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71	CO2 Ventilation, Hydrological Cycle over Southern Ocean and Clumped Isotope Thermometry in Biogenic Carbonates Prasanna, K January 2016 (has links) (PDF) The thesis presents observations on the CO2 concentration and carbon isotopes in air CO2 (δ13C) to constrain the inter-annual variability of carbon inventory over the Southern Ocean between the years 2011-2013. Based on the observation, the region of CO2 venting was identified over the Southern Ocean. Further, isotopic characterization allowed inferring about the possible sources of CO2 degassing and contribution from the dissolved inorganic carbon (DIC) that exsolved to generate CO2. It is concluded that the origin CO2 is mainly from the degassing of CO2 available from the dissociation of DIC or organic degradation. Live Foraminiferal samples of Globigerina bulloides from towing were captured, separated and analysed for δ18O and δ13C from various locations across the Southern Ocean between 10°N−60°S. A large similarities in the estimated values (deduced from simultaneous composition of ocean water 18O, δ13C in DIC and temperature i.e. SST under equilibrium condition) and measured δ18O and δ13C values were observed until 40°S from the equator, and hence it was concluded that the calcification depth of G. bulloides is confined to a depth of ~75-200m till 40°S latitude. However, further south (>40oS) disequilibrium from the estimates was detected. A number of possible reasons were cited for the observed disequilibrium such as (1) Deeper depth habitat (2) Partial dissolution (3) Non-equilibrium calcification (4) Oceanic Suess Effect and (5) Genetic Variability. A box model of isotopic mass balance was presented in this study to explain the pattern of enrichment in the 13C values of sea water DIC with latitude (up to about 43°S). The model shows that a steady state of the carbon isotope ratio of water is achieved in a relatively short time of ~5000 days. Rainwater isotope in the open marine condition across the latitudinal transects over Southern Ocean marking zone of precipitation and evaporation is another element of this thesis. A variation with excess lighter isotopes in rainwater was observed in high latitude rain in this study. Observed isotopic depletion is attributed to rainout process over the ocean. The average rainout fraction over the Southern Ocean in the region of zone of precipitation is ~44%, while it drops to ~25% in the zone of evaporation. Second part of the thesis presents a novel method of isotope thermometry which is called “clumped isotope (13C18O16O16O-2 in the calcite structure) thermometry”. A revision in the thermometry equation relating 47 vs T in synthetic carbonates precipitates and otoliths was proposed. The revised calibration was used on fish otoliths from the modern and past environment to estimate the temperatures. Together with the clumped isotope, conventional stable isotopes in the shell carbonates were measured to effectively reconstruct the seasonal fresh water fraction at seasonal time scales. Southern Ocean Clumped Isotope Geochemistry Carbon Cycle Eocene Climatic Optimum (EECO) Clumped Isotope Thermometry CO2 Ventilation Carbonate Clumped Isotope Thermometry Biogenic Carbonates Air CO2 Air Carbondioxide Ecological Sciences (CES)
72	THE IMPACT OF MELTING GLACIERS ON MOUNTAIN GROUNDWATER SYSTEMS: A MULTI-YEAR STUDY INCORPORATING ISOTOPIC TRACERS AND MICROBIOLOGY IN MOUNT HOOD NATIONAL FOREST, OREGON, AND GLACIER NATIONAL PARK, MONTANA, AND TIME SERIES ANALYSES IN THE SWISS ALPS Jordyn B Miller (11852195) 17 December 2021 (has links) <p>Alpine glaciers around the world are in retreat and are unlikely to reverse course. This dissertation focuses on improving our understanding of the impact of glacial melt on mountainous alpine groundwater systems. Studies on glacial melt-groundwater interactions have become more prevalent, particularly in the past 5 years, because we are recognizing that the contribution of glacial melt to the hydrologic cycle is not limited to melt-season surficial streamflow. The importance of glacial melt to mountain groundwater systems has the potential to not only influence spring and streamflow generation, but also the longevity of alpine specific, and frequently endangered species, dependent on this source of recharge. This recharge may be vital for human water needs such as potable water, agriculture, and hydrothermal power.