Permafrost dynamics and landscape evolution in the thermokarst plain of Old Crow Flats

The Old Crow Flats (OCF) of northern Yukon form a 5300 km² thermokarst plain recognized as a wetland of international importance by Ramsar Convention of the UNESCO and are a crucial part of Van Tat Gwitch’in traditional territory. During the last glacial maximum, OCF was covered by Glacial Lake Old Crow which deposited up to 9 m of silts and clays before draining catastrophically westward 14.8 thousand years BP. Today, the Flats are underlain by continuous permafrost, are within the forest-tundra transition, and include over 8000 thermokarst lakes and drained basins.

This presentation is an overview of recent progress in understanding interactions between thaw lakes, vegetation, and landscape evolution in this young thermokarst plain. It reflects on lessons learned from integrating perspectives in permafrost geomorphology that are transferrable to permafrost research endeavours in other landscapes.

Nun cho ga: rebirth of a mummified baby woolly mammoth found preserved in Yukon permafrost

A mummified baby woolly mammoth (Mammuthus primigenius) was discovered in the Klondike region of Yukon, Canada in the summer of 2022. This is the best preserved North American mammoth yet discovered, owing to its rapid burial and permafrost preservation, and is of similar quality to the exceptional specimens from Siberia such as Lyuba and Dima. Placer gold miners made the discovery while mechanically stripping frozen Pleistocene sediments that overlies the valley-bottom, gold-bearing gravel on Eureka Creek. The discovery and rapid recovery of Nun cho ga was made possible because of the strong relationship between Yukon government scientists and the mining industry. This collaboration has also allowed a detailed record of the stratigraphic, paleoecological and geological setting of the site.

The mammoth was appropriately named by the Tr’ondëk Hwëch’in First Nation, Nun cho ga, meaning ‘Big animal baby’ in the Hän language. They have also assumed a guardianship role of this mammoth, and importantly, introduced Indigenous spirituality to the discovery.

This talk will detail the discovery of Nun cho ga, our current understanding of the mammoth, the landscape it inhabited, its mechanism of preservation, and permafrost characteristics of the site. Importantly it will highlight how the Tr’ondëk Hwëch’in First Nation is guiding Nun cho ga’s future and providing leadership for the care of ancient animals. Finally, a summary of other extraordinary ice age mummies found preserved in permafrost across the circumpolar north will be presented.

Permafrost Thaw in a Changing Climate: A Geotechnical Perspective

Thawing of once frozen permafrost, is irrevocably altering the landscape of our Canadian North. As the once stable ground shifts and moves, overlying infrastructure is subject to damage; imminently threatening our ability to connect communities, provide stable housing, and protect our Arctic. Recent case histories help us understand the current state of practice in permafrost geotechnical engineering: the innovations; the challenges; and the opportunities, while formation of extended and inclusive communities of practice and co-development of knowledge set the scene for a vibrant future as we explore forward-looking climate adaptation and continued sustainability in our Canadian North.

A Field Experiment with Permafrost in Takhini River Valley, Southern Yukon

The Whitehorse area is in the sporadic discontinuous permafrost zone. A field experiment was conducted over seven years to determine if permafrost may be established by removing the snow cover. The purpose was to test whether the surface or thermal offset is responsible for the presence of permafrost in this region. The depth of frost penetration increased by a metre and mean ground temperatures dropped to below 0 °C.The ground temperature signal was evident in summer -not in winter -but at all depths the ground thawed out annually. The conclusion is negative in that permafrost was not established and it is evident that, in this area, as permafrost degrades it will not be re-established in the foreseeable future. The aridity of the area ensures that the thermal offset is small, on the order of 1 °C, and the change in surface offset is insufficient to effect sufficient cooling. Loss of permafrost will be slow where the ground is ice-rich, but unrecoverable under natural conditions that include persistent climate warming.