Improvements to Land Surface Modeling in Polygonal Tundra
Authors
Charles Abolt1* (cabolt@lanl.gov), Scott Painter2, Xiang Huang1, Ethan Coon2, Katrina Bennett1, Colleen Iversen2
Institutions
1Los Alamos National Laboratory, Los Alamos, NM; 2Oak Ridge National Laboratory, Oak Ridge, TN
URLs
Abstract
For over a decade, the Next-Generation Ecosystem Experiments (NGEE) Arctic project has conducted research regarding the impact of climate change on hydrologic processes in ice wedge polygonal tundra. The long-term goal of this research is to develop process representation of changing polygonal microtopography and surface inundation dynamics within the land component of the Energy Exascale Earth System Model (E3SM), DOE’s flagship Earth system model. Among the most important research questions are whether the land surface will become wetter or drier and how changes to surface wetness will impact ground-atmosphere carbon exchange. Early work focused on developing and validating the Amanzi–Advanced Terrestrial Simulator (ATS), a physics-rich surface-subsurface hydrologic code, at the spatial scale of individual ice wedge polygons. More recently, observation-constrained, basin-scale Amanzi-ATS simulations on the outer coastal plain of the Beaufort Sea have projected that ice wedge polygon landscapes are likely to become drier over the next century due to improved surface drainage in thermokarst terrain. Recent satellite remote sensing work is consistent with this finding but has also demonstrated that the response of inundation dynamics will be highly impacted by macroscale topographic setting. At present, the NGEE Arctic project is conducting a new ensemble of basin-scale simulations in five watersheds throughout the Alaskan North Slope, ranging from flat to very hilly (>100 m of relief in less than 1 square kilometer). The results are being analyzed to determine new empirical relationships between surface water storage, surface inundation fraction, and runoff, which change as a function of active layer deepening to reflect the impact of ground subsidence and microtopographic deformation on surface hydrology. These new empirical equations will be embedded within the land component of E3SM and switched on within columns representing polygonal ground. This new functionality will enable regional and pan-Arctic assessments of the extent to which changing polygonal microtopography impacts Arctic carbon cycling as air temperatures continue to rise.