Download or read book Stable isotope studies on Mono Lake California 1 Delta18O in lake sediments as proxy for climatic change during the last 150 years written by H.-C. LI and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Problems of Stable Isotopes in Tree rings Lake Sediments and Peat bogs as Climatic Evidence for the Holocene written by Burkhard Frenzel and published by Wiley-VCH. This book was released on 1995 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Long term Environmental Change in Arctic and Antarctic Lakes written by Reinhard Pienitz and published by Springer Science & Business Media. This book was released on 2007-11-08 with total page 579 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concerns about the effects of global climate change have focused attention on the vulnerability of circumpolar regions. This book offers a synthesis of the spectrum of techniques available for generating long-term environmental records from circumpolar lakes.

Download or read book Stable and Clumped Isotope Analyses of Last Glacial Maximum Pluvial Lakes to Constrain Past Hydroclimate written by Lauren Mae Santi and published by . This book was released on 2019 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Last Glacial Maximum (LGM; ~23,000-19,000 years ago) and subsequent deglaciation (~19,000-11,000 years ago) represents the last major global climatological transition. In the Western United States, the LGM and deglacial were both characterized by increased effective moisture and expansive lake systems, with most lake growth and maximum lake extents achieved during the deglacial period. In stark contrast, the modern Great Basin is characterized by aridity and low effective moisture. The factors contributing to these large-scale changes in hydroclimates are critical to resolve, given this region is poised to undergo future anthropogenic-forced climate changes with large uncertainties in model simulations for the 21st century. Furthermore, there are ambiguous constraints on the magnitude and even the sign of changes in key hydroclimate variables between the LGM and present-day in both proxy reconstructions and climate model analyses of the Western United States. In this work, I present new stable and clumped isotope data from several ancient lakes, analyze this new data in concert with previously published data, and compare both new and existing results to climate model simulations. Radiocarbon dated samples from ancient lakes constrain lake elevation and the timing of lake level fluctuations. Using a hydrological modeling framework, clumped isotope data constrain several other hydroclimate variables including temperature, precipitation rate, and evaporation rate, which are all used to assess climate model simulations of the same hydrological variables. In Chapter 1, I compile new and existing radiocarbon ages from post-LGM lake basins, and provide an analysis of changing effective moisture through time and space. In Chapter 2, I provide a detailed analysis of our data from one specific basin, Lake Surprise, and provide evidence of evaporation depression as a key driver of lake growth. Finally, in Chapter 3, I use clumped and stable isotope analysis of samples collected across the Great Basin (by UCLA students and others) to provide evidence for spatial and temporal variation in hydroclimate. Concomitant analysis of proxy data and climate model simulations provides a robust means to understand past climate change, and by extension, predict how current hydroclimates may respond to expected future climate forcings.

Download or read book An Isotopic and Geochemical Study of Lake Maharlou written by Brandy E. Coats (Graduate student) and published by . This book was released on 2021 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A 4-m long core from a wetland connected to Lake Maharlou, Fars Province, southwest Iran, was analyzed for major elemental concentrations and stable isotope analysis. [delta]18O and [delta]13C values were measured at 1-cm resolution as a proxy for effective moisture. Elemental intensities were measured by X-Ray Fluorescence (XRF) 0.3-mm resolution as a proxy for fluvial input and evaporative conditions. Both records were combined to reconstruct paleoclimatic change for the past ~8 ka. Dramatic shifts between dry and wet conditions were synchronous in both records with approximate boundaries in the Early Holocene, Mid-Holocene, and Late Holocene. From around 2,000 cal year BP to present, both elemental and isotopic values become highly variable, suggesting ongoing human interference with the natural hydrology of the lake. Isotopic data used in conjunction with statistical analysis of the XRF elemental data provide a more comprehensive picture of changes in lake hydrology and can help to distinguish changes caused by humans. Stable isotopes showed greater sensitivity to short-term changes in moisture, while elemental intensities demonstrated larger, robust climate transitions. Records were overall consistent with data from cores collected in the central basin of Lake Maharlou, and regional paleoclimate records, including [delta]18O records, pollen, and elemental intensities.

