Download or read book Influence of Early Oligocene Climate Variations on Southern Ocean Surface Productivity and Deep Water Chemistry written by Karen Amelia Salamy and published by . This book was released on 1995 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Global Changes in Paleoproductivity Biological Export and Deep Water Oxygenation Across the Eocene Oligocene Transition written by Genevieve Elsworth and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The Eocene-Oligocene transition (EOT) (~33.7 Ma) delineates the most abrupt shift from "greenhouse" to "icehouse" climates during the Cenozoic. At this time, substantial global cooling and the emplacement of the Antarctic ice sheet accompanied perturbations to the carbon cycle. Profound climatic reorganization across the EOT is often attributed to a decline in atmospheric pCO2; however, the mechanism behind this decrease is poorly understood. Considering the importance of atmospheric pCO2 drawdown for the emplacement of the Antarctic ice sheet, a more complete understanding of the controlling processes are required. The present study presents new and existing data compiled from globally distributed Ocean Drilling Program (ODP) Sites 689 (Maud Rise, Atlantic Sector of Southern Ocean), 744 (Kerguelen Plateau, Indian Sector of Southern Ocean), 925 (Ceara Rise, Western Equatorial Atlantic Ocean), 1090 (Agulhas Ridge, Southeastern Atlantic Ocean), and 1218 (Eastern Equatorial Pacific Ocean). A multi-proxy approach is applied to provide indications of silica availability (biogenic opal MAR), calcium carbonate compensation depth (carbonate MAR), biological surface export (BaEX MAR), and deep water oxygenation (MnEF and UEF). Trends in biogenic opal and carbonate deposition across the EOT suggest the weathering of both silicates and carbonates to exert control on ocean biogeochemistry on geologic timescales. A pulse of biogenic opal deposition is consistent with accelerated silicate weathering both in Antarctica and globally, while enhanced weathering of exposed carbonate shelves accompanied a deepening of the calcium carbonate compensation depth (CCD) across the EOT. The enhanced weathering of silicates and carbonates has implications for the drawdown of atmospheric pCO2 across the transition and emphasize the important role played by coupled Earth system feedbacks on climatic and oceanic reorganizations from the late Eocene to the early Oligocene." --
Download or read book Middle Eocene to Early Oligocene Paleoceanography of the Southern Ocean written by Steven Michael Bohaty and published by . This book was released on 2006 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ocean Acidification written by Jean-Pierre Gattuso and published by OUP Oxford. This book was released on 2011-09-15 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ocean helps moderate climate change thanks to its considerable capacity to store CO2, through the combined actions of ocean physics, chemistry, and biology. This storage capacity limits the amount of human-released CO2 remaining in the atmosphere. As CO2 reacts with seawater, it generates dramatic changes in carbonate chemistry, including decreases in pH and carbonate ions and an increase in bicarbonate ions. The consequences of this overall process, known as "ocean acidification", are raising concerns for the biological, ecological, and biogeochemical health of the world's oceans, as well as for the potential societal implications. This research level text is the first to synthesize the very latest understanding of the consequences of ocean acidification, with the intention of informing both future research agendas and marine management policy. A prestigious list of authors has been assembled, among them the coordinators of major national and international projects on ocean acidification.
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 Eocene Oligocene transition in the Southern Ocean written by L. DIESTER-HAASS and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Use of Proxies in Paleoceanography written by Gerhard Fischer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paleoceanographic proxies provide infonnation for reconstructions of the past, including climate changes, global and regional oceanography, and the cycles of biochemical components in the ocean. These prox ies are measurable descriptors for desired but unobservable environmental variables such as tempera ture, salinity, primary productivity, nutrient content, or surface-water carbon dioxide concentrations. The proxies are employed in a manner analogous to oceanographic methods. The water masses are first characterized according to their specific physical and chemical properties, and then related to particular assemblages of certain organisms or to particular element or isotope distributions. We have a long-standing series of proven proxies available. Marine microfossil assemblages, for instance, are employed to reconstruct surface-water temperatures. The calcareous shells of planktonic and benthic microorgan isms contain a wealth of paleoceanographic information in their isotopic and elemental compositions. Stable oxygen isotope measurements are used to detennine ice volume, and MglCa ratios are related to water temperatures, to cite a few examples. Organic material may also provide valuable infonnation, e. g. , about past productivity conditions. Studying the stable carbon isotope composition of bulk organic matter or individual marine organic components may provide a measure of past surface-water CO 2 conditions within the bounds of certain assumptions. Within the scope of paleoceanographic investigations, the existing proxies are continuously evolving and improving, while new proxies are being studied and developed. The methodology is improved by analysis of samples from the water column and surface sediments, and through laboratory experiments.
