Changes In Ice Sheet Dynamics Across The Mid Pleistocene Transition Recorded In North Atlantic Sediments

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.

Dynamics of the Bering Sea is a valuable resource for scientists, students, and managers working in the Bering Sea and similar ecosystems worldwide. The international scientific organization PICES has successfully brought together the findings of scientists, of many disciplines and countries, to provide a perspective on physical, chemical, and biological research on the Bering Sea, one of the world's most productive ecosystems.

Surveys atmospheric, oceanic and cryospheric processes, present and past conditions, and changes in polar environments.

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.

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.

Great effort has been undertaken to investigate potential geohazards in relation to the development of the Ormen Lange gas field offshore Mid-Norway. The field is located in the scar left after the giant, tsunami-generating Storegga Slide, which occurred roughly 8200 years ago, and the slide risk has consequently received particular focus. The studies have been multi-disciplinary in character, and have involved a number of companies, universities, and research institutions. The results of the project led to a significant advance in the understanding of the Storegga Slide in particular, and submarine slope instability in general, and played an important role in the approval of field development by Norwegian authorities. This book comprises 26 individual contributions representing the wide span of topics addressed in the project. The main scope is to provide a state-of-the-art report on geohazard investigations in a high latitude continental margin setting. Most of the data and results published in this book would not have reached beyond the confidential report stage unless the license partners of the Ormen Lange license had agreed that this information deserves a wider audience. Multidisciplinary and covers most themes treated in slope stability studies prior to the field development phase Provides a link between basic research and applied geohazard studies, with direct relevance for risk evaluation in relation to field development activities, such as pipeline design, drilling of wells, structure foundation etc. A state-of-the-art report on geohazard investigations in a high latitude continental margin setting in relation to field development activities

The northern North Atlantic is one of the regions most sensitive to past and present global changes. This book integrates the results of an interdisciplinary project studying the properties of the Greenland-Iceland-Norwegian Seas and the processes of pelagic and benthic particle formation, particle transport, and deposition in the deep-sea sediments. Ice-related and biogeochemical processes have been investigated to decipher the spatial and temporal variability of the production and fate of organic carbon in this region. Isotopic stratigraphy, microfossil assemblages and paleotemperatures are combined to reconstruct paleoceanographic conditions and to model past climatic changes in the Late Quaternary. The Greenland-Iceland-Norwegian Seas can now be considered one of the best studied subbasins of the world`s oceans.

European Glacial Landscapes: Last Deglaciation brings together relevant experts on the history of glaciers and their impact on the landscape of the main European regions. Soon after the Last Glacial Maximum, a rapid process of the glacial retreat began throughout Europe. This was interrupted several times by abrupt climate cooling, which caused rapid, although moderate, re-advance of the glaciers, until the beginning of the Holocene when the climate became relatively stable and warm. These successive glacial advances and retreats during the Last Deglaciation have shaped much of the European landscape, reflecting abrupt climatic fluctuations. As our knowledge of abrupt climate changes since the Last Glacial Maximum progresses, new uncertainties arise. These are critical for understanding how climate changes disseminate through Europe, such as the lag between climate changes and the expansion or contraction of glaciers as well as the role of the large continental ice sheets on the European climate. All these contributions are included in the book, which is an invaluable resource for geographers, geologists, environmental scientists, paleoclimatologists, as well as researchers in physics and earth sciences. Provides a synthesis that highlights the main similarities or differences, through both space and time, during the Last Deglaciation of Europe Features research from experts in quaternary, geomorphology, palaeoclimatology, palaeoceanography and palaeoglaciology on the Last Deglaciation in Europe during Termination 1 and the important Late Pleistocene-Holocene transition Includes detailed colour figures and maps, providing a comprehensive overview of the glacial landscapes of Europe during the last deglaciation