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Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions./
Author:	Patton, Annette.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
Description:	149 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-05, Section: B.
Contained By:	Dissertations Abstracts International81-05B.
Subject:	Geomorphology. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13898964
ISBN:	9781088305744

Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions.
Patton, Annette.

Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 149 p.

Source: Dissertations Abstracts International, Volume: 81-05, Section: B.

Thesis (Ph.D.)--Colorado State University, 2019.

This item must not be sold to any third party vendors.

Rapid permafrost thaw in the high-latitude and high-elevation areas increases hillslope susceptibility to landsliding by altering geotechnical properties of hillslope materials, including reduced cohesion and increased hydraulic connectivity. The overarching goal of this study is to improve the understanding of geomorphic controls on landslide initiation at high latitudes.In this dissertation, I present a literature review, surficial mapping and a landslide inventory, and site-specific landslide monitoring to evaluate landslide processes in permafrost regions. Following an introduction to landslides in permafrost regions (Chapter 1), the second chapter synthesizes the fundamental processes that will increase landslide frequency and magnitude in permafrost regions in the coming decades with observational and analytical studies that document landslide regimes in high latitudes and elevations. In Chapter 2, I synthesize the available literature to address five questions of practical importance, which can be used to evaluate fundamental knowledge of landslide processes and inform land management decisions to mitigate geohazards and environmental impacts. I also evaluate potential implications of increased landslide activity on local nutrient and sediment connectivity, atmospheric carbon feedbacks, and hazards to people and infrastructure. Based on the existing literature, I conclude that after permafrost thaws, landslides will be driven primarily by atmospheric input of moisture and freeze-thaw fracturing rather than responding to disconnected and perched groundwater, melting permafrost ice, and a plane of weakness between ground ice and the active layer. The transition between perennially frozen and seasonally thawed equilibrium states is likely to increase landslide frequency and magnitude, alter dominant failure styles, and mobilize carbon over timescales ranging from seasons to centuries. While a substantial body of literature exists on case studies of landslides in permafrost regions, no extensive review exists as a compilation of previous work. Last, I suggest three key areas for future research to produce primary data and analysis that will fill gaps in the existing understanding of landslide regimes in permafrost regions. These suggestions include 1) expand the geographic extent of English-language research on landslides in permafrost; 2) maintain or initiate long-term monitoring projects and aerial data collection; and 3) quantify the net effect on the terrestrial carbon budget.As described in Chapter 3, I conducted surficial geologic mapping and a comprehensive landslide inventory of the Denali National Park road corridor to identify geomorphic controls on landslide initiation in the Alaska Range, which include lithology, slope angle, and thawing ice-rich permafrost. Landslides occur on all slope aspects, primarily at high elevations (>1050 m) where topographic relief is greatest. The majority (84%) of inventoried landslides are < 1 km2 in area and occurred most frequently on slopes with a bimodal distribution of slope angles, with peaks at ~18° and 28°. A disproportionate number of landslides occurred in unconsolidated sediments (glacial deposits and relict landslide deposits) and in felsic volcanic rocks. Weathering of feldspar within volcanic rocks and subsequent interactions with groundwater produced clay minerals. The presence of clay minerals may promote landslide initiation by impeding groundwater conductivity and reducing rock shear strength. I also found that landslides preferentially initiated within permafrost, where modeled mean decadal ground temperature is approximately -0.2 °C and active layer thickness is approximately 1 m. Landslides that initiated within permafrost occurred on slope angles ~7° lower than landslides on seasonally thawed hillslopes. Shallow-angle landslides (<20° slopes) in permafrost demonstrate that permafrost/ice thaw is an important triggering mechanism in the study region. Melting permafrost reduces shear strength by lowering cohesion and friction values along ice boundaries. Increased permafrost degradation associated with climate change will make this and other high-relief areas more susceptible to shallow-angle landslides.The fourth chapter documents the development of landslides in rapidly thawing permafrost regions. To evaluate the impact of landslide age, morphology, and permafrost condition on landslide development, I conducted repeat terrestrial laser scan (TLS) surveys of three shallow-angle landslides that initiated in discontinuous permafrost in Denali National Park, including two landslides that initiated in the last 3 years (Stony Pass Slide and Ptarmigan Active Layer Detachment), and one landslide that initiated 20-50 years ago (Eielson Active Layer Detachment). I used Geomorphic Change Detection to quantify topographic deformation over a one-year study period. I also measured depth to permafrost at the Stony Pass Slide and used 2D ground-penetrating radar (GPR) to identify the permafrost surface in the landslide and adjacent undisturbed slopes. TLS differencing indicates that the two young landslides are still mobile, with maximum elevation loss of 0.8 m and 1.0 m at the landslide scarps, respectively. The older landslide appears topographically stable, which indicates that shallow-angle landslides achieved stability within several decades under previous climate conditions. Visual analysis of GPR data and measured depth to permafrost indicate that permafrost is present at 0.4-1.9 m depth in the undisturbed portions of the slope adjacent to the Stony Pass landslide. No permafrost was measured within the interior of the landslide, however. I interpret the results to suggest initial landslide failure over shallow, thawing permafrost. The observed lack of identifiable permafrost within the slide area therefore indicates that permafrost has thawed faster within the landslide than within undisturbed portions of the hillslope, which is consistent with ground surface disturbance increasing heat flux from the atmosphere to the subsurface. I postulate that a positive feedback loop exists between permafrost thaw and landslide development.