Download or read book Evidence for an earliest Oligocene abrupt cooling in the surface waters of the Southern Ocean written by W. WEI and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Terrestrial Eocene Oligocene Transition in North America written by Donald R. Prothero and published by Cambridge University Press. This book was released on 1996-06-13 with total page 708 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides the latest information in dating and correlation of the strata of late middle Eocene through early Oligocene age in North America.
Download or read book Encyclopedia of Paleoclimatology and Ancient Environments written by Vivien Gornitz and published by Springer Science & Business Media. This book was released on 2008-10-31 with total page 1062 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of Springer’s Major Reference Works, this book gives the reader a truly global perspective. It is the first major reference work in its field. Paleoclimate topics covered in the encyclopedia give the reader the capability to place the observations of recent global warming in the context of longer-term natural climate fluctuations. Significant elements of the encyclopedia include recent developments in paleoclimate modeling, paleo-ocean circulation, as well as the influence of geological processes and biological feedbacks on global climate change. The encyclopedia gives the reader an entry point into the literature on these and many other groundbreaking topics.
Download or read book Middle Eocene through Early Oligocene climate history and paleoceanography in the Southern Ocean written by A. MACKENSEN and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical Controls on Southern Ocean Biogeochemistry written by Channing Joseph Prend and published by . This book was released on 2022 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Southern Ocean plays an outsized role in the global overturning circulation and climate system by transporting mass, heat, and tracers between basins, as well as between the surface and abyssal oceans. Consequently, the Southern Ocean accounts for a disproportionately large percentage of the total oceanic carbon uptake and helps set global nutrient inventories. Therefore, understanding the coupling between physical and biogeochemical processes in this region is crucial to reducing uncertainty in future climate projections. Historically, studying the Southern Ocean has been limited by the paucity of observational data from this remote environment. However, recent advances in autonomous observing technology have provided unprecedented spatial coverage of subsurface biogeochemical measurements. This thesis uses data from an array of more than 200 autonomous profiling floats--in conjunction with satellite data, numerical models, and theory--to investigate the fundamental question: How do physical processes in the Southern Ocean drive variability of phytoplankton biomass and carbon system parameters? Naturally, the answer to this question will depend on the spatial and temporal scales of interest. Our approach is to consider multiple scales, with the central motivation of better understanding the carbon cycle on climatic timescales. First, we investigate regional patterns of phytoplankton seasonality in the Southern Ocean (Chapter 2). Results show that enhanced mixing at topographic features contributes to spatial variability in bloom magnitude and timing. Looking to smaller scales, we examine the generation of phytoplankton patchiness by turbulent stirring (Chapter 3). We find that parameterizing eddy transport as an enhanced diffusion requires timescale separation between the physical and biological processes, which raises concerns for the representation of subgrid scale primary productivity in coarse resolution climate models. Next, we turn to air-sea carbon fluxes. We show that carbon outgassing occurs preferentially in the Indo-Pacific sector of the Southern Ocean due to regional differences in the mixed-layer entrainment of upwelled carbon-rich deep water (Chapter 4). Finally, we quantify the relative importance of different frequency bands in driving year-to-year variations of Southern Ocean primary productivity. We find that changes in annual mean phytoplankton biomass are driven by intermittent sub-seasonal events associated with storms and eddies, rather than low frequency climate variability (Chapter 5). Together, these chapters use a novel combination of in situ measurements, satellite data, and model output to elucidate physical mechanisms that control Southern Ocean biogeochemistry. Understanding these drivers is necessary to improve climate models and predict the response of the ocean to climate change.