Download or read book Stable Isotopic Variations of Meteoric Water in Southwestern California written by Daniel Patrick Rodoni and published by . This book was released on 1993 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stable Isotopic and Stratigraphic Proxy Records of Local Regional and Global Climate written by Carl Norman Drummond and published by . This book was released on 1994 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Paleoclimatic Study of the Midwestern United States from the Stable Isotope Records in Lake Sediments written by Norman Alan Lovan and published by . This book was released on 1998 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Climatic Change and Global Warming of Inland Waters written by Charles R. Goldman and published by John Wiley & Sons. This book was released on 2012-11-20 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: Effects of global warming on the physical, chemical, ecological structure and function and biodiversity of freshwater ecosystems are not well understood and there are many opinions on how to adapt aquatic environments to global warming in order to minimize the negative effects of climate change. Climatic Change and Global Warming of Inland Waters presents a synthesis of the latest research on a whole range of inland water habitats – lakes, running water, wetlands – and offers novel and timely suggestions for future research, monitoring and adaptation strategies. A global approach, offered in this book, encompasses systems from the arctic to the Antarctic, including warm-water systems in the tropics and subtropics and presents a unique and useful source for all those looking for contemporary case studies and presentation of the latest research findings and discussion of mitigation and adaptation throughout the world. Edited by three of the leading limnologists in the field this book represents the latest developments with a focus not only on the impact of climate change on freshwater ecosystems but also offers a framework and suggestions for future management strategies and how these can be implemented in the future. Limnologists, Climate change biologists, fresh water ecologists, palaeoclimatologists and students taking relevant courses within the earth and environmental sciences will find this book invaluable. The book will also be of interest to planners, catchment managers and engineers looking for solutions to broader environmental problems but who need to consider freshwater ecology.

Download or read book Water Balance and Stable Isotope delta D and delta 18O Budget Within Lake Fryxell McMurdo Dry Valleys Antarctica written by Deborah L. Leslie and published by . This book was released on 2008 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stable Isotope Geochemistry written by Jochen Hoefs and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stable Isotope Geochemistry is an introduction to the use of stable isotopes in the fields of geoscience. It is subdivided into three parts: - theoretical and experimental principles; - fractionation mechanisms of light elements; - the natural variations of geologically important reservoirs. In this updated 4th edition many of the chapters have been expanded, especially those on techniques and environmental aspects. The main focus is on recent results and new developments. For students and scientists alike the book will be a primary reference with regard to how and where stable isotopes can be used to solve geological problems.

Download or read book Early Pliocene Ross Sea Paleoclimate and a New Application of the Diatom Oxygen Isotope Proxy written by Hal W. Hackett and published by . This book was released on 2016 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen isotope measurements ([delta]18O) provide valuable insight into climate conditions. These data are advantageous as paleoclimate proxies, but records are sparse in high latitude waters, where calcareous microfossils are poorly preserved in marine sediments. Over glacial timescales, high latitude regions likely have the widest variability in terms of the [delta]18O values of marine waters; therefore, the paucity of data in these regions greatly hinders our ability to reconstruct global climatic and environmental change. This research is motivated to investigate Southern Ocean diatoms as a way to begin filling the gap in our knowledge. Diatoms are a cosmopolitan group of siliceous phytoplankton with characteristic ecological affinities. Diatom silica is increasingly being analyzed as a [delta]18O archive, and has the potential to provide comparable data to [delta]18O variations recorded by benthic foraminifera, but to date, studies have focused on Holocene sediments. This thesis presents oxygen isotope values from Early Pliocene Ross Sea diatoms, assessment of purification procedures, and implications for paleoclimate and the history of the West Antarctic Ice Sheet. ANDRILL AND-1B is a 13 Ma record from the Antarctic Geologic Drilling Project in the Ross Sea, which provides Lower to Mid Pliocene diatomite units. The context provided by age models and paleoenvironmental studies, along with more geologically recent Southern Ocean diatom [delta]18O measurements, make AND-1B an ideal dataset for further exploring the use of diatom [delta]18O values as a record of changes in salinity and temperature in high latitude seawater. Samples were purified; geochemically and mineralogically assessed using x-ray diffraction (e.g. identification of amorphous opal-A vs. mineral contamination) and x-ray fluorescence (e.g. elemental quantification of clay contamination); then analyzed for [delta]18O values using a step-wise fluorination (SWF) -- CO2 laser heating technique and a Thermo MAT 253 isotope ratio mass spectrometer. Correction methods based on different assumptions place constraints on true diatom [delta]18O values, with margins of error dependent on final sample purity. The results are intermediate between Holocene Antarctic diatom [delta]18O studies, indicating that diatom [delta]18O values can remain largely or entirely unaltered for at least 4.5 Ma. Interpreting these values through the current paleotemperature model, with the contingent paleoenvironmental constraints afforded by AND-1B, suggests water [delta]18O values offset about -10% relative to today's ocean. Stacked benthic foraminifera [delta]18O values for the Pliocene suggest an ocean average less than 1% different than the present; therefore, this points to a strong component of glacial water in a warmer, fresher Pliocene Ross Sea.

Download or read book Isotopes in the Water Cycle written by Pradeep K. Aggarwal and published by Springer. This book was released on 2005-09-22 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Environmental isotope and nuclear techniques provide unmatched insights into the processes governing the water cycle and its variability. This monograph presents state of the art applications and new developments of isotopes in hydrology, environmental disciplines and climate change studies. Coverage ranges from the assessment of groundwater resources in terms of recharge and flow regime to studies of the past and present global environmental and climate changes.

Download or read book Tracking Environmental Change Using Lake Sediments written by William M. Last and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theory Instrumentation NIR analysis of sediment samples Uses of NIRS in palaeolimnology Future perspectives Summary References Fly-ash particles. Neil Rose 319 12. Introduction A brief history Methods of extraction and enumeration Temporal distribution Spatial distribution Source apportionment The future Summary Acknowledgements References Part III: Stable Isotope Techniques 13. Application of stable isotope techniques to inorganic and biogenic carbonates. Emi Ito 351 Introduction Nomenclature and systematics of lake-water Mg/Ca and Sr/Ca ratios of lake-water of dissolved inorganic carbon (DIC) Carbonates in lake-sediments Mollusks Ostracodes Charaphytes Isotope analysis Preparation of carbonate samples for isotope analysis Conclusions Summary Acknowledgments References 14. Carbon and oxygen isotope analysis of lake sediment cellulose: methods and applications. Brent B. Wolfe, Thomas W. D. Edwards, Richard J. Elgood & Kristina R. M. Beuning 373 xi Introduction Stable isotope tracers in lake Historical development Methods Key criteria for paleohydrologic reconstruction Applications Future research directions Summary Acknowledgements References Nitrogen isotopes in palaeolimnology. Michael R. Talbot 15. 401 Introduction Nitrogen in lakes: forms and distribution Nitrogen isotopes Nitrogen isotope studies in palaeolimnology: sampling and measurement Some examples Closing remarks Summary Acknowledgments References Glossary, acronyms and abbreviations 441 Index 493 xiii PREFACE The explosive growth of paleolimnology over the past two decades has provided impetus for the publication of this series of monographs detailing the numerous advances and new techniques being applied to the interpretation of lake histories. This is the second volume in the series and deals mainly with physical and geochemical analytical techniques.

Download or read book Investigating Paleoclimate Questions Using an Isotope enabled Earth System Model written by Jiang Zhu and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paleoclimate reconstructions can help us learn the evolution of climate mean state and variability in the past, understand mechanisms for climate change, and test the climate models that are extensively used for future climate projections. However, reconstructions have one major disadvantage that usually they are measurements of proxy variables (e.g., oxygen isotopes in calcium shells of foraminifera) instead of climate state variables (e.g., ocean temperature), which are directly simulated in traditional coupled climate models. This require that the model-data comparisons are indirect in paleoclimate studies and making it extremely difficult to address model-data discrepancies, especially when both models and reconstructions are subject to substantial biases and uncertainties. To overcome this obstacle, my PhD work involves developing a fully coupled water isotope-enabled Community Earth System Model (iCESM) in collaboration with other scientists. The physical climate of the iCESM is one of the best state-of-the-art fully coupled earth system models. In addition to the regular hydrologic cycle, iCESM can explicitly simulate the transport and transformation of water isotopes (e.g., H218O) in its components--the atmosphere, land, ocean, sea ice and river runoff. The iCESM can well-reproduce the major features of water isotopes in observations, including the tropical amount effect and high latitude temperature effect, as well as the continental and altitude effects in precipitation-d18Op in present day observations. The simulated d18O in seawater (d18Ow) also closely resemble the pattern in observations. Moreover, a simulation of the LGM (21,000 ka before present) shows that the model is able to simulate the glacial-interglacial changes of d18Op in ice cores, d18Ow in porefluid reconstructions, and d18Oc in ocean sediments, suggesting the model is suited for paleoclimate studies. With the water-isotope capability of the iCESM, I have investigated the following scientific questions: (1) How and why the water isotope-temperature relationship in Greenland ice cores varies during abrupt climate changes; (2) Whether the El Niño-Southern Oscillation (ENSO) was stronger or weaker at the LGM than the present day. (1) Isotope-temperature relationship. For more than 50 years, water isotope values (e.g., d18O) in ice cores have provided a tremendous amount of information about the Earth climate history during the late Quaternary. Initially based on a "modern analogue method", d18O changes in ice cores were directly interpreted as variations in local temperature, which was challenged later by independent reconstructions. Although it is now becoming clear that the temporal d18O-temperature relationship could vary both spatially and temporally in ice-core records, how the temporal slope could vary during abrupt climate changes and what is causing these changes still remain unclear. In my PhD study, I have quantitatively studied the changes in d18O-temperature relationship over Greenland in response to varied climatic forcings using the iCESM. I found that the temporal slope in Greenland increases significantly with the amount of meltwater discharged into the northern North Atlantic Ocean, due to the reduced moisture from the nearby oceans and the tracer effect from depleted meltwater (e.g., about -30 0 . Otherwise, the d18O-temperature relationships (spatial and temporal) are relatively stable in response to greenhouse gas (GHG), ice sheets and mid-Holocene orbital forcing. It is also found that part of the d18O signal in ice cores during meltwater events can be simply attributed to the tracer effect--the propagation of depleted meltwater in the hydrological cycle--instead of any changes in the climate state. These important findings imply that abrupt temperature changes during meltwater events previously inferred from ice cores could have been significantly overestimated. (2) ENSO variability at the LGM. Despite its paramount importance in climate system, the response of ENSO to anthropogenic global warming is still inconclusive in recent climate models. Studying the ENSO strength in the past can serve as a testbed for these climate models used for future projections and provide us the opportunity to investigate possible relationships between ENSO variability and the mean climate states. But, the ENSO strength at the LGM is inconclusive both in current climate models and paleoclimate reconstructions, including those records using the individual foraminifera analysis (IFA) in the eastern equatorial Pacific (EEP). Here, for the first time, I have directly compared modeled water isotopes in the iCESM with the IFA records. Synthesizing evidence from both models and reconstructions, it is found that ENSO at the LGM is most likely weaker than that of the preindustrial, because of the weakened Bjerknes feedbacks. The iCESM suggests that total variance of the IFA records may only reflect changes in the annual cycle instead of ENSO variability as previously assumed. Furthermore, the interpretation of subsurface IFA records can be substantially complicated by the habitat depth of thermocline-dwelling foraminifera and their vertical migration with a temporally varying thermocline. The model suggests an inverse relationship between ENSO variability and zonal SST gradient, thermocline depth and surface winds in equatorial Pacific, consistent with previous theoretical or observation based studies. Results indicate that ENSO variability could be stronger in response to the future anthropogenic global warming

