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 Understanding Earth s Deep Past written by National Research Council and published by National Academies Press. This book was released on 2011-08-02 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is little dispute within the scientific community that humans are changing Earth's climate on a decadal to century time-scale. By the end of this century, without a reduction in emissions, atmospheric CO2 is projected to increase to levels that Earth has not experienced for more than 30 million years. As greenhouse gas emissions propel Earth toward a warmer climate state, an improved understanding of climate dynamics in warm environments is needed to inform public policy decisions. In Understanding Earth's Deep Past, the National Research Council reports that rocks and sediments that are millions of years old hold clues to how the Earth's future climate would respond in an environment with high levels of atmospheric greenhouse gases. Understanding Earth's Deep Past provides an assessment of both the demonstrated and underdeveloped potential of the deep-time geologic record to inform us about the dynamics of the global climate system. The report describes past climate changes, and discusses potential impacts of high levels of atmospheric greenhouse gases on regional climates, water resources, marine and terrestrial ecosystems, and the cycling of life-sustaining elements. While revealing gaps in scientific knowledge of past climate states, the report highlights a range of high priority research issues with potential for major advances in the scientific understanding of climate processes. This proposed integrated, deep-time climate research program would study how climate responded over Earth's different climate states, examine how climate responds to increased atmospheric carbon dioxide and other greenhouse gases, and clarify the processes that lead to anomalously warm polar and tropical regions and the impact on marine and terrestrial life. In addition to outlining a research agenda, Understanding Earth's Deep Past proposes an implementation strategy that will be an invaluable resource to decision-makers in the field, as well as the research community, advocacy organizations, government agencies, and college professors and students.
Download or read book Isotopic and Elemental Tracers of Cenozoic Climate Change written by Germán Mora and published by Geological Society of America. This book was released on 2005-01-01 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean Circulation and Climate written by Stefan Rahmstorf and published by Elsevier Inc. Chapters. This book was released on 2013-10-22 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oceans play a crucial role in the Earth’s climate system due largely to their ability to store and transport heat. The instrumental record, spanning an order of magnitude of 100 years, is short compared with some of the important timescales of climate variability. To understand the oceans’ role in these long-term changes, proxy data from sediments, ice cores, and corals must be used. Using these proxy data, we examine the evidence for past ocean circulation and sea-level changes before instrumental oceanographic measurements began. We discuss what paleoclimatic data can tell us about past ocean states and what can be learned from ocean and climate models. Particular foci of the chapter are the ocean circulation and sea-level changes during the Quaternary and the Cretaceous, two particularly interesting periods in Earth’s history. The Quaternary covers the past 2.5 million years and is characterized by periodic glaciations, while the Cretaceous, reaching back around 100 million years, had a warm greenhouse climate with a weak temperature gradient between the tropics and the poles.
Download or read book North Pacific Climate Ocean Circulation and Productivity Over Millennial and Orbital Timescales written by and published by . This book was released on 2015 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to processes that are poorly understood, the arctic/subarctic region is currently warming at approximately twice the rate of the rest of the globe, and these regional changes may in turn have important consequences on global climate. The Bering Sea is an ideal location to study the relationship between sea ice distribution, ocean circulation, and biological productivity, which are all thought to be components of important interactions that both respond to and influence climate changes on regional (North Pacific) to global scales. Geologic records are essential for understanding and predicting future oceanic and climatic changes, but most previous studies of Bering Sea and North Pacific climate and oceanic conditions were limited by short records that only spanned one glacial-interglacial climate cycle (~100 kyr). This dissertation presents new geochemical and sedimentological records of oceanic and climatic conditions over the past 1.2 Myr using sediment cores from Integrated Ocean Drilling Program Site U1342 (54.83°N, 176.92°E, 818 m water depth) in the Bering Sea, providing an unprecedented opportunity to examine trends over multiple glacial-interglacial cycles. Long benthic foraminiferal stable isotope records from Site U1342 provide the first evidence of an important recurring relationship in which extremely cold glacial conditions lead to enhanced Bering Sea ice extent and enhanced local formation of North Pacific Intermediate Water (NPIW), the water mass primarily associated with large-scale North Pacific circulation and heat transport. These results contradict model predictions for weaker NPIW formation during extreme glacial conditions and show that North Pacific and North Atlantic circulation acted in phase on glacial-interglacial timescales. Furthermore, new records of nitrate utilization based on nitrogen isotopes demonstrate that glacial climates were consistently associated with enhanced physical stratification in the Bering Sea, which resulted in increased utilization of nutrients by phytoplankton and a reduction in the carbon dioxide released from the ocean to the atmosphere. Finally, multiple new records that demonstrate high productivity during intervals of laminated sediments, which represent brief anoxic events, indicate that interglacial climates precondition the Bering Sea for rapid oceanic and biological change.
Download or read book Carbon Cycling in the Glacial Ocean Constraints on the Ocean s Role in Global Change written by Rainer Zahn and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 579 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive progress report on the multi-disciplinary field of ocean and climate change research is given. It compiles introductory background papers and leading scientific results on the ocean-atmosphere carbon cycle with emphasis on the ocean's carbon inventory and the various components involved. The relationship between plankton productivity, carbon fixation, oceanic PCO2 and climate change is investigated from the viewpoint of long-term climatic change during the late Quaternary cycles of ice ages and warm ages. The various approaches range from micropaleontology over organic and trace element geochemistry to molecular isotope geochemistry.
Download or read book Natural Climate Variability on Decade to Century Time Scales written by National Research Council and published by National Academies Press. This book was released on 1996-08-30 with total page 645 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume reflects the current state of scientific knowledge about natural climate variability on decade-to-century time scales. It covers a wide range of relevant subjects, including the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. They clearly demonstrate the range, persistence, and magnitude of climate variability as represented by many different indicators. Not only do natural climate variations have important socioeconomic effects, but they must be better understood before possible anthropogenic effects (from greenhouse gas emissions, for instance) can be evaluated. A topical essay introduces each of the disciplines represented, providing the nonscientist with a perspective on the field and linking the papers to the larger issues in climate research. In its conclusions section, the book evaluates progress in the different areas and makes recommendations for the direction and conduct of future climate research. This book, while consisting of technical papers, is also accessible to the interested layperson.
Download or read book Modern Planktonic Foraminifera written by Christoph Hemleben and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a single volume, the authors bring together a review of current biological understanding of planktonic foraminifera and apply it to developments in sedimentology. With the growing interest in the shells of this class of protozoa as indicators of the history of the earth, revealed through the sedimentary record, a comprehensive analysis of the biology of contemporary foraminifera has become necessary. Main topics covered include Taxonomy, Collecting and Culture Methods, Cellular Ultrastructure, Host and Symbiont Relationships, Trophic Activity and Nutrition, Reproduction, Shell Ontogeny and Architecture, Ecology and Sedimentation and Settlement of Shells.
Download or read book Early Middle Pleistocene Transitions written by Geological Society of London and published by Geological Society of London. This book was released on 2005 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Early-Middle Pleistocene transition (around 1.2 to 0.5 Ma) marks a profound shift in Earth's climate state. Low-amplitude 41 ka climate cycles, dominating the earlier part of the Pleistocene, gave way progressively to a 100 ka rhythm of increased amplitude that characterizes our present glacial-interglacial world. This volume assesses the biotic and physical response to this transition both on land and in the oceans: indeed it examines the very nature of Quaternary climate change. Milankovitch theory, palaeoceanography using isotopes and microfossils, marine organic geochemistry, tephrochronology, the record of loess and soil deposition, terrestrial vegetational change, and the migration and evolution of hominins as well as other large and small mammals, are all considered. These themes combine to explore the very origins of our present biota.
