Best practices for using electrical resistivity tomography to investigate permafrost
Une étude récente de Teddi Herring suggère des moyens d'améliorer la façon dont la tomographie par résistivité électrique (Electrical Resistivity Tomography ou ERT) est utilisée pour le pergélisol et met en évidence les progrès récents dans cette approche. L'ERT est une technique extrêmement utile pour étudier le pergélisol, car elle nous permet de connaître la profondeur de la couche de pergélisol et d'identifier les zones contenant de la glace.
Le nombre de publications d'études utilisant l'ERT pour analyser le pergélisol a été multiplié par 10 au cours des 20 dernières années, et bien que des défis demeurent et qu'il n'existe pas encore de « meilleure façon » unique de le faire, l'étude formule des recommandations pour mener des études ERT afin de maximiser l’utilité des données existantes et futures.
Herring T, Lewkowicz AG, Hauck C, et al. Best practices for using electrical resistivity tomography to investigate permafrost. Permafrost and Periglac Process. 2023; 34(4): 494-512. doi:10.1002/ppp.2207
Carte mondiale résumant les emplacements des sites de terrain où la tomographie par résistivité électrique (ERT) a été utilisée pour étudier le pergélisol (2000 à 2022) sur la base de la recherche documentaire.
The Northwest Territories Thermokarst Mapping Collective: a northern-driven mapping collaborative toward understanding the effects of permafrost thaw.
Un article du Thermokarst Mapping Collective (TMC), une collaboration de recherche visant à inventorier systématiquement les indicateurs de sensibilité au dégel du pergélisol par cartographie et évaluations aériennes dans les Territoires du Nord-Ouest (NT), au Canada, a documenté le premier inventaire complet des terrains thermokarst et d’indicateurs sensibles au dégel pour une région de 2 millions de kilomètres2 carrés du nord-ouest du Canada.
Kokelj, S.V. et al. The Northwest Territories Thermokarst Mapping Collective: a northern-driven mapping collaborative toward understanding the effects of permafrost thaw. Arctic Science. E First.DOI: 10.1139/as-2023-0009.
Organisation du projet, rôles et implication institutionnelle par localisation.
Matthis Schindler has been working with us since the start of the year, so it’s about time to properly introduce our newest member of the PermafrostNet community, and tell you what he’s doing while he’s here in Ottawa with us.
Matt joined us as an intern for three months to work with both NSERC PermafrostNet and the research group of Stephan Gruber. He is an MSc student at the Karlsruhe Institute of Technology (KIT) in Germany where he studies Geoecology, which is an interdisciplinary degree program that combines different environmental and nature science courses like geology, climatology, biology, hydrology, zoology, remote sensing and many more. His interests lie in the connections and dependencies of ecosystems as well as the resulting processes.
At PermafrostNet, he is taking responsibility for a range of communications, including the winter 2023 newsletter, seminar series videos, website content and social media. He is also working with Tristan MacLean to ensure a smooth and successful International Day of Permafrost, tackling organizational duties like communicating with speakers, scheduling and handling different time zones from Vancouver to Nepal and all the other behind-the-scenes tasks that come with preparing an international conference.
“This internship has already given me a lot of insight into the importance of thorough background work for both handling scientific data and organizing a big event like the International Day of Permafrost!”
You can find further information on the International Day of Permafrost, participating organizations, the schedule and the registration link ici.
Trail Valley Creek Research Station by Charles Gauthier
In early June, I had the chance to be part of a team of scientists heading to the Trail Valley Creek Research Station. Located a 30-minute helicopter ride away from Inuvik, NT, Trail Valley Creek supports many different long-term projects. My colleague, Vincent Graveline, and I were there for two weeks during which our goal was to launch weather balloons as part of Vincent’s MSc research on planetary boundary layer dynamics. Attached to the balloons were detachable probes equipped with several instruments reading pressure, altitude and, most importantly, air temperature. Our goal was to observe the height of the planetary boundary layer in spring. The depth of the planetary boundary layer affects the land-atmosphere interactions, and its depth varies depending on land cover and atmospheric conditions. With the boreal tree line shifting northward, information on the planetary boundary layer over the tundra and a nearby forest stand will help to better understand the consequences of boreal treeline shifts on tundra-atmosphere interactions.
