Dissertations / Theses: 'Arctic lake'

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Eaton, Dewey Mitchell 1960. "Ecology of arctic grayling in Becharof Lake tributaries." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/291517.

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I studied the grayling populations in 4 tributaries of Becharof Lake. The grayling in Ruth River, and Salmon, Featherly and Becharof Creeks appear to be independent populations, with high fidelity to specific streams. All populations overwintered in the lake and migrated into the streams when water temperatures reached about 2.5 C. These populations contained some of the largest grayling in the state; generally >50% of the population exceeding 6 years in age and had fork lengths >400 mm. Interstream movement rates were about 2%, but intrastream movement was higher (18%). Spring migration into the streams extended from May-July. This extended migration may have invalidated the assumption of a closed population, and resulted in higher than actual estimated abundance. Abundance ranged from a low of 33 grayling/Km in Featherly Creek to a high of 230 grayling/Km in Becharof Creek. Survival rates were similar in all streams.

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Freitas, Nancy Louise. "Methane and Carbon Dioxide Dynamics in Arctic Lake Sediments." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/579063.

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Rising global temperatures are expected to increase concentrations of greenhouse gases emitted by northern latitudes within the current century. The impact of global warming on Arctic lacustrine systems is generally unknown, although recent studies have examined fluxes of carbon dioxide (CO₂) and methane (CH₄) produced in ebullition events. Few studies have investigated the added impact of atmospheric warming on lake sediments, which produce CO₂ and CH₄ through microbial decomposition and diffusive loss in the water column. To better understand carbon emission scenarios at elevated temperatures, sediment samples from Abisko, Sweden were analyzed for CO₂ and CH₄ production rates through incubation studies, and for concentrations of dissolved inorganic carbon (DIC) and dissolved CH₄ in sediment and porewater. Results showed that room temperature incubations emitted concentrations of CO₂ and CH₄ up to five times greater than those emitted by +5°C incubations. Furthermore, documented peat emissions were one to two orders of magnitude lower than the lake sediment incubation emissions reported in this paper. This study provides some of the first point source microbial emissions by lake sediment depth, and highlights that northern latitude sediments could have unprecedented effects on current spatial and temporal projections of Arctic warming.

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Tomkins, Jessica Diane. "Sedimentology and paleoenvironmental indicators in a High Arctic meromictic lake." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1200.

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Graves, Kelly Elise. "Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52683.

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High spatial resolution CTD profiles and Acoustic Doppler Current Profiler velocity measurements show significant rotational basin-wide, under-ice circulation in May of 2013 and 2014 at Lake Kilpisjärvi, Finland (69°01'N, 20°49'E), a seasonally ice-covered, Arctic lake with negligible through-flow. In 2013, a high-pressure horizontal density anomaly with vertically paired rotating circulations was observed. The estimated maximum cyclonic and anti-cyclonic azimuthal velocities magnitudes were 0.03 and 0.02 m s-¹. The Rossby radius (Rri), horizontal length scale at which rotational effects become as important as pressure effects, was estimated to be ∼ 160 m and the Rossby number(R⃘⃘⃘⃘⃘ ), the ratio of the centripetal acceleration to the Coriolis acceleration, ∼ 0.2. It is hypothesized that this circulation was driven by heat flux at the shorelines from warm incoming streams causing a density flow down the slopes to the centre of the lake where the flow converged. This flow was balanced with a shoreward flow beneath the ice. These flows were modified by the earth's rotation, which resulted in the rotational circulation observed. In 2014, a cyclonic, low-pressure horizontal density anomaly was observed near the centre of the lake and was vertically paired with a weak anti-cyclonic anomaly in the top 10 m (mean depth of the lake is 19.5 m). The estimated azimuthal velocities had maximum cyclonic and anti-cyclonic magnitudes of 0.006 and 0.003 m s-¹. The anomaly was estimated to have Rri ∼ 240 m, with R⃘⃘ ∼ 0.12. It is hypothesized that this circulation was driven by sediment release of heat to the overlying water causing a tilt in the isopycnals near the shores of the lake that caused an inward pressure force that was balanced by the Coriolis force and, to a lesser extent, the centripetal acceleration force. The 2013 observations were made immediately prior to ice-off, and the 2014 observations were 12 days prior to ice-off. This time difference allowed for significantly different ice and snow conditions, and the addition of warm inflows, which forced the circulation closer to the ice-off date. These observations add to the growing understanding of the relationship between thermal distribution and circulation under ice.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

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5

Schwartzburg, Richard E. C. "Physical limnology of a small sub-arctic alpine lake, Yukon Territory." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/5493.

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Ruuskanen, Matti Olavi. "Lake Sediment Microbial Communities in the Anthropocene." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39649.

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Since the Industrial Revolution at the end of the 18th century, anthropogenic changes in the environment have shifted from the local to the global scale. Even remote environments such as the high Arctic are vulnerable to the effects of climate change. Similarly, anthropogenic mercury (Hg) has had a global reach because of atmospheric transport and deposition far from emission point sources. Whereas some effects of climate change are visible through melting permafrost, or toxic effects of Hg at higher trophic levels, the often-invisible changes in microbial community structures and functions have received much less attention. With recent and drastic warming-related changes in Arctic watersheds, previously uncharacterized phylogenetic and functional diversity in the sediment communities might be lost forever. The main objectives of my thesis were to uncover how microbial community structure, functional potential and the evolution of mercury specific functions in lake sediments in northern latitudes (>54ºN) are affected by increasing temperatures and Hg deposition. To address these questions, I examined environmental DNA from sediment core samples and high-throughput sequencing to reconstruct the community composition, functional potential, and evolutionary responses to historical Hg loading. In my thesis I show that the microbial community in Lake Hazen (NU, Canada) sediments is structured by redox gradients and pH. Furthermore, the microbes in this phylogenetically diverse community contain genomic features which might represent adaptations to the cold and oligotrophic conditions. Finally, historical Hg pollution from anthropogenic sources has likely affected the evolution of microbial Hg resistance and this deposition can be tracked using sediment DNA on the Northern Hemisphere. My thesis underscores the importance of using culture-independent methods to reconstruct the structure, functional potential and evolution of environmental microbial communities.

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Gydemo, Östbom Viktor. "Lake water chemistry and the changing arctic environment : Topographic or climatic control?" Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-155903.

