Download or read book Millennial scale Climate Variability During Glacial Interglacial and Transitional Climate States written by Kevin George Cannariato and published by . This book was released on 2002 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Millennial scale Variability to 735 Ka written by Sarah Marie White and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Determining the ultimate cause and effect of millennial-scale climate variability remains an outstanding problem in paleoclimatology, partly due to the lack of high-resolution records extending beyond the last glacial period. New cores from Santa Barbara Basin provide ~5000 year "windows" of climate with ~50-year resolution dating to ~293 ka (the MIS 8.6-8.5 transition), ~460 ka (MIS 12), and ~735 ka (MIS 18). These records span the Late Pleistocene, during which the 100-kyr cycle gained power in global climate records and the magnitude of glacial-interglacial cyclicity increased. Thus, these records provide a test of the dependence of millennial-scale behavior on variations in glacial-interglacial cyclicity. Planktonic foraminiferal [delta]18O indicates that millennial-scale variability is present in all three intervals, and is similar to that during MIS 3. Stadial G. bulloides [delta]18O values were 2.75-1.75 per mil (mean 2.25 per mil) and interstadial values were 1.75- 0.5 per mil (mean 1 per mil), with rapid interstadial initiations of 1-2 per mil, as in MIS 3. Interstadials were ~300-1300 years long and spaced ~750-1500 years apart, consistent with MIS 3 interstadial durations. Upwelling increased during interstadials, but did not vary synchronously with surface water temperatures, again similar to MIS 3. These high- resolution records provide evidence that millennial-scale variability was an inherent feature of glacial climates in the Northern Hemisphere throughout the past 735 ka.

Download or read book Mechanisms of Global Climate Change at Millennial Time Scales written by Lloyd D. Keigwin and published by American Geophysical Union. This book was released on 1999-01-26 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contributors describe the current understanding of abrupt climate variations that have occurred at millennial to submillennial time scales, events now recognized as characteristics of the global climate during the last glaciation. Subjects covered include analysis of modern climate and ocean dynamics, paleoclimate reconstructions derived from the marine, terrestrial and ice core records, and paleoclimate modeling studies. The breadth of global paleoclimate knowledge presented here provides information required to answer many questions and provides a road map to address remaining problems. Most material is from a June 1998 conference. Lacks a subject index. Annotation copyrighted by Book News, Inc., Portland, OR.

Download or read book Millennial scale Climate Variability in North America During the Past 14 000 Years written by Andre Ernest J. Viau and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Variations in the Earth's climate occur on many time and space scales. A recent focus of paleoclimate research is the so-called 1500-year North Atlantic quasi-periodic cycle, and has revolved around three main themes. First, what are the underlying causes and physical mechanisms governing these millennial-scale variations? Next, are they global or restricted to certain sensitive regions of the planet? Last, what is the magnitude of the temperature changes of these variations, and do they vary in time and space? This dissertation explores millennial-scale climate variability in North America during the past 14,000 years using a dense network of fossil pollen data, which is used as proxy for climate variations. Three independent approaches are used to quantify these changes. A mixture modelling analysis of radiocarbon dates on pollen transitions, a principal component analysis of pollen diagrams from all of North America, and a mean July temperature reconstruction based on the method of modern analogue (MAT) all reveal millennial-scale climate variability throughout North America during the past 14,000 years. The identified transitions generally correlate well with other proxy-climate records from the North Atlantic region. However, certain mismatches occurred particularly at 9, 6 and 4 ka BP. If we assume the dominant millennial-scale period is 1150-years, the records become more consistent. North American temperature variability was not unidirectional nor uniformly distributed in space, suggesting large-scale ocean-atmospheric reorganizations at the transitions. Correlation between the proxy-climate and cosmogenic nuclide records supports a variable solar output hypothesis as the fundamental cause for century to millennial-scale climate variability. The mean July temperature of North America varied on the order of 0.2 to 0.4°C during the Holocene and 0.4° and 0.6°C during the deglaciation. Temperature was more variable during the late glacial, possibly due to the impact on the climate of massive meltwater pulses into the North Atlantic, further amplified through ocean dynamic processes. Recent global warming estimated as an increase in temperature of 0.4--0.6°C, is therefore greater than the estimated natural variation of the past 10,000 years, providing further evidence that recent increases in atmospheric CO2 have played a major role in modern warming.