Download or read book Application of Elemental and Isotopic Proxies to Reconstruct Pacific Ocean Circulation and Productivity During Periods of Climate Change written by Andrea Marie Erhardt and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Work presented in this dissertation investigates the response of the Pacific Ocean to climate change in the geologic record while evaluating methods to be used for future investigations. A particular focus of this work has been the interplay of ocean productivity, air and water circulation, and the resulting impacts on ocean chemistry. Investigations into ocean productivity in this dissertation have focused on changes in the accumulation rates of marine barite, an established proxy for export production. Across one of the most dramatic climate change intervals in the geologic record, the Eocene-Oligocene Transition, we found that the shift from greenhouse conditions to icehouse conditions corresponds to a sharp decline in export production. This decline in export production was synchronous with changes in the carbonate oxygen and carbon isotope shifts. Additionally, a previous unobserved peak in export production was identified before the onset of glaciation. We postulate that this increase in export production may correlate to an increase in carbon sequestration and should be further explored as a contributing factor to the CO2 drawdown proposed at this time. To understand the impacts of climate change on a more regional scale, ocean sediments from the Oregon shelf were collected. To investigate changes in oxygenation and sediment sources over the previous 1000+ years, this study utilized multiple proxies, including trace metal abundances and carbon and nitrogen isotopes. The results of this study do not show evidence of persistent hypoxia in the geologic record, inconsistent with the modern observations being driven by climate cycles which occurred pre-anthropogenically. The reminder of this dissertation focuses on the expansion of lead (Pb) isotopes for paleoceanographic reconstructions. Measurement of Pb isotopes in detrital fractions from across the Pacific Ocean, presented in Chapter 3, show the differentiation of various dust sources across the Pacific, along with the ability of this fraction to illustrate the location of the intertropical convergence zone. This study provides a more extensive description of Pb isotopes in potential source regions, creating a framework for the interpretation of future down core investigations and highlights some considerations regarding sample processing and analyses. To better understand sources of Pb to seawater, ferromanganese grain coatings were measured across the Pacific Ocean with a particular focus on the eastern equatorial Pacific (EEP). This study shows that dust deposition, particularly Chinese loess in the North Pacific and New Zealand loess in the south Pacific, is the dominant source of Pb to the open ocean. However, additional sources are needed to account for the measured Pb isotopic values, potentially including North Pacific Intermediate water in the North Pacific (Pb in which is sources from local pacific rim volcanism) and a yet unidentified source in the South Pacific (possibly South America or Australia dust). In addition, this investigation illustrates the possible regional impact of hydrothermal fluids in the EEP, with ferromanganese accumulations up to ~3000 km from the probable hydrothermal fluid source showing a measurable influence in the Pb isotopic ratios.

Download or read book Stable Isotopic Composition and Phosphorus Concentration in Sediment from Two Southern California Lakes written by Simone Claire Boudreau and published by . This book was released on 2015 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excessive nutrient loading to lakes reduces water clarity, degrades biological habitat, limits light penetration, and often results in anoxia. Increased watershed urbanization is a major contributing factor of externally loaded nutrients. But even in lakes that have successfully reduced external nutrient loading rates, high nutrient concentrations may persist due to internal nutrient recycling within lake sediments. Internal phosphorus (P) cycling dynamics are a balance between sedimentation, which depends on the mineralization rate of settling organic matter; diagenetic processes within the sediment after deposition; and remobilization of P after deposition, which depends on mobile P content and elemental composition of the sediment. The interplay between these processes determines whether phosphorus is recycled or sequestered in the sediment, as well as how long it remains bioavailable. Measurement of the stable isotopes of carbon and nitrogen in sediment have enabled assessment of the sources and degree of cycling of organic matter, which is important in controlling P burial and release. In this study, stable isotopic composition, elemental composition, and phosphorus forms in the sediment from two southern California lakes that are impaired due to nutrients are assessed to determine how dynamic hydrologic conditions and management actions have influenced water and sediment quality in order to gain insight into how sediment properties and biogeochemical processes respond to varying conditions in each lake. The results of the study provide a comprehensive understanding of the sedimentological processes occurring in the lakes, which is imperative to accurately predict eutrophication trajectories and the impact that future events will have on water quality in order to develop the most effective nutrient mitigation strategies.