Permafrost lecture notes: 15/3/21.
Write a research grant. In no more than 2 pages, describe your plan for monitoring Canadian Permafrost at a specific location using geophysical techniques.
Specifically, it would be interesting to tackle the following points:
•What is the problem that you have to address?
•Why you have chosen that specific location?
•What impact do you hope to monitor?
•Why is this impact important to this specific location?
•Which geophysical technique would you choose (ERT or GPR) and why?
There are no right or wrong answers to the choice of specific locations. The assignment is for you to try and communicate ideas clearly and succinctly.
Situation:We need to monitor Canadian Permafrost to better understand the changing conditions.
Task:We will pick a location to apply geophysical techniques based on limited funding.
Action:A field trip to conduct a geophysical survey either with Ground Penetrating Radar (GPR) or Electrical Resistivity Tomography (ERT).
Result: Through monitoring the changes to permafrost, we can better understand the potential environmental and infrastructure changes in the area.
Permafrost: ground with a temperature remaining at or below 0°C for at least two consecutive years.
Active layer: The top layer of ground subject to annual thawing and freezing in areas underlain by permafrost.
Ice-rich permafrost: Permafrost containing excess ice, defined as the volume of ice in the ground which exceeds the total pore space that the ground would have under natural unfrozen conditions.
Thaw slump: A slope failure feature caused by the melting of ground ice and downslope sliding and flowing of the resulting debris.
Thermokarst:landforms related to thawing of ice-rich permafrost. Thermokarstprocesses may cause lakes to enlarge, peatlands to collapse and landslides or thaw slumps to develop.
Talik:A layer or body of unfrozen ground in a permafrost area.
ERT: Electrical Resistivity Tomography. In Permafrost monitoring, high electrical resistivity may indicate high ice content, and lower resistivity may indicate water content (however, requires ground truthing).
Resistivity: measure of the difficulty of a current to flow through an unit length (Ohm.m).
GPR: Ground Penetrating Radar. The measurement of electromagnetic radiation waves that are reflected from subsurface structures (e.g., structures that have differing conductivity and dielectric permittivity properties)
Electrical conductivity: the measure of the ease at which an electric charge can pass through a material (𝜎, Sm-1).
Dielectric permittivity: characterizes the degree of electrical polarization a material experiences under the influence of an external electric field.