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The arctic is expected to be one of the regions most affected by ongoing climate change, with relative changes in air temperatures significantly higher than the global mean. Lakes are recognized for their potential role in the global climate system and as ecosystems of importance for local societies. As such, there is a scientific interest regarding how arctic lakes and their geochemistry will respond to climatic changes. Lakes around Kangerlussuaq (66.99 N, 51.07 W), south-west Greenland, are known for their unique geochemical composition, including oligosaline lakes, of which some are enriched in colourless dissolved organic carbon (DOC). The origin of this DOC and the importance of local catchment properties for the general water chemistry is currently being debated. This thesis aimed at: i) exploring the extent and effect of catchment morphology on lake-water chemistry in the Kangerlussuaq area; ii) determine the predominant origin of DOC, aquatic or terrestrial. I used a remote-sensing approach based on satellite imagery and digital elevation model (DEM) in deciding landscape influence on water chemistry (pH, alkalinity, conductivity, base cations, sulphate, nitrogen and absorbance). To trace the origin of the organic sources behind DOC lake water and sediments, I used a hydrogen isotope tracing method. The remote sensing approach revealed that morphological characteristics serving as proxies for lake water residence time and hydrologic connectivity (e.g. lake altitude difference and absence of outlets) explained up to 77% of the variations in lake water chemistry. The hydrogen isotopic signature of the DOC indicated a predominantly autochthonous origin, i.e. 59 to 78% was estimated to originate from algae. I conclude that lake water chemistry of the lakes in the study area is primarily controlled by the precipitation : evaporation balance, enhanced by static catchment characteristics regulating water age. Thus, the examined lake water chemical properties are likely to remain across future climatic scenarios, providing the current precipitation : evaporation balance prevails.

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JONES, BENJAMIN M. "SPATIOTEMPORAL ANALYSIS OF THAW LAKES AND BASINS, BARROW PENINSULA, ARCTIC COASTAL PLAIN OF NORTHERN ALASKA." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1155321884.

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Michelutti, Neal. "Diatom changes in Mackenzie Delta, Northwest Territories Arctic Canada, lake sediments, paleohydrological applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37970.pdf.

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10

Murray, Martin J. "Predictive empirical modelling of ice formation and decay at a turbid, glacier fed, arctic lake, Norway." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329323.

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Corrigan, Laura. "Phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) in the Lake District, UK." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/1337/.

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The general aim of this thesis was to assess the phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) populations in the Lake District, UK, in order to understand the key evolutionary mechanisms involved in the development of resource polymorphisms and their genetic divergence.

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Bondurant, Allen C. "Processes Controlling Thermokarst Lake Expansion Rates on the Arctic Coastal Plain of Northern Alaska." Thesis, University of Alaska Fairbanks, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10615802.

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Thermokarst lakes are a dominant factor of landscape scale processes and permafrost dynamics in the otherwise continuous permafrost region of the Arctic Coastal Plain (ACP) of northern Alaska. Lakes cover greater than 20% of the landscape on the ACP and drained lake basins cover an additional 50 to 60% of the landscape. The formation, expansion, drainage, and reformation of thermokarst lakes has been described by some researchers as part of a natural cycle, the thaw lake cycle, that has reworked the ACP landscape during the course of the Holocene. Yet the factors and processes controlling contemporary thermokarst lake expansion remain poorly described. This thesis focuses on the factors controlling variation in extant thermokarst lake expansion rates in three ACP regions that vary with respect to landscape history, ground-ice content, and lake characteristics (i.e. size and depth). Through the use of historical aerial imagery, satellite imagery, and field-based data collection, this study identifies the controlling factors at multiple spatial and temporal scales to better understand the processes relating to thermokarst lake expansion. Comparison of 35 lakes across the ACP shows regional differences in expansion rate related to permafrost ice content ranging from an average expansion rate of 0.62 m/yr on the Younger Outer Coastal Plain where ice content is highest to 0.16 m/yr on the Inner Coastal Plain where ice content is lowest. Within each region, lakes vary in their expansion rates due to factors such as lake size, lake depth, and winter ice regime. On an individual level, lakes vary due to shoreline characteristics such as local bathymetry and bluff height. Predicting how thermokarst lakes will behave locally and on a landscape scale is increasingly important for managing habitat and water resources and informing models of land-climate interactions in the Arctic.

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Feitl, Melina G. "Investigation of diatom endemism and species response to climate events using examples from the genera Cyclotella (Lindavia) and Surirella in the Lake El'gygytgyn sediment record." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1467979020.

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Chiasson-Gould, Sophie. "Dissolved Organic Matter Kinetically Controls Mercury Bioavailability to Bacteria in Lake Water from the Canadian Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32024.

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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.

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Khan, Habibur. "Effects of dispersal on community structure of aquatic insects in Arctic lakes and streams." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-62921.

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Shu, Song. "Satellite Radar and Laser Altimetry for Monitoring of Lake Water Level and Snow Accumulation in Arctic Regions." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1561394321584998.

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LeBlanc, Michelle. "A diatom-based Holocene paleoenvironmental record from a lake on Boothia Peninsula, central mid-Arctic, Nunavut, Canada." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6414.

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An important source of information about climate change comes from sedimentary deposits from the arctic region. However, there are few lacustrine fossil records from the central mid Arctic region of Canada. A 485 cm sediment core, from a lake unofficially called JR01, Boothia Peninsula, Nunavut, yielded a high-resolution diatom record. Five radiocarbon dates provided the chronology. Three distinct zones are revealed in the relative percent abundance and diatom concentration diagrams. A more diverse and productive flora in the first zone implies warmer temperatures in the middle Holocene. A complete shift in diatom composition to a predominantly Fragilaria flora and a reduction in diversity and production suggests a cooler climate in this region after approximately 4360 years B.P. Smaller-scale climatic trends, such as the Little Ice Age (LIA) (ca. 550--150 yr. B.P.) and the Medieval Warm Period (ca. 1000--700 yr. B.P.), caused shifts in the diatom flora and production. Subtle shifts in floristic diversity within the LIA may reflect climate variability at a decadal scale. This variability is also recorded in other high-resolution paleoclimate records from the Arctic. A gradual shift to a more diverse and productive flora in the last 180 years B.P. (1790 years A.D.) suggests a response to the recent warming trend. This study permits us to address ambiguities with respect to the timing, the geographic extent and the severity of the recent warming. Changes in total diatom concentrations, magnetic susceptibility, organic and carbonate content may also reflect changes in the diatom assemblages and indicate shifts in vegetation, soil erosion, or in hydrology from the surrounding catchment. The morphological variance of Fragilaria and other taxonomy issues are also discussed.

