Download or read book Reconstructing Past Changes in El Ni o Southern Oscillation Variability Using Geochemical Proxies from Corals written by Allison E. Lawman and published by . This book was released on 2020 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: The El Niño-Southern Oscillation (ENSO) is the leading mode of interannual (>1-9 year) climate variability and has far-reaching impacts on global temperature and rainfall patterns. That said, the instrumental record of ENSO does not have the temporal coverage necessary to characterize the full range of natural variability. Uncertainties about how ENSO variability may change in the future with anthropogenic warming motivates the study of past climate conditions when the Earth experienced different climate conditions compared to the warm, rapidly changing climate of today. Climate scientists use two primary tools to study past climate. First, general circulation models use mathematical equations based on physical principles to simulate different aspects of the climate system, including the ocean, atmosphere, land, and ice sheets. Second, various geological archives like corals, cave stalagmites and lake and ocean sediment also provide clues about how the climate varied in the past. The paleoclimate proxy records generated from geological archives thus provide independent validation of paleoclimate model simulations. Geochemical proxy records from corals are particularly well-suited for investigating past (paleo) ENSO variability as corals can provide decades to hundreds of years of climate information from the tropics at sub-annual resolution. This dissertation seeks to quantify changes in paleo-ENSO variability using geochemical proxies from corals. I first generate replicated coral records from Vanuatu in the southwest Pacific to investigate the range of ENSO variability during the 20th century and ~900 years during a time interval called the Medieval Climate Anomaly. The paleo-temperature records are based on the ratio of strontium to calcium (Sr/Ca) of massive Porites corals from Vanuatu. Next, I develop various computational algorithms to investigate how different uncertainties inherent to the coral archive impact the ability of a coral to capture changes in ENSO variability. The algorithms incorporate the impact of variable growth rates, analytical and calibration errors, and age model assumptions, and are collectively referred to a coral proxy system model (PSM). The utility of the coral PSM is demonstrated using unforced climate model output for the last millennium. I then use the PSM and apply the analytical techniques developed in the first two projects to investigate simulated and coral proxy-inferred changes in paleo-ENSO variability during the Holocene (11.65 thousand years ago to the present). The resulting model-data comparison provides a new perspective on long-term changes in ENSO variability

Download or read book El Ni o Southern Oscillation Variability During the Little Ice Age and Medieval Climate Anomaly Reconstructed from Fossil Coral Geochemistry and Pseudoproxy Analysis written by Kelly Ann Hereid and published by . This book was released on 2012 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The El Niño-Southern Oscillation (ENSO) dominates global interannual climate variability. However, the imprint of anthropogenic climate change hinders understanding of natural ENSO variability. Model predictions of the response of future ENSO variability to anthropogenic forcing are highly uncertain. A better understanding of how ENSO operates during different mean climate states may improve predictions of its future behavior. This study develops a technique to quantify the response of tropical Pacific sea surface temperature and salinity to ENSO variations. This analysis defines expected regional relationships between ENSO forcing and the tropical Pacific climate response. For example, the western tropical Pacific records El Niño events with greater skill than La Niña events; whereas the oceans near the South Pacific Convergence Zone (SPCZ) preferentially record La Niña events. This baseline understanding of regional skill calibrates interpretations of both modern and pre-instrumental coral geochemical climate proxy records. A suite of monthly resolved [delta]18O variations in a fossil corals (Porites spp.) from the tropical western Pacific (Papua New Guinea) and the SPCZ (Vanuatu) are used to develop case studies of ENSO variability under external forcing conditions that differ from the modern climate. A record from Misima, Papua New Guinea (1411-1644 CE) spans a period of reduced solar forcing that coincides with the initiation of the Little Ice Age. This record indicates that the surface ocean in this region experienced a small change in hydrologic balance with no change in temperature, extended periods of quiescence in El Niño activity, reduced mean El Niño event amplitudes, and fewer large amplitude El Niño events relative to signals captured in regional modern records. Several multidecadal (~30-50 year) coral records from Tasmaloum, Vanuatu during the Medieval Climate Anomaly (~900-1300 CE), a period of increased solar forcing, depict ENSO variability that is generally lower than modern times. However, these records often cannot be distinguished from 20th century ENSO variability due to ENSO variability uncertainty associated with record lengths. Neither record can be tied to concurrent changes in solar or volcanic forcing, calling into question the paradigm of ENSO variability being predominantly mediated by external forcing changes on multidecadal time scales.

