Download or read book Origin of Surface Undulations at the Kamb Ice Stream Grounding Line West Antarctica written by Fiona Bronwyn Seifert and published by . This book was released on 2012 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The West Antarctic Ice Sheet is drained primarily by five major ice streams, which together control the volume of ice discharged into the ocean across the grounding line. The grounding line of Kamb Ice Stream (KIS) is unusual because the ice stream upstream of it is stagnant. Here, a set of surface features--shore-parallel, long wavelength, low amplitude undulations--found only at that grounding line are examined and found to be "pinch and swell" features formed by an instability in the viscous deformation of the ice. When a relatively competent layer is surrounded by lower strength materials, particular wavelength features within the layer may be amplified under certain layer thickness and strain rate conditions. The undulations at KIS grounding line are possible due to the relatively large strain rates and particular ice thickness at that location. Several data sets are used to characterize the surface features. High resolution surface profiles are created using kinematic GPS carried on board a sled that was used to tow ice penetrating radar equipment. The radar data are used to examine the relationship between surface shape and basal crevasses. Additional surface profiles are created using ICESat laser altimeter observations. Repeat GPS surveys of a strain grid across the grounding line yields strain rate information. Analysis of repeat observations over tidal cycles and multi-day intervals shows that the features are not standing or traveling waves. Together, these observations are then used to evaluate the contributions of elastic and viscous deformation of the ice in creating the grounding line undulations.

Download or read book Principles of Glacier Mechanics written by Roger LeB. Hooke and published by Cambridge University Press. This book was released on 2019-12-05 with total page 537 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principles of glacier physics are developed from basic laws in this up-to-date third edition for advanced students and researchers.

Download or read book Grounding Zone Process written by and published by . This book was released on 2013 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lateral "corners" where Kamb and Whillans Ice Streams (KIS and WIS) discharge into the Ross Ice Shelf share common geometries and ice mechanical settings. At both corners of the now-stagnant KIS outlet, shear margins of apparently different ages confine regions with a relatively flat, smooth surface expression. These features are called the "Duckfoot" on the northern, right-lateral side and the "Goosefoot" on the other. It has been suggested, on evidence found in ice internal layers, that the flat ice terrains on KIS were afloat in the recent past, at a time when the ice stream grounding line was upstream of its present location. The overdeepening in the bed just upstream of the KIS grounding line supports this view of the past geometry. The right-lateral margin at the outlet of the currently active WIS, the location of Subglacial Lake Englehardt (SLE), appears to have many similarities with the right lateral margin of KIS, though with a less developed looking inboard margin. This paper presents a mechanical analysis using surface and bed topography and velocity datasets comparing the Duckfoot flat ice terrain with the terrain around Subglacial Lake Englehardt. At both locations mechanical thinning along shear margins and lows in the bed topography redirects basal water routing towards the features. Here, I consider the history of these features and their role in ice stream variability by comparison of the relict and modern features and via numerical modeling of ice shelf grounding and ungrounding in response to variations in ice flow. We propose two scenarios for the development of flat ice terrains/subglacial lakes at the outlets of ice streams. In the first, development of a lake in the hydraulic potential low along a shear margin forces a margin jump as shearing develops along the inboard shore of the margin lake. This thesis presents evidence for an inboard (relative to the main outboard shear margin) zone of shear along the inboard shoreline of SLE, suggesting that subglacial lakes along shear margins are capable of facilitating shear margin jumps. In the second, grounding line advance around a relative low in the bed, creating adjacent margins along the lakeshores, forms a remnant lake. Discerning which of these scenarios is appropriate at the KIS outlet has implications for understanding the history of the ice stream grounding line. An ice flow model is used to place these local conditions in a regional context by studying the effect of internal perturbations, such as ice rise stagnation or inward margin jumps, on grounding line position. Bathymetry is important in determining ice stream flow in the ways that might not be otherwise realized in 1-D flow model studies. In the numerical modeling experiments, grounding line advance across the KIS outlet is mediated by the overdeepening in the bed and proceeds not in the direction of ice flow but transverse to flow. This finding adds complexity to both a flowline view of grounding line migration and the theory that grounding lines are unstable in the presence of inward sloping bed topography.

