Prior to 1983, ice-core records of past climate came almost exclusively from the large ice sheets in Greenland and Antarctica. While extremely long records of fantastic quality emerged from these polar regions, little attention was paid to smaller bodies of ice elsewhere in the world. Geology Professor Lonnie Thompson from The Ohio State University was among the first to realize that within the tropics where 75 percent of the earths inhabitants live high-elevation ice caps might also provide suitable sites for drilling ice cores. At present, Dr. Thompsons teams have drilled through glaciers in the Andes Mountains of South America, the Himalaya in Asia, and in East Africa. Other research groups are also now pursuing non-polar ice cores, including scientists from Brazil, Canada, China, Ecuador, France, and Switzerland (photo at left shows ice-core drilling on Nevado Sajama in Bolivia).
Climatological data from high elevations are scarce, especially in the tropics. On mountains with ice caps and glaciers suitable for drilling ice cores, severe environmental conditions including high winds, lightning, heavy snowfall, and low temperatures all make weather measurements difficult. Yet fully understanding climate records recovered from ice cores requires knowledge of accumulation and ablation timing, and how the various processes occur (for example, drifting of snow, or sublimation from the snow surface). Knowledge is also required about the direction from which moisture, dust particles, and human contaminants originate. Such information is difficult to accurately determine without making measurements, over several years, right at the drill sites.
Dr. Douglas Hardy, a geoscientist at the University of Massachusetts, began high-elevation climate measurements in 1996 on Bolivias highest mountain, Nevado Sajama. At an automated weather station close to the 6,515 m summit (21,376 ft.)(see photo at right), over a four-year period, he measured wind speed and direction, air temperature and humidity, snow temperature, barometric pressure, solar radiation, and snow accumulation/ablation. Working with University of Massachusetts colleagues and Dr. Thompson, Dr. Hardy learned that not all snowfall at the site actually accumulates to ultimately be represented in the ice-core record. In fact, on an annual basis only a relatively short proportion of time is represented when net accumulation takes place. However, with knowledge about the seasonal distribution of net accumulation, the team calibrated an important parameter measured in the ice cores (oxygen isotopic ratio), and have shown how the Sajama ice core records sea-surface temperature (SST) in the tropical Pacific Ocean, thus providing a proxy record of SST going back 25,000 years.
Dr. Hardy is presently undertaking a similar investigation at the summit of Mt. Kilimanjaro in Tanzania, where climatic conditions are much dryer than on Sajama. Working with a team from the University of Innsbruck in Austria, Dr. Hardy is working to understand how precipitation and clouds govern accumulation and ablation on the mountains glaciers. However, time is running out for these studies since tropical glaciers are rapidly receding under the present climatic conditions. Once the glaciers are gone, these beautiful and fascinating natural laboratories will be lost.
Funding and support for this research was provide by the National Atmospheric and Oceanic Administration (NOAA), the National Science Foundation (NSF), and the University of Massachusetts.
Based on information here and in the Glacial and Periglacial Landscapes chapter of your text, summarize the reasons why understanding climatology is necessary for interpreting ice core records. Why is this relationship especially important at high elevations in the tropics?
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.