The impact of recent climate change on permafrost distribution was evaluated by repeating the 1964 survey of Roger Brown along the Alaska Highway from Whitehorse, YT to Fort St. John, BC in August 2007 and 2008. Results demonstrate that: (1) significant degradation of permafrost has occurred over the past four decades, especially in the southernmost part of the route where 67% of the permafrost sites in 1964 no longer exhibit perennially frozen conditions; (2) the mapped southern limit of discontinuous permafrost appears to have shifted roughly 75 km northward; (3) most of the permafrost still present in the study area is in peat or under thick organic mats, which probably relates to a large thermal offset or to the latent heat requirements of thawing permafrost; and (4) that where permafrost has persisted, it is very thin, discontinuous, at temperatures just below 0°C, and its location may relate in part to the existence of atmospheric temperature inversions in the region. Changes in permafrost are attributed to significant climatic warming, primarily in winter, at rates of 0.4°C to 0.5°C per decade from 1965-2008. The results augment the very limited number of field studies of long-term change to permafrost in Canada, and are relevant to northern residents who must adapt to changing permafrost conditions.

Different sources of uncertainties have been inevitably induced into the environmental modeling due to different reasons such as the variability in the future climate state, incomplete knowledge and complexity of the nature system, and randomness in the system properties. These uncertainties make the model predictions inherently uncertain, and uncertainty becomes an important obstacle in environmental modeling. This dissertation presents a general framework for purpose of uncertainty quantification and it provides quantitative measures for relative importance of different uncertain factors to model outputs. The framework includes two parts: uncertainty analysis which implements variance decomposition technique to decompose and quantify different types of input uncertainty sources (i.e., scenario, model and parametric uncertainties); global sensitivity analysis which develops a new set of variance-based global sensitivity indices for measuring importance of model parameters with considering multiple future climate scenarios and plausible models. To demonstrate the usage and compatibility of the uncertainty quantification framework with different types of models, it was applied into two distinct cases: a synthetic groundwater reactive transport case and a barrier island morphological case. In the groundwater case, a Bayesian network integrated groundwater reactive transport model was built and studied for a synthetic case. Different uncertainty sources are described as uncertain nodes in the Bayesian network. All the nodes are characterized by multiple states, representing their uncertainty, in the form of continuous or discrete probability distributions that are propagated to the model endpoint, which is the spatial distribution of contaminant concentrations. In the barrier island case, a new Barrier Island Profile (BIP) model which simulates the barrier island cross-section morphological evolution was developed and studied. For a series of barrier island cross-sections derived from the characteristics of Santa Rosa Island, Florida, BIP was used to evaluate their responses to random storm events and five potential accelerated rates of sea-level rise projected over a century. Monte Carlo simulation is used to decompose and quantify the predictive uncertainties for uncertainty analysis of both cases. In the global sensitivity analysis, besides quasi-Monte Carlo simulation, sparse grid collocation method was also implemented to estimate the global sensitivity index to save the computational cost in the groundwater case. The study of BIP model demonstrates that BIP is capable of simulating realistic patterns of barrier island profile evolution over the span of a century using relatively simple representations of time- and space-averaged processes with consideration of uncertainty of future climate impacts. The results of uncertainty quantification for both cases demonstrate different types of model input uncertainty sources and the relative importance of model parameters can be quantified using the developed uncertainty quantification framework. And the global sensitivity indices may vary substantially between different models and scenarios. Not considering the model and scenario uncertainties, may result biased identification of important model parameters. The framework will be very useful for environmental modelers to prioritize different uncertainties and optimize expanse of limited resources to more efficiently decrease predictive uncertainty. Although only two applications are demonstrated, this uncertainty quantification framework is mathematically general and it can be applied to a wider range of hydrologic and environmental problems. / A Dissertation submitted to the Department of Scientific Computing in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2014. / November 5, 2014. / Barrier Island Modeling, Coastal Modeling, Groundwater Reactive Transport Modeling, Multiple Scenarios and Models, Sensitivity Analysis, Uncertainty Analysis / Includes bibliographical references. / Ming Ye, Professor Directing Dissertation; Anke Meyer-Baese, Committee Member; Tomasz Plewa, Committee Member; Dennis Slice, Committee Member.

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The development of tools and techniques used in paleoenvironmental studies is important for the advancement of geoarchaeological research. Geoarchaeological studies of ancient harbours involve the integration of paleoenvironmental data with archaeological findings, allowing for a more comprehensive understanding of site development and regional maritime trade. This dissertation highlights and/or explores novel applications of microfossils and micro-X-ray fluorescence (μXRF) core scanning data in paleoenvironmental reconstructions within three ancient harbour studies. Foraminifera, diatom, pollen, μXRF, carbon stable isotope, and radiocarbon dating results from underwater cave sediments on the eastern coast of the Yucatán Peninsula indicate that the region’s wetlands developed between 1157 BCE and 312 CE. Continued sea-level rise after ~312 CE allowed canoe access through a channel from the Caribbean Sea to Muyil, a Classic Maya maritime port site. Development of the wetlands may have implications for increased maritime trade on the Yucatán’s eastern coast during the Postclassic (925–1550 CE). This study demonstrates the importance of karst cave systems for obtaining paleoenvironmental records and provides a first assessment of the diatom community that has been transported into the sampled cave system. The novel application of epiphytic foraminifera as biostratigraphic indicators was investigated at Caesarea, Israel. Benthic foraminifera assemblages indicated that the emplacement of hard harbour structures along the sandy coast between 21–10 BCE altered the environmental conditions and impacted the nearby ecological communities. Epiphytic foraminifera, in particular Pararotalia calcariformata, were found to be useful indicators for the timing of harbour construction at Caesarea. μXRF and magnetic susceptibility results also supported the presence of increased harbour material (i.e., kurkar and volcanic ash) in offshore sediments over time. This study demonstrates that epiphytic foraminifera can be cost-effective biostratigraphic indicators in geoarchaeological studies. Results also confirm that P. calcariformata is endemic to Israel and is not a recent arrival following the opening of the Suez Canal. Foraminifera, testate amoebae, μXRF, and radiocarbon dating results from sediment cores collected from two lagoons, Khor Al Balid and Khor Rori, on the southern coast of Oman indicate that the lagoons closed off from the sea between the 12th and 15th centuries CE. Prior to lagoon formation, these two sites formed natural harbours that were the locations of major maritime trade ports. Progressive siltation and sand accumulation along the coastline after the 15th century likely impacted shipping activities, contributing to abandonment of the city near Khor Al Balid. Evidence of a marine overwash event across most cores from both sites dating to the 18th–19th century CE suggests that an extreme wave event (e.g., tsunami or large tropical cyclone) may have also contributed to the decline of the city. The results of this study provide an important paleoenvironmental context for previous archaeological findings. / Dissertation / Doctor of Philosophy (PhD)

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<p>This thesis describes the geomorphology and hydrogeology of karst systems in portions of the northeastern Canyon Ranges of the Mackenzie Mountains and the Norman Range of the Franklin Mountains, N.W.T. In the region, mean annual temperatures are -6 to -8°C, total annual precipitation is 325 to 500 mm, and permafrost has a widespread to continuous distribution. The area was glaciated in the Late Wisconsinan by the Laurentide Ice Sheet.</p> <p>The Canyon Ranges and Norman Range are composed of a sequence of faulted and folded miogeoclinal sedimentary rocks that span the Proterozoic to Eocene. The geology is reviewed with an emphasis on strata that display karst. Included are several dolomite and limestone formations, two of which are interbedded with evaporites in the subsurface. The principal groundwater aquifer is the Lower Devonian Bear Rock Formation. In subcrop, the Bear Rock Formation is dolomite and anhydrite, outcrops are massive calcareous solution breccias. This is the primary karst rock.</p> <p>The regional distribution and range of karst landforms and drainage systems are described. Detailed mapping is presented from four field sites. These data were collected from aerial photography and ground surveys. The karst has examples of pavement, single and compound dolines, subsidence troughs, polje,sinking streams and lakes, and spring deposits. The main types of depressions are subsidence and collapse dolines. Doline density is highest on the Bear Rock Formation. Surficial karst is absent or less frequent in the zone of continuous permafrost or outside the glacial limit.</p> <p>At the field sites, water samples were collected at recharge and discharge locations. Samples were analyzed for a full range of ionic constituents and many for natural isotopes. In addition, several springs were monitored continuously for discharge, temperature, and conductivity. Dye tracing established linkages between recharge and discharge at some sites. These data are summarized for each site, as is the role of permafrost in site hydrology.</p> <p>The relationships between geological structure, topography, and groundwater systems are described. Conduit aquifers are present in both dolomite and limestone. These systems are characterized by discharge waters of low hardness and dissolved ion content. Aquifers in the Bear Rock Formation have a mixed flow regime and often have highly mineralized discharge. At the principal field site, there was a time lag of 40 to 60 days between infiltration and discharge in this unit. At a second site, flow through times were on the order of years. Variability in these systems is attributed to bedrock properties and boundary conditions.</p> <p>Preliminary rates of denudation are calculated from the available hydrochemical data. Total solutional denudation at the primary field site is approximately 45 m³ km^-2 a^-1 (mm ka^-l). The majority is attributed to the subsurface dissolution of halite and anhydrite. The predominance of subsurface dissolution is linked to the high frequency of collapse and subsidence dolines and depressions.</p> <p>The karst features and drainage systems of the northern Mackenzie Mountains date to the Tertiary. Glaciation has had a stimulative effect on karst development through the subglacial degradation of permafrost and the altering of boundary conditions by canyon incision.</p> / Doctor of Philosophy (PhD)

The effects of urbanization on river systems are not well understood as appropriate field parameters for representing such changes require years of consistent monitoring data for an accurate comparison. Furthermore, due to their varying degrees of urbanization and management efforts, conditions are not consistent even within the same watersheds so representative sites are difficult to distinguish. This level of data is not typically available for watersheds in Ontario due to budget and personnel constraints of organizations undertaking such monitoring activities. To direct monitoring and management efforts more effectively, a comparative aerial imagery analysis was undertaken for a ~50-year timeline for twenty study sites across the Mimico Creek, Etobicoke Creek, Highland Creek, and Duffins Creek watersheds as well as a comprehensive field analysis to characterize current conditions. A statistical analysis that included a Pearson correlation coefficient analysis and stepwise regression utilizing values obtained through the Stream Power Index for Networks (SPIN) tool and manual calculations including three ratios from Wood-Smith & Buffington (1996) was also completed. These ratios included: bankfull width (Wbf)/bankfull depth (hbf), D50/bankfull depth (hbf), and critical shear stress (τc50)/bankfull shear stress (τbf). Results indicated a strongly negative correlation between entrenchment and the Wbf⁄hbf ratio and positive correlations of varying strengths between the τc50⁄τbf ratio and both the Wbf⁄hbf and D50⁄hbf ratios. Though weak, percent imperviousness and specific stream power were able to predict the τc50⁄τbf ratio. Finally, t-tests between sites categorized as “rural” (≤30% imperviousness) and “urban” (>30% imperviousness) revealed when a control is placed on drainage area, increases in specific stream power, D50, bankfull width, bankfull depth, and slope is observed in “urban” areas. It is believed that such statistical parameters could be considered applicable as a first order estimate of further stream pattern analyses but are not strong enough correlations to be utilized for design purposes. / Thesis / Master of Science (MSc) / The effects of urbanization on river systems are not well understood as appropriate field parameters for representing such changes require years of consistent data for an accurate comparison which is not typically available in Ontario due to budget and personnel constraints. To direct monitoring and management efforts more effectively, a comparative aerial imagery analysis, field study, and statistical analysis comprised of a Pearson correlation coefficient analysis and stepwise regression were undertaken for twenty sites across four major watersheds in the Greater Toronto Area (GTA). Values obtained through the Stream Power Index for Networks (SPIN) tool and manual calculations of entrenchment and three ratios from Wood-Smith & Buffington (1996) were utilized. Results indicate that statistical parameters such as the ability for specific stream power and imperviousness to predict the shear stress ratio can be considered applicable initial estimates of river patterns but are not strong enough for design purposes.

abstract: The San Gabriel Mountains (SGM) of southern California provide the opportunity to study the topographic controls on erosion rate in a mountain range where climate and lithology are relatively constant. I use a combination of digital elevation model data, detailed channel survey data, decadal climate records, and catchment-averaged erosion rates quantified from 10Be concentrations in stream sands to investigate the style and rates of hillslope and channel processes across the transition from soil-mantled to rocky landscapes in the SGM. Specifically, I investigate (1) the interrelations among different topographic metrics and their variation with erosion rate, (2) how hillslopes respond to tectonic forcing in "threshold" landscapes, (3) the role of discharge variability and erosion thresholds in controlling the relationship between relief and erosion rate, and (4) the style and pace of transient adjustment in the western SGM to a recent increase in uplift rate. Millennial erosion rates in the SGM range from 0.03-1.1 mm/a, generally increasing from west to east. For low erosion rates (< 0.3 mm/a), hillslopes tend to be soil-mantled, and catchment-averaged erosion rates are positively correlated with catchment-averaged slope, channel steepness, and local relief. For erosion rates greater than 0.3 mm/a, hillslopes become increasingly rocky, catchment-mean hillslope angle becomes much less sensitive to erosion rate, and channels continue to steepen. I find that a non-linear relationship observed between channel steepness and erosion rate can be explained by a simple bedrock incision model that combines a threshold for erosion with a probability distribution of discharge events where large floods follow an inverse power-law. I also find that the timing of a two-staged increase in uplift rate in the western SGM based on stream profile analysis agrees with independent estimates. Field observations in the same region suggest that the relict topography that allows for this calculation has persisted for more than 7 Ma due to the stalling of migrating knickpoints by locally stronger bedrock and a lack of coarse sediment cover. / Dissertation/Thesis / Ph.D. Geological Sciences 2011

abstract: A fundamental gap in geomorphic scholarship regards fluvial terraces in small desert drainages and those terraces associated with integrating drainages. This dissertation analyzes four field-based case studies within the Sonoran Desert, south-central Arizona, with the overriding purpose of developing a theory to explain the formative processes and spatial distribution of fluvial terraces in the region. Strath terraces are a common form (Chapters 2, 3, 4) and are created at the expense of bounding pediments that occur on the margins of constraining mountainous drainage boundaries (Chapters 1, 2, 3). Base-level fluctuations of the major drainages cause the formation of new straths at lower elevations. Dramatic pediment adjustment and subsequent regrading follows (Chapter 3), where pediments regrade to strath floodplains. This linkage between pediments and their distal straths is termed the pediment-strath relationship. Stability of the base level of the major drainage leads to lateral migration and straths are carved at the expense of bounding pediments through an erosional asymmetry facilitated by differential rock decay between the channel bank and bed. Fill terraces occur within the Salt River drainage basin as a result of the integration processes that connect formerly endorheic basins (Chapter 4). The topographic, spatial, and sedimentologic relationship of the Stewart Mountain terrace (Chapter 4) points to a different genetic origin than the lower terraces in this basin. The high Stewart Mountain fill terrace records the initial integration of this river. The strath terraces inset below the Stewart Mountain terrace are a result of the pediment-strath relationship. These case studies also reveal that the under-addressed drainage processes of piracy and overflow have significant impacts in the evolution of drainages the lead to both strath and fill terrace formation in this region. / Dissertation/Thesis / Ph.D. Geography 2013

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