Download or read book The South Atlantic written by Gerold Wefer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 815 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book presents results of recent projects in oceanography and marine geosciences (e.g. WOCE, JGOFS, PAGES, ODP) regarding present and past circulation in the South Atlantic. The objective of the book is to integrate results from both oceanographic and geological studies. As the connecting link between the Antarctic and the North Atlantic, the South Atlantic plays a crucial role with regard to the heat budget of the North Atlantic and to the biogeochemical budget of the global ocean. New results from studies of meridional water mass and heat transports are presented. The central theme of geological investigations is the reconstruction of current and productivity systems in the South Atlantic during the late Quaternary.

Download or read book Diatoms of Lakes Prespa and Ohrid written by Zlatko Levkov and published by Gantner Publishing. This book was released on 2007 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lakes Preska and Ohrid belong to the old tectonic oligomicticdeep isolated lakes . A total of 450 taxa are presented, 78(17.3%) being described as new taxa (1 genus, 73 speciesand 4 varieties) 9 taxa have new combinations or status.Presence of relict species has been confirmed. Naviculaturris HUSTEDT is reported for the first time outside theKopecz Tertiary deposits in a recent lake.

Download or read book Geochemical and Geostatisical Analyses of Quaternary Climate Variability Over Millennial to Orbital Timescales written by Aaron M. Barth and published by . This book was released on 2016 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of dissertation research was to use geochemical, statistical and geological methods to constrain and understand climate variability over several different time scales. Specifically, I have addressed three questions regarding past climate change: (1) how does the record of Irish cirque glaciers constrain the dimensions of the Irish Ice Sheet during and since the Last Glacial Maximum (LGM); (2) what is the record of millennial-scale glacier variability in Ireland during the last glaciation; and (3) how did variability of various components of the climate system interact to contribute to the evolution of climate over the last 800,000 years. The first chapter involves constraining the vertical and spatial extent of the Irish Ice Sheet (IIS). Reconstructions of the LGM IIS are widely debated, in large part due to limited age constraints on former ice margins and due to uncertainties in the origin of the trimlines used to identify vertical ice limits. The greatest differences exist in southwestern Ireland where reconstructions either have complete coverage by a contiguous IIS that extends onto the continental shelf or a separate, southernsourced Kerry-Cork Ice Cap (KCIC) with more limited spatial and vertical extent. New 10Be surface exposure ages from two moraines in a cirque basin in this region provide a unique constraint on ice thickness for this region insofar as the presence of a cirque glacier at a given time clearly indicates that the site was not covered by the IIS. My new 10Be ages from these two moraines show that the central mountains in southwestern Ireland were not covered by the IIS or a KCIC since at least 24.5±1.4 ka, thus supporting the more-limited reconstructions of the IIS at the LGM, indicating a reduced contribution to sea-level change and a smaller loading of the solid Earth, which is consistent with models of glacial isostatic adjustment to the IIS. The second chapter presents research that has developed a record of millennial-scale variability in former Irish cirque glaciers between ~25 ka and 10 ka. Small alpine glaciers are sensitive to climate, and the paleo record of past smallglacier fluctuations offers an outstanding opportunity to use this glacier sensitivity for developing centennial- to millennial-scale records of climate variability. Because Ireland is immediately adjacent to, and downwind of, the North Atlantic, glacial records there are ideally located to record past climate changes associated with changes in North Atlantic Deep Water (NADW) formation and attendant feedbacks. I have developed a high-precision 10Be surface-exposure chronology of multiple moraines deposited by glaciers in eight cirque basins across Ireland to constrain this variability. The data show a remarkable record of persistent millennial-scale variability between 24.5±1.4 ka and 10.8±0.7 ka. Several of these events are associated with known climatic events during the last deglaciation such as onset of the Bølling-Allerød and end of the Younger Dryas. However, this persistent signal extends back to the Last Glacial Maximum (LGM), suggesting a previously unidentified mode of climate variability unrelated to large changes in the NADW. Multi-decadal to multi-centennial variability identified in Greenland ice cores present a mechanism for the variability recorded in the Irish glaciers. The third chapter of this research involves characterizing and explaining climate variability at orbital timescales across the mid-Brunhes Transition (MBT; ~430 ka). The MBT involved a change in the amplitude of variability associated with cooler interglacials prior to 430 ka and warmer interglacials after. The key questions I address include determining whether other components of the climate system changed at this time, and identifying the mechanism for the MBT. Statistical tests of multiple proxies (sea-surface temperature, ∂18O, ∂13C, CO2, CH4, and dust) indicate that the MBT was largely a reorganization of the global climate system perhaps driven by an increase in interglacial CO2 concentrations. Changes in marine ∂13C may provide insights into this change in the carbon cycle, perhaps associated with changes in global ocean circulation. In particular, there is a large positive ∂13C excursion during the interglacial immediately prior to the MBT, suggesting an enrichment of the Atlantic basin at this time relative to other interglacials of the past 800 kyr. Variability in the depth gradient of ∂13C from the North Atlantic show increased correlation with South Atlantic ∂13C records after the MBT, indicating more homogenous mixing of the northern- and southern-component water masses. This is accompanied by a greater difference in the ∂13C latitudinal gradient in the Atlantic basin prior to the MBT that is reduced afterwards.

