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Ice-ocean interactions remain poorly understood despite the growing recognition that they play significant roles in the complex behavior of glaciers that reach the oceans, which is of broad interest because it contributes substantially to the challenge of predicting global sea-level rise. This research focuses on the dynamics of sediment accumulation near the calving fronts of tidewater glaciers across a climatic continuum from polar to temperate conditions. Rates and spatial patterns of sediment accumulation merit close attention because they can affect glacier stability by reducing the water depth that controls the calving rate, the surface area available for submarine melting, and the ability of tidewater glaciers to advance into deep water. The sediments produced by these glaciers are also of considerable interest because they record changes in glacial, environmental, and tectonic conditions. In light of the recent, well documented changes in climate and glacier extent along the Antarctic Peninsula through much of the last century, a detailed study was developed to understand how modern sediments have recorded these regional changes. Sediment accumulation rates for sixteen cores collected in fjords across a 15° N-S transect from the Antarctic Peninsula to southern Chile were calculated using the decay of naturally occurring radioisotope 210Pb. Records from the Antarctic Peninsula show surprisingly constant rates of sediment accumulation (1-7 mm/yr) throughout the past century despite rapid warming, increase in surface melt, and glacial retreat. Cores from the South Shetland Islands, on the other hand, reveal accelerated sediment accumulation over the past few decades, likely due to warming and an increase in surface melt in this region, which straddles the boundary between subpolar and temperate conditions. In the temperate fjords of southern Chile, sediment accumulates faster (11-24 mm/yr). This increase in sediment accumulation with decreasing latitude reflects the gradient from subpolar to temperate climates, and is consistent with glacial erosion being much faster in the very wet, temperate climate of southern Chile than along the colder Antarctic Peninsula. Links between rates of glacier retreat, ice motion, sediment flux, and the evolution of glacial sediment deposits in a temperate setting are explored using a large existing dataset for Columbia Glacier, Alaska and new oceanographic data from the fjord recently exposed by its retreat. High-resolution seismic data indicate that 3.2 x 108 m3 of sediment has accumulated over the last three decades; this volume corresponds to erosion at 5.1 ± 1.8 mm/yr averaged over the entire ~1000 km2 area of the glacier. A numerical model is developed to relate known patterns of sedimentation and changes in the glacier terminus position to the accumulation of sediment in the fjord during the 30-year period of retreat. The model, which represents both primary sedimentation and secondary reworking, is used to produce a history of the sediment flux from the glacier that is compatible with the observed post-retreat sediment deposit thickness and architecture. The bathymetric history and model results corroborate that the sediment flux increased sixfold within the 1997-2000 period; interestingly this increase is not correlated with concurrent changes in glacier dynamics. It is suggested that the increase resulted from the sediment transport capacity of subglacial rivers increasing due to the retreat-related steepening of the glacier surface over a deep subglacial basin. That major variations in the sediment flux can be controlled by changes in subglacial sediment storage, in addition to changes in climate and the erosion rate, adds richness and complexity to the interpretation of the glacimarine sediment record. The sediment-flux model is also applied to Jorge Montt Glacier, a Patagonian tidewater glacier with very similar behavior to Columbia Glacier, but without the detailed record of its retreat history and other complementary glaciological data. Sediment volume calculations for both glaciers indicate that the effective erosion rate necessary to sustain the mean sediment fluxes during their respective periods of retreat is surprisingly similar, ~5 mm/yr, despite differences in the geographic, tectonic, and geologic settings. For both rapidly retreating glaciers, the numerical model yields a sediment-flux history that produces sediment packages generally consistent with observed bathymetry and internal stratigraphic architecture. On the time scale of retreat, temporal variations in the modeled sediment flux from both glaciers are not related to concurrent variations in ice velocity, as expected. Rather, changes in the sediment flux are attributed to the tendency for sediment to be flushed from subglacial basins due to the progressive steepening of the glacier terminus during retreat. In both fjords, model results corroborate that sediment accumulates rapidly (>1 m/yr) near the ice front. In addition, the model suggests that gravity-driven processes are essential for delivering and redistributing sediment within the fjords to create the observed bathymetry and internal stratigraphic architecture.
Fjords are both an interface and a buffer between glaciated continents and the oceans. They exhibit a very wide range in environmental conditions, both in dynamics and geography. Some are truly wonders of the world with their dizzying mountain slopes rising sharply from the ocean edge. Others represent some of the harshest conditions on earth, with hurricane winds, extremes in temperature, and catastrophic earth and ice movements. Fjords are unique estuaries and represent a large portion of the earth's coastal zone. Yet they are not very well known, given the increasing population and food pressures, and their present industrial and strategic importance. Temperate zone estuaries have had many more years of intense study, with multiyear data available. Most fjords have not been impacted by man but, if history repeats itself, that condition will not last long. Fjords present some unique environmental problems, such as their usually slow flushing time, a feature common to many silled environments. Thus there is presently a need for management guidelines, which can only be based on a thorough knowledge of the way fjords work. Fjords are, in many respects, perfect natural oceanographic and geologic lab oratories. Source inputs are easily identified and their resulting gradients are well developed. Throughout this book, we emphasize the potential of modeling pro cesses in fjords, with comparisons to other estuary, lake, shelf and slope, and open ocean environments.