Download or read book The Force Budget of a Stagnated Ice Stream written by Heiman Camas Tung and published by . This book was released on 2007 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Dynamic History of Kamb Ice Stream West Antarctica written by Ginny Anne Catania and published by . This book was released on 2004 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Understanding Antarctic Ice stream Flow Using Ice flow Models and Geophysical Observations written by David A. Lilien and published by . This book was released on 2019 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ice streams are the primary pathway by which Antarctic ice is evacuated to the ocean. Because the Antarctic ice sheets lose mass primarily through oceanic melt and calving, ice-stream dynamics exert a primary control on the mass balance of the ice sheets. Thus, changes in melt rates at the ice-sheet margins, or in accumulation in the ice-sheet interiors, affect ice-sheet mass balance on timescales modulated by the response time of the ice streams. Even abrupt changes in melt at the margins can cause ice-stream speedup and resultant thinning lasting millennia, so understanding the upstream propagation of marginally forced changes across timescales is key for understanding the ice sheets’ ongoing contribution to sea-level rise. This dissertation is comprised of three studies that use observations and models to understand changes to Antarctic ice-stream dynamics on timescales from decades to millennia. The first chapter synthesizes remotely sensed observations of Smith, Pope, and Kohler glaciers in West Antarctica to investigate the causes and extent of their retreat. These glaciers have displayed some of the largest measured grounding-line retreat, most rapid thinning, and largest speedup amongst Antarctic ice streams. This retreat has drawn interest in their stability both in its own right and as a harbinger of future changes to larger neighboring ice streams. In this study, recent melt rates were determined using flux divergence estimates derived from observations of ice thickness and surface velocity. Out-of-balance melt at the beginning of the study period indicates that the imbalance of this system predates the beginning of satellite velocity observations in 1996. Throughout much of 1996-2010, there was both greater melt over the ice shelves than flux across the grounding line, implying loss of floating ice and elevated melt forcing, and greater grounding-line flux than accumulation, implying adjustment of the grounded ice in response to the ongoing imbalance. The grounding line position of Kohler glacier, and a large melt channel that is unlikely to be a steady-state feature, suggest that the perturbation to this system began on Kohler glacier sometime around the 1970s. Viscosity of the ice shelves, inferred using a numerical model, indicates that weakening of the Crosson ice shelf was necessary to allow the observed speedup, though it is unable to determine whether the weakening was a cause or effect of the ongoing retreat. The second chapter uses a suite of numerical model simulations to determine the dominant drivers of the recent retreat of Smith, Pope, and Kohler glaciers, and extends those simulations that best match observations to evaluate likely future retreat. Similar to the findings of previous studies, the distribution of sub-shelf melt is found to be the primary control on the rate of grounding-line retreat, while the shelf-averaged melt rate exerts a secondary control. The model simulations indicate that, despite ongoing imbalance, the grounding-line position in 1996 was not inherently unstable, but rather elevated melt at the grounding line was required to cause the observed retreat. A weakening of the ice-shelf margins was found to hasten the onset of grounding-line retreat and led to greater speedup. However, without increases in melt beyond 1996 levels, marginal weakening was insufficient to initiate grounding-line retreat. All simulations that capture the observed retreat continue to lose mass until at least 2100, suggesting that ice in this basin may contribute over 8 mm to global mean sea level by 2100. The magnitude of thinning deep in the catchment suggests that the retreat of Kohler and Smith glacier may hasten the destabilization of the neighboring Thwaites glacier catchment. The third chapter uses the timescale of the recently drilled South Pole Ice Core (SPICEcore) and nearby geophysical observations to infer the history of ice flow near the South Pole during the last 10,000 years. The South Pole is located 180 km from the nearest ice divide and drains from the East Antarctic plateau through Academy glacier/Foundation ice stream. As a result, ice flow near the South Pole is potentially affected by the dynamics of these ice streams, and so the history of ice flow in this region has the potential to inform understanding of how marginally forced changes affect the ice-sheet interior. Because the South Pole is far from an ice divide, the accumulation record in SPICEcore incorporates both spatial variations in accumulation upstream and temporal variations in regional accumulation. Comparison between the SPICEcore accumulation record, derived by correcting measured layer thicknesses for thinning, with an accumulation record derived from new GPS and radar measurements upstream, yields insight into past ice flow and accumulation. When ice speeds are modeled as increasing by 15% since 10 ka, the upstream accumulation explains 77% of the variance in the SPICEcore-derived accumulation (vs. 22% without speedup). This correlation is only expected if the ice-flow direction and spatial pattern of accumulation were stable throughout the Holocene. The 15% speedup in turn suggests a slight (3-4%) steepening or thickening of the ice-sheet interior and provides a new constraint on the evolution of the East Antarctic Ice Sheet following the glacial termination.