Download or read book El Ni o Southern Oscillation in a Changing Climate written by Michael J. McPhaden and published by John Wiley & Sons. This book was released on 2020-11-24 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive and up-to-date information on Earth’s most dominant year-to-year climate variation The El Niño Southern Oscillation (ENSO) in the Pacific Ocean has major worldwide social and economic consequences through its global scale effects on atmospheric and oceanic circulation, marine and terrestrial ecosystems, and other natural systems. Ongoing climate change is projected to significantly alter ENSO's dynamics and impacts. El Niño Southern Oscillation in a Changing Climate presents the latest theories, models, and observations, and explores the challenges of forecasting ENSO as the climate continues to change. Volume highlights include: Historical background on ENSO and its societal consequences Review of key El Niño (ENSO warm phase) and La Niña (ENSO cold phase) characteristics Mathematical description of the underlying physical processes that generate ENSO variations Conceptual framework for understanding ENSO changes on decadal and longer time scales, including the response to greenhouse gas forcing ENSO impacts on extreme ocean, weather, and climate events, including tropical cyclones, and how ENSO affects fisheries and the global carbon cycle Advances in modeling, paleo-reconstructions, and operational climate forecasting Future projections of ENSO and its impacts Factors influencing ENSO events, such as inter-basin climate interactions and volcanic eruptions The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about this book from this Q&A with the editors.

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 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 Biogeochemical Proxies in Scleractinian Corals Used to Reconstruct Ocean Circulation written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We utilize monthly 14C data derived from coral archives in conjunction with ocean circulation models to address two questions: (1) how does the shallow circulation of the tropical Pacific vary on seasonal to decadal time scales and (2) which dynamic processes determine the mean vertical structure of the equatorial Pacific thermocline. Our results directly impact the understanding of global climate events such as the El Nino-Southern Oscillation (ENSO). To study changes in ocean circulation and water mass distribution involved in the genesis and evolution of ENSO and decadal climate variability, it is necessary to have records of climate variables several decades in length. Continuous instrumental records are limited because technology for continuous monitoring of ocean currents has only recently been available, and ships of opportunity archives such as COADS contain large spatial and temporal biases. In addition, temperature and salinity in surface waters are not conservative and thus can not be independently relied upon to trace water masses, reducing the utility of historical observations. Radiocarbon (14C) in sea water is a quasi-conservative water mass tracer and is incorporated into coral skeletal material, thus coral 14C records can be used to reconstruct changes in shallow circulation that would be difficult to characterize using instrumental data. High resolution [Delta]14C timeseries such as these, provide a powerful constraint on the rate of surface ocean mixing and hold great promise to augment onetime surveys such as GEOSECS and WOCE. These data not only provide fundamental information about the shallow circulation of the Pacific, but can be used as a benchmark for the next generation of high resolution ocean models used in prognosticating climate change.

Download or read book Encyclopedia of Modern Coral Reefs written by David Hopley and published by Springer Science & Business Media. This book was released on 2010-11-26 with total page 1226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coral reefs are the largest landforms built by plants and animals. Their study therefore incorporates a wide range of disciplines. This encyclopedia approaches coral reefs from an earth science perspective, concentrating especially on modern reefs. Currently coral reefs are under high stress, most prominently from climate change with changes to water temperature, sea level and ocean acidification particularly damaging. Modern reefs have evolved through the massive environmental changes of the Quaternary with long periods of exposure during glacially lowered sea level periods and short periods of interglacial growth. The entries in this encyclopedia condense the large amount of work carried out since Charles Darwin first attempted to understand reef evolution. Leading authorities from many countries have contributed to the entries covering areas of geology, geography and ecology, providing comprehensive access to the most up-to-date research on the structure, form and processes operating on Quaternary coral reefs.

Download or read book El Ni o written by Henry F. Diaz and published by Cambridge University Press. This book was released on 1992 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 1993 book enhances our understanding of the mechanisms involved in the low frequency behavior of the El Nino/Southern Oscillation (ENSO) phenomenon.

Download or read book Encyclopedia of Ocean Sciences written by and published by Academic Press. This book was released on 2019-04-12 with total page 4318 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oceans cover 70% of the Earth’s surface, and are critical components of Earth’s climate system. This new edition of Encyclopedia of Ocean Sciences, Six Volume Set summarizes the breadth of knowledge about them, providing revised, up to date entries as well coverage of new topics in the field. New and expanded sections include microbial ecology, high latitude systems and the cryosphere, climate and climate change, hydrothermal and cold seep systems. The structure of the work provides a modern presentation of the field, reflecting the input and different perspective of chemical, physical and biological oceanography, the specialized area of expertise of each of the three Editors-in-Chief. In this framework maximum attention has been devoted to making this an organic and unified reference. Represents a one-stop. organic information resource on the breadth of ocean science research Reflects the input and different perspective of chemical, physical and biological oceanography, the specialized area of expertise of each of the three Editors-in-Chief New and expanded sections include microbial ecology, high latitude systems and climate change Provides scientifically reliable information at a foundational level, making this work a resource for students as well as active researches

