Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2006. / Wang, Yuhang, Committee Chair ; Black, Robert, Committee Member ; Curry, Judith, Committee Member ; Huey, Greg, Committee Member ; Russell, Armistead G, Committee Member. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The Arctic marine system is currently undergoing transition as a result of climate change. This study examines the effects of this transition on rates of air-sea CO2 exchange within the eastern Canadian Arctic. Continuous seawater pCO2 measurements revealed this area to be a strong summertime sink of atmospheric CO2. Total alkalinity and stable oxygen isotopes were utilized as freshwater tracers, revealing areas of significant sea ice melt and riverine inputs. Eastern Baffin Bay and Barrow Strait were found to be strongly influenced by sea ice melt, lowering seawater pCO2; whereas Kennedy Channel contained significant river discharge, raising seawater pCO2. Primary production in surface waters was low throughout the region, with the exception of Petermann Fjord where glacial ice melt likely transports nutrients to the surface. This region is anticipated to represent a weaker CO2 sink in the future, due mainly to predicted decreases in sea ice thickness and extent. / February 2016

Direct measurements of wintertime surface heat fluxes between the ocean and atmosphere in lead and polynya environments in the Canadian Arctic are presented. Such environments can yield very large vertical temperature gradients during the winter months and are particularly dynamic micrometeorological environments. We found that sensible heat fluxes can exceed +100 W m-2 during the winter months, much larger than most regional estimates (~ 0 W m-2). In addition, large heat fluxes are shown to affect the characteristics of the near surface temperature inversion (temperature increases with height). The height, depth and strength of the characteristic wintertime inversion are shown to be influenced in cases where large surface fluxes were observed. Such findings are likely to have implications on the regional and planetary heat budget, general circulation models and larger scale weather processes, which most often omit local scale heat fluxes in their analyses and calculations. / February 2016

Arctic clouds are poorly represented in numerical models due to the complex, small-scale interactions which occur within them. Modelled cloud fractions are often significantly less than observed in this region; therefore, the radiative budget is not accurately simulated and forecasts of the melting cryosphere are fraught with uncertainty. Our ability to accurately model Arctic clouds can be improved through observational studies. Recent in situ airborne measurements from the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are presented in this thesis to improve our understanding of the cloud microphysical interactions unique to this region. Aerosol-cloud interactions - where aerosol particles act as ice nucleating particles (INPs) or cloud condensation nuclei (CCN) - are integral to the understanding of clouds on a global scale. In the Arctic, uncertainties caused by our poor understanding of these interactions are enhanced by strong feedbacks between clouds, the boundary layer, and the sea ice. In the Arctic spring, aerosol-cloud interactions are affected by the Arctic haze, where a stable boundary layer allows aerosol particles to remain in the atmosphere for long periods of time. This leads to a heightened state of mixing in the aerosol population, which affects the ability of particles to act as INPs or CCN. Aerosol particle compositional data are presented to indicate which particles are present during the ACCACIA campaign, and infer how they may participate in aerosol-cloud interactions. Mineral dusts (known INPs) are identified in all flights considered, and the dominating particle classes in each case vary with changing air mass history. Mixed particles, and an enhanced aerosol loading, are identified in the final case. Evidence is presented which suggests these characteristics may be attributed to biomass burning activities in Siberia and Scandinavia. Additionally, in situ airborne observations are presented to investigate the relationship between the Arctic atmosphere and the mixed-phase clouds - containing both liquid cloud droplets and ice crystals - common to this region. Cloud microphysical structure responds strongly to changing surface conditions, as strong heat and moisture fluxes from the comparatively-warm ocean promote more turbulent motion in the boundary layer than the minimal heat fluxes from the frozen sea ice. Observations over the transition from sea ice to ocean show that the cloud liquid water content increases four-fold, whilst ice crystal number concentrations, N_ice, remain consistent at ~0.5/L. Following from this study, large eddy simulations are used to illustrate the sensitivity of cloud structure, evolution, and lifetime to N_ice. To accurately model mixed-phase conditions over sea ice, marginal ice, and ocean, ice nucleation must occur under water-saturated conditions. Ocean-based clouds are found to be particularly sensitive to N_ice, as small decreases in N_ice allow glaciating clouds to be sustained, with mixed-phase conditions, for longer. Modelled N_ice also influences precipitation development over the ocean, with either snow or rain depleting the liquid phase of the simulated cloud.