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Sejfic, Melli. "Method Improvement for the Determination and Quantification of PCBs in the Muscle Tissues of Arctic Char (Salvelinus salvelinus) and European Whitefish (Coregonus acronius) from Lake Vättern, Sweden." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-46054.

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Lake Vättern has been contaminated with high levels of polychlorinated biphenyls (PCBs) for decades, which could be due to the release of wastes from industries and urban communities surrounding the water system. This has especially had a negative effect on fatty fishes, which could accumulate large amounts of persistent organic pollutants (POPs) and thereby also become a source of environmental toxicants to humans through consumption. Most PCB analysis only quantify a handful of congeners, the so called indicator-PCBs (I-PCBs), but this might leave out important information. In this study, an existing analytical method was improved by supplementing with additional congeners to detect a larger set of PCB congeners in Arctic char (Salvelinus salvelinus) and European whitefish (Coregonus acronius) caught from Lake Vättern, Sweden. New pre-packed multilayer silica columns from CAPE technologies were tested and used to pretreat the fish samples prior to analysis with a Gas Chromatograph coupled to low-resolution Mass Spectrometer using Atmospheric Pressure Ionization (API GC/MS). It was found that modifications of the clean up method for PCBs were necessary, such as lowering the amount of hexane in the washing step and combining the two eluent fractions. The Arctic char and the European whitefish showed a fat content of 0.18% and 0.74%, respectively. Concentrations of detected congeners ranged from 0.5 to 1470 pg g-1 fresh weight (fw) in Arctic char and varied between 1.2 to 6550 pg g-1 in European whitefish. For Arctic char and European whitefish, the WHO2005-TEQ values were 0.4 pg g-1 fw and 0.6 pg g-1 fw, respectively. The greatest total PCB concentration of 25900 pg g-1 was measured in European whitefish. The total concentration of I-PCBs (#28, 52, 101, 138, 153, 180) was 3710 pg g-1 for the Arctic char and 13900e pg g-1 for the European whitefish. All obtained results were lower than those reported from other studies. Constructed congener profiles show that the two species have similar ratios of PCB #138 and #153. Differences are observed of PCBs with a higher chlorination grade, probably due to differences in migration patterns, habitats of the lake, diets, metabolism or bioaccumulation.

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Courtney, Mustaphi Colin. "Analysis of Laminated Sediments from Lake DV09, Northern Devon Island, Nunavut, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2009. http://hdl.handle.net/10393/19603.

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A 147cm sediment core from Lake DV09, northern Devon Island, Nunavut, Canada (75° 34’34”N, 89° 18’55”W) contains annually-laminated (varved) sediments, providing a 1600-year record of climate variability. A minerogenic lamina deposited during the annual thaw period and a thin deposit of organic matter deposited during the summer and through the winter, together form a clastic-organic couplet each year. The thinnest varves occur from AD800-1050, and the thickest from AD1100-1300, during the Medieval Warm Period. The relative sediment density is also highest during this period suggesting increased sediment transport energy. The coldest period of the Little Ice Age appears to be during the AD1600s. Varve widths over the past century indicate climate warming in the region.
This research program was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS). A tuition bursary from Ultramar Inc. also helped in making this research possible. Logistical support was provided by the Polar Continental Shelf Project (PCSP Contribution number 04508).

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Svahn, Joacim. "Metal release and mobility in an arctic lake due to artificial drainage : Effects of mining and sulfide oxidation." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-58306.

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The aim of this report was to investigate the potential effects of sulfide oxidation in sediments of an arctic lake, N Luossajärvi, induced by lowered water level. Lake water, potentially contaminated by metals, was pumped into a mine tailings impoundment. The water quality in the receiving water was evaluated to see if the drainage have had an effect on the water quality. Six sediment profiles were sampled. Each profile were divided into 5 cm sections and analyzed for major elements and trace metals. Water chemistry were analyzed at six sites. As, Ni and Cu had high concentrations within undrained sediments, where As levels were classified as highly contaminated (> 27 mg kg-1 dw). Trace metals had strong statistical correlation to each other indicating a common source. The PCA analyzes performed suggests that trace metals are controlled by a common factor and drained sediments showed two additional factors controlling the variance of metals. Water chemistry had overall good status, but As, Cd, Ni and Cu exceeded natural background values. Historical data on the other hand showed no statistical difference from measured values. No effects on water quality could therefore be seen after draining of the lake, proposing high precipitation of metals within the tailing or that metals is still prevailing in the drained sediments. Metal mobility were seen within the drained sediments, where only As and Cd were presumed connected to chemical weathering and where erosion and soil properties seems to be responsible for most metal mobility.

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Scheidegger, Johanna Michaela. "Impact of permafrost dynamics on Arctic groundwater flow systems with application to the evolution of spring and lake taliks." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48711/.

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Groundwater flow in permafrost is restricted to unfrozen zones, known as taliks. There is an interaction between groundwater flow and heat flow, because the permafrost distribution determines the occurrence of groundwater, but groundwater also contributes to advective heat transport influencing the distribution of permafrost. However, the advective heat flow component is small where the hydraulic gradient is low, or where recharge is limited. Conversely, where recharge is not driven by precipitation, as for example found under a wet based glacier, groundwater fluxes can be more significant. This thesis aims to improve understanding of the impacts of permafrost dynamics on Arctic groundwater flow systems for past and predicted climate change. Numerical modelling of coupled heat and fluid flow including phase change of water/ice is used to study different environments; lakes in a periglacial environment, and lakes and springs in a proglacial terrain. Results show that the transient effects of heat storage can influence the present day distribution of permafrost. This is especially pronounced underneath surface water bodies, where there are cases for which under a steady state scenario no through talik is expected, but there are through taliks under a transient scenario. In addition, heat advection by groundwater flow can influence the permafrost distribution by permafrost erosion and aggregation. The magnitude of heat advection is driven by topographically driven groundwater flow and the release of groundwater from elastic storage. The latter is significant in previously glaciated areas that have undergone a large change in hydraulic head over time. In partially frozen ground, the choice of the permafrost permeability-reduction function is crucial to quantify groundwater flow and advective heat flow. The occurrence of through taliks is influenced by the regional scale groundwater flow, but taliks also influence the regional scale hydrogeologic system by reversal of the general groundwater flow direction.

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Klobucar, Stephen L. "The Abiotic and Biotic Controls of Arctic Lake Food Webs: A Multifaceted Approach to Quantifying Trophic Structure and Function." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7293.