</p>The impact that a transition from glacial melt to snow- or rain-dominated streamflow and recharge will have on alpine ecosystems in a continually warming climate is far reaching. This dissertation: 1) tests whether glacial melt is an important source of recharge for mountain springs and their microbial communities, 2) investigates the spatial impact of glacial-melt recharge on residence times and flowpaths that support alpine springs, and 3) explores the impact of post-peak water on alpine baseflow using a statistical, timeseries approach. My results show that the groundwater systems in glaciated mountainous, alpine regions are particularly vulnerable to climate change. Springs in Mount Hood National Forest and Glacier National Park were sampled over a 4-year period, and in addition, publicly available long-term streamflow datasets were are also utilized. The chapters composing this work build upon each other, and compare and contrast the factors most important in glacial melt recharging the mountain-block. Information that is vital to the management of alpine water resources by landowners, watershed groups, scientists, and others interested in mountain groundwater systems in glaciated alpine regions is presented in the following pages. Geology Environmental Science Hydrology Climate Science Isotope Geochemistry Geochronology Glaciology Hydrogeology Surface Processes Surfacewater Hydrology groundwater glacier climate change isotope mountain groundwater melting glaciers glacier national park mount hood national forest swiss alps glacial retreat
73	Hafnium Isotope Geochemistry of the Gabbroic Crust Sampled Along the Mid-Atlantic Ridge: Constraints on the Nature of the Upper Mantle Thomas, Christine L. 26 September 2013 (has links) No description available. Geochemistry Geology Geological Hafnium Isotope Geochemistry Trace Element Geochemistry Zircon Mid-Atlantic Ridge Gabbroic Crust Upper Mantle Slow-Spreading Ridge
74	<b>FACTORS AFFECTING THE PRESERVATION OF THE ISOTOPIC FINGERPRINT OF GLACIAL MELTWATER IN MOUNTAIN GROUNDWATER SYSTEMS</b> Ayobami O Oladapo (19218853) 26 July 2024 (has links) <p dir="ltr">Alpine glacier meltwater is an important source of recharge supporting groundwater flow processes in the high mountains. In the face of rapid ice loss, knowledge of response times of mountain aquifers to loss of glacial ice is critical in evaluating the sustainability of alpine water resources for human communities and alpine ecosystems. Glaciers are very sensitive to changes in climate, they advance during periods of global or regional cooling, and they retreat in response to global or regional warming conditions. When the glaciers grow, the equilibrium-line altitude separating the zone of accumulation and zone of ablation on the glacier moves downslope; it moves upslope when they retreat. The latter is not a sustainable condition for the glacier. Previous studies have shown that glacial meltwater is an important source of groundwater recharge. However, we lack fundamental information on the importance of glacial meltwater in mountain groundwater processes such as supporting baseflow generation to alpine streams, perennial flow to alpine springs, and the geochemical evolution of groundwater in mountain aquifers. Thus, continued glacial ice loss may have severe consequences for alpine hydrological and hydrogeological systems.</p><p dir="ltr">Glacier National Park (GNP) and Mount Hood National Forest (MH), both have alpine glaciers. These two study sites show different responses to climate change since their glaciers are in different states of retreat. GNP glaciers are in advanced stages of retreat compared to MH glaciers. Groundwater samples were collected from springs, seasonal snow, glacial ice, and glacial melt (subglacial flow) in GNP and MH. The samples were analyzed for a suite of environmental isotopes and geochemical tracers to address the following questions: 1) How are isotopic fingerprints of glacial meltwater preserved in mountain-block aquifers? What does the isotopic fingerprint of subglacial flow tell us about melting, meltwater processes, and mixing processes? 