GEOMORPHIC CHARACTERIZATION OF THERMOKARST LAKES ON THE NORTH SLOPE, ALASKA

Thermokarst lakes on Alaska’s North Slope serve as carbon sinks, overwintering fish repositories, and water sources for extraction industries. Due to their inaccessibility, thermokarst lakes have long been targets for remote sensing efforts, from WWII-era aerial photography to spaceborne radar imaging to airborne lidar. Though recent advances in lidar technology—specifically the ability to capture bathymetric topography with water-penetrating lasers—have provided unprecedented levels of data quality, from which we can gain insights into thermokarst lake geomorphology, software to process and analyze the data are insufficient or nonexistent. To address this gap in analytical ability, we developed algorithms to extract information, including statistical assessments, using terrestrial and bathymetric data collected over 1200 km² of the Alaskan North Slope, including 7000+ imaged lakes and adjacent terrain. The analytical toolkit imports rasterized topographic, bathymetric, and water surface lidar data; identifies discrete waterbodies; and, calculates geomorphic statistics for each waterbody including staggered volumes, area, elongation, orientation, fetch, bank height, elliptic fit, and the presence, length, and orientation of sublittoral bars. A rigorous comparison between our results and those compiled via traditional methods support our contention that bathymetric lidar is an excellent tool for cost-effective geomorphic characterization of thermokarst lakes. The algorithms are also flexible enough to be used in warmer weather environments, such as in Texas, including reservoirs, ponds, and river reaches. These findings and potential future uses will be discussed.