Rapid thaw-driven geomorphic change transforms fluvial, sedimentary, and biogeochemical environments in the Willow River, NT

• Author / Creator

  Smith, Jaedyn Linda Jasa

• The effects of global climate change are acute in permafrost environments. In the western Canadian Arctic, permafrost degradation of ice-rich slopes is resulting in the development of thermokarst and other forms of mass wasting, which transports previously frozen materials into aquatic systems. Here I examine the thaw-driven rejuvenation of the post-glacial sedimentary and geochemical cascade in the Willow River catchment (NT, Canada), an upland, ice-marginal setting where mass wasting is transforming erosional and depositional environments in response to shifts in thermal and hydroclimatic regimes. This transformation is evidenced by the diversion of the main Willow River channel through a delta lake (Willow Lake), causing a near-complete infill with sediments. Remote sensing analyses indicate that thaw-driven mass wasting features have increased in number (3.8¬¬¬-fold), size (9.2-fold), and density (16.3-fold) in the Willow River catchment since 1986, with expansion occurring non-linearly during the study period. This non-linear intensification has increased slope-to-stream connectivity within the system, resulting in increased turbidity within lakes lying along the new outflow channel, but decreased turbidity in lakes that lie along the abandoned channel. Cores taken from the alluvial surface of Willow Lake and nearby floodplain settings indicate clear shifts in depositional materials following the river rerouting. A coarsening upwards sequence indicates the development of a prograding delta within Willow Lake. Compositionally, materials varied with depositional energy and indicate dynamic post-depositional change in the sediment. This study provides evidence that thaw-driven erosion and mobilization of permafrost preserved glacial deposits is transforming the Mackenzie Delta, with major impacts on Arctic depositional environments and carbon sequestration, which have the potential to shift ecosystem function within aquatic systems and cascade across watershed scales.

• Subjects / Keywords

  • Biology
  • Biogeochemistry
  • Permafrost thaw

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-dymn-gx56

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.