Download or read book Climate Change in the Pacific North America Region Over the Past Millennium written by Lydia Darcy Roach and published by . This book was released on 2010 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: Decadal climate variability in the Pacific North America (PNA) region largely determines the fresh-water supply of the western United States and fisheries production of the northeast Pacific Ocean through tightly coupled ocean-atmosphere interactions. Documenting the historical manifestations of these interactions, over at least the past millennium, is an essential step towards anticipating the ramifications of future climate change on these resources. This dissertation aims to extend efforts at PNA paleoclimate reconstruction through the development of interannually resolved geochemical proxy records from annually laminated marine and lacustrine sediments. Comparison with instrumental climate measurements provides constraint on the driving mechanisms for observed geochemical variability in each record. The radiocarbon content ([Delta]14C) of benthic foraminiferal tests in the Santa Barbara Basin (SBB) proves a sensitive tracer for decadal fluctuations in vertical density structure along the southern California margin that are forced by north Pacific ocean-atmosphere interactions and tropical-midlatitude teleconnections. Enumeration of cosmopolitan benthic foraminifera in the SBB over the past ~250 years suggests that, on decadal time scales, the overall size and distribution of the SBB benthic foraminiferal community is largely a function of benthic carbon oxidation rate --- a property previously linked to regional surface productivity. In the terrestrial realm, stable hydrogen isotope ratios ([delta]D) of plant lipid biomarkers preserved in the sediments of Swamp Lake, Yosemite National Park, were measured over the 20th century and late medieval period (1160-1432 A.D). Plant lipid [delta]D exhibits a complex relationship with environmental parameters but nevertheless reflects interannual to multidecadal changes in amount of wintertime precipitation in the Sierra Nevada Mountains over the 20th century. Consistent with this observation, multidecadal [delta]D variability during the late medieval generally follows that of concomitant tree ring-derived hydrologic reconstructions and captures droughts of greater severity than any witnessed in the Sierra Nevada over the past 100 years. Comparison of the two isotopic records in terms of medieval vs. modern drought severity, however, requires further constraint on the driving mechanisms for long-term shifts in plant lipid [delta]D. Overall, this dissertation documents the novel application of benthic foraminiferal [Delta]14C and plant lipid [delta]D as a means for reconstructing decadal scale PNA climate from high-resolution sedimentary archives.
Download or read book North Pacific Environment and Paleoclimate from the Late Pleistocene to Present written by Miriam Jones and published by Frontiers Media SA. This book was released on 2020-01-13 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast area of the North Pacific, spanning ~55˚ longitude, represents a challenge for documenting and understanding the geologic history of ocean, atmosphere, and terrestrial environmental change. Nevertheless, its importance for many issues, including our fundamental understanding of ocean and atmospheric circulation patterns and teleconnections with natural modes of climate variability through time, has led to a steady rise in the numbers of study sites and proxy types. By bringing together a wide range of proxies and timescales that examine the impacts of paleoclimate on ecosystems, water, carbon, and humans, and interactions between marine and terrestrial processes, this Research Topic contributes to an improved understanding of the region’s significance at global, hemispheric, and regional scales.
Download or read book Sea surface Temperature Estimation written by C. J. Van Vliet and published by . This book was released on 1967 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: An autocorrelation analysis of six temperature records from the North Pacific and North Atlantic up to 40 years in length showed the existence of an oscillatory function with period 1 year for all the stations studied, and of another oscillatory function with period 0.5 year for most of the stations. A regression model containing annual and semiannual oscillatory terms was found to provide a good statistical fit to the observed daily temperatures. No long-term trends were detected in the sequences of annual mean temperatures, but there were significant differences among these temperatures. (Author).
Download or read book Tracing Ocean Circulation and Weathering Using Radiogenic Isotopes written by Marcus Gutjahr and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2012-06 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation aims to develop, evaluate and use new radiogenic isotopic proxies for paleoceanographic and paleoclimatic reconstructions at sub-millennial resolution. The Fe-Mn oxyhydroxide fraction in marine pelagic sediments is an ideal archive for this purpose because seawater-derived trace metals such as neodymium (Nd), hafnium (Hf) and lead (Pb) can be chemically extracted from this fraction. This archive was already successfully used in earlier studies for the reconstruction of the seawater Nd isotope evolution in the South Atlantic, but no such record at sub-millennial resolution exists for the North Atlantic. For Hf and Pb isotopes, not a single record using the Fe-Mn oxyhydroxide fraction exists to date. Especially Hf and Pb isotopes in seawater, however, potentially yield valuable information about short-term climatic changes, intensity of glaciation and the prevailing weathering regime on the continents. Therefore, using seawater-derived Hf and Pb isotopes in conjunction with Nd isotopes from the same seawater-derived fraction allow determining the provenance of a water mass and the climatic conditions prevailing at the continental source area.