Snow and Ice-Related Hazards, Risks, and Disasters provides you with the latest scientific developments in glacier surges and melting, ice shelf collapses, paleo-climate reconstruction, sea level rise, climate change implications, causality, impacts, preparedness, and mitigation. It takes a geo-scientific approach to the topic while also covering current thinking about directly related social scientific issues that can adversely affect ecosystems and global economies. Puts the contributions from expert oceanographers, geologists, geophysicists, environmental scientists, and climatologists selected by a world-renowned editorial board in your hands Presents the latest research on causality, glacial surges, ice-shelf collapses, sea level rise, climate change implications, and more Numerous tables, maps, diagrams, illustrations and photographs of hazardous processes will be included Features new insights into the implications of climate change on increased melting, collapsing, flooding, methane emissions, and sea level rise
Artists and writers portray the disorientation of a world facing climate change. This monumental volume, drawn from a 2020 exhibition at the ZKM Center for Art and Media, portrays the disorientation of life in world facing climate change. It traces this disorientation to the disconnection between two different definitions of the land on which modernizing humans live: the sovereign nation from which they derive their rights, and another one, hidden, from which they gain their wealth—the land they live on, and the land they live from. Charting the land they will inhabit, they find not a globe, not the iconic “blue marble,” but a series of critical zones—patchy, heterogenous, discontinuous. With short pieces, longer essays, and more than 500 illustrations, the contributors explore the new landscape on which it may be possible for humans to land—what it means to be “on Earth,” whether the critical zone, the Gaia, or the terrestrial. They consider geopolitical conflicts and tools redesigned for the new “geopolitics of life forms.” The “thought exhibition” described in this book can opens a fictional space to explore the new climate regime; the rest of the story is unknown. Contributors include Dipesh Chakrabarty, Pierre Charbonnier, Emanuele Coccia, Vinciane Despret, Jerôme Gaillarde, Donna Haraway, Joseph Leo Koerner, Timothy Lenton, Richard Powers, Simon Schaffer, Isabelle Stengers, Bronislaw Szerszynski, Jan A. Zalasiewicz, Siegfried Zielinski Copublished with ZKM | Center for Art and Media Karlsruhe
This book focuses in detail on all ecologically important aspects of the Kongsfjorden system such as the marine and atmospheric environment including long-term monitoring, Ecophysiology of individual species, structure and function of the ecosystem, ecological processes and biological communities. The contributed articles include review articles and research articles that have a wider approach and bring the current research up-to-date. This book will form a baseline for future work.
Mass loss from the Greenland Ice Sheet has accelerated throughout the last decade, predominantly due to a quadrupling of ice discharge by iceberg calving, submarine melting, and meltwater runoff at marine-terminating outlet glaciers. The recent acceleration has been linked to the transport of increasing amounts of meltwater, fuelled by warming temperatures. These processes include enhanced basal sliding, inefficient subglacial drainage networks, and a warming of ocean waters in contact with the glacier terminus. Understanding the impact of meltwater on tidewater glacier dynamics, both subglacially and proglacially, is a key component in predicting glacier health and future sea level rise. However, the spatial and temporal magnitude of this meltwater impact is poorly understood. The goals of this dissertation are to identify how meltwater travels subglacially through a tidewater glacier system, establish a method to monitor tidewater glacier discharge remotely, and calculate the impact of subglacial discharge on terminus stability. The inaccessibility of subglacial and terminus environments prohibits direct hydrological observations. We use combinations of remote sensing, reanalysis models, and in situ fjord data to accomplish these research goals by measuring indicators of subglacial meltwater discharge and fjord circulation (sediment plumes exiting the terminus and the movement of small icebergs in the fjord). By monitoring the timing and duration of plumes exiting a fast-flowing Greenland tidewater glacier, we found short-term variability in meltwater discharge, persistent subglacial pathways, and evidence of over-winter subglacial storage. Using glaciers in Svalbard,we established a new method to determine sediment concentration from Landsat–8 spectral reflectance, and used this sediment concentration to quantify relative seasonal meltwater discharge at tidewater glaciers. Finally, we used the movement of icebergs and ocean temperatures to establish a terminus submarine melt rate for along-terminus fjord circulation, and use this to isolate calving due solely to subglacial meltwater discharge. The results of this dissertation help answer larger questions concerning the controls of water flow under a glacier and how that flow, and fjord circulation, influence glacier stability. Ultimately these results will inform coupled ice-ocean-climate models to predict glacier melt and sea level rise.
This volume of 18 papers describes the glacial-marine sedimentary environment in a variety of temporal and spatial settings. The volume's primary emphasis is the characteri zation of Quaternary glacial-marine sedimentation to show (1) the significant differences that exist between glacial marine environments in different geographic settings and (2) their resulting glacial-marine deposits and facies. Addi tionally, papers describing ancient glacial-marine environ ments are also presented to illustrate lithified analogs of the Quaternary deposits. With the Doctrine of Uniformitarianism in mind (the present is the key to the past), it is hoped that this volume will serve to expand the horizons of geologists working on the rock record, especially those whose primary criteria for recognition of ancient glacial-marine environments is the presence of dropstones in a finer-grained matrix. As the papers presented here show, diamictite is only one of many types of deposits that form in the glacial-marine sedimentary environment. Papers presented in this volume examine the Quaternary glacia1-marine sedimentary picture in subarctic Alaska, Antarctica, the Arctic Ocean, the Kane Basin, Baffin Island, the Puget-Fraser Lowland of Washington and British Columbia, and the North Atlantic Ocean. Ancient glacia1-marine depos its described are the Neogene Yakataga Formation of southern Alaska, the Late Paleozoic Dwyka Formation of the Karoo Basin of South Africa, and the Precambrian Mineral Fork Formation of Utah. For continuity, a paper summar1z1ng the temporal and spatial occurrences of glacial-marine deposits is also presented.