NWT RESEARCH DATABASE

Tags: climate change, limnology, permafrost degradation, sediment, environmental change

Objective(s): To continue to document and understand the impacts of recent climate change on northern terrestrial and aquatic ecosystems.

Project Description: This proposed research in 2014 will continue the long term objective of documenting and understanding the impacts of recent climate change on northern terrestrial and aquatic ecosystems. The short term objectives of this research are: 1) to investigate the impacts of permafrost degradation and subsequent thaw slumping on freshwater ecosystems; 2) to examine the limnological implications of drained lakes on aquatic systems; and 3) in anticipation of the construction of the Inuvik-Tuktoyaktuk all-weather road, the research team will examine the impacts of dust on freshwater lakes using small lakes/ponds along the Dempster Highway near Fort McPherson as the study sites. Lake sediment sampling The lake sediment sampling will occur during the late winter/early spring season and during mid-summer each year. The late winter/early spring field work (late April - early May) will occur while the lakes are still ice covered. The research team will target small lakes to recover long sediment records spanning the histories of these lakes. Using the ice cover as the coring platform the research team will use a Livingstone piston corer or percussion type coring system to recover longer sediment profiles from these lakes. These coring systems allows the research team to collect several meters of sediment from lakes with depths varying from a few meters to 10-15 meters. A gas powered ice auger will be used to cut through the ice cover and a spill clean-up kit will be carried at all times. The research team will aim to only fuel the auger up at the airport in Inuvik to reduce the possibility of any accidental spills at the field sites. A member of the research team will examine these cores for their sub-fossil diatom assemblages. Surface sediment cores from the bottom of each lake will also be obtained. A Glew gravity coring system will be used to recover undisturbed sediment profiles from the lake bottom. None of the coring systems used in this study will cause any significant disturbance to the lake bottom sediments. At each lake water samples will be collected to analyze for water chemistry. Within each proposed terrain unit (till plain, lacustrine and unglaciated) 1-2 lakes will be sampled. Lakes that are impacted by retrogressive thaw slumps will be targeted at present to confirm the paleo proxy signature(s) that best characterizes thaw slumps in contemporary sediments. Based on the findings in recent sediments, the research team will apply those findings to older sediments from the Holocene to determine the occurrence and timing of thaw slump activity in the past. Specifically, the research team expects a change in particle grain size distribution and organic content due to the development of a retrogressive thaw slump along the shoreline of an impacted lake when the thaw slumps are active. The studies of contemporary sediments from north of Inuvik indicates this methodology is robust to capture these events in the past. Therefore, the research team expects that retrogressive thaw slumping in the past can be tracked using this proxy data source. Contemporary studies also indicate that dramatic changes in diatom communities can also occur in response to slumping. Therefore, the research team will also rely on these biological indicators to track the occurrence of slumping during the Holocene. Particle grain size and organic content of the sediment will be used to estimate the timing of the onset and stabilization of permafrost slumps, as will the analysis of diatoms. Impacts at higher trophic levels of these aquatic systems (e.g., cladocera and chironomids) will also be examined. Near Inuvik, the research team have identified lakes affected by recent permafrost thaw slumps in the Noell Lake region (headwalls ~10 m high and several 100s of meters across) and are comparing these lakes to ones with no slumps. The research team are examining the response of lakes in the different landscape types described above (organic rich lacustrine deposits; till plain and unglaciated terrain), to examine the nature of change experienced in these lakes due to 20th century warming. Near Ft McPherson, megaslumps similar to those north of Inuvik, but much larger in scale (headwalls 10s of meters high and >1km across), also occur. The research team will use particle grain size distribution, organic content and biological indicators preserved in lake sediments to track the occurrence of these slumps and megaslumps during the Holocene. To examine the impacts of road dust on these small lakes/ponds, the research team will also collect sediment cores from lakes along the Dempster Highway west of Fort McPherson. During the summer months these lakes receive inputs of dust as traffic moves along the Dempster. The impact that this dust has on the lake systems has not been investigated previously. The research team will examine algae (e.g., diatoms) from these lakes during the past 100 years to determine if the construction of the Dempster Highway impacted the algal communities and the rate at which sediment has accumulated in the lakes. The same sampling techniques described above will be used to collect the sediment cores. To communicate the research results to the nearby communities, the research team will submit all theses and publications to the library at the Aurora Research Institute. The research team will also communicate the results via northern meetings such as the Geoscience Forum and the Cumulative Impacts Monitoring Program Results Workshop. The research team is happy to give community presentations in any of the local communities and work with school children or college students to teach them more about our work. The fieldwork for this study will be conducted from April 13, 2014 to September 15, 2014.