Numerical Modeling Of Seasonally Freezing Ground And Permafrost

Thesis (Ph.D.) University of Alaska Fairbanks, 2007This thesis represents a collection of papers on numerical modeling of permafrost and seasonally freezing ground dynamics. An important problem in numerical modeling of temperature dynamics in permafrost and seasonally freezing ground is related to parametrization of already existing models. In this thesis, a variation data assimilation technique is presented to find soil properties by minimizing the discrepancy between in-situ measured temperatures and those computed by the models. The iterative minimization starts from an initial approximation of the soil properties that are found by solving a sequence of simple subproblems. In order to compute the discrepancy, the temperature dynamics is simulated by a new implementation of the finite element method applied to the heat equation with phase change. Despite simplifications in soil physics, the presented technique was successfully applied to recover soil properties, such as thermal conductivity, soil porosity, and the unfrozen water content, at several sites in Alaska. The recovered properties are used in discussion on soil freezing/thawing and permafrost dynamics in other parts of this thesis. Another part of this thesis concerns development of a numerical thermo-mechanical model of seasonal soil freezing on the lateral scale of several meters. The presented model explains observed differential frost heave occurring in non-sorted circle ecosystems north of the Brooks Range in the Alaskan tundra. The model takes into account conservation principles for energy, linear momentum and mass of three constituents: liquid water, ice and solid particles. The conservation principles are reduced to a computationally convenient system of coupled equations for temperature, liquid water pressure, porosity, and the velocity of soil particles in a three-dimensional domain with cylindrical symmetry. Despite a simplified rheology, the model simulates the ground surface motion, temperature, and water dynamics in soil and explains dependence of the frost heave on specific environmental properties of the ecosystem. In the final part, simulation of the soil temperature dynamics on the global scale is addressed. General Circulation Models are used to understand and predict future climate change, but most of them do not simulate permafrost dynamics and its potentially critical feedback on climate. In this part, a widely used climate model is evaluated and the simulated temperatures are compared against observations. Based on this comparison, several modifications to the Global Circulation Models are identified to improve the fidelity of permafrost and soil temperature simulations. These modifications include increasing the total soil depth by adding new layers, incorporating a surface organic layer, and modifying the numerical scheme to include unfrozen water dynamics

PEDESTRIAN TRAVEL-TIME MAPS FOR WHITTIER, ALASKA: An anisotropic model to support tsunami evacuation planning

Tsunami-induced pedestrian evacuation for the community of Whittier is evaluated using an anisotropic modeling approach developed by the U.S. Geological Survey. The method is based on path-distance algorithms and accounts for variations in land cover and directionality in the slope of terrain. We model evacuation of pedestrians to exit points from the tsunami hazard zone boundary. The pedestrian travel is restricted to the roads only. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards

PEDESTRIAN TRAVEL-TIME MAPS FOR KODIAK, ALASKA: An anisotropic model to support tsunami evacuation planning

Tsunami-induced pedestrian evacuation for the City of Kodiak, U.S. Coast Guard Base and the community of Womens Bay is evaluated using an anisotropic modeling approach developed by the U.S. Geological Survey. The method is based on path-distance algorithms and accounts for variations in land cover and directionality in the slope of terrain. We model evacuation of pedestrians to exit points from the tsunami hazard zone. The pedestrian travel is restricted to the roads only. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards.Tsunami-induced pedestrian evacuation for the City of Kodiak, U.S. Coast Guard Base and the community of Womens Bay is evaluated using an anisotropic modeling approach developed by the U.S. Geological Survey. The method is based on path-distance algorithms and accounts for variations in land cover and directionality in the slope of terrain. We model evacuation of pedestrians to exit points from the tsunami hazard zone. The pedestrian travel is restricted to the roads only. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards

PEDESTRIAN TRAVEL-TIME MAPS FOR PERRYVILLE, ALASKA: An anisotropic model to support tsunami evacuation planning

Tsunami-induced pedestrian evacuation for the community of Perryville is evaluated using an anisotropic modeling approach developed by the U.S. Geological Survey. The method is based on path-distance algorithms and accounts for variations in land cover and directionality in the slope of terrain. We model evacuation of pedestrians to exit points located at the tsunami hazard zone boundary. Pedestrian travel-time maps are computed for two cases: i) travel to an existing evacuating shelter and ii) travel to either the evacuation or an alternative shelter. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards

Maritime Guidance for Distant and Local Source Tsunami Events: Valdez Harbor, Alaska

These documents provide response guidance for Valdez Harbor in the event of tsunamis for small vessels such as recreational sailing and motor vessels, and commercial fishing vessels. The developed documents follow the guidance developed by the National Tsunami Hazard Mitigation Program (NTHMP) and are based on anticipated effects of a maximum-considered distant and locally generated tsunami event

Maritime Guidance for Distant and Local Source Tsunami Events: Cordova Harbor, Alaska

These documents provide response guidance for Cordova Harbor in the event of tsunamis for small vessels such as recreational sailing and motor vessels, and commercial fishing vessels. The developed documents follow the guidance developed by the National Tsunami Hazard Mitigation Program (NTHMP) and are based on anticipated effects of a maximum-considered distant and locally generated tsunami event

Maritime Guidance for Distant and Local Source Tsunami Events: Kodiak, Alaska

These documents provide response guidance for Kodiak Harbor in the event of tsunamis for small vessels such as recreational sailing and motor vessels, and commercial fishing vessels. The developed documents follow the guidance developed by the National Tsunami Hazard Mitigation Program (NTHMP) and are based on anticipated effects of a maximum-considered distant and locally generated tsunami event.These documents provide response guidance for Kodiak Harbor in the event of tsunamis for small vessels such as recreational sailing and motor vessels, and commercial fishing vessels. The developed documents follow the guidance developed by the National Tsunami Hazard Mitigation Program (NTHMP) and are based on anticipated effects of a maximum-considered distant and locally generated tsunami event

Propagation of tsunami-induced acoustic-gravity waves in the atmosphere

A dynamical core of an atmospheric GCM is utilized for assessing the qualitative picture of propagation of atmospheric acoustic-gravity waves in response to perturbations generated by tsunami waves at the surface. Both resting isothermal atmosphere and model- generated atmosphere with realistic stratification and circulation features were considered. Shallow water tsunami model was run in two different configurations: ocean of equal depth of 4 km and ocean with realistic continents and bottom topography. Amplitude and timing of atmospheric response is analyzed as a function of vertical stratification and configuration of atmospheric jets. This approach has a potential for early tsunami detection by measuring changes in electric properties of the upper atmosphere in response to acoustic-gravity waves generated by tsunami.DJN was supported in part by Cooperative Institute for Alaska Research with funds from NOAA under cooperative agreement NA08OAR4320751 with the University of Alaska