Download or read book Patterns Mechanisms and Legacies of Abrupt Climate Change written by David Fastovich and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing global temperatures from anthropogenic greenhouse gas emissions are driving widespread climatological and ecological changes globally. Abrupt global changes that share rates of climate change similar to those experienced today (Overpeck et al. 2003; Williams and Burke 2019) are recorded throughout the geologic record and offer important insights that can help predict future anthropogenic change. The Deglacial period (19,000 to 11,000 years before present) after the Last Glacial Maximum has been a key interval for understanding ecological and climatological responses to increasing greenhouse gas concentrations and a warming climate (COHMAP Project Members 1988; Nolan et al. 2018; Mottl et al. 2021). Imposed on this gradual warming are abrupt climate oscillations that onset within decades to centuries, last for millennia, and are commonly attributed to changes in the Atlantic meridional overturning circulation forced by the input of freshwater into the North Atlantic Ocean. The most recent of these millennial-scale climate events is the Younger Dryas (ca. 12,900 to 11,700 years before present) and caused spatially complex climate changes globally. In this dissertation, we first aim to determine the spatial patterns of climate change and the atmospheric mechanisms responsible for driving abrupt climate change regionally in eastern North America through the use of organic temperature biomarkers (brGDGTs) and climate models. Second, we seek to disentangle the contributions of glacial and millennial-scale climate variability upon modern patterns of species richness in eastern North America. Chapter 2 seeks to determine the spatial fingerprint of Younger Dryas temperature changes in eastern North America. We develop a spatially dense multiproxy network of temperature reconstructions relying upon statistical transfer functions applied to fossil-pollen abundances and an independent proxy, based on organic biomarkers (brGDGTs). This analysis indicates that temperature changes during the Younger Dryas followed a dipole pattern in eastern North America. Temperatures lowered abruptly in maritime Canada and the northeastern United States nearly synchronously with temperature records from Greenland (Severinghaus et al. 1998). Cooling is also reconstructed in the Great Lakes region but delayed by ~400 years. Sites south of 35℗ʻN exhibited an antiphased response and lack YD cooling, with Florida sites indicating a thermal maximum. Warming in Florida during the Younger Dryas suggests that the 'bipolar-seesaw' conceptualization is an oversimplification of the spatial patterns of global climate changes. Focus must be placed on constraining regional climate changes to refine the mechanisms of abrupt climate change. Chapter 3 aims to better understand the atmospheric mechanisms for these antiphased temperature changes in eastern North America. We accomplish this by combining our multiproxy temperature network with a synthesis of hydroclimate reconstructions to compare against four climate models with meltwater hosing experiments that resemble the onset of the Younger Dryas. Precipitation changes followed a tripole pattern with wetting in the northeastern United States and Florida and drying from the Great Lakes region to the Carolinas, in contrast to the temperature dipole resolved in Chapter 2. Analysis of the climate models highlights the dual role of ice sheets and meltwater-induced weakening of the Atlantic meridional overturning circulation as the key drivers of the reconstructed warming and wetting in the southeastern United States. Reduced northward oceanic heat transport in the Atlantic Ocean increased the latitudinal temperature gradient and strengthened the jet stream, leading to upper-level divergence over eastern North America and the transport of warmer and moister air into the southeastern United States. For Chapter 4, we use our multiproxy temperature and precipitation reconstruction from prior chapters, alongside 11 climate simulations of millennial- scale climate events forced by meltwater pulses, to assess whether legacies of these climate changes can be detected in the contemporary diversity of amphibians, birds, mammals, reptiles, and trees in eastern North America. Generalized additive models that use both contemporary and paleoclimatic predictors suggest that past millennial scale climate oscillations have left an imprint on contemporary amphibian and arboreal biodiversity, though the exact role of past climate changes remains uncertain. Generalized additive models that use the multiproxy network of Younger Dryas climate reconstructions and a subset of the climate models analyzed suggest that greater millennial scale climate variability is predictive of greater contemporary biodiversity. However, generalized additive models that use four of the climate models suggest that millennial-scale climate stability is predictive of greater contemporary richness in eastern North America. Disagreement in the sign, magnitude, and spatial fingerprint of climate changes among the 11 climate simulations and the multiproxy climate reconstructions precludes further refining the role of millennial-scale climate oscillations at this time. This uncertainty highlights that caution should be used when attempting to model contemporary biodiversity based on individual paleoclimatic simulations. Higher resolution climate simulations forced with accurate boundary conditions are necessary to constrain the relationship between past millennial-scale climate changes and contemporary biodiversity.

