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Impact of landscape disturbances and climate change on lakes in the Canadian Arctic

Impact of landscape disturbances and climate change on lakes in the Canadian Arctic

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Joshua Thiepont

Professor Josh Thienpont’s research and teaching are focused on the connection between physical and ecological processes. His research is primarily focused on the impacts of landscape disturbances and climate change on lakes in the western Canadian Arctic region. Ecosystem changes often occur prior to the onset of environmental monitoring, and so Thienpont uses lake sediments (the science of paleolimnology) to infer and reconstruct environmental changes over long timescales (decades to thousands of years).

A major component of Thienpont’s research studies the impact of marine storm surge-induced coastal flooding on the outer Mackenzie Delta region of the western Canadian Arctic. The Mackenzie Delta itself is a large (more than double the area of the GTA) water-rich landscape with tens of thousands of small lakes and ponds, located at the end of the mighty Mackenzie River, where it enters the Beaufort Sea of the Arctic Ocean. The vast alluvial (river sediment) plain of the Delta is low-lying, more than 100 km inland from the coast the Delta is still below 5-10 m above sea level, with much of the outer delta less than 2 metres in elevation. This means the system, naturally dominated by the freshwater flowing from the Mackenzie, is susceptible to the impacts of saltwater intrusion in the event of a marine storm surge. Just such an event occurred in September of 1999, when a tropical storm equivalent weather event whipped up saltwater sufficient to flood the outer 20 – 30 km of coast.

Dead vegetation killed by saltwater intrusion on the shore of a small lake in the outer Mackenzie Delta

Thienpont’s research showed that the impact this storm had on lake ecosystems of the region was unprecedented in the more than 1000-year history of the region, as reconstructed from the sediment record and likely the consequence of decreased sea ice, rising sea levels, and increased fall storm activity in the Beaufort Sea. It was more than 10 years ago (fall of 2009) that Thienpont first visited the outer Mackenzie Delta area impacted by a massive storm surge, and now more than 22 years since that September 1999 storm event. His ongoing research, in collaboration with Prof. Michael Pisaric (Brock University) and funded by the Cumulative Impact Monitoring Program of the Government of the Northwest Territories, will see the researchers return to the outer delta to examine how much (if any) recovery has occurred in the two decades since the initial transformative 1999 storm. They are also interested to see if more recent storms, including one that produced a sizeable surge in 2016, have “reset the clock” on recovery in the region, suggesting these types of events may be the new normal for this ecosystem.

A lake with a large retrogressive thaw slump in the Mackenzie Delta uplands of the western Canadian Arctic

Thienpont works in close collaboration with Prof. Jennifer Korosi and her students on research centred on the Mackenzie Delta region of the western Arctic. They primarily study the environmental impacts of permafrost thaw on the lakes in the region. The permafrost degradation often manifests as conspicuous, spectacular mass-wasting scars called retrogressive thaw slumps. The impacts of these landscape disturbances on impacted lake ecosystems manifest in several chemical and biological ways. These changes can also be inferred through the use of lake sediment records, the focus of the graduate research by several of Prof. Korosi’s students, working closely with Dr. Thienpont.

With a great passion for undergraduate teaching, Thienpont has taught many of the physical geography courses in the Faculty. He regularly teaches the classes focused on geomatics and geomorphology, including Rivers: Environment and Process, in which he has worked over the past two years to integrate the use of the hydraulic flume in his teaching. He was awarded the Department of Geography Undergraduate Teaching Award in 2019, and nominated for the President’s University-Wide Teaching Award (category: faculty less than 10 years experience) in 2021. Beyond teaching at the university, Thienpont co-hosts Core Ideas: A Paleolimnology Podcast, dedicated to all things related to lake sediments. Thienpont is a Fellow of the Royal Canadian Geographical Society, elected in 2015 for outreach associated with the 2014 Victoria Strait Expedition, which found HMS Erebus, one of the ships of the ill-fated Franklin Expedition in the Canadian Arctic.

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