The Arctic region shows a particularly high susceptibility to climate change, which historically manifests in an amplification of the near-surface warming in the Arctic relative to the global mean. This Arctic amplification (AA) has impacts on the climate system also beyond the northern polar regions, which highlights the importance to adequately represent it in numerical models. While state-of-the-art climate models widely agree on the presence of AA, they simulate a large spread in the magnitude of Arctic-amplified warming. This thesis addresses the need to evaluate the performance of global climate models in projecting AA and its most important drivers. For the latter, the focus is on the three amplifying climate feedbacks (ACFs) that largely drive the meridional warming structure leading to AA. The ACFs include the sea-ice-albedo feedback (SIAF), the Planck feedback, and the lapse-rate feedback (LRF). These feedbacks arise from the relevant changes in Arctic sea ice, near-surface temperatures, and the deviation from the near-surface temperature change through the atmosphere, respectively. In the thesis, two observational constraints are presented to narrow the range of climate models of the sixth Coupled Model Intercomparison Project (CMIP6) regarding their projection of AA and the ACFs in both past and future climate. While for the past, the models representation of near-surface processes can often be directly evaluated against observations, it is particularly the LRF that is difficult to constrain as it incorporates the entire atmospheric warming structure. As a consequence, the historical constraint focuses on the LRF, while the future constraint gives a prediction range for the evolution of AA and all three ACFs through the 21st century. The main results are highlighted in the view of the changing atmospheric energy budget (AEB) of the Arctic under anthropogenic climate forcing. The AEB provides a framework to address Arctic climate change at large scales, and further helps to decide on the relevant aspects that provide appropriate metrics for constraining both AA and the ACFs. In other words, the perspective of a changing Arctic AEB highlights important alterations of the energetics under climate change, that further link to changes in climate aspects that partly explain the inter-model spread in simulated AA and the ACFs. The main results of the cumulative thesis are formulated on the basis of three published research papers, papers I, II, and III. Paper I addresses the Arctic AEB which is typically characterised by an equilibrium between net radiative cooling and advective heating, and mostly an absence of convection. This radiative-advective equilibrium (RAE) approximates well the energy budget and thermal structure of the Arctic atmosphere. The main outcome of paper I is that with continuous warming as simulated by CMIP6 models in an idealised setup, a deviation from the RAE increasingly develops, resulting from sea ice retreat and increased ocean-to-atmosphere heat fluxes. These changes are further concomitant with a depletion of the typical surface-based temperature inversion and a decrease in advective heating, which is byword for the convergence of atmospheric energy transport in the Arctic. Since the RAE currently explains much of the basic thermal structure of the Arctic atmosphere, those changes have the potential to further mediate the LRF. Paper II builds on paper I and evaluates the performance of climate models in representing the key aspects of the Arctic LRF in CMIP6 historical simulations that have the best estimates of the transient climate forcings during the observational period. In particular it is found that CMIP6 models that realistically simulate both the lower thermal structure of the atmosphere and the poleward atmospheric energy transport are more trustworthy in informing about the LRF and how much it contributed to Arctic warming during the past few decades. The evaluation is based on observations of surface-based temperature inversions during the year-long Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, and atmospheric energy transport convergence computations from reanalyses. Paper III expands the constraint approach of paper II and carries out an emergent constraint (EC) on future AA and the ACFs that further elaborates on the physical relationships between the constraining metrics and future climate projections. Previous work has highlighted that parts of the inter-model spread in simulated AA is explained through the spread in contemporaneous sea ice loss across climate models. The thesis confirms this link by showing that CMIP6 models with a stronger climatological sea ice loss project a stronger AA in the future under the assumption of a high emission scenario. By further linking the degree of future ice loss to the current-climate sea ice amount in CMIP6 models, paper III facilitates an EC on the future evolution of AA and the ACFs. In particular, models with a lower contemporary sea ice amount project a larger magnitude of AA by setting the stage for stronger climatological ice loss and near-surface warming, linking to the relevant ACFs. From the corresponding prediction it is evident that AA is expected to continue at a warming rate that is more than twice or three times larger than global-mean warming. Furthermore, the three ACFs continue to contribute to Arctic warming, with the SIAF leading the warming contribution response. Lastly, the consideration of statistically strong and physically plausible relationships across climate models makes the EC a valuable technique to constrain climate model simulations in conjunction with observations. This thesis highlights the potential of combining the advantages of both presented constraints: Using multiple process-relevant aspects instead of one singular metric (paper II), but considering the mechanistic couplings between these metrics and the climate projection of interest (paper III) will improve our model-evaluation techniques and further help guiding the design of future climate simulations.:Summary of the dissertation List of papers Author’s contribution Supervision statement 1 Introduction 2 Research focus 3 The Arctic atmospheric energy budget 3.1 The atmospheric column model 3.2 The annual atmospheric energy budget 4 Arctic amplification and climate feedbacks 4.1 Amplifying climate feedbacks 4.2 A comment on process coupling 5 Methods and data 5.1 Energy budget equations 5.2 Quantifying Arctic amplification and climate feedbacks 5.3 Climate model data 5.3.1 CMIP6 idealised simulations 5.3.2 CMIP6 historical simulations 5.3.3 CMIP6 ssp585 simulations 5.4 Observational constraints 5.4.1 Constraint on historical Arctic lapse-rate feedback 5.4.2 Constraint on future Arctic amplification and relevant climate feedbacks 6 Results 6.1 Paper I - Deviations from the Arctic radiative-advective equilibrium under anthropogenic climate change 6.2 Paper II - Constraining the Arctic lapse-rate feedback during past decades by contemporary observations 6.3 Paper III - Constraining future Arctic amplification and the relevant climate feedbacks based on the recent sea ice climatology 7 Summary and outlook References Lists Acknowledgements Appendix A: Paper I Appendix B: Paper II Appendix C: Paper III

