Download or read book Ice Shelf Response to Ice Stream Discharge Fluctuation I Unconfined Ice Tongues written by Douglas R. MacAyeal and published by . This book was released on 1987 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unsteady thickness and flow observed on the Ross Ice Shelf are thought to result primarily from fluctuations of ice streams and outlet glaciers that feed the ice shelf at its inland boundaries. Ice-stream discharge fluctuations constitute an independent means of forcing unsteady ice-shelf behavior, and their effect must be distinguished from those of oceanic and atmospheric climate to understand ice-shelf change. Ice-stream-generated fluctuations of a one-dimensional ice shelf are found to propagate through the ice shelf environment along the two characteristics of the hyperbolic governing equations. One characteristic permits instantaneous transmission of grounding-line velocity changes to all points downstream. The other characteristic represents slow transmission of grounding-line thickness changes along Lagrangian particle paths.
Download or read book Glaciers written by Peter Knight and published by Routledge. This book was released on 2013-05-13 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a comprehensive and detailed summary of our knowledge and understanding of glaciers and sets them within a global environment context. The text explains the significance both of recent advances in glaciology, and of teh many research problms that remain to be solved. The accessible style adopted in the text facilitates a clear understanding of glaciers and the role they play in global issues such as environmental change, geoorphology and hydrology. The use of complex mathematics is avoided as the reader is introduced to important concepts and techniques in modern glaciology such as deforming beds, migrating ice-divides and stable isotope analysis. This is an essential reference book for sutdents, professional geologists and researchers and would be ideal for those who want either a rapid up-date or an introduction to the subject. The books' discussion of recent discoveries and of reserch issues for the future, supported by a thorough reference list, enables readers to pursue their own areas of particular interest.
Download or read book Glaciers written by Peter G. Knight and published by Psychology Press. This book was released on 1999 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview from 1999 of a general introduction to glacier study.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1988 with total page 1020 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transient Behavior of the West Antarctic Ice Streams written by Marion Bougamont and published by . This book was released on 2003 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Reports Awareness Circular TRAC written by and published by . This book was released on 1988-03 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Stability of the Drygalski Ice Tongue written by Christine Indrigo and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Antarctica has the potential to contribute to sea-level rise by up to 58 m if it were to entirely melt. The Antarctic Ice Sheet is fringed by floating ice in the form of ice shelves and ice tongues, which help to buttress and slow the flow of grounded ice into the ocean. Monitoring the stability of these ice shelves and ice tongues is increasingly important in a warming world, as several areas of floating ice across Antarctica are already experiencing considerable mass loss and thinning due to warming air and ocean conditions. The primary goal of this thesis is to examine several factors contributing to the stability of the Drygalski Ice Tongue in East Antarctica using a combination of remote sensing imagery analysis and subglacial hydrology modelling. The Drygalski Ice Tongue is ~140 km long with an unconfined length of 90 km extending into the Ross Sea. This unconfined length influences local ocean conditions and has a significant control on the size of the nearby Terra Nova Bay polynya, keeping the area free of sea ice. The ice tongue has experienced three large scale calving events in its recorded history since the early 1900s. In this study, Landsat imagery from 1988 to 2018 is used to track the advance of the ice tongue, marginal fracture propagation, and to derive velocity using manual feature tracking. The Glacier Drainage Systems (GlaDS) model is applied to the David Glacier catchment, which feeds into the ice tongue, to reveal the locations and discharge from subglacial channels along the grounding line. These channels are compared with basal channels beneath the floating ice tongue that are identified using airborne radar-derived ice thickness and hydrostatically-derived ice thickness, which can reveal channels in basal draft beneath the ice tongue. The results of this study propose a cyclical relationship between the occurrence of large calving events and large marginal fracture formation, in which large calving events result in the formation of new large fractures where the ice tongue emerges from the coast. When these fractures advance to the ice front, they create an area of weakness where future large calving events can occur. The model output produces three subglacial channels at the grounding line, which align with three channels identified through ice thickness. The propagation of the marginal fractures into the width of the ice tongue is controlled by the presence of these basal channels, as fractures can propagate through the areas of thinner ice in the centre of the northmost channel and stops once they reach the channel keel where ice is thicker. These findings provide insight on the roles that subglacial hydrology, ice draft, and marginal rifting have on ice tongue stability for the Drygalski Ice Tongue and for other floating ice bodies.
Download or read book Government Reports Annual Index written by and published by . This book was released on 1988 with total page 1424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1988 with total page 1222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Symposium on Ice Dynamics written by and published by . This book was released on 1989 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers and abstracts from the Symposium on Ice Dynamics, including drift of sea ice and movement of glaciers.
Download or read book Government Reports Annual Index Keyword A L written by and published by . This book was released on 1988 with total page 1600 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 United States Antarctic Research Report No 31 to the Scientific Committee on Antarctic Research SCAR 1 April 1988 31 March 1989 written by National Research Council (U.S.). Polar Research Board and published by . This book was released on 1990 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geotitles written by and published by . This book was released on 1991 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Polar and Glaciological Literature written by and published by . This book was released on 1988 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Glaciers ocean atmosphere Interactions written by Vladimir Mikhaĭlovich Kotli︠a︡kov and published by . This book was released on 1991 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Current Antarctic Literature written by and published by . This book was released on 1988 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt:
