Download or read book Comparison of Late Pleistocene Arctic Ocean Climates with the O18 Record Using Spectral Analysis written by Robin Francis Boyd and published by . This book was released on 1981 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Late Pleistocene Central Equatorial Pacific Temperature Drivers written by Victoria Yuan and published by . This book was released on 2018 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tropical Pacific sea surface temperatures (SSTs) are a critical component of the global climate system with oceanic and atmospheric teleconnections through meridional and latitudinal heat transport. Understanding the climate drivers and dynamics of this region enables a better understanding of global climate. Orbital scale climate drivers for eastern and western Pacific SSTs have been studied; however, SSTs and thermocline structure have not been studied in the central equatorial Pacific (CEP). Studying temperature dynamics in the CEP upper water column can help determine which mechanisms control SST and thermocline structure and test previously proposed hypotheses. Here, I present CEP SST and subsurface temperature records from the Line Islands (ML1208-17PC) that span the last 380,000 years. Using two species of foraminifera, G. ruber and G. tumida, I respectively generated Mg/Ca based SST and subsurface temperature records and compared them to published records from the equatorial Pacific. This comparison indicates an expanded west pacific warm pool (WPWP) during interglacial periods but no expansion of the eastern Pacific cold tongue during glacial periods. Based on the thermocline depth proxy, the thermocline was deeper in glacial periods and shallower in interglacial periods. Cross-spectral analysis demonstrates which climate drivers are the likely forcings for CEP SST and thermocline behavior. The CEP SSTs are distinct from those to the east or the west as they are not directly driven by CO2 or insolation at orbital frequencies; instead, the CEP SST record is linked to subsurface temperature at eccentricity and obliquity bands. However, changes in thermocline conditions at the CEP are potentially driven by CO2 and Antarctic temperature changes. This study agrees and supports previous studies that indicate deeper thermocline depths in glacials and shallower depths in interglacials.

Download or read book Ocean Temperature Variability During the Late Pleistocene written by Jeremy Scott Hoffman and published by . This book was released on 2016 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO2. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation.

Download or read book The Stratigraphy and Late Pleistocene Sedimentological History of the Lomonosov Ridge Makarov Basin Central Arctic Ocean written by Thomas Henry Morris and published by . This book was released on 1983 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book North Pacific Environment and Paleoclimate from the Late Pleistocene to Present written by Miriam Jones and published by Frontiers Media SA. This book was released on 2020-01-13 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast area of the North Pacific, spanning ~55˚ longitude, represents a challenge for documenting and understanding the geologic history of ocean, atmosphere, and terrestrial environmental change. Nevertheless, its importance for many issues, including our fundamental understanding of ocean and atmospheric circulation patterns and teleconnections with natural modes of climate variability through time, has led to a steady rise in the numbers of study sites and proxy types. By bringing together a wide range of proxies and timescales that examine the impacts of paleoclimate on ecosystems, water, carbon, and humans, and interactions between marine and terrestrial processes, this Research Topic contributes to an improved understanding of the region’s significance at global, hemispheric, and regional scales.

