Researchers at the University of Colorado at Boulder continued their search in southeast Alaska last summer to pinpoint rapidly melting glaciers and ice fields that hold prehistoric human artifacts before exposure triggers their decomposition.
For thousands of years, humans hunted on the glaciers and ice fields that cover what is now the Wrangell-St. Elias National Park and Preserve in southeast interior Alaska. During the summer months these ancient ice fields attracted caribou and other animals seeking refuge from insect swarms that blanket Alaska during summer.
At the same time, humans hoping to feed their families visited ice fields with the goal of finding meat. Unfortunately for the ancient hunters, they dropped some of their tools, or perhaps missed when they shot their arrows or spears. Over time, those weapons and tools were encased in ice, until now.
As global warming continues to melt glaciers and ice fields at a rapid rate, discarded or lost tools that were frozen in glaciers are being released from the ice, according to James Dixon, curator of the Museum and Field Studies program at the CU Museum of Natural History and a fellow at CU-Boulder's Institute of Arctic and Alpine Research, or INSTAAR.
Among their most significant finds this year were wooden arrow shafts, one with red ochre paint, and a stone point still lashed to its wooden shaft. They also found a birch bark container or basket recently thawed from the ice. What is significant about the findings is that because they are organic materials, they can be radiocarbon dated. However, when stone spear points and other stone artifacts are found, their age can only be estimated.
"Global warming has exposed artifacts from the ice that has kept them preserved for hundreds and even thousands of years," he said. "So there is some urgency to our search for these artifacts, because once exposed they decompose or are destroyed quickly."
It helps to know where to look, so Dixon and INSTAAR Research Scientist William Manley have spent three years developing, testing and refining a Geographic Information System model, or GIS, to identify glaciers and ice fields in the Wrangell-St. Elias National Park and Preserve that are likely to hold artifacts. To create their model, they pulled together datasets including topographic, cultural, biological and glacial information, and then layered all of the maps on top of each other to help pinpoint areas most likely to be artifact sites, according to Manley.
On their first trip to Alaska in summer 2001, they identified 32 promising sites and found several artifacts. They also had some help. A local sheep hunter in one of the areas found what turned out to be a 750-year-old antler projectile point used for hunting. Over the past two years, the researchers gathered more data and tweaked their GIS model.
"For example, we looked at how glaciers melt, which glaciers are close to known rock sources that could have been used to make tools, and we looked for the easiest routes across rough terrain," Manley said.
"We were trying to focus on smaller areas," he said. "These models are used to guide us in the field. After compiling the data, we go to the field and test it."
This summer, the researchers investigated 141 sites, five of which yielded prehistoric artifacts and many others that had more recent artifacts.
"The work of responsible and innovative outside researchers like Dr. Dixon of the University of Colorado is of great benefit to the National Park Service," said Ted Birkedal, an archaeologist in the Alaska Region of the National Park Service. "Not only has he brought our attention to the fact that there are archaeological sites located in the snowfields and icefields of Wrangell-St. Elias National Park and Preserve, but he and his co-researchers have also helped with the overall archaeological inventory of the vast park acreage."
Birkedal added that visitors to the park should not look for the artifacts on their own because it is a federal crime to collect artifacts without an authorized permit and outside the context of scientific research.
"These discoveries help us to see the organic component of these ancient cultures," Dixon said. "They provide us with insight into human adaptation at high altitudes and latitudes and into human culture that we haven't seen before."
The National Science Foundation's Office of Polar Programs funded the research in 2001 and again in 2003.