The biogeochemical cycling of oceanic dissolved cadmium (dCd) has been an active area of research for the past ~40 years, due in part to the close correlation with phosphate (PO4). The global Cd:PO4 relationship has led to the use of microfossil Cd/Ca as a paleoproxy for ocean circulation and nutrient utilization; however considerable spatial and temporal variability in the relationship - particularly in surface waters - limits the utility of the proxy. Understanding the global biogeochemical cycling of Cd is an active area of research; however the Arctic Ocean is largely omitted from global models due to lack of data. This work presents depth profiles of dCd and Cd/PO4 ratios from 18 individual stations in the Canadian Arctic, collected during the Canadian GEOTRACES cruises GN02 and GN03, which connect the Arctic Ocean to the North Atlantic through the Canadian Arctic Archipelago (CAA). Salinity-driven water mass stratification exerts a primary control on the spatial distribution of Cd in the region, with elevated dCd and high Cd/PO4 ratios (~0.37 pM/μM) associated with waters of Pacific-origin. The elevated dCd and Cd/PO4 ratios are used as a tracer of Pacific-origin waters, identifying the presence of Pacific-origin water through the CAA and into Baffin Bay. High surface Cd/PO4 ratios were observed across the transect, consistent with a general global increase in surface water Cd/PO4 with increasing latitude. The analysis of Cd and other bioactive trace metals (Mn, Fe, Ni, Cu, Zn and Pb) still presents considerable analytical challenges due to the high-risks of contamination, low concentrations and complex matrices. I present a novel multi-element analytical method, which combines the commercially-available seaFAST pico preconcentration system with ICP-MS/MS analysis. In this work, we demonstrate that ICP-MS/MS, which combines two mass-selecting quadrupoles separated by an octopole collision/reaction cell, effectively removes common interferences (ArO+ on 56Fe and MoO+ on Cd) when pressurized with O2 gas. Accurate and precise measurements of iv the consensus references standards SAFe S and SAFe D and the certified reference material NASS-6 are presented as validation of the method. This thesis presents a novel method for the analysis of trace / Graduate

The dynamics of the Arctic ocean are studied on a polar projection of the sphere. The density structure is idealized as a two-layer system, and a general formulation is developed which allows inclusion of latitudinal and longitudinal depth variations as well as asymmetries in the boundaries of the ocean. For simplicity, the density structure is neglected when depth variations are present. Time dependent displacements from equilibrium levels are assumed to be waves of constant zonal wave number; no radial propagation is considered. Amplitude equations are derived for these displacements, subject to the assumption that the polar basin is small enough to keep only a first approximation to the curvature of the Earth. A semi-qualitative investigation of the possible solutions is made in the case of a symmetrical basin, using the Method of Signatures, and existence criteria are found for the solutions in the presence of radial depth variations. Concentrating thereafter on planetary waves, explicit solution for such motions in the simplest case (depth constant, symmetrical boundaries) allows comparison with the results of other investigators (Longuet-Higgins, 1964 b; Goldsbrough, 1914 a) . It is found that the polar projection and first approximation to the curvature give quite good results, so that this method may be applied to polar regions in the same way as the β-plane is used in mid-latitudes. The general effects of radial bottom slopes are discussed and a simple example treated more explicitly. Some theorems of Ball (1963) on the motions of shallow rotating fluids in paraboloidal basins are found to hold for such basins in the polar plane approximation to the sphere. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The repercussions of rapid climate-change are felt worldwide, but particularly in Arctic and Subarctic regions. Evidence of recent changes in water chemistry is being recorded in Arctic aquatic ecosystems, bringing further attention to contaminant dynamics in these environments. I assessed the role of dissolved organic matter (DOM) in controlling the bioavailability of mercury (Hg), a top priority among Arctic contaminants, to aquatic food webs using a bacterial bioreporter under oxic conditions. Experiments were performed under pseudo- and non-equilibrium conditions, in both defined media and water samples from tundra lakes with a large gradient in DOM. Inorganic HgII was considerably more bioavailable under non-equilibrium conditions than when DOM was absent or when HgII and DOM had reached pseudoequilibrium (24h). Under these enhanced uptake conditions, HgII bioavailability followed a bell shaped curve as DOM concentrations increased, both for defined media and field samples, suggesting that complexation kinetics and binding thresholds on DOM determine HgII bioavailability to methylating bacteria, and likely MeHg concentrations, the bioaccumulative neurotoxic form of Hg. Experiments also suggest that DOM may alter cell wall properties to facilitate the first steps toward HgII internalization via facilitated or active transport, and yet without altering overall cell wall permeability. While further research on ternary (HgII-cell-DOM) interaction is warranted, I propose a molecular shuttle model for DOM in facilitating bacterial HgII uptake, and the existence of a short-lived yet critical time window (<24h) during which DOM facilitates the entry of newly deposited HgII from the atmosphere into aquatic food webs.

