The decline of Arctic sea ice extent is one of the most spectacular signatures of global warming, and studies converge to show that this decline has been accelerating over the last 4 decades, with a rate that was not anticipated by forecasting models. In order to improve these models, relying on comprehensive and accurate field data is essential. While sea ice extent and concentration are accurately monitored from microwave imagery, we are still lacking an accurate and comprehensive measure of its thickness. In addition, models could benefit from including other observables related to the ability of the ice cover to resist cracking and to heal/reform when cracking occurs.
The ICEWAVEGUIDE project introduces a methodology based on seismic waves propagation to meet these needs, and aims at completing current knowledge so far acquired mostly from Radar and Sonar data. Based on continuous, passive recordings of seismic ambient noise at an array of geophones, the ICEWAVEGUIDE project will demonstrate that propagation of leaky seismic waves guided in the thickness of the ice can be measured. Guided waves being sensitive to the geometrical and mechanical properties of the waveguide, the measures will be inverted to recover important markers of ice mechanical resistance, such as thickness, elastic properties and damage level.
This new methodology was successfully tested on data acquired in a lab-scale experiment. The experiment consisted in leaving a water tank in a cold room so as to grow an ice layer at its surface. While its thickness was increasing, ultrasonic guided waves were generated in the ice with a piezoelectric source, and measures were subsequently inverted to monitor the thickness and mechanical properties of the ice. The goal of the proposal is to extend this proof of concept on actual geophysical data acquired on a frozen lake in Svalbard (Norway) during winter.
The project will be decomposed in 5 packages: data acquisition at Vallunden Lake (WP1), data processing (WP2), forward modelling (WP3), data inversion (WP4), and identification of ice resilience markers (WP5).
Monsieur Ludovic Moreau (Institut des Sciences de la Terre)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ISTerre Institut des Sciences de la Terre
Help of the ANR 228,588 euros
Beginning and duration of the scientific project: September 2018 - 42 Months