Base de données de recherche des TNO

étiquettes: physical sciences, climate change, lake ice, food web, lake productivity, prediction models

Objectif(s): To improve our knowledge on lake ice and its effect on food webs/productivity in small Arctic lake systems in order to better predict changes that could occur under changing climate.

Description du projet: The overall objective of this research component is to improve our knowledge on lake ice and its effect on food webs/productivity in small Arctic lake systems in order to better predict changes that could occur under changing climate. The methodology described here pertains to research activities involving an automated ice buoy and instrumented subsurface mooring system for continuous monitoring of weather conditions, lake ice cover (formation, growth over winter, breakup in spring), light penetration into the lake (through ice in winter), and water quality in Noell Lake. All other research activities related to this work have been reviewed/approved/fully-licensed for 2011 as part our overall research project “Hydro-ecological Responses of Arctic Tundra Lakes to Climate Change and Landscape Perturbation” (ARI Scientific Research Licences 14832 & 14833). The ice buoy and mooring system is composed of two parts: (i) a lake buoy with weather instruments on top (to measure sunlight, windspeed, wind direction, air temperature, relative humidity, and air pressure), and sensors along its length below the waterline to measure light penetration into the lake water (through ice in winter) and to measure water quality information near the lake surface (temperature, dissolved oxygen, and water chemistry); (ii) a subsurface mooring which includes a tethered array of water quality probes to measure temperature, dissolved oxygen, and water chemistry at a variety of depths down to the lake bottom, and an Ice Profiler Sensor (IPS) to measure the development, growth and decay of the lake ice cover through the cold season. Data collected by the subsurface mooring system is transmitted to the adjacent Ice Buoy using an acoustic modem located at the base of the mooring. These data are added to the data collected by the instruments on the buoy, and then transmitted by the buoy to a satellite which, in turn, transmits to a base station located at the Water & Climate Impacts Research Centre (W-CIRC) located at the University of Victoria by satellite telemetry. There is a 2-way capability using the satellite telemetry which allows remote system management of both the ice buoy and subsurface mooring components. The system is designed for year round deployment and due to an acoustic release on the subsurface mooring; all components are recoverable and will be removed from the lake at the end of the research project. The Ice Buoy and Mooring System was pre-assembled and then deployed by helicopter in late September, 2010, prior to freeze-up of the lake. The buoy was lowered into the lake near the shore, and then towed by boat to its mooring location. A location was selected in Noell Lake for installation of the buoy system – after consulting with local people to ensure that the system would not interfere with the use of the lake for ice fishing, transportation (e.g. snowmobile trails), local hunting and harvesting activities, etc. The lake will be visited through the winter to check on the buoy system and to take manual lake ice thickness measurements to compare with those measured by the buoy system. Now that the buoy system has been deployed, fieldwork will involve visiting the buoy each year: (i) in late-June/early July (after all the ice is gone) to replace the water quality instruments with fresh ones, and to attach an additional water quality sensor to the buoy at 1 meter depth for the ice-free period; and (ii) in late September before the ice cover starts forming to remove the 1 meter depth water quality sensor (else it would freeze into the ice-cover damaging the instrument). At the end of the study, the ice buoy and mooring will be removed from the lake by helicopter by simply hooking up a tether to the buoy, lifting it out of the lake, and flying it back to Inuvik. Data collected using the buoy system will be used to monitor lake ice development through the entire ice season (initial freeze-up in the fall, its growth through winter to its maximum thickness, and breakup in spring). Lake water quality measurements collected continuously through the entire year will be used along with our other field observations for analyses related to food webs/productivity as described in our previously approved/licensed project descriptions. The entire dataset including our new information on lake ice will allow us to look at the effects that lake ice has on food webs/productivity. Computer modelling activities will also be conducted to validate lake ice models using our new information on lake ice. Other field assistants and students needed to assist in the project will be identified through the Inuvialuit Joint Secretariat and the Aurora Research Institute. Through a Grants & Contribution Agreement from Environment Canada combined with Aurora Research Institute (ARI) in-kind support, ARI is undertaking research contributing to our project. ARI helps to: (i) conduct and support the collection of laboratory and field-based biogeochemical, hydrological and ecological information, and (ii) to organize and convene community consultation / outreach meetings related to the dissemination of research results. To communicate results to individuals and communities in the North, the researchers plan to hold annual community-based meetings and consultations in northern communities to inform local residents in the region of the nature and significance of the research, what the team is trying to find out and why, and to provide updates on what has been learned (key findings) as the work progresses. The researchers will also visit the schools to reach out to the youth. Information will also be made available through a project website, posters, brochures, fact sheets, etc. The fieldwork for this study will be conducted from July 15, 2011 to December 31, 2011.