NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: physical sciences, climate change, tree rings, ice wedges, Holocene, fire

Objective(s): To collect tree-ring and wedge-ice samples that will be studied to better understand changes in climate over the last 11,700 years and to identify lake sites that will be suitable for lake-sediment coring.

Project Description: This licence has been issued for the scientific research application No.5216. During the 2022 field season, the main objectives are to collect tree-ring and wedge-ice samples that will be studied to better understand changes in climate over the last 11,700 years and to identify lake sites that will be suitable for lake-sediment coring in the early spring field season. This fieldwork will focus on collecting wood samples for tree-ring analysis, ice samples from ice wedges for geochemistry analysis and identifying lake sites for future lake-sediment coring. The research team are particularly interested in finding old, dead trees that were living 1,000 or more years before present. Locating such old samples will be a major challenge. However, as the team learned from 2019 fieldwork, there is potential for old sub-fossil trees on the Campbell Dolomite Uplands. The team will spend 7 days in this study area, accessed by helicopter or boat from East Channel or Campbell Lake. The team will focus the search along the southern edge of Campbell Dolomite Upland where dead trees have fallen off the escarpment and accumulated, especially where trees may have been buried in peat, rocks and other debris which help to preserve dead trees over long periods of time. Cross-sections (or 'disks') of dead tree trunks will be collected by chainsaw. Additionally, cores will be collected from 40 living trees using an increment tree borer, which is harmless to the trees. The samples will be shipped to the University of Toronto for further processing and analysis. In the laboratory, the age of these samples will be determined using standard tree-ring cross-dating methods. Once the ages of the samples are known, the ring-widths and chemical measurements from the wood will be used to estimate the climate at the time the samples were alive using methods that have already been applied to younger samples in this area. Ice blocks will be sampled across the face of ice wedges exposed in the headwalls of thaw slumps. These ice block samples will be cut using a chainsaw. The research team will spend 4-5 days at the Richardson Mountain Foothills study area collecting ice samples and kept frozen in the field in coolers and in a walk-in freezer in Inuvik until the samples can be shipped to the University of Toronto for further processing and analysis. In the laboratory, stable H and O isotope ratios will be measured from the ice samples to understand long-term changes in winter climate at the time the ice veins were formed. The team will radiocarbon date organic material within the ice veins to determine the age of the ice, so that climatic information from the stable isotopes can be organised into a long time-series and used to reconstruct winter temperature changes in this region over the last 11,700 years. The research team will search for a suitable lake for future lake-sediment coring, to be collected in spring. The team will simply focus on finding a suitable lake for the future research. The team have identified two lakes of interest on this application (M Lake and L Lake – informal names), which are located on the Campbell Dolomite Uplands and have been studied previously. The team will visit these sites and surrounding lakes to assess their suitability for future lake-sediment coring research, and to take field notes about the surrounding catchment. The team will measure lake depths with a drop line and an inflatable raft. Deep lakes with a small surface area are preferred to ensure a relatively undisturbed lake-sediment record. A small lake sediment sample from the lake edge and lake water will be collected and analysed to determine the concentrations of bulk carbon and organic residues of interest (pyrogenic PAHs) that will be the target of the coring expedition. These reconnaissance research objectives will require 1-2 days of fieldwork. Upon successful completion of this research, the principal investigator (PI) will ensure that all reports and publications stemming from this work will be forwarded to the Aurora Research Institute (ARI) and local stakeholders (Gwich’in community in Inuvik) whose traditional lands overlap with our study area. The PI is also interested to give a public presentation in Inuvik (possibly hosted at ARI) upon completion of this project, and will reach out to ARI staff to help coordinate this. In the scientific community, the PI anticipate this research will be presented in the peer-reviewed literature and at international geoscience conferences such as the American Geophysical Union Fall Meeting. The fieldwork for this study will be conducted from June 15, 2022 to August 31, 2022