Base de données de recherche des TNO

étiquettes: physical sciences, permafrost, climate change, remote sensing, UAV, ground penetrating radar

Objectif(s): To investigate the possibility of linking field-measured characteristics of tundra landscapes with remotely-sensed data.

Description du projet: The proposed project will investigate the possibility of linking field-measured characteristics of tundra landscapes (e.g., active layer thickness, soil moisture, plant distribution and ecosystem composition, etc.) with remotely-sensed data. The overall objective of the project is to identify the connections that exist between observable surface properties and their associated subsurface/permafrost conditions. The findings will contribute to an increased understanding of surface-subsurface interactions at multiple spatio-temporal scales, which in turn will allow for further understanding of how permafrost landscapes in the Western Canadian Arctic respond to climate change. This research is an international cooperation between Carleton University (Ottawa, Canada), the Government of Canada (i.e. Environment and Climate Change Canada), the University of Würzburg (Würzburg, Germany), and the Alfred Wegener Institute - Helmholtz Centre for Polar and Marine Research for Polar and Marine Research Bremerhaven, Germany) and is academic in nature. The project is funded by the German Research Foundation (DFG). The fieldwork will commence on August 14th and end on August 31st, 2018. Dates are approximate and are subject to change under certain circumstances (e.g., travel delays, inclement weather, etc.). A majority of the 2018 fieldwork will be completed along the Dempster Highway between the Peel Plateau, NT (67.05°;-136.20°) and the Tuktoyaktuk Peninsula, NT (69.44°;-133.02°). Field sites will be visited on a daily basis with a vehicle (e.g. pickup truck). Sampling locations will be adjacent to highway (within 500 meters) and accessed by foot. It is anticipated that a total of 20 to 30 field sites will be sampled along the highway between these two locations. Additional field sites will be located on Richards Island, NT (69.36°;-134.58°). Access to Richards Island will be by air (e.g., helicopter). A total of three to five sampling sites will be visited at this location. Minimally-invasive electric resistivity surveying will be conducted at each field site. Thirty-six small steel rods with a diameter of about 2 centimetres and a length of 30 centimetres will be placed in the ground at intervals of 5 meters. These rods will be connected with a cable; the electrical resistivity of the ground at various depths system will then be measured. This instrument/technique allows for the investigation of active layer thickness, subsurface moisture conditions, ground-ice content, and permafrost table depth. All probes placed in the ground are non-permanent and will be removed from the ground once measurements are taken. The electrical currents used by the system are low voltage and will have no impact on plants or animals. Non-invasive ground penetrating radar (GPR) data will be recorded at each field site. The GPR system will be placed on the ground at intervals of 1 meter along transects at each sampling location. The system works by actively sending electromagnetic pulses into the ground at frequencies of 100 and 200 MHz (i.e. microwaves). The pulses reflect and scatter at layers in the ground that have different physical properties. For example, reflections of the GPR signal will be returned at the permafrost table depth. GPR allows for a highly detailed measurement of active layer thickness within the upper soil layers (i.e. properties of the subsurface) without the need for digging, thus leaving soils and plants undisturbed. Minimally-invasive steel rod probing of the active layer thickness will be conducted at intervals of 1 meter at each sampling location. A steel rod with a diameter of about 3 centimetres and a length of 100 centimetres will be pressed into the ground until the permafrost table is reached. This technique allows for the quick measurement of active layer thickness without the need for digging. At the sampling locations, battery-powered data loggers and probes will be installed to measure ground temperature and soil moisture for a period of 1 year. The combined ground probe/data logger units, which have a length of about 15 centimetres and a diameter of 2 centimetres, will be manually pressed into the ground to a maximum depth of 20 centimetres. Their small size and shallow installation depth will be minimally invasive to tundra ecosystems; probes will be recovered without digging. The collection and read-out of the loggers will be completed during the 2019 field season. Non-invasive spectral reflectance data will be recorded at each field site. The spectral properties of the ground surface (i.e., that of soils and vegetation) will be measured at each sampling location using a battery-powered hand-held spectrometer. A spectrometer is a light-sensing device that records reflected electromagnetic energy between 400 nm and 2500 nm without making contact with the surface. Spectra of each field site will be used for calibrating optical remote sensing data, model building, and creating spectral library of the various surface types. Each field site will be photographed using a small (under 2 kg), battery-powered, unmanned aerial vehicle (UAV). The in-air-time of this UAV will be approximately 10 minutes for each plot and the UAV will be raised to a maximum elevation of 60 meters (200 ft). The UAV will carry standard photographic equipment (i.e. a camera). The images recorded by the UAV will allow for the creation of a digital representation of the terrain surface and will support the vegetation mapping efforts. The low altitude, small airframe size, and minimal flying time will be minimally disruptive to local wildlife. Further, the UAV will not be used in the presence of wildlife, nor will it be used to photograph or harass wildlife. The results of the study will be communicated through academic reports/thesis and scientific publications (journals and conference proceedings). All documents generated will be sent to all parties, communities, organizations affected by this research and those who may be interested. The fieldwork for this study will be conducted from August 14, 2018 to August 31, 2018.