The three approaches followed herein aim to improve our understanding of the paleobiodiversity andevolution of Silurian radiolarians. The first approach provides an exhaustive taxonomic description ofan entirely new radiolarian fauna recovered from two sections of the Cape Phillips Formation in theCanadian Arctic which accumulated in two different paleoenvironmental settings. The samples are datedby graptolites of the Gorstian Lobograptus progenitor Zone. The obtained radiolarian fauna includes 28species, of which 3 are new, and exhibits some of the best preserved Silurian radiolarians known so far.The stratigraphic range of several species was also extended. Then, in a second approach, a CT-Scan3D reconstruction of a specimen of Gyrosphaera cavea was conducted in order to resolve significantinternal structure taxonomic issues. Higher level radiolarian classification is based on internal structures,and classical methods of observing these features repeatedly failed to uncover them. The 3D imagingrevealed a «double» coiling of the specimen that has proved useful in understanding how it grew.Eventually, the third approach is a completion of published taxonomic works in the Silurian with theaim of providing diversity trends through analyses of these radiolarian occurrences. A biotic crisis canbe observed in the Homerian, exhibiting both high extinction and low origination rates, and may belinked with enhanced marine productivity. / De tre projekten som utvecklas här har som mål att fokusera på trender inom evolutionen ochmångfalden av en grupp planktoniska mikroorganismer från Silur (från -443 till -419 Ma). I ett förstaprojekt beskrivs en helt ny fauna radiolarier som hittats i två lokaliteter på de kanadensiska arktiskaöarna, och som har deponerats i olika miljöförhållanden under Silur. Detta material daterades med hjälpav graptoliter, en grupp utdöda svalgsträngsdjur som är mycket användbara för paleozoiska dateringar,till en ålder överensstämmande med Gorstian (-427 till -425 Ma). Denna kanadensisk-arktiska fauna avradiolarier består av 28 arter (varav 3 är nya) och uppvisar några av de bäst bevarade fossilerna frånSilur överhuvudtaget. Den stratigrafiska bredden, vilket är livstiden, av flera arter har också förlängts.Därefter, i ett andra projekt, skapades en 3D-rekonstruktion av ett exemplar av Gyrosphaera cavea medhjälp av mikrotomografi för att observera och beskriva komplexa interna strukturer. Faktum är attklassificeringen av Radiolaria består till stor del av analysen och beskrivningen av dessa internastrukturer och många klassiska metoder som har använts för att observera dem, såsom med hjälp avsvepelektronmikroskop, har misslyckats konsekvent. 3D-avbildningen visade en komplex dubbelrullandeav strukturen i exemplaret, som har visat sig vara användbart i sökandet för att förstå dennesutveckling. Det tredje projektet är slutförandet av en samling av samtliga publicerade arbeten röranderadiolarier från Silur med syfte att klargöra trender inom diversitet för hela perioden genom analyser avförekomsten av dessa radiolarier. Ett utdöende kan observeras under Homerian (-430 till -427 Ma), somtroligen orsakades av frekventa utdöenden och en låg artbildningshastighet.