A typical day could be split in three parts: the launch of the balloon, the wait for it to climb to a specific, pre-determined altitude and the retrieval of the probe. We walked over 70 km in the tundra, a radio receiver in hand looking for the white probe the size of a styrofoam cup with a single flashing LED light. This research trip allowed me to visit a changing arctic tundra research site where permafrost is rapidly thawing, a sight that I don’t normally see while modeling permafrost change from the comfort of campus. Science aside, the landscapes, the berries and the sneaky ptarmigans were worth all the soreness in our legs!
In August, I went to the Scotty Creek research station in the Northwest Territories. As a modeler, being able to go to the field was a great opportunity: it allowed me to better understand one of the sites I am trying to model.
The goal of my project is to simulate the climatic conditions of higher latitude regions, often underlain by permafrost, in a more accurate way. To achieve this, I will be including mosses in CLASSIC, the Canadian Land Surface Scheme Including Biogeochemical Cycles, as a plant functional type. Seeing Scotty Creek improved my understanding of just how much mosses are important in northern regions.
I was in Scotty Creek to help with a drone data collection project: I climbed an eddy covariance tower to ensure there was always someone who could see the drone, while the drone pilot was back in camp. This allowed me to see the drone above the trees.
I also took active layer depth measurements around the eddy covariance tower. This allows us to monitor permafrost thawing, which happens rapidly at Scotty Creek. We can see the impact it has on trees at the limit between the forested permafrost plateaus and the permafrost free bogs: they start to tilt from the instability of the ground.
For several scientists and students, the highlight of research is fieldwork. Sometimes, to produce high-quality data in permafrost-related research, the study sites can be isolated. Now, they are not only remote because they are north (from a southerner’s perspective), but rather because they are secluded from the communities. For instance, the Trail Valley Creek (TVC) research station is situated north of Inuvik, NWT, in the middle of the tundra. As field season is extremely busy and dense, the researchers rarely have time to exchange and connect with local communities. They live and work out of the research station for most of the time they spend in the region. This poses the issue of creating a gap between researchers and community members. Indeed, it feels counterintuitive since research’s primary goal is to inform decision-making and produce tools to build resilience for local communities.
In the past year, thanks to funding from Future Skills Center, NSERC PermafrostNet, IVADO and other sources, the situation is in remediation. During our fieldwork in TVC, my colleagues and I had the opportunity to work with several members of the community. One of our colleagues, Camellia, planned a marvellous barbecue with family and friends from Inuvik and, at last, scientists were stepping out of the research station and into building relationships with folks from the community. These kinds of activities and partnerships at the sites are concrete steps towards crafting research projects for, and with, the community and ultimately bridging the gap between scientists, students, and community members.
Finalizing a “nested” Arctic tundra flux set-up by Oliver Sonnentag
After several years of planning, and delayed by the Covid-19 pandemic, the Sonnentag lab completed a “nested” Arctic tundra flux set-up (landscape > ecosystem > plot) at Trail Valley Creek Research Station near Inuvik, NT. The flux set-up comprises three eddy covariance (EC) towers, and automated and manual chamber systems. The 20-m landscape EC tower measures net carbon dioxide, methane, and latent and sensible heat exchanges between the terrestrial-aquatic landscape (including extensive shrub patches) and the atmosphere. Given prevailing wind characteristics, nested within the landscape flux footprint (i.e., the temporally varying source area) are a 5-m and a 7-m ecosystem EC towers, one “seeing” fluxes originating from polygonal tundra, or, depending on wind direction, a small lake, and one “seeing” fluxes originating from mineral upland tundra, respectively. Nested within the ecosystem flux footprint (mineral upland tundra) is a custom-made chamber system to measure plot-scale net carbon dioxide and methane exchanges. The system comprises 18 automated chambers (nine ‘transparent’ and nine ‘opaque’ chambers), each with three replicates for three distinct plant communities: dwarf shrub, tussock, and lichen cover. Manual chamber measurements are collected from additional plant communities and land cover types (e.g., polygonal tundra and lakes). The chamber measurements are complemented by ancillary measurements of air and soil temperature, photosynthetic photon flux density, active layer depth, plant community composition, spectral characteristics, greenness, and soil moisture, temperature, and oxygen. Additional measurements to understand the underlying biogeochemical processes governing the carbon dioxide and methane sink-source behaviour: soil physical-chemical properties and gas profile dynamics, isotopic signal of d13C in soil carbon dioxide and methane, soil pore water and lake nutrient concentrations, quality and microbial degradability of aquatic dissolved organic matter and microbial community composition. The goal of these comprehensive observations is to shed light on how tall shrub encroachment affects vegetation diversity and associated surface-atmosphere interactions across scales in the Southern Arctic ecozone of western Canada.
