Drained thaw lake basin recovery on the western Arctic Coastal Plain of Alaska using high-resolution digital elevation models and remote sensing imagery

Abstract

The landscape on the Arctic Coastal Plain (ACP) of Alaska is dominated by thousands of thaw (thermokarst) lakes and associated drained thaw lake basins (DTLBs). Knowledge of the DTLBs benefits our understanding of thaw lake dynamics, carbon cycles, and paleo-climatic change on the ACP since the end of the Late Glacial. This study initializes the application of high-resolution digital elevation models (DEMs) into a systematic reconstruction of DTLBs on the western ACP and adjacent northern Arctic Foothills. The method combines a machine-based detection algorithm automating the delineation of basin paleoshorelines on IfSAR DEM data and a posterior quality control with the aid of high-resolution aerial photograph and Landsat-5 TM imagery. A total of ~3590km2 of thaw lakes and ~10130km2 of DTLBs were mapped, with an overall accuracy of 99.2% and a Kappa coefficient of 0.988. The delineated DTLB extents are conservative, as validated from eleven field-sampled paleoshorelines. A variety of topologic patterns such as merging, nesting, and overtopping are presented in the reconstructed DTLBs. Basin paleoshoreline levels are subject to average uncertainties of 0.4–0.7 m. The combined area of thaw lakes and DTLBs accounts for 57.1% of the western ACP and 23.2% of the northern Arctic Foothills in the study site. Regional analysis of several spatial and topographic characteristics demonstrates a distinct heterogeneity among the younger Outer Coastal Plain (YOCP), Outer Coastal Plain (OCP), Inner Coastal Plain (ICP), and the Arctic Foothills. Generally, the areal density of DTLBs decreases progressively on higher and older surfaces. The ICP has a lake–DTLB area ratio (0.37) greater than that in the other regions. DTLB bathymetry presents a positive correlation with surface elevation: basin maximum depths range from ~2.0m on the YOCP to ~ 8.0m on the Arctic Foothills. Given the reconstructed DTLBs, a total of 31.9 (±4.9) gigatons of net water drainage were estimated for the entire study area.