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The Arctic is warming faster than any other region of the globe. To conserve and manage many thousands of lakes across arctic landscapes, scientists need to understand historic and present conditions within these lakes to predict how the lakes, and the organisms that inhabit them, may respond to a changing climate. The goal of my research was to improve our understanding of what physical, chemical, and biological factors contribute to: 1) how lake food webs are assembled; and, 2) how these food webs may change in the future. First, I used long-term observations and lab experiments to determine how fish food, including zooplankton and snails, may respond to a warming climate. I then used field measurements of arctic char (Salvelinus alpinus) body characteristics, genetic samples, and fish diets to investigate if, and potentially why, populations of arctic char across a series of lakes achieve different maximum body sizes. Finally, as a method of monitoring population-level changes of fish abundance, I collected samples of arctic char DNA in lake water to test if estimated arctic char population abundances within a given lake correspond to the amount of DNA collected. Fish will require more food to eat as their metabolism increases with warming lake temperatures. Based on a thirty-year period of record, I determined zooplankton abundance increases in warmer years, indicating there is likely to be enough food for fishes in the future. Accordingly, zooplankton and snail abundance and development was also faster in warmer treatments of my lab experiments. My field observations indicated these are important prey items for arctic char. Small arctic char eat more zooplankton and large arctic char eat more snails, and these observations were consistent whether or not other predators are found in the particular lake. Similarly, my analyses did not indicate morphological or genetic differences between small and large arctic char within the same lake, suggesting arctic char size structure is determine by biological characteristics, including primary productivity and arctic char density. Indeed, estimates of arctic char population abundances across a series of lakes followed a gradient of arctic char densities, and my DNA sampling corresponded with this gradient. As there are thousands of lakes across the Arctic, my research demonstrates lake food webs, and the fishes within them, are likely to adapt to a warming climate. However, biological, chemical, and physical properties of these lakes can vary widely such that management and conservation plans may need to be developed at relatively small spatial scales across a large landscape.

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Harrison, Jeffrey Michael. "A CORRELATION OF WESTERN ARCTIC OCEAN SEDIMENTATION DURING THE LATE HOLOCENE WITH AN ATMOSPHERIC TEMPERATURE PROXY RECORD FROM A GLACIAL LAKE IN THE BROOKS RANGE, ALASKA." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1366295554.

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Lindeberg, Carola. "Long-term changes of mercury, lead and persistent organic pollutants in arctic environments." Doctoral thesis, Umeå : Department of Ecology and Environmental Science, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1060.

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Griffith, Fritz. "Holocene and Recent Paleoclimate Investigations Using Carbon and Nitrogen Isotopes from Bulk Sediment of Two Subarctic Lakes, Central Northwest Territories." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30197.

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The Tibbitt-to-Contwoyto Winter Ice Road (TCWR) is the sole overland route servicing diamond mines north of Yellowknife, Northwest Territories (NWT), Canada. The road is 568 km long, 85% of which extends over frozen lakes. As such, its operational season is highly dependent upon the length of the winter season. This was exemplified in 2006, when an El Niño event caused an unusually short ice road season and resulted in a costly reduction of shipments to the mines. For future use and development of the TCWR, a comprehensive understanding of past regional climate variability is required. This study is an integral component of a larger-scale study designed to develop a comprehensive database of high-resolution paleoclimate data for the NWT, using a variety of proxies. As part of the larger study, freeze cores were taken from numerous lakes along the TCWR and sliced at 1-mm intervals using a custom-designed sledge microtome. Bulk 13C and 15N isotope analysis was completed at preliminary 1-cm intervals through the cores of two lakes on opposite sides of the tree line. Results from this analysis show clear trends with distinct transitions in both cores, whose closely-matched timing suggests regional-scale climate events. These results indicate that the Early Holocene was warm and dry, with a sudden shift to wetter conditions around 7200-6900 cal yr BP. Another shift to cooler conditions occurred at 4000 cal yr BP, and a final transition to even cooler temperatures occurred around 755-715 cal yr BP, coinciding with the Little Ice Age. Additionally, a modern lake survey was completed using surface sediments of numerous lakes throughout the Arctic and Subarctic. This survey verifies the strong influence of boreal forest vs. tundra conditions in affecting various environmental properties within lakes, including carbon and nitrogen isotopes. Lastly, time-series analysis was completed on two sections of Danny’s Lake core at high resolution (up to 2 mm), in order to determine short-term climate cycles. These results highlight specific climate frequencies which may be related to the Pacific Decadal Oscillation. These results offer insight to short-term climate phenomena in the Northwest Territories which will allow future climate modellers to make more accurate predictions of future climate and its impact on the ice road.

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Holmgren, Bror. "Tracing the source of colourless carbon in an arctic lake on SW Greenland : Insights of organic matter origin from hydrogen isotope analyses of samples prepared using steam equilibration." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-121524.

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Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

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Åberg, Jan. "Production and emission of CO2 in two unproductive lakes in northern Sweden." Doctoral thesis, Umeå universitet, Ekologi, miljö och geovetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-26967.

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Unproductive lakes are one of few natural landscape compartments with net release of carbon to the atmosphere. Lakes also generally decrease the net terrestrial carbon uptake, since most of the CO2 production in unproductive lakes are derived from organic carbon produced on land (e.g. in forests). High latitude lakes are predicted to be particularly affected by the global climate change. The carbon cycling in these lakes and their role in the landscape are therefore important to study. In this thesis, carbon turnover processes were studied in two lakes above the arctic circle (Lake Diktar-Erik and Lake Merasjärvi) in year 2004 and 2005. Both lakes were net heterotrophic, with large variations in CO2 concentrations both on shorter (30min) and longer (24h) time-scales. The pelagic habitat supported a major part of the net production of CO2, with larger dynamics in the CO2 production than the sediments. The CO2 variations of the surface water were related to respiration of allochthonous organic carbon, and were affected by the concentration and quality of the DOC, as well as the whole lake water temperatures, and vertical water movements. The emission of CO2 from Lake Merasjärvi was measured with the eddy covariance technique. The results showed that the gas transfer rate during moderate winds were higher than expected, causing the two most commonly used models to underestimate the long term fluxes of CO2 from the lake. Taken together, the results of the thesis show that the studied lakes contributed to bring terrestrial organic carbon back into the atmosphere, driven by a substantial internal CO2 production based on mineralization of allochthonous organic carbon. Major results are that the eddy covariance technique indicated that commonly used models tend to underestimate the net release rate of CO2 from lakes to the atmosphere, and that the lake CO2 dynamics can be the results of interactions between biogeochemical and physical processes in the lake water.

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Tamo, Camille. "Late Holocene Environmental Change Across the Canadian Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38837.