Polar desert environments are limiting in plant available nutrients, mainly nitrogen (N) and phosphorus (P) that severely limit plant growth and establishment. Cryogenic activity regularly patterns the ground into a patchwork of frost boils – sorted circles that are associated with an increase in moisture, fertility and plant cover. Within some frost boils, the accumulation of ice-rich soil at the permafrost table can cause an upward flow of soil organic carbon (SOC) enriched permafrost material into the active layer. These diapiric intrusions are predicted to fuel microbial activity and enrich the horizon in N and P; however, the enrichment of the diapir horizon and accessibility by plants has yet to be studied. The aim of this research was to characterize the N distribution within diapir horizons located in frost boils and the effect of these intrusions on vascular plant N uptake in a polar desert ecosystem of the Canadian High Arctic. Natural abundance and enriched isotope 15N techniques were used to trace the flow of N through the soil-plant system. Surface and diapir horizons contained the highest total C and total N content within frost boils. Natural abundance δ15N analysis indicated that uptake by Salix arctica plants located on frost boils in the absence of a diapir horizon were sourcing N from the surface. However, when diapir nutrients became available, S. arctica plants began sourcing N from the diapir horizon and underlying low SOC sources in the soil, while reducing uptake from the surface. The altered foraging strategy of S. arctica in response to diapir horizon formation was further indicated by significant uptake of atom%15N nutrients that were injected directly into diapir horizons. These findings suggest diapir horizons are enriched in N and accessible by plants roots as an important nutrient source that is instrumental in their survival within frost boils of a polar desert ecosystem in the high arctic.

The Arctic—warming at twice the rate of the rest of the planet—is a source of striking imagery of amplified environmental change in our time, and has come to serve as a spatial setting for climate crisis discourse. The recent alterations in the Arctic environment have also been perceived by some observers as an opportunity to expand economic exploitation. Heightened geopolitical interest in the region and its resources, contradicted by calls for the protection of fragile Far North ecosystems, has rendered the Arctic an arena for negotiating human interactions with nature, and for reflecting upon the planetary risks and possibilities associated with the advent and expansion of the Anthropocene—the proposed new epoch in Earth history in which humankind is said to have gained geological agency and become the dominant force over the Earth system. With the Arctic serving as a nexus of crosscutting analytical themes spanning contemporary history (the late twentieth and the early twenty-first century until 2015), this dissertation examines defining characteristics of the Anthropocene and how the concept, which emerged from the Earth system science community, impacts ideas and assumptions in historiography, social sciences and the environmental humanities, including the fields of environmental history, crisis management and security studies, political geography, and science and technology studies (STS). The primary areas of empirical analysis and theoretical investigation encompass constructivist perspectives and temporal conceptions of environmental and climate crisis; the role of science and expertise in performing politics and shaping social discourse; the geopolitical significance of telecoupling—a concept that reflects the interconnectedness of the Anthropocene and supports stakeholder claims across wide spatial scales; and implications of the recent transformation in humankind’s long duration relationship with the natural world. Several dissertation themes were observed in practice at the international science community of Ny-Ålesund on Svalbard, where global change is made visible through a concentration of scientific activity. Ny-Ålesund is furthermore a place of geopolitics, where extra-regional states attempt to enhance their legitimacy as Arctic stakeholders through the performance of scientific research undertakings, participation in governance institutions, and by establishing a physical presence in the Far North. This dissertation concludes that this small and remote community represents an Anthropocene node of global environmental change, Earth system science, emergent global governance, geopolitics, and stakeholder construction in an increasingly telecoupled world.

This thesis assesses the potential success of the United States’ newly assumed role as chairman of the Arctic Council in light of its own record of development in Alaska, its only Arctic territory. Using primary and secondary qualitative research, perspectives from multiple stakeholders are analyzed to assess the United States’ current capabilities in the Arctic versus its rhetoric and responsibilities. To gauge this more effectively, the theory of problem-solving capacity is used to analyze the United States’ potential capacity in the Arctic Council, while the theory of environmental security is used to analyze the United States’ level of investment and commitment to Alaska. With development in Alaska minimal at best and local communities at risk from environmental impacts, the ideal tool for addressing these deficiencies is identified to be icebreakers operated by the United States Coast Guard. Impediments to acquiring sufficient icebreaking capacity are explored, with the conclusion that if the United States is to take effective action on the Arctic stage, investment in icebreakers and therefore the environment and inhabitants of the Arctic is necessary. Not doing so reveals the USA’s agenda to be empty rhetoric and consequently this lost opportunity for leadership may lead to catastrophic results for the region.