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 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 Millennial Scale Climate Variability During the Last 6000 Years Tracking Down the Bond Cycles written by Jonathan Bütikofer and published by . This book was released on 2007 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Millennial Scale Climate Variability in the Sea ice ocean System written by Todd K. Dupont and published by . This book was released on 1996 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Decadal to millennial scale Climate Variability written by Michael Sarnthein and published by . This book was released on 2002 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Report written by United States. Interdepartmental Committee for Atmospheric Sciences. Ad Hoc Panel on the Present Interglacial and published by . This book was released on 1974 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Second Assessment of Climate Change for the Baltic Sea Basin written by The BACC II Author Team and published by Springer. This book was released on 2015-04-03 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: ​This book is an update of the first BACC assessment, published in 2008. It offers new and updated scientific findings in regional climate research for the Baltic Sea basin. These include climate changes since the last glaciation (approx. 12,000 years ago), changes in the recent past (the last 200 years), climate projections up until 2100 using state-of-the-art regional climate models and an assessment of climate-change impacts on terrestrial, freshwater and marine ecosystems. There are dedicated new chapters on sea-level rise, coastal erosion and impacts on urban areas. A new set of chapters deals with possible causes of regional climate change along with the global effects of increased greenhouse gas concentrations, namely atmospheric aerosols and land-cover change. The evidence collected and presented in this book shows that the regional climate has already started to change and this is expected to continue. Projections of potential future climates show that the region will probably become considerably warmer and wetter in some parts, but dryer in others. Terrestrial and aquatic ecosystems have already shown adjustments to increased temperatures and are expected to undergo further changes in the near future. The BACC II Author Team consists of 141 scientists from 12 countries, covering various disciplines related to climate research and related impacts. BACC II is a project of the Baltic Earth research network and contributes to the World Climate Research Programme.