Download or read book Carbon Cycling in the Glacial Ocean Constraints on the Ocean s Role in Global Change written by Rainer Zahn and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 579 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive progress report on the multi-disciplinary field of ocean and climate change research is given. It compiles introductory background papers and leading scientific results on the ocean-atmosphere carbon cycle with emphasis on the ocean's carbon inventory and the various components involved. The relationship between plankton productivity, carbon fixation, oceanic PCO2 and climate change is investigated from the viewpoint of long-term climatic change during the late Quaternary cycles of ice ages and warm ages. The various approaches range from micropaleontology over organic and trace element geochemistry to molecular isotope geochemistry.
Download or read book The Vegetation of Antarctica through Geological Time written by David J. Cantrill and published by Cambridge University Press. This book was released on 2012-11-22 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fossil history of plant life in Antarctica is central to our understanding of the evolution of vegetation through geological time and also plays a key role in reconstructing past configurations of the continents and associated climatic conditions. This book provides the only detailed overview of the development of Antarctic vegetation from the Devonian period to the present day, presenting Earth scientists with valuable insights into the break up of the ancient supercontinent of Gondwana. Details of specific floras and ecosystems are provided within the context of changing geological, geographical and environmental conditions, alongside comparisons with contemporaneous and modern ecosystems. The authors demonstrate how palaeobotany contributes to our understanding of the paleoenvironmental changes in the southern hemisphere during this period of Earth history. The book is a complete and up-to-date reference for researchers and students in Antarctic paleobotany and terrestrial paleoecology.
Download or read book From Greenhouse to Icehouse written by Donald R. Prothero and published by Columbia University Press. This book was released on 2003 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt: The marine Eocene-Oligocene transition of 34 million years ago was a critical turning point in Earth's climatic history, when the warm, high-diversity "greenhouse" world of the early Eocene ceded to the glacial, "icehouse" conditions of the early Oligocene. This book surveys the advances in stratigraphic and paleontological research and isotopic analysis made since 1989 in regard to marine deposits around the world. In particular, it summarizes the high-resolution details of the so-called doubthouse interval (roughly 45 to 34 million years ago), which is critical to testing climatic and evolutionary hypotheses about the Eocene deterioration. The authors' goals are to discuss the latest information concerning climatic and oceanographic change associated with this transition and to examine geographic and taxonomic patterns in biotic turnover that provide clues about where, when, and how fast these environmental changes happened. They address a range of topics, including the tectonic and paleogeographic setting of the Paleogene; specific issues related to the stratigraphy of shelf deposits; advances in recognizing and correlating boundary sections; trends in the expression of climate change; and patterns of faunal and floral turnover. In the process, they produce a valuable synthesis of patterns of change by latitude and environment.
