Download or read book A High Resolution Record of Ocean Circulation During the Last Glacial Cycle from Neodymium Isotopes written by Alexander Piotrowski and published by . This book was released on 2005 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Last Glacial and Deglacial Ocean Circulation Using an Isotope enabled Ocean Model written by Sifan Gu and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean circulation during the last deglaciation can help to improve the understanding of the mechanisms underlying the ocean circulation. However, previous model-data comparisons suffer from indirect comparison because both reconstruction and climate model have uncertainties. To meet this challenge, my PhD work contributes to the isotope enabled Community Earth System Model (iCESM) project by developing a Neodymium (Nd) model and a Protactinium (231Pa) and Thorium (230Th) in the ocean model of CESM. With the isotope enabled ocean model (iPOP2), I investigated two scientific questions: (1) Deglacial AAIW in the Atlantic. AAIW plays important roles in the global climate system and the global ocean nutrient and carbon cycles. However, neodymium isotopic composition ([epsilon]Nd) reconstructions from different locations from the tropical Atlantic, have led to a debate on the relationship between northward penetration of AAIW into the tropical Atlantic and AMOC variability during the last deglaciation. Our results suggest a coherent response of AAIW and AMOC: when AMOC weakens, the northward penetration and transport of AAIW decreases while its depth and thickness increase. Moreover, the inconsistency among different tropical Atlantic [epsilon]Nd reconstructions is reconciled by considering their corresponding core locations and depths, which were influenced by different water masses in the past. (2) Using 18Oc to reconstruct AMOC. 18Oc gradient can be used to reconstruct density gradient, therefore the AMOC strength. 18Oc from the Florida Straits has been used to reconstruct AMOC evolution during the last deglaciation but the strength of Florida current can also be influenced by surface wind stress. Our model simulation suggests that in the western boundary, the Florida current strength is dominated by AMOC through the last deglaciation, instead of surface wind. However, in the South Atlantic, the basin-wide 18Oc contrast is decoupled from density contrast through the deglaciation in the upper ocean because of the deglacial density contrast change is dominated by salinity, which is caused by the deglacial change of AAIW. Our model suggests that 18Oc contrast across the western boundary is a good indicator for AMOC strength and 18Oc contrast across the whole basin only works for the North Atlantic.
Download or read book Holocene Ice Sheet Dynamics and Detrital Provenance Shifts Along the West Greenland Margin written by Lina Madaj and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the effect of Arctic Amplification the Arctic is currently warming at least twice as fast as the rest of the planet. Seasonal sea-ice extent has been alarmingly declining in the past decade. Glaciers and ice caps along the Greenland coast and in the Canadian Arctic have been losing mass on an accelerated rate during the past century. As the global climate system is a complex system connecting different regions via atmospheric transport, changes in Arctic climate patterns are affecting the climate and weather conditions in the lower latitudes. The Greenland Ice Sheet as well as glaciers and ice caps in the Canadian Arctic are the largest freshwater storages on the northern hemisphere and expected to be among the highest contributors to global sea level rise. Freshwater input through meltwater discharge is not only affecting sea level rise but further influencing deep water formation in the Labrador Sea and the subpolar North Atlantic and hence global ocean circulation and climate patterns. To be able to sufficiently predict future developments of the Greenland Ice Sheet with respect to mass loss and resulting impacts on the global climate, data from past climate and Greenland Ice Sheet extents are crucially important. The Holocene spanning the last period of the deglaciation after the Last Glacial Maximum culminating in the Holocene Thermal Maximum when atmospheric temperatures were warmer and glacier and ice-sheet extent smaller than today represents the closest analogue to current atmospheric warming and Greenland Ice Sheet mass loss. The wide west Greenland shelf of Baffin Bay and Labrador Sea hosts thick marine sediments archiving around ten thousand years of this past climate and ice-sheet history. Siliciclastic detrital material discharged into Baffin Bay and the Labrador Sea via meltwater and erosion can be separated from those sedimentary archives and traced back to its source region. Radiogenic isotopes (Sr, Nd, Pb) label the source regions of those sediments by fingerprinting the isotopic composition of the prevailing bedrock. Hence, they can be used as reliable provenance tracers. Retreating land-ice masses expose bedrock that before was not subject to erosion, influencing the isotopic signatures delivered into the surrounding ocean. Based on this theory, radiogenic isotopes can record changes in siliciclastic detrital sediment provenance and hence, indirectly trace ice-sheet dynamics. The overall aim of this thesis work is to reconstruct changes in detrital sediment provenance along the west Greenland shelf to gain new insights into Holocene Greenland Ice Sheet dynamics and ocean current-induced sediment transport. Sedimentary archives from three main research areas (eastern Labrador Sea, northeastern Baffin Bay, and Kane Basin, central Nares Strait) record obvious shifts in sediment provenance throughout the Holocene. Those shifts coincide with major regional climatic changes in the research area. Generally, all records reveal the local bedrock as the main source region of detrital material and distal-sourced material transported along the coast via the West Greenland Current as a secondary source. Although the proportion of distal sourced material appears to be small, changes in West Greenland Current strength have been recorded in the isotopic composition. In southwestern Greenland and the Labrador Sea radiogenic isotope records reveal a shift towards a higher proportion of the local Archean Block in the