Date of Award

2024-12-01

Degree Name

Doctor of Philosophy

Department

Biological Sciences

Advisor(s)

Craig E. Tweedie

Abstract

As climate change accelerates in the Arctic, the degradation of permafrost is leading to significant landscape transformation in tundra landscapes. This dissertation investigates the multifaceted responses of permafrost systems to warming, focusing on the dynamics of surface elevation changes and active layer thickness (ALT) across the North Slope of Alaska. In this study, I explore the capacity of repeat Terrestrial Laser Scanning (TLS) technology for modeling tundra features and detecting surface subsidence, specifically how different climate and landscape conditions during scanning impact TLS model precision. We also compare TLS model precision estimates to TLS model accuracy by comparing elevation values derived from TLS models to DGPS models. The findings indicate that adverse climate and landscape conditions can significantly reduce TLS precision. In general model precision decreased by 45% when transitiong from ideal (clear skies, dry tundra, no wind) conditions to less-than-ideal (windy and wet) conditions. Under both conditions TLS precision most under preformed in trough features, but this effect was significantly impacted by less-than-ideal conditions. We also found that individual less-than-ideal conditions (windy vs wet) impacted TLS precision differently, emphasizing the necessity for optimized survey protocols to enhance change detection between repeat surveys. Using our understanding of TLS model precision, we analyzed over a decade of high-resolution TLS data, along with differential GPS (DGPS) data across the North Slope to access landscape elevation change over time. This analysis documents landscape elevation changes at multiple spatial and temporal scales, revealing that broad-scale landscape subsidence is mostly driven by solid earth dynamics (related to tectonic movement and changes in earth crust). The magnitude of solid earth movement often surpassed surface elevation changes (due to isotropic subsidence and thermokarst development), revealing the impact that solid earth movement may have on our understanding of landscape elevation change in the Arctic. The study also highlights the significant spatial and temporal variability of surface elevation change across the Arctic, that became apparent once we separated solid earth dynamics. These results suggest that decadal trends in vulnerable areas may not be changing as previously assumed, as five out of our seven sites had linear surface elevation gain trends, with only two having surface subsidence trends. These insights challenge conventional understanding of surface subsidence in permafrost landscapes impacted by global warming and highlight the need for long-term monitoring of permafrost regions and the separation of solid earth movement from surface elevation change calculations. This dissertation uses our understanding of surface elevation change in the North Slope to then examine the influence of surface elevation changes on ALT and ecosystem processes. Contrary to prevailing assumptions that ALT is uniformly increasing, my analysis demonstrates potential decreases in ALT in some areas, influenced by local geomorphic conditions and soil moisture dynamics. Overall, this dissertation underscores the complex interplay between atmospheric warming, surface changes, and permafrost dynamics, calling for a reevaluation of existing paradigms regarding permafrost evolution and its implications for global climate systems. By refining our understanding of these processes, this work contributes valuable insights to the field of permafrost research and underscores the urgency of long-term ecological monitoring in the Arctic. These findings underscore the intricate interplay between atmospheric warming, surface dynamics, and permafrost processes. This work provides critical insights into how landscape-scale changes interact with permafrost thaw, with implications for carbon release, hydrology, and ecosystem stability. By refining our understanding of the patterns and processes of permafrost evolution, this study can inform the development of strategies for monitoring and mitigating the impacts of Arctic climate change on global systems related to fate of carbon, vegetation change, sea level rise, and infrastructure, improving resilience planning for Arctic communities, and guiding international climate policy focused on the preservation of permafrost.

Language

en

Provenance

Recieved from ProQuest

File Size

210 p.

File Format

application/pdf

Rights Holder

Tabatha Lynn Fuson

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