Download or read book Quaternary Grounding line Fluctuations in Antarctica written by Trevor Ray Hillebrand and published by . This book was released on 2019 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: The West Antarctic Ice Sheet may be prone to rapid collapse under climates warmer than today due to a dynamic instability at the grounding line, where the ice sheet goes afloat over seawater. However, there is to-date no conclusive evidence that the ice sheet has gone away in last few million years. Thus, characterizing and understanding the transitions between the glacial and interglacial states of the ice sheet is a fundamental step towards predicting its response to future warming. Here, I investigate the history of ice sheet fluctuations in the Ross and Weddell Sea sectors of Antarctica over thousand- to million-year timescales, using cosmogenic nuclide analysis of glacial deposits and glaciated bedrock surfaces, ice-penetrating radar surveys, and numerical modeling of radar waveforms and ice flow. I have mapped and dated glacial deposits from Darwin and Hatherton glaciers, which have been used to constrain the last deglaciation in the Ross Embayment. I find that these glaciers thinned slowly and steadily through the Holocene, thousands of years later than other glaciers in the region. I use ice flow models to show (1) that their thickness changes require changing catchment boundaries upstream, and (2) that ice thickness changes at the glacier mouth are not a simple proxy for grounding line position. Next, I present new ice-penetrating radar surveys from Crary Ice Rise, a promontory in the Ross Ice Shelf that provides stability to portions of the West Antarctic Ice Sheet. I find that the ice rise contains large amounts of marine ice that accreted in basal crevasses and rifts before or during ice rise formation. Marine ice could have strengthened the damaged ice shelf, facilitating ice rise formation. Finally, I use cosmogenic nuclide concentrations in a subglacial bedrock core and a large ensemble of ice sheet model simulations to investigate the long-term stability of the West Antarctic Ice Sheet. The concentrations in the core preclude 150 m of ice sheet thinning at the Pirrit Hills since at least 2 Ma. The ice sheet model results show that continuous burial of the bedrock core requires a stable Filchner-Ronne ice shelf.

Download or read book Post LGM Grounding Line and Calving Front Translations of the West Antarctic Ice Sheet in the Whales Deep Paleo ice stream Trough Eastern Ross Sea Antarctica written by Austin James McGlannan and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Influence of Subglacial Hydrology on the Flow of West Antarctic Ice Streams written by Narelle Paula Marie Baker and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subglacial hydrology is known to influence the flow of ice. However, difficulty in accessing the base of large ice sheets has made determining the interaction between ice streams, basal sediment and water difficult to discern. The aim of this thesis is to determine the influence of subglacial hydrology on the flow of the West Antarctic ice streams. This is achieved through development of a numerical flowline model, the Hydrology, Ice and Till (HIT) model. Ice thermodynamics are coupled to a till layer of Coulomb plastic rheology. The porosity of the till changes with basal melt and freeze and can be augmented by water transported through a subglacial conduit system. Water availability strongly affects ice flow, as till porosity influences the till failure strength and thereby the basal resistance of the ice. The model was developed in four stages and a number of sensitivity tests were performed. It was then applied to Kamb Ice Stream (Ice Stream C) and Whillians Ice Stream (Ice Stream B), West Antarctica. Results confirm that ice streams are capable of oscillating between fast and slow velocity states. Cycles are generated at the grounding line of an ice stream and the speed of the transition from slow to fast flow is governed by water availability. The period of oscillation of the cycles for the West Antarctic ice streams was found to be several hundred years, which is in line with observations of stagnation and reactivation of these ice streams. This shows that subglacial hydrology has a role in modulating the flow variability of ice streams and that rather large changes in the flow of the West Antarctic ice streams are likely to occur this century.

Download or read book Glacial Geology written by Matthew M. Bennett and published by John Wiley & Sons. This book was released on 2011-09-20 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The new Second Edition of Glacial Geology provides a modern, comprehensive summary of glacial geology and geomorphology. It is has been thoroughly revised and updated from the original First Edition. This book will appeal to all students interested in the landforms and sediments that make up glacial landscapes. The aim of the book is to outline glacial landforms and sediments and to provide the reader with the tools required to interpret glacial landscapes. It describes how glaciers work and how the processes of glacial erosion and deposition which operate within them are recorded in the glacial landscape. The Second Edition is presented in the same clear and concise format as the First Edition, providing detailed explanations that are not cluttered with unnecessary detail. Additions include a new chapter on Glaciations around the Globe, demonstrating the range of glacial environments present on Earth today and a new chapter on Palaeoglaciology, explaining how glacial landforms and sediments are used in ice-sheet reconstructions. Like the original book, text boxes are used throughout to explain key concepts and to introduce students to case study material from the glacial literature. Newly updated sections on Further Reading are also included at the end of each chapter to point the reader towards key references. The book is illustrated throughout with colour photographs and illustrations.

Download or read book Atlas of Submarine Glacial Landforms written by J.A. Dowdeswell and published by Geological Society of London. This book was released on 2016-12-16 with total page 631 pages. Available in PDF, EPUB and Kindle. Book excerpt: New geophysical techniques (multibeam echo sounding and 3D seismics) have revolutionized high-resolution imaging of the modern seafloor and palaeo-shelf surfaces in Arctic and Antarctic waters, generating vast quantities of data and novel insights into sedimentary architecture and past environmental conditions. The Atlas of Submarine Glacial Landforms is a comprehensive and timely summary of the current state of knowledge of these high-latitude glacier-influenced systems. The Atlas presents over 180 contributions describing, illustrating and discussing the full variability of landforms found on the high-latitude glacier-influenced seafloor, from fjords and continental shelves to the continental slope, rise and deep-sea basins beyond. The distribution and geometry of these submarine landforms provide key information on past ice-sheet extent and the direction and nature of ice flow and dynamics. The papers discuss individual seafloor landforms, landform assemblages and entire landsystems from relatively mild to extreme glacimarine climatic settings and on timescales from the modern margins of tidewater glaciers, through Quaternary examples to ancient glaciations in the Late Ordovician.