2) Is the preservation of the isotopic fingerprint of glacial meltwater affected by aspect controls on ice preservation? Aspect is defined as the compass direction of the slope where the glacier is found. 3) What controls groundwater flow and flowpath connectivity from high elevations (near glacier) to lower elevations? What geologic units support groundwater flow to local- and regional-scale springs and flowpath connectivity across spatial scales in each study site?</p><p dir="ltr">The flow of groundwater in mountainous terrain is heavily dependent on the hydraulic properties of the bedrock including presence/absence of dipping layers and structural features, primary and secondary porosity, and presence/absence of ongoing tectonic activity. Strontium isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr) were used to identify the rock units that host groundwater flowpaths and to quantify flowpath connectivity across spatial scales in both study sites. The <sup>87</sup>Sr/<sup>86</sup>Sr data show that flowpaths in GNP are primarily hosted in the Helena Formation and permeable facies in the Snowslip Formation. Groundwater also flows through alluvium and younger bedrock units, and there is some flow along or through the volcanic sill in the Helena Formation. Hydrostratigraphy also affects groundwater flow and the spatial distribution of alpine springs in GNP. At MH, the rock units hosting flowpaths are young reworked volcanic rock units that are Quaternary in age. Flowpaths in MH appear to be connected across spatial scales since warm springs emerging along the lower southern slopes of Mount Hood preserve stable isotopic signatures of glacial meltwater. In comparison, nearly all the sampled springs in GNP emerge on south-facing slopes. This is not an indication of ice preservation, instead it’s controlled by hydrostratigraphy. In fact, it’s unlikely that high-elevation groundwater is strongly connected to low-elevation sites due to hydrostratigraphy. There are more springs on south-facing slopes at MH as well; however, they do not preserve an isotopic signature of recharge from glacial meltwater except for the warm springs. Springs on north-facing slopes in MH, however, do preserve the signature.</p><p dir="ltr">Tritium (<sup>3</sup>H) and chlorine-36 (<sup>36</sup>Cl/Cl) were measured to assess how the isotopic fingerprint of glacial meltwater is preserved in mountain aquifers. The <sup>3</sup>H activities in spring water are elevated in GNP and it’s difficult to differentiate between modern precipitation and glacial meltwater. Tritium activities are lower in MH, but it’s also difficult to differentiate between potential endmembers. This discrepancy could imply that glacial meltwater doesn’t contribute to groundwater recharge, but this doesn’t support the Bayesian stable isotope mixing model results of an earlier study. Instead, I infer that englacial mixing processes are affecting the isotopic fingerprint of subglacial melt. An englacial mixing model (EMM) was developed to explain how the isotopic fingerprint of subglacial flow (glacial meltwater) changes in relation to the stage of retreat. The stage of retreat is important because it controls the proportion of glacial meltwater to runoff from snowmelt and rain that enters the englacial network from the surface of the glacier. Mixing occurs in the englacial network, and the mixed water is transported to the base of the glacier. Englacial mixing in conduits, fractures, and moulins affects the <sup>3</sup>H and <sup>36</sup>Cl/Cl fingerprint of subglacial flow and will, in turn, affect the isotopic fingerprint of recharge from glacial meltwater. For this study, the <sup>3</sup>H is not robust by itself; however, <sup>36</sup>Cl/Cl shows some additional benefits over <sup>3</sup>H. The EMM suggests that the impact of englacial mixing and the influence of modern precipitation on the isotopic composition of subglacial flow increases as the glacier retreats in both GNP and MH. This model is novel to the best of our knowledge. Additional testing of the EMM should be prioritized in the near future.</p> Isotope geochemistry Geology not elsewhere classified Groundwater hydrology Surface water hydrology Quaternary environments Natural resource management Alpine glaciers Isotope glacier response Glacier retreat 87Sr/86Sr in groundwater 36Cl ratios in hydrology Glacier Meltwater Tritium 3H isotope Mountain Groundwater Englacial Network Aspect Hydrostratigraphy
