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Thursday, April 24

Toward More Detailed Representations of Land Surface Processes in the Arctic

Scott Painter, , Computational Earth Sciences Group, Earth and Environmental Sciences Division, Los Alamos National Laboratory
Climate Change Science Institute Seminar
10:00 AM — 11:00 AM, Joint Institute for Computational Sciences (Building 5100), Auditorium (Room 128)
Contact: John Sanseverino (sanseverinoj@ornl.gov), 865.576.9093

Abstract

Much of the approximately 1500 Pg of perennially frozen organic carbon in the northern permafrost region is susceptible to thawing as the Arctic warms. Reliable models for the hydrologic response of Arctic tundra are critical to understanding the fate of that carbon. Simulating the hydrologic system in degrading permafrost regions is challenging because of strong coupling among thermal and hydrologic processes, the important role of organized microtopography in controlling water flows, and the potential for topographic changes as ground ice melts. A highly parallel simulation tool, the Arctic Terrestrial Simulator (ATS), is being developed to model the critical set of coupled processes that control soil moisture and greenhouse gas emissions from the northern permafrost region. To manage the high level of complexity in the multiple coupled process models, ATS uses a novel hierarchical process model management framework that allows individual models to be developed and tested in isolation and then combined at runtime in a dynamically configured simulation. Models for the key thermal hydrologic processes are currently implemented and tested, including new models for heat transport and moisture dynamics in variably saturated frozen soils, nonisothermal surface flows with freezing and thawing, spatial redistribution of snow on the surface microtopography, and topographic changes due to melting ice wedges. A conventional surface energy balance model with and without snow is also implemented, and we are currently refining coupling schemes to bring all of those thermal hydrologic processes together in high-resolution simulations of polygonal tundra at the Barrow Environmental Observatory. The computational strategy, process model representations, efforts to estimate model parameters, strategies for model evaluation, ongoing numerical experiments, and new ideas for capturing the effects of microtopography at the scale of an Earth system model grid cell will be presented.