GROUND-PENETRATING RADAR OBSERVATION OF LAKE ICE PROPERTIES

In order to understanding ice growth processes and to estimate trapped gas and water content, it is important to have non-invasive measurement methods to image lake ice column properties. Estimating lake ice properties using direct drilling or visual assessment of gas trapped in lake ice is common. However, a repeatable, quantitative method to estimate lake ice properties between the ground scale (< 1 m2) and the scale of satellite remote sensing (> 100 m2) measurements is desirable. This gap can be closed using ground (ice) penetrating radar (GPR) to non-invasively image the ice column and estimate lake ice thickness radar wave velocity. We conducted GPR measurements on 12 Alaskan lakes, including ten Arctic lakes on the North Slope and two subarctic near Fairbanks. Our results indicate that lake ice that is thicker than the long-term seasonal average is related to faster radar velocity, which may be interpreted as higher entrapped gas content. Analysis of ice cores demonstrate that tubular bubbles (non-ebullitive) volumetric gas content is low, less than about 2.5%. Approximately 54% of the locations measured in the field showed radar wave velocities lower than for pure ice, which we speculate may attributed to small amounts of liquid water content remaining in the ice. This study helps to build new understanding about the properties of lake ice that may be used to project the impacts of climate warming and may contribute to assessments of ice for engineering purposes.