Download or read book Polar Remote Sensing written by Robert Massom and published by Springer Science & Business Media. This book was released on 2006-08-31 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polar Remote Sensing is a two-volume work providing a comprehensive, multidisciplinary discussion of the applications of satellite sensing. Volume 2 focuses on the ice sheets, icebergs, and interactions between ice sheets and the atmosphere and ocean. It contains information about the applications of satellite remote sensing in all relevant polar related disciplines, including glaciology, meteorology, climate and radiation balance and oceanogaraphy. It also provides a brief review of the state-of-the-art of each discipline, including current issues and questions. Various passive and active remote sensor types are discussed, and the book then concentrates on specific geophysical applications. Its interdisciplinary approach means that major advances and publications are highlighted. Polar Remote Sensing: Ice Sheets summarizes fundamental principles of detectors, imaging and geophysical product retrieval includes a chapter on the important new field of satellite synthetic-aperture radar interferometry is a "one stop shop" for polar remote sensing information contains significant new information on the Earth's polar regions describes sophisticated groundbased remote sensing applications with specific reference to their use in polar regions.

Download or read book Fundamentals of Geomorphology written by Richard John Huggett and published by Routledge. This book was released on 2011-03-15 with total page 909 pages. Available in PDF, EPUB and Kindle. Book excerpt: This extensively revised, restructured, and updated edition continues to present an engaging and comprehensive introduction to the subject, exploring the world’s landforms from a broad systems perspective. It covers the basics of Earth surface forms and processes, while reflecting on the latest developments in the field. Fundamentals of Geomorphology begins with a consideration of the nature of geomorphology, process and form, history, and geomorphic systems, and moves on to discuss: structure: structural landforms associated with plate tectonics and those associated with volcanoes, impact craters, and folds, faults, and joints process and form: landforms resulting from, or influenced by, the exogenic agencies of weathering, running water, flowing ice and meltwater, ground ice and frost, the wind, and the sea; landforms developed on limestone; and landscape evolution, a discussion of ancient landforms, including palaeosurfaces, stagnant landscape features, and evolutionary aspects of landscape change. This third edition has been fully updated to include a clearer initial explanation of the nature of geomorphology, of land surface process and form, and of land-surface change over different timescales. The text has been restructured to incorporate information on geomorphic materials and processes at more suitable points in the book. Finally, historical geomorphology has been integrated throughout the text to reflect the importance of history in all aspects of geomorphology. Fundamentals of Geomorphology provides a stimulating and innovative perspective on the key topics and debates within the field of geomorphology. Written in an accessible and lively manner, it includes guides to further reading, chapter summaries, and an extensive glossary of key terms. The book is also illustrated throughout with over 200 informative diagrams and attractive photographs, all in colour.

Download or read book Continuum Mechanics and Applications in Geophysics and the Environment written by Brian Straughan and published by Springer Science & Business Media. This book was released on 2001-03-13 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: The topics covered include soil mechanics and porous media, glacier and ice dynamics, climatology and lake physics, climate change as well as numerical algorithms. The book, written by well-known experts, addresses researchers and students interested in physical aspects of our environment.

Download or read book Detection and Interpretation of Glacial Landforms Under Kamb Ice Stream West Antarctica written by Wenzo Jou Lin and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radar signals from an aerial survey detected elongated km-scale structures at the bed of currently-stagnant Kamb Ice Stream in West Antarctica. These elongated structures are most likely to be mega scale glacial lineations (MSGL), which are known to be associated with fast flowing ice streams. The MSGL signals under Kamb Ice Stream have a general pattern with increasing size and increasing concentration from upstream to downstream. MSGL that formed under thinner ice (~ 800 meters) in regions of less varying topography are more persistent and continuous than MSGL formed under thicker ice (~1200 meters) in areas of more varying topography. Identification of the MSGL help develop a better understanding of the bed properties of Kamb Ice stream and may be helpful for future research on the reason and mechanism of the Kamb Ice Streams stagnation.

Download or read book On the Surging Potential of Polar Ice Streams written by Uwe Radok and published by . This book was released on 1987 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Crustal Structure Beneath Ice Stream C and Ridge BC West Antarctica from Seismic Refraction and Gravity Measurements written by Clifford G. Munson and published by . This book was released on 1991 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: