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 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Dynamics of Tropical African Climate and Marine Sediment During Major Climate Transition written by Olubunmi Eniola and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the late Miocene/early Pliocene climate transition (7-5 Ma) as recorded in marine sediments from Ocean Drilling Programme (ODP) Site 959 in the equatorial Atlantic off tropical West Africa, and a reconstruction of changing Holocene environments of the Eastern Tropical Atlantic (CHEETA) based on surface and core sediments from a transect along the Portuguese and NW African margin. The late Miocene to early Pliocene climate transition had irreversible consequences for atmospheric and ocean circulation leading to global cooling, northern hemisphere glaciations and modern climate conditions. In this study, continental climate, vegetation change and surface ocean dynamics at millennial time scale resolution is investigated from U\7' alkenone derived SST, leaf wax lipids and organic carbon records (TaG). Despite low TOC "1 %) which was highly variable at cm-scale (-2.5-5 kyr) resolution, ubiquitous evidence from alkenones (C37:2 and C37:3) and leaf wax lipids indicate that the primary climate signal was preserved. The UK3y' based SST estimates (24.8-29°G) showed pronounced warm and cool cycles in the magnitude of 4°C. Elevated leaf wax lipids n-alkanes (Cn C29, and C31) correspond with cool SSTs and indicate a coupled relationship between upwelling and atmospheric ocean circulation patterns which intensified around 5.6 Ma arguing for wind driven deposition from terrestrial sources related to the position and strength of the ITCZ. The high amplitude cyclic patterns in the ODP Site 959 records were investigated by time frequency analyses. The common 41 kyr in all records supports a response to high latitude climate forcing. The 75 kyr variations and lead/lag observed in the leaf waxes and SST records during the late Miocene to early Pliocene are probably related to continental ice volume variations. The study on surface sediments from the Portuguese and NW African margins, confirm the presence of two soil-specific biomarkers, branched GDGTs (expressed as the BIT index) and bacteriohopanepolyols (BHPs), in this region of almost exclusive aeolian export. TOC exceeding 2% and 013Corg gradients from -22.5%0 off Portugal to - 19%0 off W Africa identify areas of upwelling off Cape Blanc and the transition from C3 to C4 vegetation habitats in Northern Africa, respectively. Despite low signals of the molecular records, slightly stronger response of soil-marker BHPs in the sediments is attributed to preferential erosion of the upper, (oxic) part of the soil column in central African source areas, the proposed source for soil BHPs. An alternative explanation is that in situ production of the branched GDGTs may be responsible for the low BIT index. As yet there is no evidence of the soil BHPs, adenosylhopane produced in situ in marine systems and aeolian transport of GDGTs is yet to been proven. More studies on dust samples from continental margins needs to be carried out to validate this transport mechanism of branched GDGTs and BHPs. A compilation of first bulk geochemical and molecular results from a selection of cores from the Portuguese and NW African margin within an integrated chronological framework document the variations in marine sedimentation and constrain regional variations in continental climate and terrigenous supply since the last glacial period. TOC accumulation records document millennial scale variability in response to the African Humid Period. Carbon isotope trends pronounced during the last glacial maximum support organic matter input from C4 type vegetation during colder glacial periods. Preliminary molecular isotopic records of n-alkanes identify gaps in this study that will need further investigation to assess and confirm vegetation sources and continental climatic conditions over Northwest Africa.
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 The Ocean s Role in Global Change written by Ocean Studies Board and published by . This book was released on 1994-01-15 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: What role does the ocean play in global climate change? Although not fully understood, there is general agreement that it is significant. Therefore, the scientific community has initiated large-scale research programs based on studies of the ocean and its relation to global climate and climate-related processes. This volume provides brief summaries and reports on the progress of the major oceanographic research programs. It looks at both programs that study processes that occur over periods ranging from days to hundreds of yearsâ€"the contemporary systemâ€"and those that seek to understand long-term variations ranging from thousands to millions of yearsâ€"the geological perspective.
Download or read book The Ocean and Cryosphere in a Changing Climate written by Intergovernmental Panel on Climate Change (IPCC) and published by Cambridge University Press. This book was released on 2022-04-30 with total page 755 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Download or read book Oceanic and Atmospheric Response to Climate Change Over Varying Geologic Timescales written by Stella Woodard and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Global climate is controlled by two factors, the amount of heat energy received from the sun (solar insolation) and the way that heat is distributed Earth's surface. Solar insolation varies on timescales of 10s to 100s of thousands of years due to changes in the path of Earth's orbit about the sun (Milankovitch cycles). Earth's internal boundary conditions, such as paleogeography, the presence/absence of polar icecaps, atmospheric/oceanic chemistry and sea level, provide distribution and feedback mechanisms for the incoming heat. Variations in these internal boundary conditions may happen abruptly or, as in the case of plate tectonics, take millions of years. We use geochemical and sedimentological techniques to investigate the response of ocean chemistry, regional aridity and atmospheric and oceanic circulation patterns to climate change during both greenhouse and icehouse climates. To explore the connection between orbitally-forced changes in solar insolation, continental aridity and wind, we generated a high-resolution dust record for ~58 Myr old deep-sea sediments from Shatsky Rise. Our data provide the first evidence of a correlation between dust flux to the deep sea and orbital cycles during the Early Paleogene, indicating dust supply (regional aridity) responded to orbital forcing during the last major interval of greenhouse climate. The change in dust flux was comparable to that during icehouse climates implying subtle variations in solar insolation have a similar impact on climate during intervals of over-all warmth as they do during glacial-interglacial states. The Carboniferous Period (359-299 Ma) marks a critical time in Earth's history when a series of tectonic and biological events caused a shift in the mean climate state from a global "greenhouse" to an "icehouse". Geochemical records extracted from sedimentary rocks deposited in shallow epicontinental seaways are increasingly being used to infer relationships between tectonism, carbon cycling and climate and therefore are assumed to reflect global ocean processes. We analyzed radiogenic isotopes in biogenic apatite along a North American transect to constrain the degree of geochemical coupling between the epicontinental seas and the open ocean. Our results argue strongly for decoupling of North American seaways from the open ocean by latest Mississippian time.
Download or read book The Glacial World According to Wally written by Wallace S. Broecker and published by . This book was released on 1995 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Northern North Atlantic written by Priska Schäfer and published by Springer Science & Business Media. This book was released on 2001-04-02 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: The northern North Atlantic is one of the regions most sensitive to past and present global changes. This book integrates the results of an interdisciplinary project studying the properties of the Greenland-Iceland-Norwegian Seas and the processes of pelagic and benthic particle formation, particle transport, and deposition in the deep-sea sediments. Ice-related and biogeochemical processes have been investigated to decipher the spatial and temporal variability of the production and fate of organic carbon in this region. Isotopic stratigraphy, microfossil assemblages and paleotemperatures are combined to reconstruct paleoceanographic conditions and to model past climatic changes in the Late Quaternary. The Greenland-Iceland-Norwegian Seas can now be considered one of the best studied subbasins of the world`s oceans.
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 Decade to Century Scale Climate Variability and Change written by National Research Council and published by National Academies Press. This book was released on 1998-12-24 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Society today may be more vulnerable to global-scale, long-term, climate change than ever before. Even without any human influence, past records show that climate can be expected to continue to undergo considerable change over decades to centuries. Measures for adaption and mitigation will call for policy decisions based on a sound scientific foundation. Better understanding and prediction of climate variations can be achieved most efficiently through a nationally recognized "dec-cen" science plan. This book articulates the scientific issues that must be addressed to advance us efficiently toward that understanding and outlines the data collection and modeling needed.
Download or read book Abrupt Climatic Change written by W.H. Berger and published by Springer Science & Business Media. This book was released on 1987-10-31 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Research Workshop, St. Hugues de Biviers, France, October 16-22, 1985
Download or read book Environment and Society in the Long Late Antiquity written by and published by BRILL. This book was released on 2019-01-04 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Environment and Society in the Long Late Antiquity brings together scientific, archaeological and historical evidence on the interplay of social change and environmental phenomena at the end of Antiquity and the dawn of the Middle Ages, ca. 300-800 AD.
Download or read book Abrupt Climate Change written by National Research Council and published by National Academies Press. This book was released on 2002-04-23 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The climate record for the past 100,000 years clearly indicates that the climate system has undergone periodic-and often extreme-shifts, sometimes in as little as a decade or less. The causes of abrupt climate changes have not been clearly established, but the triggering of events is likely to be the result of multiple natural processes. Abrupt climate changes of the magnitude seen in the past would have far-reaching implications for human society and ecosystems, including major impacts on energy consumption and water supply demands. Could such a change happen again? Are human activities exacerbating the likelihood of abrupt climate change? What are the potential societal consequences of such a change? Abrupt Climate Change: Inevitable Surprises looks at the current scientific evidence and theoretical understanding to describe what is currently known about abrupt climate change, including patterns and magnitudes, mechanisms, and probability of occurrence. It identifies critical knowledge gaps concerning the potential for future abrupt changes, including those aspects of change most important to society and economies, and outlines a research strategy to close those gaps. Based on the best and most current research available, this book surveys the history of climate change and makes a series of specific recommendations for the future.
Download or read book Surface Temperature Reconstructions for the Last 2 000 Years written by National Research Council and published by National Academies Press. This book was released on 2007-01-05 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: In response to a request from Congress, Surface Temperature Reconstructions for the Last 2,000 Years assesses the state of scientific efforts to reconstruct surface temperature records for Earth during approximately the last 2,000 years and the implications of these efforts for our understanding of global climate change. Because widespread, reliable temperature records are available only for the last 150 years, scientists estimate temperatures in the more distant past by analyzing "proxy evidence," which includes tree rings, corals, ocean and lake sediments, cave deposits, ice cores, boreholes, and glaciers. Starting in the late 1990s, scientists began using sophisticated methods to combine proxy evidence from many different locations in an effort to estimate surface temperature changes during the last few hundred to few thousand years. This book is an important resource in helping to understand the intricacies of global climate change.
Download or read book Global Environmental Change written by National Research Council and published by National Academies Press. This book was released on 1999-09-14 with total page 621 pages. Available in PDF, EPUB and Kindle. Book excerpt: How can we understand and rise to the environmental challenges of global change? One clear answer is to understand the science of global change, not solely in terms of the processes that control changes in climate and the composition of the atmosphere, but in how ecosystems and human society interact with these changes. In the last two decades of the twentieth century, a number of such research effortsâ€"supported by computer and satellite technologyâ€"have been launched. Yet many opportunities for integration remain unexploited, and many fundamental questions remain about the earth's capacity to support a growing human population. This volume encourages a renewed commitment to understanding global change and sets a direction for research in the decade ahead. Through case studies the book explores what can be learned from the lessons of the past 20 years and what are the outstanding scientific questions. Highlights include: Research imperatives and strategies for investigators in the areas of atmospheric chemistry, climate, ecosystem studies, and human dimensions of global change. The context of climate change, including lessons to be gleaned from paleoclimatology. Human responses toâ€"and forcing ofâ€"projected global change. This book offers a comprehensive overview of global change research to date and provides a framework for answering urgent questions.
Download or read book Abrupt Climate Change written by Harunur Rashid and published by American Geophysical Union. This book was released on 2011-01-10 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 193. Abrupt Climate Change: Mechanisms, Patterns, and Impacts brings together a diverse group of paleoproxy records such as ice cores, marine sediments, terrestrial (lakes and speleothems) archives, and coupled ocean-atmosphere climate models to document recent advances in understanding the mechanisms of abrupt climate changes. Since the discovery of the Dansgaard-Oeschger events in Greenland ice cores and the subsequent discovery of their contemporary events in the marine sediments of the North Atlantic, the search for these abrupt, millennial-scale events across the globe has intensified, and as a result, the number of paleoclimatic records chronicling such events has increased. The volume highlights include discussions of records of past climate variability, meridional overturning circulation, land-ocean-atmosphere interactions, feedbacks in the climate system, and global temperature anomalies. Abrupt Climate Change will be of interest to students, researchers, academics, and policy makers who are concerned about abrupt climate change and its potential impact on society.