The Arctic is a region undergoing unprecedented and unequivocal climate change. The seas of this extreme region form a major component of the oceanic thermohaline conveyor and natural carbon cycle. Using a combination of recent and historical datasets this study examines the distribution, diversity, photophysiology and primary productivity of phytoplankton in the Atlantic sector of the Arctic Ocean. CHEMTAX analysis reveals a diverse phytoplankton community structure in the Greenland Sea comprising six main phytoplankton groups. The influence of sea-ice and water column stratification are key factors in the presence or absence of groups such as haptophytes and prasinophytes. Group-specific differences are observed in spectral absorption and photophysiological parameters. However, the influence of environmental factors has a stronger influence than taxonomic composition on photophysiology. A clear division between the photoacclimatory response of algal communities beneath sea-ice and those of open-ocean stations is predominantly due to ‘E_k independent’ photoacclimation beneath sea-ice. This occurs due to the combined effect of sea-ice decreasing irradiance entering the water column and a positive correlation between P_m ^B and temperature. This variation in photophysiology is important for primary production models as a sensitivity analysis shows that errors in these parameters propagate to give the largest final errors in primary production values. The importance of other model parameters varies with the level of biomass in the water column and the presence or absence of sea ice. Accelerated ice-melt and an increase in open water due to climate change are likely to increase primary production in the Atlantic Arctic alongside an altered distribution of phytoplankton groups, with an increase in the importance of prasinophytes or haptophytes.

Constructing Arctic Sovereignty: Rules, Policy and Governance 1494--‐201 is a meta-narrative of the development of state sovereignty in the Arctic. It investigates the evolution of the rules of the international system over the longue durée, in so far as they frame Arctic sovereignty. It examines in particular the increasing importance of the legal dimension of territory and the transitions that have occurred with the introduction of new rules used by states to establish sovereignty. The thesis analyses the policy of the United States, Canada and Russia as they pursue their national interests in the region with reference to (and at times in contravention of) international rules and codes, and it situates governance within the framework of the international system as a mechanism for states to pursue their interests in the Arctic beyond their sovereign borders. This thesis makes an original contribution to knowledge through its distinctive methodology and theoretical approach, as well as through its analysis of primary materials. Using the pillars of a constructivist research framework including rules and interests over the longue durée to develop a meta- narrative of Arctic sovereignty, it situates contemporary Arctic foreign policy and governance within the evolving framework of the international system, identifying imperialism as a common thread in the relationship between the Arctic states and Arctic territory. It concludes that the expansion of sovereignty over this new territory represents the continuation of imperialism within the international system by states, perpetuating an asymmetric relationship that allows states to absorb this territory for the purposes of resource exploitation in the pursuit of national interests with international cooperation maintaining the primacy of the Arctic states within the region.

In glacierised regions, suspended sediment fluxes are highly responsive to climate-driven environmental change and can provide important information regarding the relationships between glacier variations, climate and geomorphic change. As a result, understanding patterns of suspended sediment transport and their relationship with meltwater delivery is of critical importance. However, studies of glacial suspended sediment transport are often limited by interpreting patterns of suspended sediment transfer based on whole-season data, allowing precise patterns to become masked. This thesis aims to contribute to the understanding of suspended sediment transfer in glacierised basins through the investigation of patterns of suspended sediment delivery to the proglacial area of Storglaciären, a small polythermal valley glacier located in the Tarfala valley, Arctic Sweden. High temporal resolution discharge and suspended sediment concentration data were collected during two summer field campaigns at Storglaciären. Interpretations of suspended sediment transport data were made using diurnal hysteresis and sediment availability data, combined with suspended sediment shape and magnitude data classified by applying principal component and hierarchical cluster analyses. Analysis of the dominant discharge generating processes at Storglaciären was also conducted using principal component analysis, allowing patterns of discharge to be better understood. This was complemented by analysis of the structure and evolution of the glacier drainage system by linear reservoir modelling and flow recession analysis. The results suggest that patterns of discharge and suspended sediment transport at Storglaciären are complex, with distinct processes and magnitudes of transport evident at both proglacial outlet streams, Nordjåkk and Sydjåkk. These processes are intrinsically linked to meteorological variables, with both ablation-driven and precipitation-driven discharge exerting influence over patterns of suspended sediment transport in the proglacial area of Storglaciären.