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Lake sediment cores spanning the last 2000 years from four sites across the Canadian Arctic Archipelago (CAA) document the responses of terrestrial and freshwater ecosystems to regional climate variability. Biogenic silica (BSi) records in cores from Banks Island, NWT (Lake B503; 72.3245, -123.4036, 84 masl), Bathurst Island, Nunavut (PR01; 75.6497, -99.1144, 30 masl), Prince of Wales Island, Nunavut (SW08; 72.3177, -97.2678, 104 masl), and Ellesmere Island, Nunavut (CV03; 79.9211, -82.9348, 363 masl) were used to examine the relationship between diatom production and climate. A pollen record from Prince of Wales Island provided the first high-resolution July temperature reconstruction for the last 1000 years for the central CAA. Dissolution was evident in three out of the four lakes; core SW08 contained no BSi above detection and cores CV03 and PR01 only contained values above detection in the uppermost sediments, suggesting that the preservation of biogenic silica (BSi) in the sediment is likely influenced by sedimentary carbonates. A BSi sequence from core B503 showed that diatom production was affected by climate changes such as the Medieval Climate Anomaly and the Little Ice Age. The vegetation on southern Prince of Wales Island underwent marked transitions during the Little Ice Age and Medieval Climate Anomaly, which was mainly observed in the proportion of Cyperaceae and Poaceae. The mean July temperature reconstruction showed a long-term cooling from 1080-1915 CE with a sustained cold period from 1800-1915 CE prior to 20th-century warming. A synthesis of paleoclimate records from across the Arctic demonstrated that pollen-based reconstructions record both high and low frequency climate variability, when sampling resolution is sufficient, and can improve regional climate reconstructions.

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Eickmeyer, David. "The Effects of Retrogressive Thaw Slump Development on Persistent Organic Pollutants in Lake Sediments of the Mackenzie River Delta Uplands, NT, Canada." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/25998.

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Using a comparative spatial and temporal analysis on sediment cores from 8 lakes in the Mackenzie River Delta uplands region, NT, Canada, this study assessed how persistent organic pollutant (POP) deposition to lake sediments was affected by: (1) the presence of retrogressive thaw slumps on lake shores; and (2) changes occurring with increased autochthonous primary productivity. POPs examined included polychlorinated biphenyls (PCBs), penta- and hexachlorobenzenes (CBzs), and dichlorodiphenyltrichloroethane and metabolites (DDTs). Surface sediments of slump-affected lakes contained higher total organic carbon (TOC)-normalized POP concentrations than nearby reference lakes unaffected by thaw slumps. Inorganic sedimentation rates were positively related to contaminant concentrations, suggesting that the influx of siliciclastic material reducing organic carbon in slump-affected lake water indirectly results in higher concentrations of POPs on sedimentary organic matter. This explanation was corroborated by an inverse relationship between sedimentary POP concentrations and TOC content of the lake water. Deposition proxies of autochthonous carbon were not significantly correlated to POP fluxes of surface sediments, and historical profile fluctuations did not coincide with variation in POP deposition. Thus this study does not support the contention that algal-derived organic carbon increases the delivery of organic pollutants to sediments (the algal-scavenging hypothesis), as previously proposed for mercury. Higher POP concentrations observed in surface sediments of slump-affected lakes are best explained by simple solvent switching processes of hydrophobic contaminants onto a lower pool of available organic carbon when compared to neighbouring lakes unaffected by thaw slump development.

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30

Evans, John Rhys. "Late Neogene agglutinated foraminifera from the central Arctic Ocean." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267751.

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31

Hanslik, Daniela. "Late Quaternary Biostratigraphy and Paleoceanography of the central Arctic Ocean." Doctoral thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-57245.

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The central Arctic Ocean is one of the least explored deep sea regions and long biostratigraphic sediment records are sparse. The main focus of this thesis is the Arctic Ocean foraminiferal record and its application to reconstruct paleoceanographic variations and summer sea ice cover changes between late Quaternary interglacial periods. One of the studied cores was retrieved from the central Lomonosov Ridge Intra Basin. This core contains a relatively high-resolution biostratigraphic record spanning Marine Isotope Stages (MIS) 1–3, although with a hiatus encompassing the Last Glacial Maximum. Radiocarbon age calibrations in this core show a decreasing trend of high marine reservoir ages of about 1400 years during the last deglaciation to 700 years in the late Holocene. The cores from the Lomonosov Ridge off Greenland and the Morris Jesup Rise contain preserved calcareous microfossils further back in time than most previously studied central Arctic Ocean cores. The calcium content estimated by X-ray fluorescence scanning of these cores shows a distinct pattern of calcium rich intervals coinciding with peaks in foraminiferal abundance in the sediment record of MIS 1–7. The calcium peaks originate from material accumulated during interglacials, primarily through detrital carbonate and dolomite input from the decaying North American ice sheet and secondarily from biogenic material. Intervals of calcareous benthic foraminifera are found in pre MIS 7 sediments on both the southern Lomonosov Ridge and Morris Jesup Rise. Their assemblage composition and stable carbon isotope data suggest increased primary production and decreased summer sea ice cover compared to the Holocene central Arctic Ocean. This is also suggested for an interval of high abundance of the subpolar planktic foraminifera Turborotalita quinqueloba on the southern Lomonosov Ridge with a proposed MIS 11 age.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted.

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Omma, Jenny Eide. "Provenance of Late Paleozoic and Mesozoic sediment to key Arctic basins : implications for the opening of the Arctic Ocean." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608740.

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33

Hill, Mark A. "The benefit of the gift exchange and social interaction in the Late Archaic western Great Lakes /." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/m_hill_042309.pdf.

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34

Mortazavi, Emily. "Chronology and Correlations of High Arctic Lakes Based on Magnetic Properties." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192523.

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35

Zhan, Shengan. "Spatio-Temporal Analysis of Gyres in Oriented Lakes on the Arctic Coastal Plain of Northern Alaska Based on Remotely Sensed Images." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427982971.

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36

Ó, Cofaigh Colm. "Late-Quaternary glaciation and postglacial emergence, southern Eureka Sound, high-Arctic Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq39576.pdf.

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37

Gíslason, Davíd. "Genetic and morphological variation in polymorphic Arctic charr, Salvelinus alpinus, from Icelandic lakes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ33225.pdf.

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38

Stevenson, Mark Andrew. "Carbon cycling in Arctic lakes : sedimentary biomarker reconstructions from Disko Island, West Greenland." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/46579/.