ISBN: 9781088305744Subjects--Topical Terms:

542703
Geomorphology.
Subjects--Index Terms:

Landslides

Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions.
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245 1 0 $a Landslide Response to Climate Change in Denali National Park, Alaska, and Other Permafrost Regions.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2019
300 $a 149 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-05, Section: B.
500 $a Includes supplementary digital materials.
500 $a Advisor: Rathburn, Sara.
502 $a Thesis (Ph.D.)--Colorado State University, 2019.
506 $a This item must not be sold to any third party vendors.
520 $a Rapid permafrost thaw in the high-latitude and high-elevation areas increases hillslope susceptibility to landsliding by altering geotechnical properties of hillslope materials, including reduced cohesion and increased hydraulic connectivity. The overarching goal of this study is to improve the understanding of geomorphic controls on landslide initiation at high latitudes.In this dissertation, I present a literature review, surficial mapping and a landslide inventory, and site-specific landslide monitoring to evaluate landslide processes in permafrost regions. Following an introduction to landslides in permafrost regions (Chapter 1), the second chapter synthesizes the fundamental processes that will increase landslide frequency and magnitude in permafrost regions in the coming decades with observational and analytical studies that document landslide regimes in high latitudes and elevations. In Chapter 2, I synthesize the available literature to address five questions of practical importance, which can be used to evaluate fundamental knowledge of landslide processes and inform land management decisions to mitigate geohazards and environmental impacts. I also evaluate potential implications of increased landslide activity on local nutrient and sediment connectivity, atmospheric carbon feedbacks, and hazards to people and infrastructure. Based on the existing literature, I conclude that after permafrost thaws, landslides will be driven primarily by atmospheric input of moisture and freeze-thaw fracturing rather than responding to disconnected and perched groundwater, melting permafrost ice, and a plane of weakness between ground ice and the active layer. The transition between perennially frozen and seasonally thawed equilibrium states is likely to increase landslide frequency and magnitude, alter dominant failure styles, and mobilize carbon over timescales ranging from seasons to centuries. While a substantial body of literature exists on case studies of landslides in permafrost regions, no extensive review exists as a compilation of previous work. Last, I suggest three key areas for future research to produce primary data and analysis that will fill gaps in the existing understanding of landslide regimes in permafrost regions. These suggestions include 1) expand the geographic extent of English-language research on landslides in permafrost; 2) maintain or initiate long-term monitoring projects and aerial data collection; and 3) quantify the net effect on the terrestrial carbon budget.As described in Chapter 3, I conducted surficial geologic mapping and a comprehensive landslide inventory of the Denali National Park road corridor to identify geomorphic controls on landslide initiation in the Alaska Range, which include lithology, slope angle, and thawing ice-rich permafrost. Landslides occur on all slope aspects, primarily at high elevations (>1050 m) where topographic relief is greatest. The majority (84%) of inventoried landslides are < 1 km2 in area and occurred most frequently on slopes with a bimodal distribution of slope angles, with peaks at ~18° and 28°. A disproportionate number of landslides occurred in unconsolidated sediments (glacial deposits and relict landslide deposits) and in felsic volcanic rocks. Weathering of feldspar within volcanic rocks and subsequent interactions with groundwater produced clay minerals. The presence of clay minerals may promote landslide initiation by impeding groundwater conductivity and reducing rock shear strength. I also found that landslides preferentially initiated within permafrost, where modeled mean decadal ground temperature is approximately -0.2 °C and active layer thickness is approximately 1 m. Landslides that initiated within permafrost occurred on slope angles ~7° lower than landslides on seasonally thawed hillslopes. Shallow-angle landslides (<20° slopes) in permafrost demonstrate that permafrost/ice thaw is an important triggering mechanism in the study region. Melting permafrost reduces shear strength by lowering cohesion and friction values along ice boundaries. Increased permafrost degradation associated with climate change will make this and other high-relief areas more susceptible to shallow-angle landslides.The fourth chapter documents the development of landslides in rapidly thawing permafrost regions. To evaluate the impact of landslide age, morphology, and permafrost condition on landslide development, I conducted repeat terrestrial laser scan (TLS) surveys of three shallow-angle landslides that initiated in discontinuous permafrost in Denali National Park, including two landslides that initiated in the last 3 years (Stony Pass Slide and Ptarmigan Active Layer Detachment), and one landslide that initiated 20-50 years ago (Eielson Active Layer Detachment). I used Geomorphic Change Detection to quantify topographic deformation over a one-year study period. I also measured depth to permafrost at the Stony Pass Slide and used 2D ground-penetrating radar (GPR) to identify the permafrost surface in the landslide and adjacent undisturbed slopes. TLS differencing indicates that the two young landslides are still mobile, with maximum elevation loss of 0.8 m and 1.0 m at the landslide scarps, respectively. The older landslide appears topographically stable, which indicates that shallow-angle landslides achieved stability within several decades under previous climate conditions. Visual analysis of GPR data and measured depth to permafrost indicate that permafrost is present at 0.4-1.9 m depth in the undisturbed portions of the slope adjacent to the Stony Pass landslide. No permafrost was measured within the interior of the landslide, however. I interpret the results to suggest initial landslide failure over shallow, thawing permafrost. The observed lack of identifiable permafrost within the slide area therefore indicates that permafrost has thawed faster within the landslide than within undisturbed portions of the hillslope, which is consistent with ground surface disturbance increasing heat flux from the atmosphere to the subsurface. I postulate that a positive feedback loop exists between permafrost thaw and landslide development.
590 $a School code: 0053.
650 4 $a Geomorphology. $3 542703
650 4 $a Geology. $3 516570
653 $a Landslides
653 $a Permafrost
653 $a Review
653 $a Surficial mapping
690 $a 0484
690 $a 0372
710 2 $a Colorado State University. $b Geosciences. $3 3174840
773 0 $t Dissertations Abstracts International $g 81-05B.
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791 $a Ph.D.
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856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13898964