Download or read book Cretaceous Oceanic Red Beds written by Xiumian Hu and published by SEPM Soc for Sed Geology. This book was released on 2009 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Primary Productivity and Ocean Circulation Changes on Orbital and Millennial Timescales Off Northwest Africa During the Last Glacial Interglacial Cycle written by Michelle Zarrieß and published by . This book was released on 2010 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reconstruction of Quaternary Paleo circulation in the Western Arctic Ocean Based on a Neodymium Isotope Record from the Northwind Ridge written by Rachael E. Gray and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: An understanding of past ocean circulation in the Arctic is critical for interpretations of past global ocean and atmospheric circulation, as well as predictions of future conditions. The Arctic Ocean plays a major role in global climate, due to its contributions to both the North Atlantic Deep Water (and subsequently the Atlantic Meridional Overturning Circulation) and the planet's albedo (due to sea ice cover). A sediment core from the Northwind Ridge in the western Arctic Ocean, ~800 km north of Alaska, has been sampled for measurement of radiogenic isotope ratios of neodymium and strontium. Sediment grain coatings were leached from the bulk sediment and measured for 87/86Sr and [epsilon]Nd, a proxy for seawater source. Two leaching solutions, one using buffered acetic acid and the second using hydroxylamine hydrochloride, were applied to sediments. Strontium data suggests that acetic acid best captures the seawater signal, while hydroxylamine hydrochloride leaching likely caused clay contamination of the hydrogenous data. [epsilon]Nd ratios were compared with independent lithologic proxies measured on the core and with results of earlier radiogenic-isotope studies in the Arctic Ocean. Data obtained suggest that radiogenic waters dominated the western Arctic Ocean during the estimated Early Pleistocene, probably due to increased Pacific water inputs and/or enhanced brine exclusion from sea ice formation on the Siberian shelves. These conditions likely indicate relatively warm climatic environments with predominantly seasonal sea ice, and thus can be potentially used as a paleo-analog for the projected near-future state of the Arctic. Further upcore, in the estimated Middle to Late Pleistocene, [epsilon]Nd values decrease overall, with high-amplitude fluctuations corresponding to glacial-interglacial cyclicity. Strongly non-radiogenic values in glacial intervals suggest the predominance of inputs from the Canadian Shield eroded by the Laurentide ice sheet. More radiogenic but gradually decreasing interglacial values indicate a change from Pacific to Atlantic water influence during the Middle to Late Pleistocene. Further isotope work on other cores may clarify the mechanisms and extent of this shift in circulation patterns.
Download or read book Reconstructing Ocean History written by Fatima Abrantes and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is one outcome of the 6th International Conference on Paleoceano graphy (ICP VI). The conference was held August 23-28, 1998 in Lisbon, Portugal. The meeting followed the traditional format of a small number of invited oral presentations complemented by a large number ofcontributed posters. Over 550 participants attended, representing thirty countries and nearly 450 posters were presented. The invited speakers addressed the main themes of the 5oral sessions. The session topics were: Polar-Tropical and Interhemisphere Linkages; Does the Ocean Cause, or Respond to, Abrupt Climatic Changes?; Biotic Responses to Major Paleoceanographic Changes; Past Warm Climates; and Innovations In Monitoring Ocean History. This is the first time in ICP history that the Conference Proceedings are published. The aim of the organisers with the publication of this book is two-fold: to provide a useful review of the field and to document the ideas/controversies raised during the con ference that may stimulate future work. The book reflects the initial intentions of the conference, but it is not a conven tional conference proceedings, given that the papers have been reviewed by formal exter nal referees. Each of the conference topics is introduced by a review article designed to summarize the state of the art in each theme followed by articles prepared by the invited speakers. As with most conference proceedings, each theme is covered heterogenously. Some topics have all the expected contributions, others are less well covered.
