Focus on Research

Ancient artifacts discovered in ice patches

An interdisciplinary team of scientists is working to retrieve ancient hunting tools preserved in patches of ice high in the Mackenzie Mountains of the Northwest Territories as the structures shrink in the face of warming temperatures.

Brian Moorman, University of Calgary permafrost and geophysics expert, is part of the team working on an International Polar Year project to examine ice patches, which are accumulations of annual snow that remain frozen all year. For millennia, caribou seeking relief from summer heat and insects have made their way to these ice patches where they bed down until cooler temperatures prevail. Hunters noticed caribou were making extensive use of these ice islands and took advantage. In the process, tools were dropped or left behind.

Warming temperatures are melting the patches and as they shrink, these ancient tools are being revealed. In fact, one of Moorman’s student researchers, Haley Peterson, found the first spearhead. Researchers on the team have discovered 2400-year-old spear-throwing tools, a 1000-year-old ground squirrel snare, and bows and arrows dating back 850 years.

“This is very exciting stuff,” says Moorman, who extracted core samples from the ice as part of his work. “In the core you get layers of dung, perfectly preserved, so you can radiocarbon date the organic matter.”

As a permafrost expert, Moorman is not on site to hunt for artifacts – that’s just an added bonus. His work involves examining the size and composition of the ice patches. In the first stage of his research, he used GPS mapping to determine the extent of the patches. This data is currently being compared to 60-year-old aerial photos.

Next, ground-penetrating radar showed the internal layers and density of the patches. “We wanted to see how they grow,” says Moorman. Finally, core samples were extracted to verify the results of the radar. From these samples, caribou dung was extracted and sent for 14C dating. Results show the patches are over 4,400 years old.

Moorman’s data, collected between 2007 and 2009, shows the patches are changing.

“Yes, they are shrinking, but not at a regular rate. It’s variable from year to year.” The size and stability of the patches, which are only two-and-a-half metres deep at their thickest points, are determined by a combination of summer heat and winter precipitation.

The future of the ice patches is anyone’s guess. Two of the eight in the original study have already disappeared.

“It doesn’t look good, but at the same time, this one was 4,000 years old and if it does disappear it will really say something about the climate we are entering into.”