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A palaeolimnological study of three lakes on Disko Island, West Greenland was conducted across a hydrogeomorphic landscape gradient, to reconstruct principally changes in algal pigments, lipid biomarkers and carbon isotopes (δ13C) to investigate carbon cycling at multiple scales and resolutions. All three records reconstructed recent change on Disko, with records from lake Disko 2 additionally spanning since ~7640 cal. yr BP and lake Disko 4 since ~1260 cal. yr BP. Changes in sedimentary proxies were broadly consistent with the spatially and temporally heterogeneous environmental change known to have occurred across the Arctic over these periods, including recent warming (RW), the Little Ice Age (LIA) and the Medieval Climate Anomaly (MCA). However, the individual lake responses to these changes were highly landscape specific. Changes in algal pigments were linked to variations in the inputs of nutrients and DOC from soil microbial activity, variations in permafrost melt regime and glacier melt. Evidence of disturbance from catchment freeze-thaw processes, glacier inputs and the effects of permafrost melt on algal communities varied between lakes. At the highest position in the landscape gradient, lake Disko 2 had poorly developed soils and lower glacier coverage, with simple algal communities, but pigment and δ13CTOC changes since ~7640 cal. yr BP reflected individualistic responses to overarching drivers, consistent with the current understanding of heterogeneous pan-Arctic environmental change. Replicate cores with proximity to talus and debris flow had differing signatures, highlighting the role of geomorphology. In lake Disko 2 there was some similarity between Greenland Ice Sheet surface area and pigment biomarkers of cryptophytes (alloxanthin), which suggests if locally similar, catchment ice variation may regulate nutrient and DOC release from catchments, stimulating algae. At a mid-elevation position in the catchment, lake Disko 1 meltwater inputs from an upstream retreating glacier (since the end of the LIA) may be stimulating algae through increased nutrients and DOC supply, although soil nutrient cycling and permafrost release present in the catchment U-shaped valley may also be contributing to these increases. At the lowest position in the landscape, lake Disko 4 has a complex and variable pigment response likely influenced by multiple glacier inputs, thicker permafrost, greater vegetation and more developed wetland areas, together regulating the cycling of nutrients and DOC. Higher maximum pigment concentration during the MCA, compared with the LIA reflect the spatially and temporally heterogeneous expression of these events across the Arctic. Despite individuality in catchment filtering, all three lakes on Disko Island were found to have recent increases in algal production, which when combined with recent increases in carbon burial suggests these lakes are becoming increased carbon sinks. Although this increased carbon burial reflects a minor store in lakes compared with release to downstream waterbodies, if upscaled across the Arctic this change could be globally significant and should be integrated in future models. With future warming, catchment processes are likely to play a pronounced role in mediating algal community structure in lakes across the Arctic.

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Akerstrom, Frida. "Carbon Cycling-Climate Change Feedback in Lakes in Arctic Alaska: Monitoring Methane Emissions." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479476238261354.

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40

Johnson, Cody R. "Consumer-Driven Nutrient Recycling in Arctic Alaskan Lakes: Controls, Importance for Primary Productivity, and Influence on Nutirient Limitation." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/417.

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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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41

Wang, Aiqing. "Clause-internal preposing in Late Archaic Chinese." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/13738/.

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In this thesis I investigate the preverbal positioning of wh and non-wh-phrases in Late Archaic Chinese (LAC) and the Intervention Effect (Beck 1996a). I first explore non-wh-fronting and discover two landing sites for preposed DPs. Non-wh-objects fronted to the higher position in the left periphery are consistent with a topical interpretation, yet those moved to the lower position between the subject and negation are consistent with a focal interpretation. In the context of negation, pronouns normally move to negation and target a position exclusively for them. I then discuss two types of wh-preposing in LAC. D-linked which-phrases in LAC are topical, therefore they appear in an internal topic position. With respect to non-D-linked wh-DPs, they target one of the two focused positions in the medial domain, either between the internal topic position and negation or between negation and vP. The higher focus position above negation is expected to exclusively permit wh-phrases base-generated above negation, and the lower focused position below negation accommodates wh-adverbials base-generated between negation and vP. I also propose that the inverted order of wh-P is generated via PP inversion followed by separate preposing of wh and P. I finally explore the Intervention Effect. Negation, rather than focus or quantificational phrases, functions as a barrier for the Q-binding of wh-phrases in LAC. Wh-items that have the option to stay in-situ, along with wh-arguments and adverbials that usually move to the lower focus position below negation, are subject to the Intervention Effect caused by negation. As a consequence, these wh-phrases have to land in the higher focus position above negation which is expected to accommodate ‘high’ adverbials exclusively. I propose that the Intervention Effect in LAC is a consequence of Q-binding as feature movement of [wh], interacting with fronting into the hierarchy of clause-internal positions driven by [Topic] or [Focus] features.

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Hodgetts, Lisa Maye. "Animal bones and human society in the late Younger Stone Age of Arctic Norway." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4491/.

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In recent decades anthropologists and archaeologists have divided hunter-gatherer groups into two types; "simple" and "complex". However, many documented foraging communities display traits associated with both types, and the placement of past and present hunter-gatherers into either category is problematic. The substantial house remains of the late Younger Stone Age hunter-gatherers of Varangerfjord, North Norway, have been connected by many archaeologists with sedentism and, by extension, with "complexity" and permanent social hierarchies. This analysis takes a more direct approach social organisation, using faunal remains to better define the social relationships between households within this community. The large mammal remains from a series of houses are compared to determine whether all households had equal access to prey species and to different parts of large mammal carcasses. Towards this end, the climate and available resources are established for North Norway during the Younger Stone Age. Previous interpretations of the archaeology of the period, including the argument for "complexity" are then discussed. The study sites and associated faunal assemblages are presented. Seal hunting patterns are compared between households in terms of both the choice of species and the age breakdown of each hunted seal population. Local differences in the numbers of ringed seal are attributed to the preference of ringed seal for certain types of coastline. Strong similarities are noted between all sites in terms of both the season of seal hunting activity and the selection of adult versus juvenile harp seal and ringed seal. Distribution of seal and reindeer body parts are also compared between and within houses. Again, there are more similarities than differences between households. Seals were returned whole to all houses and reindeer body part representation appears to be mediated by the utility of each part for artefact manufacture. The implication of these results are discussed in terms of the structure of social relationships, symbolic behaviour and territoriality. The utility of this approach in a broader context is also considered.

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Cincio, Paige. "Quantifying the Vulnerability of Arctic Water Supply Lakes to Environmental Change Through Paleolimnological Assessment." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41488.