75	LIFE IN THE RAIN SHADOW: UNDERSTANDING SOURCES OF RECHARGE, GROUNDWATER FLOW, AND THEIR EFFECTS ON GROUNDWATER DEPENDENT ECOSYSTEMS IN THE PANAMINT RANGE, DEATH VALLEY, CALIFORNIA, USA Carolyn L. Gleason (5930639) 16 January 2019 (has links) <div> <p>Despite its location in the rain shadow of the southern Sierra Nevada, the Panamint Range within Death Valley National Park, CA hosts a complex aquifer system that supports numerous springs. These springs, in turn, support unique groundwater-dependent ecological communities. Spring emergences range in elevation from 2434 m above sea level (within the mountain block) to 77 m below sea level (in the adjacent basins). Waters were collected from representative Panamint Range springs and analyzed for environmental isotopes and geochemical tracers to address the following questions: 1) What is the primary source of recharge for the springs? How much recharge occurs on the Panamint Range? 2) What groundwater flowpaths and geologic units support springflow generation? and 3) What are the residence times of the springs? The stable isotopic composition (δ<sup>18</sup>O and δ<sup>2</sup>H) of spring water and precipitation indicate that localized high-elevation snowmelt is the dominant source of recharge to these perennial springs, though recharge from rainfall is not wholly insignificant. Geochemical evolution was evaluated using principle component analysis to compare the concentrations of all major spring cations and anions in a multidimensional space and group them according to dominant geochemical signatures. These resulting geochemical groups are controlled primarily by topography. The Noonday Dolomite and other carbonate units in the range are identified as the water-bearing units in the mountain block based on the <sup>87</sup>Sr/<sup>86</sup>Sr of spring waters and rock samples. These units also offer higher hydraulic conductivities than other formations and are chemically similar. Radiocarbon- and <sup>3</sup>H derived residence times of these spring waters range from modern to approximately 1840 years, with the shortest residence times at higher altitudes and Hanaupah Canyon and increasing residence times with decreasing altitude. This residence time-altitude relationship is likewise likely topography-driven though there are significant disparities in mountain block storage between the various canyons of the range resulting in variable residence times between drainages. Lower Warm Springs A and B, however, are the exceptions to this trend as they emerge at lower altitudes (750m above sea level) and are likely driven by the transport of groundwater to the surface along faults which increases both the temperature and groundwater residence times of waters from these springs. Benthic macroinvertebrates and benthic and planktonic microbes were also sampled for each spring studied. BMI and microbial community structure in the Panamint Range is likewise topography-controlled with more tolerant communities at lower elevations (within more chemically evolved waters) and less tolerant species in the unevolved waters at higher elevations.</p></div> Geology Ecology Hydrology Isotope Geochemistry Hydrogeology Panamint Range Panamint Panamint Mountains Death Valley stable isotopes hydrogeology spring residence times mountain block recharge mountain block hydrogeology mountain system recharge spring ecology microbial ecology benthic macroinvertebrates microbes Chlorine-36 Environmental isotopes tritium hydrogeochemistry radiocarbon carbon-14
