The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform
Tore O. Vorren - One of the best experts on this subject based on the ideXlab platform.
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Weichselian Ice Movement in South Norway and adjacent areas
Boreas, 2008Co-Authors: Tore O. VorrenAbstract:Three main phases of Ice-Movement pattern in South Norway during the Weichselian are reconstructed. During Phase II (possibly of Middle Weichselian age) the Ice divide was located far to the west. Phase III (assumed Middle/Late Weichselian age) had an easterly situated Ice divide. During Phase IV (Preboreal age) the Ice divide had moved back to the west and had partly fragmented into separate domes. The migration of the Ice divide from west to east may be due to glacier surges, whilst the Ice-divide migration from Phase III to IV was probably a result of a general reduction in size of the Ice sheet.
C. L. Tang - One of the best experts on this subject based on the ideXlab platform.
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detection of the labrador current using Ice floe Movement in synthetic aperture radar imagery and Ice beacon trajectories
Atmosphere-ocean, 1992Co-Authors: Motoyoshi Ikeda, C. L. TangAbstract:Abstract Two sets of Synthetic Aperture Radar (SAR) images were collected, as part of the Labrador Ice Margin Experiment (LIMEX), over the Newfoundland Shelf on consecutive days in April 1990. Ice Movement is detected from the displacement of Ice floes between the two images sets and compared with Ice drift data from six satellite‐tracked beacons and in situ CTD data. The Ice velocity data derived from the SAR images and the beacons are used to generate a map of Ice velocity vectors. A streamfunction map of ocean currents is produced by removing the direct wind‐driven component in the Ice Movement data, and by using an objective analysis method. The resulting flow pattern contains the offshore branch of the Labrador Current with a speed of 30 to 50 cm s−1. The current closely follows the shelf break topography from north to south through the study area (47–50.5°N) as a continuous flow. In comparison, if the wind effect was not removed from the Ice velocity data, the calculated Labrador Current north of 50...
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Detection of the Labrador current using Ice‐floe Movement in synthetic aperture radar imagery and Ice beacon trajectories
Atmosphere-Ocean, 1992Co-Authors: Motoyoshi Ikeda, C. L. TangAbstract:Abstract Two sets of Synthetic Aperture Radar (SAR) images were collected, as part of the Labrador Ice Margin Experiment (LIMEX), over the Newfoundland Shelf on consecutive days in April 1990. Ice Movement is detected from the displacement of Ice floes between the two images sets and compared with Ice drift data from six satellite‐tracked beacons and in situ CTD data. The Ice velocity data derived from the SAR images and the beacons are used to generate a map of Ice velocity vectors. A streamfunction map of ocean currents is produced by removing the direct wind‐driven component in the Ice Movement data, and by using an objective analysis method. The resulting flow pattern contains the offshore branch of the Labrador Current with a speed of 30 to 50 cm s−1. The current closely follows the shelf break topography from north to south through the study area (47–50.5°N) as a continuous flow. In comparison, if the wind effect was not removed from the Ice velocity data, the calculated Labrador Current north of 50...
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A two‐dimensional thermodynamic model for sea Ice advance and retreat in the Newfoundland marginal Ice zone
Journal of Geophysical Research, 1991Co-Authors: C. L. TangAbstract:A time dependent two-dimensional Ice-ocean coupled thermodynamic model is developed to study the Ice edge advance and retreat, development of the oceanic mixed layer, and oceanic response to Ice Movement, Ice melt, and heat balance in the Newfoundland marginal Ice zone. The model domain is a vertical section of the ocean along the direction of the Ice velocity. Initially, the ocean is free of Ice and has a deep mixed layer formed by winter surface cooling. An Ice sheet then moves into the domain from the upstream boundary at constant velocity. It melts from the bottom and a shallow mixed layer beneath the Ice is developed. Heat and buoyancy fluxes at the air-sea and Ice-water interfaces and at the bottom of the mixed layer determine the melt rate and change of the mixed layer properties. The Ice edge reaches a maximum distance and starts to retreat when the Ice is being melted by the warm water faster than it is being advected into the area. The oceanic properties change with the Ice Movement. During the advancing phase of the Ice Movement, the heat loss to the Ice bottom from Ice melting exceeds the heat gain by surface heating and entrainment, causing the mixed layer temperature to drop. But since the buoyancy created by the melting is not sufficient to overcome the effect of wind mixing, the mixed layer deepens rapidly. During the retreating phase, the mixed layer becomes shallower and warmer because of the increasing surface heating and buoyance production by Ice melting. The most important factors controlling the melt rate and the excursion distance are the air temperature and the ambient water temperature. Higher wind speeds increase the mixed layer depth but do not have a strong effect on the melt rate.
Oll Fkedrik Bergersen - One of the best experts on this subject based on the ideXlab platform.
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Distribution and genesis of tills in central south Norway
Boreas, 2008Co-Authors: Karl Garnls, Oll Fkedrik BergersenAbstract:The morphogenesis of tills below the culmination zones of the Weichsclian inland Ice has been studied an an upland area with a relief of 1500 m. The thickness of the tills varies considerably, depending principally on gee-morphology, Ice-Movement directions, and glaciofluvial drainage during the last deglaciation period. The thickest tills, found in valleys, accumulated in three ways. Glaciofluvial/lacustrine sediments of prcsumed Mid-Weichselian age have been discovered beneath the tills at niorc than 10 localities. The overlying tills are correlated with different phases of Ice Movement reconstructed on the basis of detailed studies of stt-iae. The till stratigraphy of one locality, Stenseng, is described in detail. Based upon combined analyses of texture, structure, and fabric, four different hasal tills are recognized, each corresponding to a particular Ice direction. A characteristic boulder layer represents a change in thc direction of glacial Movement. Boulder layers in till are thought to he essential for the development of earth pillars.