This thesis presents a detailed study of recent changes in the mass balance and dynamics of Penny Ice Cap (PIC), and projects its evolution under a warming climate. Mass losses from 2005-2014 were quantified from airborne altimetry elevation change measurements, and adjusted for vertical ice motion caused by firn compaction and/or ice dynamics. Mass loss from PIC increased four-fold between the mid-1990s (-1.3 ± 0.7 Gt a-1) and 2005-2013 (-5.4 ± 1.9 Gt a-1). The adjustment calculations indicate that mass loss may be overestimated by 19% if vertical motion is not properly accounted for. The velocity response to increased surface melt was quantified using satellite imagery and historical ground measurements from Highway Glacier, on the southern part of PIC. Over the period 1985-2011, the six largest outlet glaciers on the ice cap decelerated at an average rate of 21 m a-1 over the 26 year period (0.81 m a-1), or 12% decade-1. Highway Glacier decelerated by 71% between 1953 and 2009/11. The recent slowdown of outlet glaciers has coincided with increases in mass loss and an inferred reduction in basal sliding. The ice-cap-wide mass balance was modeled from 1958 to 2099 with an enhanced temperature index model. Since the mid-1990s mass balance rates over PIC have become increasingly negative. Peak mass loss is projected to occur in the late 2070s and PIC is expected to lose 16-20% of its 2014 ice volume by 2099 assuming a moderate climate warming scenario (RCP4.5). If a +2°C offset is applied to this scenario, the ice cap is expected to lose 30-40% of its initial ice volume by 2099. These results provide the first comprehensive evaluation of the impact of vertical ice motion on mass loss derived from geodetic measurements over a large Arctic ice cap. The ice velocity record provides insights into the relationship between surface melt rates and glacier motion over the past 30-60 years. This study projects the mass change of the largest ice cap in the southern Canadian Arctic to 2099, calibrated and validated with a wealth of spatially distributed data for the first time.

