NWT RESEARCH DATABASE

Tags: physical sciences, climate change, permafrost degradation, slumping, freshwater ecosystem, tree growth

Objective(s): To examine the impacts of climate and environmental change on freshwater ecosystems in the Inuvik region across a variety of spatial and temporal scales. Specifically, the research team are examining the impacts of permafrost degradation and subsequent thaw slumping on freshwater ecosystems and the impact of climate change on tree growth in the Mackenzie Delta.

Project Description: The objectives of this research are to examine the impacts of climate and environmental change on freshwater ecosystems in the Inuvik region across a variety of spatial and temporal scales. Specifically, the team is examining the impacts of permafrost degradation and subsequent thaw slumping on freshwater ecosystems and the impact of climate change on tree growth in the Mackenzie Delta. Lake sediment sampling The lake sediment sampling will occur during the late winter/early spring season and during mid-summer in 2013. 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 most of the Holocene. Using the ice cover as the coring platform a Livingstone piston corer will be used to recover longer sediment profiles from these lakes. The piston coring system allows the research team to collect several metres of sediment from lakes with depths varying from a few metres to 10-15 metres. A gas powered ice auger will be used to cut through the ice cover and a spill cleanup kit will be carried at all times. The aim is to only fuel the auger up at the airport in Inuvik to reduce the possibility of any accidental spills at the field sites. These cores will be examined 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 obtain 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 terrain unit (till plain, lacustrine and unglaciated) 1-2 lakes will be sampled. Using the ice cover as the coring platform, the team will collect lake sediment cores with the aim of recovering sediments spanning the entire Holocene. 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. Both gravity and percussion-type coring systems will be used to recover the sediment cores. Based on the findings in recent sediments, the research team will apply those findings to older sediments from the early Holocene to determine the occurrence and timing of thaw slump activity in the past. The 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 LOI of the sediment will be used to estimate the timing of the onset and stabilization of permafrost slumps. Timing and impact of the slumps will also be determined through the analysis of diatoms. Impacts at higher trophic levels on communities of cladocera and chironomids will also be examined. Near Inuvik, lakes affected by recent permafrost thaw slumps (headwalls ~10 m high and several 100s of metres across) have been identified and are comparing these lakes to ones with no slumps. The team is 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. Longer cores spanning the full Holocene have been collected previously. Near Ft McPherson, megaslumps similar to those north of Inuvik, but much larger in scale (headwalls 10s of metres high and >1km across), also occur. Particle grain size distribution, organic carbon content and biological indicators preserved in lake sediments will be used to track the occurrence of these slumps and megaslumps during the Holocene. Tree sampling The other aspect of the research activities will focus on the examination of tree growth at two sites in the Inuvik region. Sites will be visited north of Inuvik near the Eskimo Lakes to develop a long tree ring record from that region. The team will also aim to collect tree cores from the Campbell Dolomite Upland. Approximately 30 trees will be sampled at each site. A small core (~4.3 mm in diameter) is removed from each tree. If dead snags or old logs are present on the ground, 1-inch thick cookies will be cut from these samples. In the case of dead standing snags trees that appear to be nesting sites for any birds will not be disturbed. The research team anticipate visiting approximately 3-5 sites during the tenure of this research licence. The results of all components of this project will be communicated in a number of media including, but not limited to, written reports, scientific publications, oral presentations, and poster presentations. Copies of these communications will be made available to the Aurora Research Institute upon completion. This research will also form a significant component of the thesis research of a number of students. These theses will be submitted to the ARI once they have been accepted by the respective School of Graduate Studies. The fieldwork for this study will be conducted from April 15, 2013 to December 31, 2013.