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Anthropogenic stressors to freshwater environments have perpetuated water quality and quantity challenges for northern communities across Arctic Canada, making drinking water resources a primary concern for Arctic populations. To understand the ecological trajectory of freshwater supply sources, we conducted a paleolimnological assessment on two supplemental sources of freshwater in Igloolik, Nunavut, Canada. A stratigraphic examination of bioindicators (Insecta: Diptera: Chironomidae) allowed for paleotemperature reconstructions with decadal and centennial resolution over the past 2000 years. Between 200 and 1900 CE, the sub-fossil chironomid community was comprised of cold-water taxa, such as Abiskomyia, Micropsectra radialis-type, and Paracladius. Reconstructed temperatures were consistent with known climate anomalies during this period. A rapid shift in the composition of the chironomid community to warm-water adapted taxa (Chironomus anthracinus-type, Dicrotendipes, and Tanytarsus lugens-type) in the late 20th century was observed in both systems. Our results demonstrate that these lake ecosystems are undergoing marked transformations to warmer, more nutrient-rich environments, and suggest water sustainability pressures on freshwater and human systems will likely continue in tandem with ongoing climate change. To contextualize the influence of recent warming and elucidate the status of water resource vulnerability over the longer term, paleolimnological methods can be usefully applied as components of vulnerability assessments.

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Perin, Sofia Lucille. "Effect of UVB radiation on ecosystems of selected lakes in the Canadian High Arctic." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/29247.

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Two studies on the effects of enhanced ultraviolet-B radiation (UVB; 280--320 nm) on planktonic organisms of Canadian High Arctic lakes are presented. In the first study, the long-term effects of a moderate increase in UVB levels on the planktonic community of a lake were evaluated using in situ mesocoms. Four mesocosms (3 m square and 3 m deep) were placed in Two Basin Lake, a small lake (14.2 ha) located on Ellesmere Island (79°55.5'N, 84°40'W; Nunavut, Canada). For 27 days, two mesocosms were exposed to full sunlight (including ambient UVB) while two others were exposed to sunlight plus artificially enhanced UVB. Chlorophyll a, zooplankton mean length and carbon allocation into macromolecular constituents were not affected by enhanced UVB. Phytoplankton productivity displayed diverse and inconsistent responses to enhanced UVB. Picocyanobacteria abundance decreased in the enhanced UVB mesocosms, but only at the surface. Enhanced UVB generally increased heterotrophic bacterial abundance and activity. Heterotrophic nanoflagellates and zooplankton abundances increased in the enhanced UVB treatment after 14 days. The cladocerans and rotifers were positively affected by UVB, while the copepods were negatively affected. The high levels (≥ 5 mg L -1) of dissolved organic carbon (DOC) in this lake combined with vertical mixing generally protected the planktonic community from direct damage by enhanced UVB. It is hypothesized that UVB may have indirectly stimulated the microbial food web and the rest of the food chain through increased photodegradation of high molecular weight refractory dissolved organic matter into more bioavailable nutrients. In the second study, the short-term (2 to 24 h) effects of enhanced UVB on carbon uptake rates, photosynthetic fractionation into three size classes (picoplankton [0.2-2 mum], nanoplankton [2-20 [mum] and netplankton [> 20 mum]) and carbon assimilation into the four main end-products (low molecular weight metabolites [LMW], lipid, polysaccharide and protein) were assessed for nine lakes located near Resolute (74°15'N, 94°50'W) on Cornwallis Island (Nunavut, Canada). These lakes have low DOC levels (≤ 2 mg L-1). For each lake, 14C-inoculated water samples were exposed to 6, 25, 50 and/or 100% surface irradiance levels (E o) under natural solar radiation (including ambient UVB) or solar radiation plus artificially enhanced UVB. (Abstract shortened by UMI.)

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45

Kekonen, T. (Teija). "Environmental information from the Svalbard ice core for the past 800 years." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514281853.

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Abstract Major water soluble ions (Cl-, NO3-, SO42-, CH3SO3-, Na+, K+, NH4+, Mg2+, Ca2+) were determined and the results interpreted from a 121 m long ice core drilled at the summit of the Lomonosovfonna dome, Svalbard. The core covers about the past 800 years. The reliability of anion chemistry for paleoenvironmental studies, and various insoluble particles were also investigated. The ice core studied in this Thesis is the first relatively deep ice core from the central Svalbard that has been analyzed and the results interpreted and published at high resolution for all major ions. One of the clearest features of the ion profiles is anthropogenic impact. SO42- and NO3- concentrations show significant increases by the mid-20th century with slight increases already at the end of the 19th century. In addition excess Cl- and NH4+ from anthropogenic sources are detected arriving after the mid-20th century. Anthropogenically derived SO42- and NO3- have different sources on Lomonosovfonna. NO3- is correlated with NH4+ and requires interpretation in terms of both natural and anthropogenic NH4NO3 sources. The ice core ionic load consists mostly of sea salt ions (Na+, Cl-, K+ and Mg2+). Water soluble Ca2+ are mostly terrestrial in origin. Ion balance together with the Na+/Cl- ratio shows considerable change about 1730 that is most probably due to Na2CO3 input to the ice cap before 1730. Marine biogenic CH3SO3- concentrations are high and stable during the Little Ice Age. CH3SO3- concentrations show a clear change in concentrations in 1920, that is the end of the Little Ice Age in Svalbard. Regardless of anthropogenic impact, marine biogenic SO42- is appreciable in total SO42- budget even in the 20th century. The Laki volcanic eruption in Iceland in 1783 is identified in the ice core as a volcanic tephra layer and high SO42- concentration and acidity peaks. These show that SO42- arrived to the Lomonosovfonna ice cap 6–12 months later than insoluble tephra and the SO42- aerosol caused a drop in temperature. The reliability of ice core ion chemistry analyses was estimated – for the first time in an ice core using two different analytical procedures on 500 adjacent samples from the same depth. Small-scale inhomogeneity in ion concentrations shows that information from ice core layers is representative of the regional environmental and suitable for paleoclimate studies.

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Kaparulina, E. (Ekaterina). "Eurasian Arctic ice sheets in transitions:consequences for climate, environment and ocean circulation." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526217765.