Download or read book Stable Isotope Stratigraphy and Paleoceanography of the Arctic Ocean written by Thomas Henry Morris and published by . This book was released on 1986 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bibliography and Index of Geology written by and published by . This book was released on 1988 with total page 1178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Late Cenozoic Glacial Ages written by and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Middle to Late Pleistocene Paleoenvironmental Reconstructions from Lake El gygytgyn Arctic Russia written by Mary Helen Habicht and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is a major issue challenging the world today. Our global society faces rising temperatures, variable weather patterns, and rising sea level among other associated issues. Our action (or inaction) to address current changes will have serious ramifications for life on our planet in the coming centuries and millennia. In order to provide context for these present and future changes, we can utilize the paleo record to understand the natural variability of Earth's climate system. One region of the world is changing more rapidly than the global average. Over recent decades, the Arctic has experienced warmer temperatures, reduced sea ice, melting permafrost, and shifts in the amount and seasonality of precipitation. Unfortunately, paleoclimate and environmental records from the terrestrial Arctic, particularly beyond the last 120 ka, are few. This is due to the repeated extensive glaciation of the northern hemisphere high latitudes during the ice ages of the Quaternary. One area of the Arctic, in the Anadyr mountains of Chukotka, has remained unglaciated through the Pleistocene. Lake El'gygytgyn, a meteorite impact crater lake formed 3.6 million years ago lies in this area and so provides a continuous sedimentary sequence from the Mid-Pliocene to present. This dissertation includes four studies of Lake El'gygytgyn sediments over the last 800 thousand years. A variety of biogeochemical and stable isotope proxies are used to reconstruct climate and environmental variability throughout the study interval. These studies provide novel information about the natural variations of terrestrial Arctic climate on glacial-interglacial timescales. Chapter 2 of this dissertation involves the analysis of bacterial membrane lipids called branched glycerol dialkyl glycerol tetraethers (brGDGTs) and plant leaf wax n-alkanes to provide records of relative temperature change and terrestrial vegetation turnover in response to aridity during the glacial-intergacial cycles of the Mid-Pleistocene. Our data suggests that regional temperature is strongly influenced by local summer insolation while aridity changes derive from sea level driven changes in continentality. Comparison of our data with previously published paleoclimate records from Lake El'gygytgyn highlights the difference in proxy response to climatic variables and the utility of a multi-proxy approach. Additionally, we use our extensive records to identify the presence of a global climatic transition, the Mid-Brunhes Event (MBE), for the first time in the terrestrial Arctic. In Chapter 3, we analyze algal lipid biomarkers from the same samples used in Chapter 2. We also incorporate stable carbon and nitrogen isotopes to determine changes in primary production and organic matter preservation in Lake El'gygytgyn across multiple glacial-interglacial cycles. Chapter 4 spans the Holocene and Late Pleistocene (280 ka to present). We use the hydrogen isotopic composition of long chain plant leaf wax n-alkanes to reconstruct temperature and hydroclimate changes. We find that MIS 7 was a stronger interglacial period than MIS 5e in the terrestrial Arctic and attribute the variability in hydrogen isotopes predominantly to temperature and moisture source changes. In Chapter 5, we compare the hydrogen isotope composition of n-alkanes measured in Chapter 4 to the isotopic composition of n-alkanoic acids in the same samples previously analyzed by Wilkie (2012). This is a novel approach for paleoclimate records. Our results indicate that the type of compound selected for analysis can have a significant impact on the paleoclimatic interpretations of a study. Finally in Chapter 6, a summary and avenues for future research are provided. Overall, this dissertation is a testament to the utility of biomarkers and stable isotopes in Arctic lake sediments. Each study provides unique information about the terrestrial Arctic climate during the Quaternary and contributes to our understanding of climatic variability and the dynamics of this sensitive region.

Download or read book The South Atlantic in the Late Quaternary written by Gerold Wefer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 742 pages. Available in PDF, EPUB and Kindle. Book excerpt: The South Atlantic plays a critical role in the couplingofoceanic processes between the Antarctic and the lower latitudes. The Antarctic Ocean, along with the adjacent southern seas, is of substantial importance for global climate and for the distributionofwater masses because itprovides large regions ofthe world ocean with intermediate and bottom waters. In contrast to the North Atlantic, the Southern Ocean acts more as an "information distributor", as opposed to an amplifier. Just as the North Atlantic is influencedby the South Atlantic through the contributionofwarm surface water,the incomingsupply ofNADW - in the area of the Southern Ocean as Circumantarctic Deep Water - influences the oceanography ofthe Antarctic. The competing influences from the northern and southern oceans on the current and mass budget systems can be best studied in the South Atlantic. Not only do changes in the current systems in the eastern Atlantic high-production regions affect the energy budget, they also influence the nutrient inventories, and therefore impact the entire productivity ofthe ocean. In addition, the broad region of the polar front is a critical area with respect to productivity-related circulation since it is the source of Antarctic Intermediate Water. Although theAntarctic Intermediate Watertoday liesdeeper than the water that rises in the upwelling regions, it is the long-term source ofnutrients that are ultimately responsible for the supply oforganic matter to the sea floor and to sediments.