Recent field observations suggest that the radiative forcing of aerosol and clouds in the Arctic may be seasonally regulated by the oceanic emissions of the climatically-important biogenic trace gas dimethylsulfide (DMS). However, the validity of the proposed argument is challenged by the limited spatio-temporal coverage of these earlier studies in this difficult-to-access region. In particular, little is known about the pan-Arctic distribution of the oceanic DMS emissions, its temporal variability, and the impacts of sea-ice biogeochemistry on these emissions. In this dissertation, I investigated these unexplored subjects through numerical modelling. Using a one-dimensional (1-D) column modelling framework, I developed a coupled sea ice-ocean biogeochemical model and assessed the impacts of bottom-ice algae ecosystems on the underlying pelagic ecosystems and the associated production and emissions of DMS. The model was calibrated by time-series measurements of snow and melt-pond depth, ice thickness, bottom-ice and under-ice concentrations of chlorophyll-a and dimethylsulfoniopropionate (DMSP), and under-ice irradiance obtained on the first-year landfast sea ice in Resolute Passage during May-June of 2010. Many of the model parameters for the DMSP and DMS production and removal processes were derived from recent field measurements in the Arctic, which is advantageous over the previous Arctic-focused DMS model studies as their model parameters were based on the measurements in extra-polar regions. The impacts of sea-ice biogeochemistry on the DMS production in the underlying water column and its potential emissions into the overlying atmosphere were quantified through sensitivity experiments. To extend the study domain to the pan-Arctic, I implemented the sea-ice ecosystem and the coupled sea ice-pelagic DMS cycling components of the 1-D column model into a three-dimensional (3-D) regional modelling framework. A multi-decadal model simulation was performed over the period 1969-2015 using realistic atmospheric forcing and lateral boundary conditions. The results of the simulation were evaluated by direct comparisons with available data products and reported values based on field and satellite measurements and other model simulations. The decline of Arctic sea ice was successfully simulated by the model. The magnitude of the pan-Arctic sea-ice and pelagic annual primary production and their general spatial patterns were comparable to other model studies. The mean seasonal cycle and the spatial distribution of the model-based surface seawater DMS climatology within the pan-Arctic showed some similarities with in situ measurement- and satellite-based climatologies. However, at the same time, the comparison of the DMS climatologies was challenged by the bias in the measurement-based climatology, emphasizing the need to update this data product, which was created almost a decade ago, by incorporating data acquired during the recent field campaigns. The analysis of the modelled fluxes of DMS at the ice-sea and sea-air interfaces revealed different responses to the accelerated decline of sea ice over the recent decades (1996-2015). There was no trend in the pan-Arctic ice-to-sea DMS flux due to the counteracting effect of vertical thinning and horizontal shrinking of sea ice that drove ice algal production. In contrast, the pan-Arctic sea-to-air DMS flux showed a consistent increase (about 40 % over the last two decades) driven by the reduction of sea ice cover that promoted outgassing and biological productivity. This finding suggests that the climate warming in the Arctic causes an increase in DMS emissions, and encourages further exploration of the biological climate regulation in the Arctic. / Graduate

Indigenous peoples as political actors in the Arctic Council is an understudied subject.Indigenous peoples have a unique status as Permanent Participants to the Arctic Council,enabling them to affect the policy-making and decisions made within the Council. There areconcerns, however, to the level of Indigenous peoples’ inclusion. Research shows that theworking relationships between the eight Arctic member states of the Council and thePermanent Participants creates dependency, among other things because the PermanentParticipants rely on funding from the member states. This in turn questions the status of thePermanent Participants, and whether they are included into the Arctic Council as independentpolitical actors. This paper aims to build upon research done by Michaela Louise Coote andMonica Tennberg, researchers whom both have contributed to this field of research.

This thesis aims to describe and compare how the securitization of the Arctic is represented in mainstream media of Norway and Canada. As two Arctic nations part of the likeminded group in international relations it is interesting to see how national media frames respective nations’ Arctic interests and strategy. Based on securitization and framing theory this thesis identifies themes and trends surrounding the Arctic by using three different security concepts: economic security, traditional security and environmental security. The data for study will be in total 189 full-text articles from both nations’ mainstream media, where search terms relating to a security grammar will be used. A qualitative content analysis will be employed on articles from Norwegian media, specifically Aftenposten, and Canadian media, The Globe and Mail. The analysis will show that both Norwegian and Canadian mainstream media thematically framed the securitization of the Arctic predominantly through the same security concepts. Yet there were differences in relation to attitudes towards Arctic securitization where Canadian media showed a more assertive disposition towards other nations involvement. Norwegian media, on the other hand was more inclined towards regional cooperation.

Photoautotrophic microorganisms, i.e. cyanobacteria and microalgae, are ubiquitous in the glacial ecosystem of the high Arctic archipelago of Svalbard. Their communities play significant roles in the ecosystem, including organic carbon production on the glacier surface and its supply to downstream environments, initiating microbial colonisation after glacier retreat and preparing proglacial substrata for further succession.