.
— 4. How much of Kilimanjaro’s ice remains from 100 years ago? (A) 20 percent, (B) 50 percent, (C) 80 percent
— 5. A volcanic crater is called a (A) caldera. (B) fumarole. (C) kibo.
— 6. Which explanations do scientists suggest may be causing Kilimanjaro’s ice to disappear? (A) dry weather, (B) global warming, (C) both A and B
— 7. Kilimanjaro was formed from how many volcanoes? (A) two, (B) three, (C) four
— 8. Vents from which hot volcanic gases escape into the atmosphere are called (A) calderas. (B) fumaroles. (C) ice cores.
— 9. What is released into the atmosphere when water vapor condenses into rain or snow? (A) heat, (B) oxygen, (C) carbon dioxide
— 10. Which reflects more of the sun’s rays? (A) fresh, white snow; (B) old, dirty snow; (C) They both reflect the same amount.
Page 3 Massif Meltdown
1. B, 2. C, 3. B, 4. A, 5. A, 6. C, 7. B, 8. B, 9. A, 10. A
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