Bison horse and bones near Chirskii, Siberia. Photograph Julian Murton

Our preliminary data suggests that sulfur isotopes in the bones of fossil animals may have captured the permafrost conditions in the area the animal lived. This is because sulfur is passed from the soils to plant and on to animals through their diet.

Our hypothesis is that sulfur isotope in soils and plants are affected by changes in biogeochemical cycling as soil redox status altered during permafrost thaw, and that these changes are recorded in the animal bones.To test our hypothesis we are undertaking environmental sampling (soil, plant and water/ice) from present day permafrost thawing environments and are combining this with a targeted programme of fossil bone sampling.

Environmental Sampling:

Environmental sampling will develop an in-depth mechanistic understanding of sulfur biogeochemistry in permafrost environments, related to the relationship between plant δ34S, permafrost characteristics, redox status and soil conditions. As little to no isotopic fractionation occurs during the uptake of sulfur by animals from plants, developing this understanding of plant δ34S will enable the drivers of animal bone δ34S to be understood.

Rapid permafrost thaw indicated by massive ice and icy sediments exposed in the headwall of a megaslump, Peel Plateau, NWT, Canada. Photograph Julian Murton

Our fieldwork will focus on a latitudinal transect in NW Canada from arctic tundra in the north (Tuktoyaktuk, North West Territories) to boreal forest in the south (Whitehorse, Yukon). This transect represents a strong spatial gradient in permafrost and vegetation conditions, broadly analogous to the permafrost and vegetation conditions thought to have been present across extensive areas of Eurasia and North America at the end of the last ice age.

Our fieldwork is undertake on First Nation's land. We recognize and respects Indigenous Peoples as traditional stewards of this land and the enduring relationship that exists between Indigenous Peoples and their traditional territories. Our research is conducted in consultation with Tr’ondëk Hwëch’in, Teslin Tlingit Council, Ta’an Kwäch’än Council, Little Salmon Carmacks First Nation, Kwanlin Dün First Nation, Champagne and Aishihik First Nations, and we have a Yukon Scientists and Explorers Act Licence for our work.

Sampling a Late Pleistocene animal bone for isotope analysis. Photograph Hazel Reade

Fossil Sampling:

We are collecting fossil bones from locations of known Pleistocene permafrost presence, thaw, and absence in North America and Eurasia. The bones are held in museum and research archived and we will sample them for isotope analysis. The bone have or will be radiocarbon dated so we will be able to make a high resolution, spatially resolved record of palaeo-permafrost thaw during the last major period of global warming. Through comparison with palaeoclimate records we will show how quickly permafrost responded to global and regional temperature change, thus providing vital information about the potential rate and nature of modern permafrost thaw.