Download or read book Impact of Atmospheric CO2 and Atlantic Arctic Gateway Evolution on Miocene Climate and Ocean Circulation Changes written by Akil Hossain and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Miocene (23.03-5.33 Ma) was a time period with a warmer climate than today. During this period, changes in ocean gateways and atmospheric CO2 levels largely control ocean circulation and climate changes. However, the underlying ocean processes and dynamics are poorly understood and it remains a challenge to simulate Miocene climate key characteristics such as pronounced polar warming and a reduced meridional temperature gradient. By applying state-of-the-art fully coupled atmosphere-ocean-sea-ice model approaches Miocene climate conditions at different atmospheric CO2 concentrations are simulated and thermohaline changes in response to the subsidence of Atlantic-Arctic gateways for various Greenland-Scotland Ridge (GSR) and Fram Strait (FS) configurations are investigated. For a singular subsidence of the GSR, warming and a salinity increase in the Nordic Seas and the Arctic Ocean is detected. As convection sites shift to the north of Iceland, North Atlantic Deep Water (NADW) is formed at cooler temperatures. The associated deep ocean cooling and upwelling of deep waters to the Southern Ocean surface can cause a cooling in the southern high latitudes. These characteristic responses to the GSR deepening are independent of the FS being shallow or deep. An isolated subsidence or widening of the FS gateway for a deep GSR shows less pronounced warming and salinity increase in the Nordic Seas. Arctic temperatures remain unaltered, but a stronger salinity increase is detected, which further increases the density of NADW. The increase in salinity enhances the contribution of NADW to the abyssal ocean at the expense of the colder southern source water component. These relative changes cause a negligible warming in the upwelling regions of the Southern Ocean. For a sill depth of ~1500 m, ventilation of the Arctic Ocean is achieved due to enhanced import of saline Atlantic water through a FS width of ~105 km. Moreover, at this width and depth, a modern-like three-layer stratification in the Arctic Ocean is detected. The exchange flow through FS is characterized by vertical separation of a low salinity cold outflow from the Arctic Ocean confined to a thin upper layer, an intermediate saline inflow from the Atlantic Ocean below and a cold bottom Arctic outflow. These characteristics are comparable to the present-day hydrography, in spite of significantly shallower and narrower FS configurations during the early Miocene, suggesting that the ventilation mechanisms and stratification in the Arctic Ocean have been similar. In simulations with different CO2 levels (280, 450 and 720 ppm) surface temperatures show the best fit to proxy reconstructions for atmospheric CO2 concentrations of 720 ppm, since in particular the high latitude cooling bias becomes least pronounced. For a CO2 increase from 280 to 450 ppm polar amplification is simulated in the northern high latitudes, which is stronger than for the same radiative CO2 forcing from 450 to 720 ppm. At higher CO2 levels the Miocene climate also shows a reduced climate sensitivity, since the warmest Miocene climate scenario with a CO2 level of 720 ppm is characterized by a seasonality breakdown in the Arctic Ocean. A pronounced warming in boreal winter is detected for a CO2 increase from 450 to 720 ppm, in contrast to a moderate boreal summer temperature increase. This change in the seasonal temperature signature is accompanied by a strong sea-ice concentration decline and enhanced moisture availability promotes cloud formation in the summer months. As a consequence the planetary albedo increases and dampens the temperature response to the CO2 forcing at a warmer Miocene background climate.
Download or read book Evolution of Atlantic Deep water Circulation from the Greenhouse to the Icehouse written by Rachael Kathleen Via and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To better understand how the evolution of Cenozoic deep-water circulation related to changes in global climate and ocean basin configuration, we generated Nd isotope records from Ocean Drilling Program sites in the southeastern Atlantic to track deep water mass composition through time. We used fossil fish debris from ODP Sites1262-1264 (Leg 208), spanning present-day water depths of 2500-4750 m, to reconstruct the isotopic signature of deep waters over the past ~53 Ma. The data indicate an initial transition from relatively non-radiogenic values ([epsilon]Nd=~-10) at 53 Ma to more radiogenic values (~-8.5) at ~32 Ma. From ~32 Ma to 3.85 Ma, the Nd signal becomes more nonradiogenic, ~-12.3 at the top of the record. Comparison of our data with Nd isotopic records derived from a North Atlantic Fe-Mn crust show similar non-radiogenic values (~-10.5) in the 53-32 Ma interval and a trend toward more non-radiogenic values beginning at ~20 Ma. The data likely reflect an overall shift from a Southern Ocean deep water source to the ultimate incursion of deep waters from the North Atlantic. The non-radiogenic values at the base of the record reflect a Southern Ocean source of deep water. The shift toward more radiogenic values indicates an increased contribution of Pacific waters to the Southern Ocean source as the tectonic gateways changed after ~35-33 Ma. The subsequent trend toward more non-radiogenic Nd isotope values is approximatelyconcurrent with the increase of benthic foraminiferal [delta]18O values, based on comparison with a compilation of global data. Thus, changes in oceanic gateway configuration in addition to overall cooling and the build-up of continental ice on Antarctica may have altered the Nd isotope character of Southern Ocean deep waters during the early Oligocene.
