| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2020 Changes in climate across the Arctic in recent decades and especially the increase of near-surface air temperature promote signicant changes in key natural components of the Arctic including permafrost (defined as soil experiencing subzero temperature for more than two consecutive years). Recent borehole observations exhibit signicant increase in ground temperatures below the depths of seasonal variations. Modeling studies on a global scale suggest a steady decrease in area underlain by near-surface permafrost in the northern hemisphere in recent decades. Global projections for the next century predict further permafrost degradation depending on the greenhouse gas concentration trajectory. Permafrost degradation is not only associated with climate feedbacks but can also result in signicant changes in coastal and terrestrial ecosystems and increased risks of costly infrastructural damage for Arctic settlements. In addition, permafrost plays an important role in the terrestrial part of the Arctic freshwater cycle as the volumes of frozen ground are practically impermeable for subsurface moisture transport and contain excess water in the form of ground ice. Since geophysical observations bear signicant costs in the Arctic, especially in the remote areas, simulations performed with physically based numerical models allow researchers to assess the current state of permafrost in Arctic regions and make future projections of its dynamics and resulting hydrological impacts. In this dissertation we use numerical modeling in two distinct ways: 1) to estimate current and future ground temperature distribution with high resolution on a regional scale and 2) to evaluate the role permafrost degradation plays in changes in water balance of watersheds under changing climate. First, we study the permafrost evolution of the Seward Peninsula, Alaska over the 20th and 21st century using a distributed heat transfer model. Model parameters are calibrated with a variational ...
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