"We are working urgently to understand the dramatic retreat of glaciers currently underway on Kilimanjaro before the evidence - and the historical record - disappear," said Douglas Hardy, who is heading up the UMass portion of the project.
The researchers are seeking to understand the retreat of the glaciers on Africa's tallest mountain by studying both its present and its past. While a team at Ohio State University is studying a series of ice cores that reveal detailed information about the mountain's climate and environmental past, the UMass team is focusing on its present, by gathering continuous data from a mountaintop weather station and by monitoring the glaciers. "It's important to consider both the contemporary situation as well as the mountain's history, in order to better understand the way in which the glaciers are responding to current climate changes. Having both pieces of the puzzle enables us to put each other's findings into context," said Hardy.
No glacier measurements were made on Kilimanjaro for many decades until this project was launched in 2000, Hardy said. UMass scientists have returned to the summit three more times, most recently in July of 2002. The UMass work also marks the first time meteorological measurements have been made at the mountain's summit.
Glaciers today cover a tiny fraction of Kilimanjaro compared with their extent when they were first mapped. Using aerial photographs and GPS technology to update previous surface area determinations, the OSU and UMass scientists found an 80 percent decrease between 1912 and the end of the 20th century. The glaciers measured 12 square kilometers in 1912; in 2000, that figure was down to just 2.6 square kilometers. Hardy offers this overview of a glacier's dynamics: "Glaciers and bank accounts are both entities that grow, provide storage, and shrink, governed by the balance between credits (e.g., accumulation of precipitation) and debits (e.g., melting)." By tracking accumulation and loss of ice, scientists can determine the glacier's overall change in mass.
The UMass team has been measuring mass changes on the glaciers since February of 2000. The three subsequent expeditions have found continued decreases in both the surface area and thickness of the glaciers. During the past 2 ½ years, the glaciers' marginal retreat and thickness decrease have both been about 1 meter, Hardy said. Current predictions in the Science article point to the disappearance of glaciers on the mountain between 2015-2020.
In addition to monitoring the size and thickness of the glaciers, the UMass team has installed a weather station on Kilimanjaro's summit. The station records air temperature, humidity, incoming solar radiation, wind speed and direction, barometric pressure, and changes in the surface height of the ice cap (snow and ice accumulation or loss). Every few hours, the information is sent from Kilimanjaro's peak to a computer on the UMass campus, via satellite transmitter.
"The weather station gives us a comprehensive, real-time look at the meteorological situation on Kilimanjaro's summit," said Hardy. "All of these weather elements, and the interplay between them, play a role in the glacier's health. We are especially interested in the snows of Kilimanjaro, because although snow has always come and gone seasonally, these glaciers are very sensitive to changes in annual amount and seasonal distribution." The work is one aspect of UMass geosciences research on environmental change in the tropics. Other participants include UMass climatology professor Raymond Bradley, researcher Mathias Vuille, doctoral candidate Carsten Braun, and climate lab manager Frank Keimig.
Although the retreating glaciers have caused many to wonder whether the phenomenon is related to global warming, Hardy notes that in the late 19th century, there were approximately 20 square kilometers covered by ice: "It's difficult to ascribe the decrease solely to humans." Without adequate diagnostic evidence, a definitive link to global warming is on thin ice, he cautions. "Evidence is mounting that human influences on climate are causing glaciers to retreat dramatically, around the world and especially at high elevations in the tropics, but Kilimanjaro's glaciers have little in common with mid-latitude Alpine glaciers, and we must accept that simple explanations are not always possible. Kilimanjaro is a mountain that defies expectations and shatters assumptions." Hardy adds that "further research is needed to determine to what extent global warming and/or natural climate variability are responsible for the demise of Kilimanjaro's glaciers."