late Holocene caused by Neoglacial ice advance and a reduction in West Greenland Current speed delivering less material from southern most Greenland. Farther north in the Upernavik region, midwest Greenland coast, the isotopic composition marks a change with the transition from early to mid Holocene caused by increased West Greenland Current strength and the opening of Vaigat Strait which enabled erosion and transport of freshly exposed basalts from the Disko Bay area due to ice-sheet retreat. This basalt input is, however, not transported all the way to northernmost Melville Bay (northern Baffin Bay) where the detrital sediment composition is clearly dominated by contribution of the local Committee-Melville Belt without any significant provenance changes throughout the Holocene. Farthest north, the sedimentary record from Kane Basin records provenance shifts that confirm the opening of Nares Strait around 8.3 ka BP. This event is followed by an increased delivery of carbonate-rich detrital sediments from northern Ellesmere Island due to the newly established gateway of Arctic Ocean water transporting sediments from further north to the core location. Additionally determined mineralogical composition of the sedimentary records along the west Greenland coast supports the interpretation drawn from the radiogenic isotopic composition. Furthermore, it points out the additional value of radiogenic isotopes through variations only visible in isotopic composition but not in the mineralogical composition. Further comparison to other studies from the region based on different tracers confirms the reliability and sufficient application of radiogenic isotopes in provenance studies as well as the advantage of multi-proxy approaches in paleoclimatological studies. Overall, this study highlights the advantages and reliability of radiogenic isotopes in provenance studies with regards to reconstructions of ice-sheet dynamics. The combination of the three isotopic systems (Sr, Nd, Pb) enables source region determination with a higher probability compensating for overlapping signatures within individual isotopic systems. The transect of sedimentary records along the west Greenland coast identifies clearly distinguishable isotopic ranges for the different Greenland bedrock terrains, qualifying this approach for further high-resolution investigation in past Greenland Ice Sheet development.
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 Ocean Circulation and Climate written by and published by Academic Press. This book was released on 2013-10-22 with total page 893 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book represents all the knowledge we currently have on ocean circulation. It presents an up-to-date summary of the state of the science relating to the role of the oceans in the physical climate system. The book is structured to guide the reader through the wide range of world ocean circulation experiment (WOCE) science in a consistent way. Cross-references between contributors have been added, and the book has a comprehensive index and unified reference list. The book is simple to read, at the undergraduate level. It was written by the best scientists in the world who have collaborated to carry out years of experiments to better understand ocean circulation. - Presents in situ and remote observations with worldwide coverage - Provides theoretical understanding of processes within the ocean and at its boundaries to other Earth System components - Allows for simulating ocean and climate processes in the past, present and future using a hierarchy of physical-biogeochemical models
Download or read book Isotope Geochemistry written by Heinrich D Holland and published by Academic Press. This book was released on 2010-09-27 with total page 750 pages. Available in PDF, EPUB and Kindle. Book excerpt: After the discovery that elements were commonly composed of isotopes, there developed a range of studies of the variability of isotopic compositions in Earth materials, which was able to add to our understanding of Earth processes and history. This collection of chapters from the Treatise on Geochemistry describes the range of isotopic studies. The chapters are grouped into the following categories: light stable isotopes, radiogenic tracers, noble gases and radioactive tracers. The first three groups depend on mass spectrometric measurements. The section on radioactive tracers employs both radioactive counting techniques and the newly developed accelerator mass spectrometric techniques. Comprehensive, interdisciplinary and authoritative content selected by leading subject experts Robust illustrations, figures and tables Affordably priced sampling of content from the full Treatise on Geochemistry
Download or read book The Mediterranean Sea written by Gianluca Eusebi Borzelli and published by John Wiley & Sons. This book was released on 2014-03-10 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface, intermediate, and deep-water processes and their interaction in time and space drive the major ocean circulation of the Mediterranean Sea. All major forcing mechanisms, such as surface wind forcing, buoyancy fluxes, lateral mass exchange, and deep convection determining the global oceanic circulation are present in this body of water. Deep and intermediate water masses are formed in different areas of the ocean layers and they drive the Mediterranean thermohaline cell, which further shows important analogies with the global ocean conveyor belt. The Mediterranean Sea: Temporal Variability and Spatial Patterns is a comprehensive volume that investigates the temporal and spatial variability patterns in the ocean basin. Volume highlights include: Discussions of state-of-the-art physical and biogeochemical properties of the Mediterranean Sea Multiple physical ocean circulation processes, both in time and spatial scales (basin, sub-basin, and mesoscale) How different regional phenomena in the sea influence the biogeochemistry of the basin and the ocean dynamics Spatio-temporal variability of the surface circulation in the western Mediterranean Deep-water variability and inter-basin interactions in the eastern Mediterranean Sea Understanding the link between global ocean circulation patterns and the global climate The Mediterranean Sea will be a valuable resource for geoscientists, oceanographers, and meteorologists.