Prior to 1963 no previous vegetation studies had been undertaken in this region of the Low Arctic Subalpine/Foothill Zone of the Canadian Western Arctic, although several studies had been completed in similar regions in Arctic Alaska. This study was initiated in 1965 to obtain quantitative and qualitative data on vegetation and environmental relationships, including soil data for characterization of Low Arctic Subalpine/Foothill Zone soils. With these basic data it was considered possible to analyze, integrate and interpret community and soil relationships and to propose a usable classification system for the recognizable ecosystematic units in this portion of the zone. Initial criteria for selecting communities were based on uniformity and discreteness. Vegetation in each community was studied by the single plot method employing phytosociological techniques of the Zurich - Montpellier School as modified by Krajina (1933). Data on environmental conditions collected for each of 166 communities included degree of slope, profile, pattern of topography, exposure, altitude and wind influence. Coefficients of similarity between communities were computed using the formula 2W/A+B X 100, where A is the sum of all measures (abundance and presence) for one community, B is the sum of all measures for another community, and W is the sum of the lower values for each species which the two communities have in common. To determine the degree of affinity and relative hiatus points between groups of communities cluster analysis using the weighted pair - group method was employed. A two-dimensional dendrogram illustrated the individual plots and succeeding clusters. One soil pit was dug in every analyzed plot to either permafrost, water table, coarse ice shattered parent material or bedrock. A total of 498 soil samples for laboratory analysis were collected from all recognizable horizons. Chemical analyses were undertaken to determine organic matter content, total nitrogen, carbon/nitrogen ratio, absorbed phosphorus, exchangeable calcium, magnesium, potassium and sodium, cation exchange capacity pH. Because soil profiles showed considerable variation the results of the chemical analyses were averaged for the organic, organic - mineral and mineral horizons. On the basis of similarity of species composition six orders, eight alliances, fourteen associations, ten subassociations and thirteen variations were distinguished. The order Betuletalia glandulosae dominated the two study areas, occurring on moderately to well drained mesic to xeric slopes. Community development within this order appeared stable under the present topographic and climatic conditions. The Vaccinio - Betuletum glandulosae closely approximated the climatic climax in mesic habitats. Successional concepts on upper slopes appeared of limited value because communities tended to be discrete. Communities dominant on the lower slopes and in the wetlands were characterized by a narrow active, poor to impeded drainage conditions and more intensive frost action. Classification was more difficult in such areas because communities appeared to be less stable. Successional development in such areas with permanent seepage was toward the Betulo - Eriphoretum vaginati. Snow bed habitats were characterized by the order Petasitetalia frigidii , which was distinguished for the first time in North America, and included the previously undescribed Salicetum chamissonis. Sharp environmental gradients between chionophilous and chionophobous communities suggested that the climate had undergone no significant change in the recent past. Similarities between the Low Arctic Subalpine/Foothill Zone communities and those in other arctic regions, especially Scandinavia, were shown to occur. Twelve soil types were distinguished. In all but two cases each soil type was associated with a particular plant association. A form of podzolization previously described in Arctic Alaska was recognized in the Arctic Brown soils. Gleization, however, appeared to be the major soil forming process in this region of the zone. It was associated with both chionophobous and chionophilous vegetation. In the former, it was favoured by poor drainage, a shallow active layer and intensive frost action; in the latter, it appeared related to materials deposited on the snow that were later incorporated into the soil following snow melt. The high organic content and cation exchange capacity and the low acidity and base saturation were concluded to be important chemical characteristics of these soils. Final results using classification methods showed that the present position of the communities in this region of the Low Arctic Subalpine/Foothill Zone were related to elevation, exposure, soil moisture, thickness of the active layer, duration of snow cover, congeliturbation and topography. / Science, Faculty of / Botany, Department of / Graduate

This is a study of human response to the Arctic and Antarctic environments. It is based on two sources of data: the content analysis of original diaries of polar explorers, and the behavioural evaluation of contemporary crews in polar locations. In the latter, four polar stations were chosen, two in each polar region with a total of fifty-five experimental subjects. Twenty-seven other subjects acted as controls for both polar regions: a northern control group located at a semi-isolated site in Canada, and the southern group located in an Argentinian city. Methods applied in this research included the design and coding of categories which were content analyzed from the original diaries of explorers, and on-site procedures. On-site procedures included psychometric material, participant-observation reports and unstructured interviews. Fifteen behavioural measures within the domain of personality, perception of the environment, affection, social stress and community behaviour were administered. It was hypothesized that the human response would be similar in both polar regions because of environmental and sociological similarities, and that the polar setting would affect men and women in a negative way. Results showed that: (i) the polar environment is not perceived as stressful by the crews - a low anxiety state across both polar regions was found, (ii) traumatic experiences of the explorers had led to the perception of the environment in a negative perspective - yet the winter seemed to be a relaxing phase for the crews rather than stressful, (iii) personnel stationed at polar sites may possess special characteristics which distinguish them from the majority of the population, (iv) although cross-cultural differences exist, they are not as strong as might be anticipated - the environment exerts a unifying influence, (v) differences in gender-response are difficult to assess due to the small number of women subjects, but some differences with controls were noted. / Graduate and Postdoctoral Studies / Graduate