Download or read book Catalogue of Accessioned Publications written by World Data Center A--Oceanography and published by . This book was released on 1976 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Late Pleistocene History of Ocean atmosphere Interaction in the Eastern Equatorial Pacific written by Hilde Snoeckx and published by . This book was released on 1995 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Global Palaeoclimate of the Late Cenozoic written by V.A. Zubakov and published by Elsevier. This book was released on 1990-03-20 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a detailed description of the history and chronology of global climate based on event-signal stratigraphy. The history of global climate is described for the last fifty million years with the description for the last one million years in detail. Climatostratigraphic sequences of twelve key regions are taken as a basis, eight of them situated in the USSR territories. Chronology of climatic events of the Pleistocene, Pliocene and Miocene is developed based on palaeomagnetic and radiometric data. The authors' version of its correlation with oxygene-isotope scales of deep-sea sediments is given. Theoretical problems of climatic stratigraphy and palaeoclimatology are discussed, in particular, the causes of climatic change. The Northern Hemisphere palaeoclimatic reconstructions are made for the Holocene, Eemian and Pliocene temperature optima, considered as possible palaeoanalogues of climate of the 21st Century. The book is intended primarily for a wide circle of scientific workers, palaeoclimatologists and palaeogeographers, but will also interest geologists, biologists, palaeomagnetologists and archaeologists.

Download or read book Climate Climatic Change and Water Supply written by National Research Council and published by National Academies Press. This book was released on 1977-02-01 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Early Middle Pleistocene Transitions written by Geological Society of London and published by Geological Society of London. This book was released on 2005 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Early-Middle Pleistocene transition (around 1.2 to 0.5 Ma) marks a profound shift in Earth's climate state. Low-amplitude 41 ka climate cycles, dominating the earlier part of the Pleistocene, gave way progressively to a 100 ka rhythm of increased amplitude that characterizes our present glacial-interglacial world. This volume assesses the biotic and physical response to this transition both on land and in the oceans: indeed it examines the very nature of Quaternary climate change. Milankovitch theory, palaeoceanography using isotopes and microfossils, marine organic geochemistry, tephrochronology, the record of loess and soil deposition, terrestrial vegetational change, and the migration and evolution of hominins as well as other large and small mammals, are all considered. These themes combine to explore the very origins of our present biota.

Download or read book Reconstruction of Quaternary Paleo circulation in the Western Arctic Ocean Based on a Neodymium Isotope Record from the Northwind Ridge written by Rachael E. Gray and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: An understanding of past ocean circulation in the Arctic is critical for interpretations of past global ocean and atmospheric circulation, as well as predictions of future conditions. The Arctic Ocean plays a major role in global climate, due to its contributions to both the North Atlantic Deep Water (and subsequently the Atlantic Meridional Overturning Circulation) and the planet's albedo (due to sea ice cover). A sediment core from the Northwind Ridge in the western Arctic Ocean, ~800 km north of Alaska, has been sampled for measurement of radiogenic isotope ratios of neodymium and strontium. Sediment grain coatings were leached from the bulk sediment and measured for 87/86Sr and [epsilon]Nd, a proxy for seawater source. Two leaching solutions, one using buffered acetic acid and the second using hydroxylamine hydrochloride, were applied to sediments. Strontium data suggests that acetic acid best captures the seawater signal, while hydroxylamine hydrochloride leaching likely caused clay contamination of the hydrogenous data. [epsilon]Nd ratios were compared with independent lithologic proxies measured on the core and with results of earlier radiogenic-isotope studies in the Arctic Ocean. Data obtained suggest that radiogenic waters dominated the western Arctic Ocean during the estimated Early Pleistocene, probably due to increased Pacific water inputs and/or enhanced brine exclusion from sea ice formation on the Siberian shelves. These conditions likely indicate relatively warm climatic environments with predominantly seasonal sea ice, and thus can be potentially used as a paleo-analog for the projected near-future state of the Arctic. Further upcore, in the estimated Middle to Late Pleistocene, [epsilon]Nd values decrease overall, with high-amplitude fluctuations corresponding to glacial-interglacial cyclicity. Strongly non-radiogenic values in glacial intervals suggest the predominance of inputs from the Canadian Shield eroded by the Laurentide ice sheet. More radiogenic but gradually decreasing interglacial values indicate a change from Pacific to Atlantic water influence during the Middle to Late Pleistocene. Further isotope work on other cores may clarify the mechanisms and extent of this shift in circulation patterns.

Download or read book Statistical Treatment of Environmental Isotope Data in Precipitation written by International Atomic Energy Agency and published by . This book was released on 1981 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: