As a temperature-delineated boundary, Arctic treeline is predicted to shift poleward and tree growth is expected to increase in response to rapid warming. The massive scale of the Arctic treeline magnifies these changes to impact energy balance, carbon balance, and climate-related feedbacks at local, regional, and global scales. Yet, not all sections of the Arctic treeline are reporting growth, suggesting factors other than temperature may be becoming more limiting as the climate continues to change. This dissertation investigates how water availability and tree size may modify the response to climate change of a dominant conifer species (white spruce, Picea glauca) growing at an Arctic treeline site in the Brooks Range, Alaska, USA. The first chapter examines the influence of temperature and water availability on population regeneration and individual tree growth during the 20th century. A climatic shift towards a warmer and drier climate after 1975 caused divergent responses of sapling regeneration and mature tree growth, suggesting that, while individuals have grown, this section of treeline has remained relatively stationary. The second chapter explores the present-day relationships between tree size, temperature, moisture availability, and tree growth by examining the response of intra-annual radial stem growth rate to changing environmental conditions at the Arctic treeline. Tree size and water availability play important roles in moderating the growth response to increasing temperature. Finally, in the third chapter, the environmental cues which trigger the onset of radial stem growth in spring are identified. The results suggest a combination of winter chilling and subsequent spring heat accumulation initiates onset, like trees growing at lower latitudes. However, the chilling and heating thresholds at this Arctic treeline site were far colder than those identified at lower latitudes, suggesting local adaptation to harsh Arctic winters and springs. Through these new findings, this dissertation advances our understanding of Arctic treeline dynamics and will help to predict the future of the Arctic treeline more accurately in a rapidly changing climate.

With widespread increases in air temperature, it is expected that the temperature of aquatic ecosystems will also increase, especially at high latitudes. Warmer streams and rivers could have severe, direct impacts on cold-adapted aquatic fauna but may also indirectly influence species by reducing the amount of suitable habitat. Yet, increases in air temperature alone ara potentially insufficient to cause stream warming, which is also influenced by a range of other factors that govern the energy balance of individual stream reaches. Here, I used long-term water temperature data from seven streams in the Krycklan Catchment Study (KCS) to ask whether there are recent trends in warming, and to evaluate how catchment properties regulate the sensitivity of streams to air temperature change during summer. Mann Kendall trend analysis at one headwater site showed that there has indeed been a warming trend in the KCS, but only during a brief time-window in early summer. Across, KCS sites, air temperature-water temperature regressions highlighted notable variation in the thermal sensitivity of streams depending on their catchment features. Finally, observations during extreme warm and dry years did not indicate strong responses in terms of stream temperature. In fact, extreme low-flow conditions seem to reduce the downstream propagation of warm lake water during these events. Collectively, my results suggest that ongoing climate changes in the boreal region have not had dramatic influences on stream temperature, although future changes occurring around the snowmelt season are likely.

Soils contain the largest terrestrial pool of carbon (C), but the magnitude and distribution of the soil C sink may be sensitive to climate change. My dissertation aims to identify key processes that mediate patterns of belowground carbon storage across the globe and quantify the effect of environmental perturbations associated with global change on existing soil carbon stocks in peatland ecosystems. Using meta-analysis, I show that the relationship between plant growth, C allocation, and soil nutrient availability varies on a global scale and high-latitude ecosystems allocate >60% of fixed C to belowground structures. As high latitude ecosystems are warming faster than the global mean, the future of this belowground C store is potentially sensitive to climate change. In high latitude ecosystems in particular, I further show that belowground warming increases the rate of peatland carbon dioxide (CO2) and methane (CH4) losses, although CH4 emissions are more sensitive to warming than CO2 emissions, which is likely to shift the nature of greenhouse gas emissions and increase the importance of CH4 as a radiative forcing agent in the near-term. I also use a natural peatland water table gradient to identify the effect of water table reduction on peatland C and N cycling and find that microbial community shifts in C and N demand may attenuate production of C-degrading enzymes and C mineralization in the presence of plant roots and in areas with low water tables. Together, my dissertation work highlights the important role of belowground plant and microbial processes in high latitude ecosystems, and identifies the potential influence of factors associated with global change on belowground C and nutrient cycling.

The importance of Hydrogen (H2) in current global energy systems is undeniable. Moving from the energy systems depending on fossil fuel to energy systems that are carbon-free is a necessity, thus solutions such as hydrogen economy is required. Especially after recent geopolitical challenges in Europe which could make the energy acquisition a crucial problem. Liquid organic hydrogen carriers (LOHC) are applicable pathways for transitioning H2 into energy and to avoid the storage and transportation limitations of gaseous and liquid H2. Formic acid (FA) is an attractive alternative for such purposes due to its minimal level of toxicity and its significant volumetric storage capacity for H2. In this study, a Life cycle assessment (LCA) of the supply chain involving the Trans-Atlantic export of energy from Canada to Germany is conducted using formic acid as a LOHC and OxFA process to convert biomass to formic acid. The environmental impacts of all units and processes involved in this supply chain are examined, and the results are compared against other traditional systems for hydrogen production. A sensitivity analysis was also performed to recognize the crucial contributors and assess the processes and units that impose considerable influence on the overall environmental impact. / Thesis / Master of Applied Science (MASc) / Hydrogen (H2) plays a crucial role in transitioning from fossil fuel-based to carbon-free energy systems, a shift highlighted by recent geopolitical challenges in Europe. Liquid organic hydrogen carriers (LOHC) offer a solution for hydrogen storage and transport issues associated with its gaseous and liquid states. Formic acid (FA) is particularly promising as a LOHC due to its low toxicity and high hydrogen storage capacity. This study conducts a Life Cycle Assessment (LCA) of a supply chain that uses formic acid to export energy from Canada to Germany, involving the OxFA process for converting biomass to formic acid. The environmental impacts of all processes in this supply chain are evaluated and compared with traditional hydrogen production methods. Additionally, a sensitivity analysis identifies key contributors and assesses their impact on the overall environmental footprint.

Polar amplification (PA), defined as the enhanced warming of the polar region relative to the global average, is a robust feature of historical observations and simulations of future climate. Because PA has yet to be realized in the Antarctic, I mainly focus on Arctic amplification (AA). Despite the far-reaching consequences of Arctic warming and sea ice loss, the causes of AA and their relative importance remain contested. This dissertation highlights some of the most important AA-producing mechanisms by analyzing the different timescales over which AA develops following an increase in CO₂ in climate model simulations. First, an Arctic and global average energy budget analysis is derived for a collection of Coupled Model Intercomparison Project version 5 (CMIP5) models subjected to an instantaneous quadrupling of CO₂ (4xCO₂). I quantify the relative contributions of various AA mechanisms using radiative kernels for 150 years after 4xCO₂ and compare mechanisms important at the beginning of the simulations against those when the models are in a quasi-equilibrium state. To focus on the fast timescales of AA, a new ensemble of Community Earth System Model (CESM) simulations was generated to observe the development of AA on ultrafast timescales (< 1 month) and to investigate the impact of the season in which CO₂ is increased. Finally, AA mechanisms and their seasonality are compared to those acting to produce Antarctic amplification (AnA). Motivated by this analysis, a new Python package called ClimKern was developed to simplify feedback calculations using radiative kernels and intercompare results based on different kernels. This work shows that AA occurs on incredibly fast timescales following CO₂ forcing, developing within three months in CMIP5 models and on the order of days in the CESM simulations in which CO₂ increases in January. The feedbacks important for AA immediately following CO₂ increase are not the same as those important decades afterward, demonstrating a strong time dependence of AA mechanism strength. Although sea ice loss and the associated surface albedo feedback play leading roles in the long-term development of AA, other mechanisms more clearly explain the rapid development of AA, namely, temperature feedbacks and the surface latent heat flux response. AnA also develops on ultrafast timescales, though on timescales greater than one month, AA is considerably greater than AnA. This results from a stronger SHU response and temperature feedbacks in the Arctic compared to the Antarctic. Lastly, I find that the magnitudes of feedbacks, especially the surface albedo feedback, exhibit considerable sensitivity to the kernel choice, indicating that using several different sets of kernels will make future feedback studies more robust.

IPCC, WHO and FAO have recently published reports connecting the animal industry with Global warming, cancer and 70% of modern diseases. In fact, IPCC (2014) indicated that the greatest potential for reducing emissions is placed on the consumer’s level. For this context, grounded in concepts of the Foucauldian Discourse Analysis and the Compositional Analysis (Rose, 2001) this study analyzed a series of advertisements issued in the period after the reports (2013-2015). The analysis was guided by three central questions: (1) Which linguistic and visual approaches, as well as their organization and strategies applied in the discourse, is the Animal Industry using in the construction of their advertisements and how they react to this moment of crises? (2) Considering Barthes ́ approach of food as symbols containing a communicational construction, what are the meanings built around animal products understood from the perspective of discourse? (3) How is the Animal Industry positioning themselves towards audiences and culture and what functions are they giving to themselves in society? Following a political theoretical framework, the proposition that the animal commodification is an ideology affirmed in western societies will be discussed. Advertisements from seven enterprises of the Animal Industry in EU will be used, selected for having leading positions in their sectors (meat and dairy). Among the results, it was verified that the relation toward human interaction is the major enunciator in the advertisements. The following lines of enunciation were identified: example and empathy; imperative discourses; tradition. The enunciations of meat have emotional basis; while the constructions around dairy focuses on the western representation of archaic nature (Haraway, 1989). The denotative qualities of the foods where very little considered. The political and ethical questions around the animal products were absent. This study focuses on the necessity of a political and critical approach of the marketing strategies of the Animal Industry. KEY WORDS: Animal Industry, Global Warming, Discourse Analysis, Foucault

Juvenile rainbow trout were chronically exposed to acidified softwater, alone and in combination with a slight temperature increase in order to understand the possible effects of global warming and environmental acidification in freshwater fish. The second goal was to determine the role of diet in the response to acid stress and elevated temperatures. In the first two exposures, a simulated global warming scenario (+2°C) was applied for 90 days in winter (8-12 °C), in the presence and absence of sublethal acidity (pH 5.2). In the first trial, fish were fed to satiation twice daily, while in the second trial, fish were fed only 1% of their wet body weight every four days (~0.25% daily). A slight increase in temperature caused a marked increase in oxygen consumption, nitrogenous waste excretion and growth, although there did not appear to be any specific pH effects. During the Satiation Exposure, fish exposed to low pH especially at slightly elevated temperatures had increased appetites compared to non-acid exposed fish. This increased appetite suggested that NaCl losses brought about by low pH exposure, stimulated appetite in some way, thereby alleviating any ionoregulatory disturbances. During the Limited Ration Exposure, ionoregulatory disturbances occurred during low pH exposure, with more dramatic effects in fish at slightly elevated temperatures. Trout maintained on a limited diet had a higher mortality rate, lower plasma and whole body Na⁺ and Cl⁻ concentrations, and elevated cortisol levels compared with fish fed to satiation. Thus, it became clear that fish could use food to compensate for the stresses of increased temperature and low pH. The third exposure was conducted to determine whether food simply provided the necessary fuel to meet the increased cost of living in a low pH environment, or whether food directly provided the dietary salts necessary to replace branchial ion loss. Diets were formulated at two levels of energy (regular: 16.31MJ/kg or low: 9.77MJ/kg) and two levels of NaCl (regular: 263 mmols/kg or low: 43 mmols/kg) using a factorial design (2x2=4 treatments). In addition, a fifth group of fish were not fed during the exposure. All five groups of fish were challenged with pH 4.0 to induce a rapid ionoregulatory disturbance and then held at pH 5.2 for the next 28 days. During this month, fish were fed 0.6% of their body weight of one of the four diets. Fish fed the low salt diets incurred typical long-term ionoregulatory disturbances with decreased whole body Na+, K+ and Cl concentrations. These effects were not seen in fish fed regular salt diets, regardless of energy content, showing that it is the salt content of the food rather than the energy content which is critical in protecting against the deleterious effects of low environmental pH. Interestingly, fish fed the regular energy/low salt diet had high cortisol levels and increased mortality while fish fed the regular salt diets, low energy/low salt diets and starved fish did not have a high rate of mortality. These results may have been due to differences in metabolic rate and therefore oxygen consumption (M₀₂). Starved fish had the lowest M₀₂. Fish fed the regular energy diet had increased post-prandial M₀₂ due to the specific dynamic action evoked in fish by ingestion of protein-rich food. An increase in oxygen consumption may have caused an increase in branchial ion loss, thereby exacerbating the ionoregulatory deficit associated with chronic acid exposure. This is detrimental when dietary salts are unavailable to replace branchial losses. Overall, the salt content of food may play an important role in ameliorating the deleterious effects of chronic low pH, while the energy content of food may complicate the response. / Thesis / Master of Science (MS)

