In order to predict how the earth will respond to pollution and other changes caused by the activities of humankind, scientists must first understand how the climate system works on regional and global scales. Clues to climate conditions from ages past may be found in ice cores, the cylindrical columns of ice drilled and removed from glacier ice. "Ice cores from glaciers and ice sheets around the world provide some of the best records of environmental conditions and climate change," says Edwin D. Waddington of the UW geophysics department.
Waddington and colleagues Minze Stuiver and Piet Grootes obtained a deep ice core from Antarctica in 1994 which has provided an unprecedented record of climate conditions in a near-coastal area of Antarctica. They have obtained a climate record going back 140,000 years, through a complete ice age cycle. The record extends much farther back than previously available in that sector, which was the site of major changes in glacier cover affecting sea level at the end of the last ice age.
Waddington explains that atmospheric impurities and gases are trapped and preserved in otherwise extremely clean ice when annual layers of snow are compacted into glacier ice. These impurities and gases in ice cores can be detected and measured; the age of the impurity is determined from its depth in the core. When many climate-related geochemical and physical parameters can be measured and correlated in the same ice core, they can provide important clues to the subtle causes of past climate change.
In the late 1980s, Waddington and Piet Grootes (then at the UW Quaternary Research Center, now at Christian Albrechts University, Germany) began planning their project to recover an ice core for paleoclimate studies from a site called Taylor Dome (77° 50' S, 158° 40' E) in South Victoria Land, Antarctica. They obtained funding from the National Science Foundation Office of Polar Programs for the work in 1990.
"One of the major questions about climate change is the role of the West Antarctic ice sheet in raising sea level," says Waddington. "Taylor Dome is very near the Ross Ice Shelf, which is a major outlet of ice from the West Antarctic Ice Sheet." That means the climate record from Taylor Dome is likely to shed light on climate changes that have influenced sea level changes in the past.
Before taking the ice core, the UW research teams had to study the Taylor Dome area in order to select the best possible site. For three years, the team studied the weather and snowfall patterns, the quality of preservation of climate signals in the snow and ice, the ice thickness, and the ice flow patterns. Researchers from the QRC concentrated on investigations of the stratigraphy and chemistry of the snow, while the geophysics team concentrated on studying the physical environment of the site. These studies were necessary to ensure that the integrity of the chemical clues and the stratigraphy, or layering, of the cores were preserved intact in the ice at the selected site.
A 554-meter-deep ice core to bedrock was removed in January 1994. Since then, UW scientists plus about a dozen additional university and federal research labs funded by NSF have measured climate-related properties in the recovered ice core under the coordination of the UW Quaternary Research Center.
Until the early 1990s, only a handful of ice cores had been recovered from the Southern Hemisphere, and the majority were shallow, or were not studied with the widest range of modern high-resolution techniques.
"The VOSTOK ice core project at the Russian station Vostok in central East Antarctica provides the only other comparable record," says Waddington. "The Vostok project has been underway for well over a decade, and has produced a climate record that is 300,000 years long as of September 1995. The record at Vostok is so long because the snowfall rate is very low there deep in the polar desert, and the layers are very thin. The Vostok coring project has been a major effort by the Russians, who do the drilling all year round, the French, and the U.S. Antarctic Program, which has provided major logistical support in recent years to get the ice safely out of Antarctica to research labs in France, the U.S., and Russia."
But Waddington emphasizes that one record like Vostok does not give information about how climate varied across Antarctica. "It provides only a single point," he stresses. "Trying to understand the complex climate system from just one ice core is like trying to infer the climate all over North America--for example in New Orleans, Seattle, Barrow, and Halifax--using only data from a single weather station located for example in Lincoln, Nebraska. The earth's climate is a very complicated thing, and the data on paleoclimate must come from many places as well as from many eras in time before climate change can be understood." The Taylor Dome ice core essentially doubles the data coverage in Antarctica throughout much of the last ice age. "It is like having two weather stations in North America, instead of just one," says Waddington.
Furthermore, the snowfall rate is higher at Taylor Dome than at Vostok, so the snow layers from the most recent 10,000 years are thicker at Taylor Dome and give a higher-resolution paleoclimate record for that period than at Vostok. "At Taylor Dome, we can see most of the same major climate events seen in the Vostok ice core in the past 140,000 years, but their character is not identical to their character in the Vostok record," notes Waddington. "We see for the first time how climate changes were different at a near-coastal site like Taylor Dome compared to an area like Vostok deep in the heart of the continent."