Download or read book Coral Reefs and Climate Change written by Jonathan Turnbull Phinney and published by American Geophysical Union. This book was released on 2006-01-10 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Coastal and Estuarine Studies, Volume 61. The effects of increased atmospheric carbon dioxide and related climate change on shallow coral reefs are gaining considerable attention for scientific and economic reasons worldwide. Although increased scientific research has improved our understanding of the response of coral reefs to climate change, we still lack key information that can help guide reef management. Research and monitoring of coral reef ecosystems over the past few decades have documented two major threats related to increasing concentrations of atmospheric CO2: (1) increased sea surface temperatures and (2) increased seawater acidity (lower pH). Higher atmospheric CO2 levels have resulted in rising sea surface temperatures and proven to be an acute threat to corals and other reef-dwelling organisms. Short periods (days) of elevated sea surface temperatures by as little as 1–2°C above the normal maximum temperature has led to more frequent and more widespread episodes of coral bleaching-the expulsion of symbiotic algae. A more chronic consequence of increasing atmospheric CO2 is the lowering of pH of surface waters, which affects the rate at which corals and other reef organisms secrete and build their calcium carbonate skeletons. Average pH of the surface ocean has already decreased by an estimated 0.1 unit since preindustrial times, and will continue to decline in concert with rising atmospheric CO2. These climate-related Stressors combined with other direct anthropogenic assaults, such as overfishing and pollution, weaken reef organisms and increase their susceptibility to disease.

Download or read book Proxy Records of the Indonesian Low and the El Ni o Southern Oscillation ENSO from Stable Isotope Measurements of Indonesian Reef Corals written by Michael Donald Moore and published by . This book was released on 1995 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Corals and Coral Reefs of the Gal pagos Islands written by Peter W. Glynn and published by Univ of California Press. This book was released on 1983-01-01 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: 00 This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells This scientifically thorough,lucidly written work explores the nature, development, and extent of the archipelago's reef-building corals. Also included is an annotated list of the Scleractianian Corals by John W. Wells

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 Holocene Coral Reef Development in the Tropical Eastern Pacific written by Lauren Trent Toth and published by . This book was released on 2013 with total page 804 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent decades, a variety of local- to global-scale disturbances have caused the global degradation of coral-reef ecosystems. In most regions, large-scale coral mortality is a recent phenomenon. In contrast, my records from the tropical eastern Pacific (TEP) have revealed a period of limited coral-reef development, beginning about 4000 cal BP (calibrated calendar years before 1950), which lasted for the next 2500 years. This protracted hiatus in reef growth provides the opportunity to test explicit predictions about the causes of reef collapse, the controls on reef resilience, and the likely trajectories of reef development in the future. Reefs of the TEP are subject to a variety of modern environmental stressors, the most important of which are seasonal upwelling and interannual impacts of the El Niño-Southern Oscillation (ENSO); however, the relative roles of these stressors in shaping past reef development are unknown. Although it is generally accepted that reef growth in the TEP is slow compared with other regions around the world, this assumption has never been tested, and the paleoecological record from reefs in this region is limited. Using data from cores of reef frameworks collected throughout Pacific Panamá, this study evaluated trends in reef development from ~7000 cal BP to the present to assess the impacts of environmental variability on reef growth during the Holocene. To further characterize the observed hiatus in reef growth and investigate the impact of seasonal upwelling on past reef development, I compared trends in vertical reef accretion among three sites situated along a contemporary gradient of seasonal upwellling: Contadora Island, which received the most intense seasonal upwelling; Iguana Island, where upwelling was moderate; and Canales de Tierra Island, where there was no upwelling. By reconstructing the age of the local radiocarbon reservoir for each of these sites, I confirmed that this general upwelling regime existed from at least ~7000 cal BP to the present. I also used geochemical analyses of fossil coral skeletons and reef sediments from Contadora to reconstruct the regional climatic and oceanographic conditions over the last 7000 years and evaluated their impacts on coral condition. Coral reefs at all three sites stopped growing from ~4100-1600 cal BP, coincident with the shutdown of reef development at several other locations elsewhere in the Pacific. There was a dramatic and significant reduction in reef accretion during the depositional hiatus. Contrary to earlier surmises that reef growth was slow in the TEP, however, millennial rates of reef accretion in Pacific Panama ́before and after the hiatus were similar to those documented in the Caribbean region. There was no significant difference in reef accretion among sites, which suggests that although upwelling has an impact on the short-term growth of corals, upwelling does not impact long-term reef accretion. Upwelling did, however, have a significant impact on the duration of reef collapse. The hiatus in reef accretion began earlier, ended later and, therefore, lasted significantly longer at Contadora, where reefs are subject to the strongest seasonal upwelling. Although upwelling was most likely not the ultimate cause of the hiatus, persistent upwelling may reduce the capacity of a reef to recover from major disturbances. Correlative evidence from regional paleoclimate proxies suggested that the ultimate cause of the hiatus was most likely enhanced climatic oscillations, particularly variability associated with ENSO. In the TEP, El Niño and La Niña events result in dramatic changes in sea temperatures, nutrient inputs, turbidity, and sea level, all of which can be problematic for reef development. ENSO activity increased 4500-4000 cal BP, coincident with the onset of the hiatus. Additionally, ENSO variability was likely enhanced from 4000-2000 cal BP due to it becoming in-phase, or "coupled", with the Intertropical Convergence Zone (ITCZ). Overall, hiatus was a time of stronger and more frequent El Niño and La Niña events and this period of enhanced climatic variability likely overwhelmed the capacity of reefs to recover. Reef growth resumed when there was a change in the mode of ENSO, with more El Niño events, but fewer La Niña events after ~2000 cal BP. Climatic reconstructions from this study suggested that oceanic productivity at Contadora was higher in the mid-Holocene, 6000-4000 cal BP, likely as a result of increased upwelling, compared with the period 4000-2000 cal BP. These results supports the conclusion of other researchers that the early to middle Holocene, may have been more "La Niña-like", compared with the late Holocene, when mean climate had shifted to a more "El Niño-like" state. Furthermore, my environmental reconstructions before and after the hiatus in reef accretion reveal that climatic and oceanographic variability in the TEP were greater over centennial scales than previously surmised. From 5000-4500 cal BP, conditions were warmer and drier, and there was less upwelling, than at other times in the Holocene. Oceanic productivity and climatic variability both increased in the 100-200 yr preceding the shutdown of reef growth. These changes are consistent with the hypothesis of escalating ENSO variability overall, and in particular an increase in La Niña activity. I used coral [lower case delta]13C, a measure of productivity and coral health, and B/Ca, a measure of carbonate saturation state within the coral, to track changes in coral condition through time. Dramatic declines in both coral productivity and coral saturation state occurred just before the hiatus, indicating that sublethal declines in coral health could serve as early warning signs of ecosystem collapse. Although coral productivity was high just after the hiatus, it gradually declined over the period ~1500 cal BP to present. One explanation for the deteriorating health of corals during this interval was that the increase in the number of El Niño events through the late Holocene resulted in an increasing frequency and severity of coral bleaching events. The parallel between the reduction in coral productivity before the collapse of Panamanian reefs ~4100 cal BP and the slow decline of coral productivity through the late Holocene may indicate that reefs in the TEP are headed toward another significant interruption in reef development in the future. There is no clear consensus on how anthropogenic climate change will affect ENSO in the future; however, many of the same conditions that occurred during the hiatus are also expected under reasonable scenarios of future climate change. If the history of reef development in Pacific Panamá is any indication of what may happen in the future, climate change could indeed be pushing some Pacific reefs towards another major collapse. On the other hand, these reefs were able to recover after a 2500-yr hiatus in reef development. Thus, if the current trajectories of climate change can be reversed, there may yet be hope for the reefs of the future.

Download or read book Reconstruction of El Ni o Southern Oscillation Variability During the Holocene written by Timme Hendrik Donders and published by . This book was released on 2005 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Elements of Physical Oceanography written by John H. Steele and published by Academic Press. This book was released on 2009-12-16 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Elements of Physical Oceanography is a derivative of the Encyclopedia of Ocean Sciences, 2nd Edition and serves as an important reference on current physical oceanography knowledge and expertise in one convenient and accessible source. Its selection of articles—all written by experts in their field—focuses on ocean physics, air-sea transfers, waves, mixing, ice, and the processes of transfer of properties such as heat, salinity, momentum and dissolved gases, within and into the ocean. Elements of Physical Oceanography serves as an ideal reference for topical research. References related articles in physical oceanography to facilitate further research Richly illustrated with figures and tables that aid in understanding key concepts Includes an introductory overview and then explores each topic in detail, making it useful to experts and graduate-level researchers Topical arrangement makes it the perfect desk reference

Download or read book Geochemistry of Slow growing Corals written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Three WHOI fellowships supported my time in the Joint Program: Stanley W. Watson Foundation Fellowship, Paul M. Fye Teaching Fellowship and the Ocean and Climate Change Institute Fellowship (OCCI). Research funding from NSF (OCE-0402728) and WHOI to Konrad Hughen, Anne Cohen, and Michael McCartney supported this project. Research support was also awarded to the author from the OCCI and the education office Ditty Bag Fund.