Quantitative information about halogenated hydrocarbons is important for understanding their impact on atmospheric ozone chemistry and climate change, their regulation, and the devising of improved substitutes. The Montreal Protocol aimed to regulate the utilization and manufacturing of hydrochlorofluorocarbon compounds (HCFCs), contributing to ozone layer depletion. The 2016 Kigali Amendment to the Montreal Protocol agreement, Annex C listed 274 HCFCs. Only 16 of them have been measured experimentally. The rest were set to zero by default. These reported global warming potentials (GWPs) play a crucial role in formulating policies for gradually reducing the usage and production of HCFCs to prevent atmospheric impact. Here we are studying 1-chloro-1-fluoro-ethane (CH3CHFCl) as a test of past theory. There are no prior experimental measurements of the reactivity of CH3CHFCl with hydroxyl (OH) radicals, which primarily determines its atmospheric lifetime, nor of its infrared (IR) spectrum. Saturated hydrofluorocarbons (HFCs) are non-ozone depleting substitutes for chlorofluorocarbons deprecated under the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, but they exhibit high global warming potentials (GWPs) and the Kigali Amendment adopted in 2016 outlines their phase down. Unsaturated HFCs offer more reactive alternatives, whose likely short atmospheric lifetimes would imply small GWPs. Because their GWPs are smaller than those for saturated HFCs by several orders of magnitude, and especially for fully fluorinated examples, several halogenated olefins are under consideration for practical application. We studied HCF2CF2CF=CF2, cis-HCF=HCF, trans HCF=HCF, CF2=CH2 unsaturated HFCs.

This research studied the efficacy of enhancing information-based appeals with social influence strategies in order to encourage environmental activism and efficiency behaviors in response to global warming. A secondary goal was to study the relationship between pro-environment attitudes as measured by the New Ecological Paradigm (NEP) and the activism/efficiency behaviors. After hearing a 15-minute presentation about the threat of global warming, 270 participants were encouraged to take relevant action by (a) signing web-based petitions asking automakers to build more environmentally friendly cars, (b) sending web-based letters to their state senators asking them to pass legislation to curb global warming, and (c) replacing their own inefficient incandescent light bulbs with compact fluorescent light bulbs (CFLs). The primary independent variable was the intervention technique used to encourage the three behaviors. The Information Only condition received a standard informational presentation, and a Social Influence condition received a presentation enhanced by the social psychological principles of authority, social validation, and consistency. A third group—Social Influence and Commitment—received the social influence manipulations and also signed a commitment statement. Overall compliance was relatively low, with 30.7% of participants across all conditions completing one or more activism/efficiency behavior. Statistical comparisons of the compliance rates of the three groups were insignificant, and thus failed to support the efficacy of the social influence approach. Participants who held stronger pro-environment attitudes were more likely to complete the tasks. Those who completed at least one of the environmental actions scored significantly higher on a pre-presentation NEP (m = 54.9) than those who completed none (m = 50.3). In addition, political conservatism was negatively related to the NEP and task compliance. Finally, individuals who completed at least one of the requested behaviors showed a significant increase in pro-environment attitude on a second (post intervention) NEP, while the NEP scores of non-compliers remained unchanged. / Ph. D.

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