Although climate change is a global phenomenon, the Arctic is warming faster than any other region on earth. These climatic changes have driven rapid regional changes over the past half-century in both the physical landscape and the ecosystems therein. One such ecological interaction is between migratory shorebird survival and local insect emergence. Annually, tens of millions of migratory shorebirds travel to the Arctic to rear their young in the relative absence of predators, but in a relative abundance of food (insects). Over evolutionary time, these trophic levels have coupled: shorebird chicks tend to hatch during the period of highest terrestrial insect availability. However, climate change is currently uncoupling this food-web synchrony, creating potential for trophic mismatch. In the High Arctic near Utqiaġvik (formerly Barrow), Alaska, trophic mismatch between nesting shorebirds and their insect food base is already detectable. In this ecosystem, flies in the Family Chironomidae (non-biting midges) dominate the prey trophic level in the avian food web. We have found that the pre-emergence development of one particular midge, Trichotanypus alaskensis, defies conventional wisdom of the Family, as this species molts to an additional fifth larval instar prior to pupation and emergence (all other chironomids are known to have four larval instars). We discovered an Utqiaġvik midge that reproduces asexually, a species that was not documented in the 1970s. Utilizing controlled temperature rearings of Utqiaġvik midge larvae, we discovered that as temperatures rise, emerging chironomid adults are generally smaller in size. We have found that chironomid pre-emergence developmental rates follow a positive exponential relationship as temperatures increase, can vary by taxon, yet are consistent across field and lab settings for a given taxon. At Utqiaġvik in the 2010s, chironomid emergence occurs 8-12 days earlier than it did in the 1970s. These findings shape our understanding of trophic mismatch in this arctic food web. / Arctic Landscape Conservation Cooperative; NDSU Graduate School Dissertation Fellowship; U.S. National Fish and Wildlife Foundation; Environmental and Conservation Sciences Program; Department of Biological Sciences

Human demographic changes in association to environmental fluctuations were studied for the North American Arctic and boreal region. Using the frequency of archaeological radiocarbon dates from the Canadian Archaeological Radiocarbon Database as a proxy for population size, past changes in population density were estimated and quantitatively examined in relation to reconstructions of temperature and sea ice conditions. This was conducted across three spatial scales: the entire area, the four major cultural-environmental regions and sixteen subregions in order to identify both broad-scale and local phenomena. There was a high correspondence between millennial and centennial-scale climate variability and paleodemographic changes across the region, with increasing population density during warmer periods and lower density during cooling episodes. An abrupt Late Holocene cooling (neoglaciation) beginning at 3.9 ka triggered a nearly-synchronous population decline across the region. Cooling temperatures and increased sea ice coverage also influenced large-scale migration patterns of Paleo-Inuit peoples as well as their cultural evolution.

In lakes, fish and zooplankton can be both sources and sinks of nitrogen (N) and phosphorus (P) through the consumption of organic N and P, and subsequent excretion of bioavailable inorganic forms. These source/sink dynamics, known as consumer-driven nutrient recycling (CNR), may, in turn, control the availability of potentially limiting nutrients for algal primary production. In this dissertation I investigate the importance and controls of CNR as a source of inorganic N and P for primary production (Chapter 2). I then examine zooplankton CNR as a mechanism for increasing nutrient mean resident time (MRT) in the mixed layer of lakes (Chapter 3). Finally, I assess whether zooplankton communities dominated by different taxa can affect N versus P deficient conditions for phytoplankton production through differential N and P recycling rates (Chapter 4). Direct excretion of N and P by fish communities was modest in arctic lakes, and accounted for < 4 % of the N and P required for primary production. Recycling of N and P by zooplankton communities was relatively high, and the fraction of algal N and P demand supplied by zooplankton CNR ranged from 4 - 90% for N and 7 - 107% for P. MRT of 15N, measured in the mixed layer of an arctic lake, was ~16 days, compared to 14 days predicted by a ecosystem model simulation with zooplankton N recycling and 8 days in a model simulation where zooplankton N recycling was absent. The 75% increase in N MRT between model simulations with and without zooplankton recycling suggests that zooplankton N recycling is an important mechanism for retaining N in lake ecosystems. I observed relatively high negative correlations between precipitation and phytoplankton N (r = -0.33) and P (r = -0.30) deficiencies. I also observed a significant positive correlation (r = 0.42, p = 0.03) between zooplankton communities with higher copepod biomass, relative to cladoceran biomass, and phytoplankton N-deficient conditions. These results suggest that when precipitation is high N and P deficiency is low in the phytoplankton. When precipitation is low, however, zooplankton communities composed primarily of copepods contribute to N-deficient conditions for phytoplankton production.

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