NWT RESEARCH DATABASE

Regions: North Slave Region

Tags: physical sciences, fossils, paleoclimatology, environmental change, archaeology, winter road, climatic history

Objective(s): To develop a comprehensive sub-decadal to centennial-scale late Holocene climatic history along a 2° latitudinal gradient in the central NT.

Project Description: Through analysis of sediment/water interface samples, freeze cores, and dendrochronology, the researchers intend to: i) develop a comprehensive sub-decadal to centennial-scale late Holocene climatic history along a 2° latitudinal gradient in the central NT, variously based on microfossils (pollen, diatoms, thecamoebians, chironomids), sedimentologic, cyclostratigraphic, stable isotopic, and elemental geochemical and grain size analysis of freeze cores from lakes along the route of the Tibbitt to Contwoyto Winter Road (TCWR); ii) determine the relationship between modern lake catchments and water property data in 70 lakes along the route of the TCWR, through analyses of surface sediment isotopic and elemental geochemistry, rock-eval pyrolysis of organic material, grain-size analysis, SEM/TEM, and microfossil proxies (e.g., thecamoebians, chironomids, diatoms); iii) develop transfer functions based on calibration training set results from 70 lakes arrayed along climatic gradient of the TCWR to quantify paleoclimatic data derived from microfossil (e.g. thecamoebians, diatoms, chironomids) and other proxies; iv) recognize any cycles or trends in the late Holocene climatic records archived in the lakes from sub-decadal to centennial scales using time series analyses with particular emphasis on estimates of paleo-ice cover variability and fire regimes; v) develop an annual-scale comprehensive temperature and precipitation history for central NT south of the tree-line spanning at least the last 200 years using dendrochronological techniques; vi) review NSMA journals for data predating instrument record to glean information on ice cover duration and seasonality to better calibrate our dendrochronological and paleolimnological data; vii) combine paleontological, isotopic and elementary geochemical and sedimentological results to distinguish the climatic significance of observed changes in lakes and dendrochronological data; viii) recognize climatic cycles or trends at annual resolution archived in dendrochronological records during the 20th century when anthropogenic greenhouse gas production increased significantly, and determine whether they deviate from previous climatic conditions; and ix) use cross-spectral time series analyses in conjunction with global climate model projections to predict possible trends in climate and ice cover along the TCWR in the coming decades. In order to document climate variability that has impacted the TCWR corridor through the Late Holocene, it is important to distinguish subtle changes recorded in the sedimentary archives of examined lakes and tree-ring records. Characterization of these parameters using an integrated multi-environment, multi-parameter approach will allow us to recognize subtle paleolimnologic and paleoclimatic (principally temperature and precipitation) variation with more precision than is achievable using a single methodology. Dominant scales and measurable characteristics of paleoclimate cycles and trends will be quantified, and they will be correlated with continental climate signals recorded elsewhere in North America. The results will be interpreted in the context of subtle variations in the strength of the oceanographic domains and air masses that influence climate in the region. There are innumerable lakes found along the length of the TCWR. The 70 lakes chosen for micropaleontological and geochemical analysis of sediment-water interface samples and subset chosen for coring will be selected to span as broad a climatic gradient as possible. A suite of water property data parameters will also be collected from the lakes (e.g. pH, dissolved oxygen, temperature, conductivity) to better characterize our data for the development of accurate calibration training sets. The researchers do not anticipate that recent (26 year history) industrial winter transportation activity on these lakes will have a large impact on surface diatom communities because the large volume of water in targeted lake basins would probably dilute the small amount of contaminants entering the lakes. Regardless, the team will collect and analyze bulk water-sediment interface samples for contaminants and will include some lakes from off the route of the TCWR as controls. Detailed core analysis will be restricted to portions of core records deposited within the last ~3500 years, which encompasses the Late Holocene when modern circulation and climatic conditions developed. With the constraint of operating under extreme subarctic winter conditions, and for health and safety reasons, sites will be chosen within a 100 km radius of rest stops along the TCWR. These ‘bases’ will include the Lockhart Lake Rest Stop (175 km) at the tree line and Lac de Gras Rest Stop (350 km) on the open tundra, and also possibly the Dome Lake Maintenance Camp (DLMC; 25 km). With operations at the Jericho Diamond Project near Contwoyto Lake mothballed it will not be possible to sample the end of the TCWR, as the road is not currently maintained. To ensure consistency as the researchers develop transfer functions for interpretation of core data, lakes selected for analysis will be of similar circular shape and simple morphometry. Undisturbed lake systems will also be studied that are not significantly influenced by upstream lakes or rivers. Lake sediments will be collected using sediment coring devices and will be collected from basins no deeper than 4-5 m to minimize the impact of cold bottom water temperatures on the productivity of benthic biological proxies, as most lakes in the region are dimictic. The primarily winter field research will require use of a truck mounted augers supplied by the TCWRJV, and freeze coring equipment, water property sampling devices (modified Ekman grabs or Glew corers), as well as subbottom imagery. Collection of dendrochronological cores will take place during summer, as it is not possible to core frozen trees. This research will require floatplane or helicopter support. This project is also consistent with a fundamental theme of the GSC, which is to better understand, document and conserve Canada's changing environmental history. As the supporting organizations are playing an integral role in the implementation of the research program they will have an ongoing understanding of the progress of the research. Co-investigators will also hold yearly meetings to brief stakeholders. This research will be of strategic importance to Canada in general, and the people of the Northwest Territories in particular, as it will provide sound scientific basis to guide policy makers and planners in their efforts to anticipate the impact of climate change on the viability of the TCWR. The first results from the project will be made available to stakeholders within two years of the start of the project and will be fully realized well within the National Science and Engineering Research Council Strategic Project Grant 10 year time frame. Preliminary research findings from this project were presented in November 2009 at the Yellowknife Geoscience Forum. The research team will continue to present research findings as the program progresses as various conferences and seminars. Publications arising from this project will be available to the public at the NWT-NTGO. Additionally, a website will be erected to transmit research updates and progress. As the supporting organizations are playing an integral role in the implementation of the research program, they will have ongoing communication and participation in the progress of the research. The fieldwork for this study will be conducted from August 2, 2011 to September 14, 2011.