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Abstract In this Ph.D. thesis sediment cores from the central Arctic Ocean, southwestern Barents Sea and sediment exposures from the Kola Peninsula were investigated in order to reveal interactions between the late middle Pleistocene and late Pleistocene Arctic ice sheets, between Marine Isotope Stages 6 and 1 (MIS 6 and MIS 1). One of the main objectives of this work is to establish provenance areas for the sediments studied in the central Arctic, the southwestern (SW) Barents Sea and the Kola Peninsula, their transport mechanisms and through that their relationship to glaciations in the Arctic and to development in the Kola Peninsula during the late middle and late Pleistocene. Mineralogical and geochemical data from the core 96/12-1pc on the Lomonosov Ridge, central Arctic Ocean was studied to evaluate ice transport from circum-Arctic ice sheets and variability in sediment drainage systems associated with their decay. SW Barents Sea sediments contain important information on Late Glacial and Holocene sediment provenance characteristics in relation to ice flow patterns and ice rafting from different regional sectors. The studied SW Barents Sea sediment cores show that sediments were most likely derived from a combination of far-field Fennoscandian sources, local subcropping Mesozoic strata below the seafloor and sea ice transport. The investigation carried out on the Kola Peninsula indicates that the Eemian (MIS 5e) marine environment in the White Sea Basin and onshore coastal areas gradually changed into a glaciolacustrine environment during MIS 5d to MIS 5a. Subsequently, the Scandinavian Ice Sheet (SIS) covered the Kola Peninsula, most probably during MIS 4. The final deglaciation of the SIS on the Kola Peninsula took place, however, during the late Weichselian (MIS 2) between 16–12 ka
Tiivistelmä Tässä väitöstutkimuksessa tutkittiin sedimenttikairanäytteitä keskeiseltä Jäämereltä ja Lounais-Barentsinmereltä sekä tarkasteltiin sedimenttiseurantoja Kuolan niemimaalla tarkoituksena selvittää myöhäisen keskipleistoseeni- ja myöhäispleistoseeniajan Arktisten jääkenttien keskinäiset vuorovaikutukset erityisesti merellisten isotooppivaiheiden 6 ja 1 (MIS 6 ja MIS 1) välillä. Tämän työn yhtenä päätavoitteena on määritellä sedimenttien lähdealueet keskeisellä Arktiksella, lounaisella Barentsinmerellä ja Kuolan niemimaalla, sedimenttien kuljetusmekanismit ja näiden perusteella riippuvuudet Arktisiin jäätiköihin ja Kuolan niemimaalla tapahtuneeseen myöhäiskeski- ja myöhäispleistoseenin kehitykseen. Mineraloginen ja geokemiallinen tieto Lomonosovin harjanteen kairauksesta 96/12-1pc, keskeisellä Jäämerellä on perusta arvioitaessa jääkuljetusmekanismeja ympäröiviltä sirkum-Arktisilta jäätiköiltä ja arvioitaessa valuma-alueiden osuutta suhteessa näiden jäätiköiden häviämiseen. Lounaisen Barentsinmeren sedimentit sisältävät tärkeätä tietoja viimeisen jäätiköitymisen loppuvaiheen ja holoseeni-ajan sedimenttien lähdealueista ja suhteista jäävirtauksiin ja jääkuljetukseen eri aluesektoreilta. Tutkitut Lounais-Barentsinmeren sedimentit osoittavat, että sedimentit olivat todennäköisimmin peräisin suhteellisen kaukaisilta Fennoscandian lähdealueilta, paikallisista mesotsoosista merenpohjan kerrostumista ja merijään kuljettamasta materiaalista. Kuolan niemimaalla tehty tutkimus osoittaa, että Eem-kauden (MIS 5e) meriympäristö Vienanmeren altaassa ja rannikkoalueilla vähitellen muuttui glaciolakustriseksi ympäristöksi MIS 5d:n ja MIS 5a:n välisenä aikana. Sen jälkeen Skandinavian jääkenttä (SIS) peitti Kuolan niemimaan, todennäköisimmin koko MIS:n 4 ajanjakson. SIS:n lopullinen deglasiaatio alkoi Kuolan niemimaalla kuitenkin myöhäisen Veiksel-jääkauden (MIS 2) aikana noin 16–12 ka sitten

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47

Vega-Centeno, Rafael. "The Study of Late Archaic Social Complexity on the North-Central Coast of Perú." Pontificia Universidad Católica del Perú, 2012. http://repositorio.pucp.edu.pe/index/handle/123456789/113312.

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The study of the characteristics of the Late Archaic Period societies on the North-Central Coast probably is one of the most important areas of archaeological research in the last ten years. This paper evaluates the quality of the current archaeological data. A review of the reported information reveals a need to establish a more precise characterization of the architectural designs and construction processes that shaped the conspicuous public buildings of this period. Also revealed is the need to refine the occupational sequences of the Late Archaic architectural complexes of the North-Central Coast, which is necessary for a better understanding of the processual characteristics of their cultural development. As a beginning point, data recovered from excavations in the site of Cerro Lampay, a small architectural compound of the Fortaleza Valley, are studied. Information from Cerro Lampay is compared with published data from other sites, including Áspero, Chupacigarro, Caral, Caballete, and Porvenir.
La naturaleza de las sociedades del Periodo Arcaico Tardío en la costa norcentral ha sido, probablemente, uno de los temas más recurrentes en los últimos 10 años. Para contribuir a esta discusión, se hace necesaria una evaluación de la calidad de la base empírica existente hasta el día de hoy en el registro arqueológico. Una revisión de los datos documentados revela la necesidad de establecer con mayor precisión las características del diseño arquitectónico y el proceso constructivo de los conspicuos edificios públicos de este periodo. Además, muestra que es necesario el afinamiento de las secuencias ocupacionales de los distintos complejos arquitectónicos del Periodo Arcaico Tardío en la costa norcentral como requisito para entender las características procesales del desarrollo cultural que allí se dio. Esta revisión parte de los datos recuperados en las excavaciones en Cerro Lampay, un pequeño conjunto arquitectónico del valle de Fortaleza. Esta información es comparada con la de otros sitios, como Áspero, Chupacigarro, Caral, Caballete y Porvenir.

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48

Linden, Sandra van der. "Icy rivers heating up : modelling hydrological impacts of climate change in the (sub)arctic /." Amsterdam : Utrecht : Koninklijk Nederlands Aardrijkskundig Genootschap ; Faculteit Ruimtelijke Wetenschappen, Universiteit Utrecht, 2002. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=010495642&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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49

Doubleday, Nancy Colleen. "A paleolimnological survey of combustion particles from lakes and ponds in the eastern Arctic, Nunavut, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ54410.pdf.

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50

Morrison, Catriona Anne. "Late Quaternary glacial and sea level history of west-central Axel Heiberg Island, High Arctic Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ59853.pdf.

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Dissertations / Theses on the topic 'Arctic lake'

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