Åke Mattsson - One of the best experts on this subject based on the ideXlab platform.
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Glacial striae, glacigenous sediments and Weichselian Ice Movements in southernmost Sweden
Sedimentary Geology, 1997Co-Authors: Åke MattssonAbstract:Abstract The southernmost part of Sweden is a classical area to study Ice-Movement patterns. During the course of time, different hypotheses about glacial events and Ice dynamics have been proposed, and there is still no consensus of opinion. The author has tried to integrate studies of glacial erosional features registered on bedrock with glacigenic sediments on top of the eroded rock-surfaces. This paper concentrates on Ice directions according to glacial striae and clast fabrics from the Hardeberga quarry in Skane. The results from Hardeberga are discussed in a regional context. The youngest Ice Movement registered comes from the SW (striae, fabrics, overturned sandwedges and displaced shattered bedrock). Most probably this flow direction is due to quite different Ice flow conditions in the flat and low-lying areas south of the Fennoscandian Border Zone (environment with deforming-bed conditions), in contrast to the Ice dynamics in the higher crystalline shield-areas and the horst ridges of hard Palaeozoic and crystalline rocks crossing Skane from NW to SE.
Terry D. Prowse - One of the best experts on this subject based on the ideXlab platform.
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under Ice Movement of cohesive sediments before river Ice breakup
Hydrological Processes, 2002Co-Authors: David Milburn, Terry D. ProwseAbstract:A significant body of research exists on river hydraulics and sediment transport during open-water conditions, and to a lesser extent during the period of Ice-cover. Most of the Ice-related studies, however, are based on controlled laboratory experiments or field studies conducted under stable Ice-cover conditions. They have largely ignored the most dynamic periods, such as breakup, when hydraulic conditions are most rapidly changing and energy levels are maximized. Moreover, the entire pre-breakup to Ice-clearance period is virtually devoid of even standard hydrometric measurements of suspended sediment, largely because of safety and logistic problems. Some recent work has pointed to the formation of a sediment plume comprising fine-grained sediments that develops before the main breakup fracturing of the Ice cover. This plume has been noted as being particularly ecologically significant because it can contain the winter-long deposition of contaminants that preferentially attach to fine-grained material. Unfortunately, however, because measurements of the critical parameters affecting sediment transport during these periods are rarely taken, much uncertainty remains about the hydraulic forces that resuspend and transport sediments under an Ice cover, and particularly for cohesive fine-grained sediments. This paper describes a field experiment designed to broaden our understanding of sediment transport during this critical pre-breakup period. Detailed measurements of river stage, Ice elevations, flow velocity profiles and suspended sediment were taken over a 17-day period just before the 1998 river-Ice breakup at Hay River, Northwest Territories, Canada. Results indicated that just before breakup, the shear stress, which governs the beginning of sediment motion, increases dramatically and drives the development of the under-Ice sediment plume of very fine-grained, cohesive sediments. The shear stress in this case became critical at a mean under-Ice velocity of 0·4 m/s. Copyright © 2002 John Wiley & Sons, Ltd.
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Under‐Ice Movement of cohesive sediments before river‐Ice breakup
Hydrological Processes, 2002Co-Authors: David Milburn, Terry D. ProwseAbstract:A significant body of research exists on river hydraulics and sediment transport during open-water conditions, and to a lesser extent during the period of Ice-cover. Most of the Ice-related studies, however, are based on controlled laboratory experiments or field studies conducted under stable Ice-cover conditions. They have largely ignored the most dynamic periods, such as breakup, when hydraulic conditions are most rapidly changing and energy levels are maximized. Moreover, the entire pre-breakup to Ice-clearance period is virtually devoid of even standard hydrometric measurements of suspended sediment, largely because of safety and logistic problems. Some recent work has pointed to the formation of a sediment plume comprising fine-grained sediments that develops before the main breakup fracturing of the Ice cover. This plume has been noted as being particularly ecologically significant because it can contain the winter-long deposition of contaminants that preferentially attach to fine-grained material. Unfortunately, however, because measurements of the critical parameters affecting sediment transport during these periods are rarely taken, much uncertainty remains about the hydraulic forces that resuspend and transport sediments under an Ice cover, and particularly for cohesive fine-grained sediments. This paper describes a field experiment designed to broaden our understanding of sediment transport during this critical pre-breakup period. Detailed measurements of river stage, Ice elevations, flow velocity profiles and suspended sediment were taken over a 17-day period just before the 1998 river-Ice breakup at Hay River, Northwest Territories, Canada. Results indicated that just before breakup, the shear stress, which governs the beginning of sediment motion, increases dramatically and drives the development of the under-Ice sediment plume of very fine-grained, cohesive sediments. The shear stress in this case became critical at a mean under-Ice velocity of 0·4 m/s. Copyright © 2002 John Wiley & Sons, Ltd.