Arctic ecosystems are undergoing rapid environmental transformations. Climate change is affecting permafrost temperature, vegetation structure, and wildlife populations, and increasing human development is impacting a range of ecological processes. Arctic indigenous communities are particularly vulnerable to environmental change, as subsistence harvesting plays a major role in local lifestyles. In the Inuvialuit Settlement Region (ISR), in the western Canadian Arctic, indigenous land-users are witnessing a broad spectrum of environmental changes, which threaten subsistence practices. Local cumulative effects monitoring programs acknowledge the importance of subsistence land use; however there are few cumulative effects assessments that measure the impact of environmental change on land-based activities. My MSc addresses this gap with a broad-scale spatial inventory that measures the distribution of multiple disturbances in the mainland ISR, and assesses their overlap with community planning areas, land management zones, and caribou harvesting areas. I also generated nine future disturbance scenarios that simulate increases in both human development and wildfire occurrence, in order to understand how additional environmental change may affect the availability of un-impacted harvesting lands. I used the conservation planning software, Marxan, to assess the impact of increasing environmental perturbations on the availability and contiguity of 40 subsistence harvesting areas. Results show that the study region is already impacted by multiple environmental disturbances, and that these disturbances overlap considerably with wildlife harvesting areas. This limits the success of Marxan runs that attempt to conserve high percentages of subsistence use areas. It becomes increasingly difficult to conserve large, contiguous assortments of wildlife harvesting areas when using Marxan to assess conservation potential in future disturbance scenarios. In a separate study, I conducted 20 semi-structured interviews in the communities of Inuvik, Aklavik, and Tuktoyaktuk that explored the impact of environmental change on Inuvialuit land-users. Participants in my study indicated that wildlife harvesting in the region is being affected by a range of environmental disturbances and that this change is typically considered to be negative. Climate change-related disturbances were noted to affect travel routes, access to harvesting areas, wildlife dynamics, and the quality of meat and pelts. Human activity, such as oil exploration, was noted to impact both wildlife populations and harvesters’ ability to use the land. These observations are an important contribution to local cumulative effects monitoring because they highlight local accounts of environmental change, which are often missed in broad-scale assessments, and they emphasize the concerns of local land-users. This underscores the importance of including indigenous insights in cumulative effects monitoring and suggests that combining quantitative assessments of environmental change with the knowledge of local land-users can improve regional cumulative effects monitoring. / Graduate

Vegetation community patterns and processes are indicators and integrators of climate. Recently, scientists have shown that climate change is most pronounced in circumpolar regions. Arctic ecosystems have traditionally been sequestering carbon and accumulating large carbon stores. However, given enhanced warming in the Arctic, the potential exists for intensified global climate change if these ecosystems transition from sinks to sources of atmospheric CO2. In the Mid and High Arctic, ecosystems exhibit extreme levels of spatial heterogeneity, particularly at landscape scales. High spatial-resolution (e.g., 4m) remote sensing data capture heterogeneous vegetation patterns of the Arctic landscape and have the potential to model ecosystem biophysical properties and CO2 fluxes. The following conditions are required to model arctic ecosystem processes: (i) unique spectral signatures that correspond to variations in the landscape pattern; (ii) models that transform remote sensing data into derivative values pertaining to the landscape; and (iii) field measures of the variables to calibrate and validate the models. First, this research creates an ecosystem classification scheme through ordination, clustering, and spectral-separability of ground cover data to generate ecologically meaningful and spectrally distinct image classifications. Classifications had overall accuracies between 69% - 79% and Kappa values of 0.54 - 0.69. Secondly, biophysical variable models of percent vegetation cover, aboveground biomass, and soil moisture are calibrated and validated using a k-fold cross-validation linear bivariate regression methodology. Percent vegetation cover and percent soil moisture produce the strongest and most consistent results (r2 ≥ 0.84 and 0.73) across both study sites. Finally, in situ CO2 exchange rate data, an NDVI model for each component flux, which explains between 42% and 95% of the variation at each site, is generated. Analysis of coincidence indicates that a single model for each component flux can be applied, independent of site. This research begins to fill a gap in the application of high spatial-resolution remote sensing data for modelling Arctic ecosystem biophysical variables and carbon dioxide exchange, particularly in the Canadian Arctic. The results of this research also indicate high levels of functional convergence in ecosystem-level structure and function within Arctic landscapes. / Thesis (Ph.D, Geography) -- Queen's University, 2013-01-03 22:24:20.157