Community training workshops in the NWT: Yellowknife (2 – 13 May) and Inuvik (6 – 9 September) by Oliver Sonnentag
The Sonnentag lab hosted two community training workshops this summer. With 15 (Yellowknife) and 10 participants (Inuvik), both workshops were well attended. Primarily funded through the Future Skills Centre, the first week of the workshop in Yellowknife included safety certifications for wilderness first aid, fall protection and wildlife awareness. The second week focused on hands-on training in micrometeorological instrumentation and scientific instrumentation maintenance, used in combination with traditional experiences and perspectives.
Presentations, practical sessions and discussions were led by industry, academic, territorial government non-governmental organizations and Indigenous government representatives. The workshop in Inuvik was hosted through Sonnntag’s involvement in an IVADO-funded project on artificial intelligence, biodiversity and climate change. Presented by ASPECT-drone solutions, the focus of the workshop was on preparing participants for the Small Advanced Exam required by Transport Canada for advanced drone operation.
Permafrost subsidence is a big problem for northern roads. It can reduce their stability, cause cracks to appear, and if left unchecked may even render the roads inoperable.
Snow is an excellent insulator. Like a thick down jacket, it traps air in the pockets between the accumulated snowflakes, protecting the ground from cold air temperatures. When snow becomes compacted — by piling it up beside a road, for example — the air is squeezed out and the properties of the snow change to allow heat through more easily, like a thin windbreaker.
The goal of Patrick Jardine’s research is to improve the longevity and sustainability of infrastructure in permafrost regions by developing active snow management techniques for the purpose of reducing thaw subsidence along highways.
Scientists do not always account for mosses, simple, small and ubiquitous plants in their climate models, even though doing so could help us better understand climate change.
Most plants are “vascular”. This means they can control the water entering or leaving their tissues via stomata, tiny pores in leaves and, sometimes, stems that allow gasses to enter and exit the plant. Mosses, however, have no stomata.
The goal of Rose Lefebvre’s Master’s research is to include mosses as a vegetation type in Environment and Climate Change Canada’s Canadian Land Surface Scheme Including Biogeochemical Cycles climate model – called CLASSIC for short.
Rose is a student at the Université de Montréal under the supervision of Dr. Oliver Sonnentag (Université de Montréal) and Dr. Joe Melton (Environment and Climate Change Canada). Her research focuses on using the Canadian Land Surface Scheme including Biogeochemical Cycles model (CLASSIC) to reproduce the climatological conditions at Scotty Creek, in the Northwest Territories.
Students in NSERC PermafrostNet’s Theme 1, led by postdocs Michel Paquette and Samuel Gagnon, have digitized 2 historic reports (Hodgson, 1982 et Hodgson, & Nixon 1998) containing profile data from more than 250 boreholes in polar desert environments. Information on ground ice content, ground ice descriptions, soil type, grain size and more, is now available for re-use in a variety of formats using the PermafrostNet ERDDAP data server. Data can be accessed and searched from a single borehole, or from the entire report. Both the data et metadata can be downloaded as a csv.
These data take advantage of the new additions to the CF standard name list to make the data more interoperable and reuseable. Nick Brown has also documented a set of standardized variable names and their associated CF Names – Standardized permafrost variable names and equivalent CF Names. This technical note document describes the variables that are on the NSERC PermafrostNet ERDDAP and their associated metadata. It can also be used as a guide to connect commonly-used permafrost variables to the recommended CF standard_name.
