Date of Award

2025-12-01

Degree Name

Master of Science

Department

Environmental Sciences

Advisor(s)

Craig E. Tweedie

Abstract

Climate change is amplified in the Arctic. As a result, Arctic tundra landscapes are undergoing physical changes through accelerated thaw and ice-wedge degradation. Understanding the magnitude and direction of these changes in the Arctic is a necessary step toward understanding the response of the Arctic to climate change and feedbacks to the Climate System. Through repeat measurements collected from 1973 through 2018, we were able to assess decadal time scale changes in polygon geomorphology, thaw depth, land surface compression and expansion, and vertical elevation within a highly polygonized tundra system, and their implications when scaled to a regional level. This study examines nearly five decades of biophysical change at the historic U.S. International Biological Program (IBP) Microtopographic Grid (MTG) near Utqiagvik, Alaska. While not large in size, the longevity of the 1 by 34-meter grid, the breadth and integrated nature of measurements made, availability of historic data, and data from periodic resampling efforts, make this a relatively unique site, providing an opportunity to determine the magnitude and direction of changes in polygonized tundra, in response to climatic change. This study revealed consistent degradation of ice-wedge polygons over time. Rim features exhibited a decline in spatial extent by 27%, while troughs expanded by 100%, indicating a thermokarst-induced landscape shift. Surface elevation profiles revealed subsidence in troughs and low centers with rates of decrease ranging from -0.43cm/year and -0.23cm/year, respectively. Compression and expansion metrics and peg height indicated land surface displacement. Subsidence was observed at troughs and low centers, whereas rims displayed a modest expansion with occasional heaving. Thaw depth increased significantly across all geomorphic features, with the deepest record of thaw depth obtained during the record warm summer of 2017. This highlights the sensitivity of polygonized tundra to interannual climate extremes where a single warm year can have measurable impacts. Combined, these results demonstrate that the MTG has been transitioning towards a flatter and more hydrologically connected landscape, consistent with pan-Arctic patterns of ice-wedge degradation. A new geomorphic landscape could be apparent if warmer summers become more frequent. This study reinforces the potential for sustained observations to prove fine-scale insight into the process and pace of physical change in tundra ecosystems and highlights the importance of historical research sites for detecting climate-driven landscape change. At the same time, the deterioration of the MTG was evident and it illustrates the challenges of preserving historical sites. Future monitoring efforts would greatly benefit from the integration of non-destructive remote sensing technologies such as LiDAR and UAS-based surveys.

Language

en

Provenance

Received from ProQuest

File Size

65 p.

File Format

application/pdf

Rights Holder

Mariana Mora

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