76	Evaluation of the mechanisms of trace elements transport (Pb, Rare Earth Elements,... ) and the elemental and isotopic fractionation (Ca and Sr) at the interface water-soil-plant / Évaluation des mécanismes de transport des éléments traces (Pb, REE, ...) et du fractionnement des rapports élémentaires et isotopiques (Ca et Sr) à l'interface eau, sol, plante Gangloff, Sophie 28 January 2016 (has links) Ce travail est axé sur l’étude d’un profil de sol et des solutions de sol prélevés sur une parcelle expérimentale couvertes d’épicéas. Tous ces échantillons proviennent du Bassin Versant du Strengbach (Observatoire HydroGéochimique de l’Environnement – OHGE), ont été échantillonnés à différentes profondeurs (5, 10, 30 et 60 cm) et durant la période comprise entre 2009 et 2013.Les caractérisations des extraits des sols par spectroscopie Infra-Rouge ont permis de mettre en évidence les modifications des groupements fonctionnels organiques avec la profondeur et que ces modifications ont une forte incidence sur le comportement des cations (majeurs et traces) dans le sol. Des expérimentations d’ultra-filtration ont permis d’identifier les flux colloïdaux et dissous du carbone organique ainsi que ceux des éléments majeurs et traces présents dans les solutions de sol. L’utilisation conjointe des traceurs isotopiques (87Sr/86Sr et δ44/40Ca) et chimiques (Terres Rares) ont mis en évidence des processus ayant lieu aux interfaces eau-sol-plante, comme le prélèvement racinaire ou l’altération des sols. / This work is focused on the study of a profile of soil and soil solutions collected on an experimental plot covered with spruce. All these samples come from the watershed of the Strengbach (environment - OHGE Hydrogeochimique Observatory), were sampled at different depths (5, 10, 30 and 60 cm) and during the period between 2009 and 2013. Characterizations of soil extracts by infrared spectroscopy allowed to highlight changes in the organic functional groups with depth and that these changes have a significant impact on the behaviour of the cations (major and trace) in the soil. Ultrafiltration experiments helped to identify flows of colloidal and dissolved organic carbon as well as those of the major and trace-element present in soil solutions. The joint use of isotope tracers (87Sr / 86Sr and δ44 / 40 Ca) and chemical (Rare Earth Elements) have highlighted processes taking place at the water-soil-plant interface, as the uptake by root or soil alteration. Carbone et fonction organique Ultra-filtration Flux chimiques colloïdaux et dissous Géochimie isotopique Calcium et Strontium Terres rares Prélèvement racinaire Activité bactérienne Altération du sol Organic carbon Organic functional groups Ultrafiltration Colloidal and dissolved chemical fluxes Isotope geochemistry Calcium and Strontium REE Uptake by root Bacterial activity Soil alteration 551.9
77	Postglazialer Anstieg des Meeresspiegels, Paläoklima und Hydrographie, aufgezeichnet in Sedimenten der Bermuda inshore waters / Postglacial rise of sea level, palaeoclimate and hydrography, recorded in sediments of the Bermuda inshore waters Vollbrecht, Rüdiger Dr. 13 January 1997 (has links) No description available. 550 Geowissenschaften Mathematics and Computer Science Postglazial Meeresspiegel Paläoklima Hydrography Bermuda Sedimente Pleistozän Holozän Quartär Seen Küste Laminite Solarzyklen Sonnenzyklen marin lakustrin Geologie Karbonate Böden Karst Torf Isotopen-Geochemie Altersbestimmung Fazies Paläökologie postglacial sea level palaeoclimate paleoclimate hydrography Bermuda sediments Pleistocene Holocene Quaternary inshore waters lakes laminites solar cycles lacustrine marine geology carbonates soil karst peat isotope geochemistry radiocarbon dating facies palaeoecology paleoecology 38.48 Marine Geologie 38.41 Sedimentation 38.82 Klimatologie 38.19 Historische Geologie: Sonstiges 38.32 Geochemie 38.88 Regionale Hydrologie 38.47 Moore 38.90 Ozeanologie Ozeanographie VAT 250 Litorale Sedimente VCA 520 Quartärgeologie VDI 210 Pleistozän VDI 220 Holozän VEW 200 Karibischer Raum VEZ 130 Inselgruppen TWC 600 Paläoklimatologie VKB 380 Sedimente bestimmter Regionen VKB 378 Rhytmite VKB 376 Organogene Sedimentgesteine VKB 340 Fazieskunde VKB 333 Sonstige Sedimentationsprozesse VKB 332 Sedimentationsbedingungen UHA 700 Marine Geologie (Küsten Watt Inselbildung etc.) UHA 440 Schwankungen

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