One of the steps involved in redistributing these data on the ERDDAP server is converting them into the NetCDF data format. This is a way of distributing scientific data that is gaining popularity because it is self-documenting and uses a several well-established community-built standards to increase data interoperability. These include the CF conventions and the Attribute Convention for Data Discovery (ACDD). There are a number of data distribution platforms (ERDDAP, THREDDS, HYRAX) that can be used to easily distribute NetCDF files using a standardized API and web interface. NSERC PermafrostNet uses ERDDAP as a data distribution platform for these reasons and because it offers a graphical web interface for those who want to access data interactively. It also makes it possible to adopt the associated data standards as one way to increase the interoperability of permafrost data generated by and used within the network.
The NetCDF format and associated standards were originally developed for atmospheric, oceanographic and climatic data, so there are few examples of these files being used to represent observed soil profiles or geotechnical borehole data, and the CF standard_name table lacks many variables that are relevant to permafrost science. A new technical document – Representing geotechnical borehole profile data with netCDF and ERDDAP provides considerations and recommendations for structuring observed borehole profile data in a way that complies with existing standards, is distributable on ERDDAP, and useable by permafrost scientists.
Permafrost is changing as Earth’s climate warms. Across northern Canada, the effects are already apparent: slow-moving landslides threaten highways, buildings are sinking and collapsing, and traditional food sources are threatened. The annual cost of permafrost thaw in the Northwest Territories has been estimated at $51 million.
Because permafrost occurs underground, data about permafrost are difficult and costly to collect. Once they’ve drilled a borehole, scientists insert instruments to record ground temperatures at regular intervals, sometimes collecting measurements every hour. This is exactly the kind of information permafrost modellers need. However, once these data have been used for a particular experiment, they might not be shared in a way that is easily accessible for other researchers. In fact, they may not be shared at all.
In Whitehorse, Panya Lipovsky, a surficial geologist with the Yukon Geological Survey, has been working to create a permafrost database for the Yukon. The effort is part of a Canada-wide trend to make historic permafrost datasets more available.
Nick Brown is the NSERC PermafrostNet data scientist, where he develops tools to support permafrost simulation and data handling and also promotes the adoption of standards for permafrost data
“So, it’s frozen mud?” my roommate asks when I try to explain my research topic to him. Since starting his own research in quantum physics, he has mastered the art of simple idioms. Perks of the trade, I suppose.
This frozen mud, however, covers half of Canada’s land mass. It is the soil on which many Indigenous communities are built, and it is thawing at alarming rates. With northern latitudes warming twice as fast as the rest of the world, scientists are racing to understand permafrost dynamics. Having this knowledge can help us ensure that Canada is equipped to face the coming climate crisis………..
Charles is a student at the Université de Montréal under the supervision of Dr. Oliver Sonnentag (Université de Montréal) et Dr. Joe Melton (Environment and Climate Change Canada). His research aims to reduce uncertainty in predicted soil carbon dynamics.
Everyone’s been there. You are about to publish your dataset, but you’ve just spent the last half-hour trying to decide on the best formatting and naming conventions. Should that column be named “ground temperature”, “soil_temperature”, or just “Tg”? Maybe you should include units too; “ground_temperature_degree_C” has a ring to it. But how will other people know exactly what your dataset represents? Good metadata is the answer.
You may not realize it, but there are resources to help you in this situation. The CF Standard name table is a curated list of terms used to unambiguously identify the kinds of measurements in a dataset. For self-describing formats like netcdf, you can include these attributes directly in your data file, following the CF standards. Or, if you are publishing your data in a text file, like a CSV, you can include the information about each column in your dataset in a separate metadata file. This way, the name of your data column doesn’t have to do so much work describing itself.
Michel Paquette, Theme 1 Post-doctoral Fellow (Université de Montréal, NSERC PermafrostNet) and I have coordinated the inclusion of 12 additional permafrost-related terms (see table below) in the latest release of the Standard Names vocabulary (version 78). These terms will be particularly useful for field scientists wanting to make their published datasets more interoperable and for data publishers who host permafrost-related data. An additional 14 terms relevant to permafrost science have since been requested. The addition of permafrost-related terms contributes to improved data interoperability with the atmospheric science and modelling communities, where the CF terms are widely used.
For an up-to-date list of permafrost-related terms added to the CF names list by NSERC PermafrostNet, visit the Data Standard Recommendations page.