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 The Benthic Boundary Layer written by I. McCave and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Conference on the Benthic Boundary Layer was held under the auspices of the NATO Science Committee as part of its continuing effort to promote the useful progress of science through international cooperation. Science Committee Conferences are deliberately designed to focus attention on unsolved problems, with carefully selected participants invited to provide complementary expertise from a variety of relevant disciplines. Through inten sive discussion in small groups they seek to reach a consensus on assessments and recommendations for future research emphasis, which it is hoped will be of value to the larger scientific community. The subjects treated over the past few years have been as varied as science itself-e.g., computer software engineering, chemical catalysis, and materials and energy research. The present effort evolved from informal discussions between marine geolo gists, chemists, and biologists which underlined the desirability of improved communication among those concerned with the benthic layer. In both scien tific and technological terms this is an exciting frontier, rich in promise but poorly understood at present. It is particularly striking to realize that there are at least as many definitions of the benthic layer as there are disciplines involved, and it seemed clear that there was much to be gained by a detailed exchange of views on research capabilities, trends, and priorities. The results of the meeting appear to have confirmed the hopes of the sponsors.
Download or read book Paleoclimates written by Thomas M. Cronin and published by Columbia University Press. This book was released on 2010 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: "When combined with computer model simulations, paleoclimatic reconstructions are used to test hypotheses about the causes of climatic change, such as greenhouse gases, solar variability, earth's orbital variations, and hydrological, oceanic, and tectonic processes, This book is a comprehensive, state-of-the art synthesis of paleoclimate research covering all geological timescales, emphasizing topics that shed light on modern trends in the earth's climate." --Book Jacket.
Download or read book Changes in the mode of Southern Ocean circulation over the last glacial cycle revealed by foraminiferal stable isotopic variability written by U.S. NINNEMANN and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Methods and advances in marine geology and hydrodynamics environment written by Nan Wu and published by Frontiers Media SA. This book was released on 2024-01-29 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oceanographic Literature Review written by and published by . This book was released on 2000 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multi Scale Ocean Dynamical Processes and Their Climatic Ecological and Sedimentological Effects in the Eastern Indian Ocean written by Zexun Wei and published by Frontiers Media SA. This book was released on 2024-03-06 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Oceans and Marine Geochemistry written by H. Elderfield and published by Elsevier. This book was released on 2006-06-20 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Treatise on Geochemistry is the first work providing a comprehensive, integrated summary of the present state of geochemistry. It deals with all the major subjects in the field, ranging from the chemistry of the solar system to environmental geochemistry. The Treatise on Geochemistry has drawn on the expertise of outstanding scientists throughout the world, creating the reference work in geochemistry for the next decade. Each volume consists of fifteen to twenty-five chapters written by recognized authorities in their fields, and chosen by the Volume Editors in consultation with the Executive Editors. Particular emphasis has been placed on integrating the subject matter of the individual chapters and volumes. Elsevier also offers the Treatise on Geochemistry in electronic format via the online platform ScienceDirect, the most comprehensive database of academic research on the Internet today, enhanced by a suite of sophisticated linking, searching and retrieval tools.
Download or read book The Oceans and Rapid Climate Change written by Dan Seidov and published by John Wiley & Sons. This book was released on 2001-01-09 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 126. Until a few decades ago, scientists generally believed that significant large-scale past global and regional climate changes occurred at a gradual pace within a time scale of many centuries or millennia. A secondary assumption followed: climate change was scarcely perceptible during a human lifetime. Recent paleoclimatic studies, however, have proven otherwise: that global climate can change extremely rapidly. In fact, there is good evidence that in the past at least regional mean annual temperatures changed by several degrees Celsius on a time scale of several centuries to several decades.
Download or read book Ocean Circulation and Climate written by Thomas F. Stocker 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: A broad perspective of the ocean as a key component of the Earth System and of its role in the past, present, and future climate change is provided. The ocean is a huge reservoir of heat, mass, carbon, and many other quantities, and their estimated exchange fluxes suggest characteristic timescales of adjustment ranging from decades to many thousands of years. Surface patterns and meridional fluxes of these quantities highlight the important role of the wind-driven circulation and the deep ocean flow systems through all ocean basins. Ocean-dominated phenomena of natural variability, in particular associated with the tropical oceans, are explained. The relevance of the ocean circulation for abrupt climate change, as recorded from a variety of paleoclimate records, is discussed. This includes the bipolar seesaw concept which explains many features of interhemispheric response during the sequence of rapid warmings in the past ice age. Finally, the ocean’s role during the anthropocene, the time epoch which is dominated by the human-caused increase in greenhouse gases to levels unprecedented in the past 800,000 years, is explored. Both the warming and the increase in atmospheric transport of water polewards create conditions for the ocean that may induce large and irreversible changes in the Atlantic meridional overturning circulation.
