			Home About us Contact

Surface Velocities (surface + velocity)

Distribution by Scientific Domains

Humanities and Social Sciences	62%

Selected Abstracts

Hydrology and dynamics of a polythermal (mostly cold) High Arctic glacier

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2006
Robert G. Bingham
Abstract To improve our understanding of the interactions between hydrology and dynamics in mostly cold glaciers (in which water flow is limited by thermal regime), we analyse short-term (every two days) variations in glacier flow in the ablation zone of polythermal John Evans Glacier, High Arctic Canada. We monitor the spatial and temporal propagation of high-velocity events, and examine their impacts upon supraglacial drainage processes and evolving subglacial drainage system structure. Each year, in response to the rapid establishment of supraglacial,subglacial drainage connections in the mid-ablation zone, a ,spring event' of high horizontal surface velocities and high residual vertical motion propagates downglacier over two to four days from the mid-ablation zone to the terminus. Subsequently, horizontal velocities fall relative to the spring event but remain higher than over winter, reflecting channelization of subglacial drainage but continued supraglacial meltwater forcing. Further transient high-velocity events occur later in each melt season in response to melt-induced rising supraglacial meltwater inputs to the glacier bed, but the dynamic response of the glacier contrasts with that recorded during the spring event, with the degree of spatial propagation a function of the degree to which the subglacial drainage system has become channelized. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Temporal and spatial variations in periglacial soil movements on alpine crest slopes

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2005
Norikazu Matsuoka
Abstract This paper describes up to ten years of continuous monitoring of frost heave, creep and associated parameters on high mountain crest slopes in the Japanese and Swiss Alps, aiming to evaluate spatial and interannual variations in the rates and controls of soil movement. Shallow frost creep re,ecting diurnal frost heave activity dominates the crest slopes that lack a vegetation mat and have a thin debris mantle with good drainage. Seasonal frost heave activity can induce slightly deeper movement where ,ne soil exists below the depth reached by diurnal freeze,thaw penetration, although the shallow bedrock impedes movements below 20 cm depth. As a result, downslope velocity pro,les display strong concavity with surface velocities of 2,50 cm a,1. The frost creep rates vary spatially, depending on the soil texture, slope gradient, frequency of temperature cycling across 0 °C and moisture availability during freeze,thaw periods. Soil movements recur in every freeze,thaw period, although with some interannual variations affected by the length of seasonal snow cover and the occurrence of precipitation during freeze,thaw periods. The Swiss Alps encounter more signi,cant interannual variations than the Japanese Alps, re,ecting the large variability of the annual snow regime. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Flow velocities of active rock glaciers in the Austrian Alps

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2006
Karl Krainer
ABSTRACT. High surface flow velocities of up to 3 m a,1 were measured near the front of three active rock glaciers in the western Stubai Alps (Rei-chenkar) and Ötztal Alps (Kaiserberg and Ölgrube) in Tyrol (Austria) using differential GPS technology. Flow velocities have increased since about 1990. The highest velocities were recorded in 2003 and 2004, but showed a slight decrease in 2005. At the Reichenkar rock glacier, flow rates are constant throughout the year, indicating that meltwater has no significant influence on the flow mechanism. At Ölgrube rock glacier, flow velocities vary seasonally with considerably higher velocities during the melt season. Meltwater is likely to influence the flow of Ölgrube rock glacier as evident by several springs near the base of the steep front. Because the high surface velocities cannot be explained by internal deformation alone on Reichenkar rock glacier, we assume that horizontal deformation must also occur along a well defined shear zone within a water-saturated, fine-grained layer at the base of the frozen body. The increased surface flow velocities since about 1990 are probably caused by slightly increased ice temperature and greater amounts of meltwater discharge during the summer, a product of global warming. [source]

Two decades of responses (1986,2006) to climate by the Laurichard rock glacier, French Alps

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 4 2009
Xavier Bodin
Abstract The Laurichard active rock glacier is the permafrost-related landform with the longest record of monitoring in France, including an annual geodetic survey, repeated geoelectrical campaigns from 1979 onwards and continuous recording of ground temperature since 2003. These data were used to examine changes in creep rates and internal structure from 1986 to 2006. The control that climatic variables exert on rock glacier kinematics was investigated over three time scales. Between the 1980s and the early 2000s, the main observed changes were a general increase in surface velocity and a decrease in internal resistivity. At a multi-year scale, the high correlation between surface movement and snow thickness in the preceding December appears to confirm the importance of snow cover conditions in early winter through their influence on the ground thermal regime. A comparison of surface velocities, regional climatic datasets and ground sub-surface temperatures over six years suggests a strong relation between rock glacier deformation and ground temperature, as well as a role for liquid water due to melt of thick snow cover. Finally, unusual surface lowering that accompanied peak velocities in 2004 may be due to a general thaw of the top of the permafrost, probably caused both by two successive snowy winters and by high energy inputs during the warm summer of 2003. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Heat transfer for Marangoni-driven boundary layer flow

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2002
David M. Christopher
Abstract Marangoni convection induced by variation of the surface tension with temperature along a surface influences crystal growth melts and other processes with liquid,vapor interfaces, such as boiling in both microgravity and normal gravity in some cases. This paper presents the Nusselt number for Marangoni flow over a flat surface calculated using a similarity solution for both the momentum equations and the energy equation assuming developing boundary layer flow along a surface. Solutions are presented for the surface velocity, the total flow rate, and the Nusselt number for various temperature profiles, Marangoni numbers, and Prandtl numbers. For large bubbles, the predicted boundary layer thickness would be less than the bubble diameter, so the curvature effects could be neglected and this analysis could be used as a first estimate of the effect of Marangoni flow around a vapor bubble. © 2002 Scripta Technica, Heat Trans Asian Res, 31(2): 105,116, 2002; DOI 10.1002/htj.10019 [source]

Seasonal variability in velocity and ablation of Te Moeka o Tuawe/Fox Glacier, south Westland, New Zealand

NEW ZEALAND GEOGRAPHER, Issue 1 2008
Heather L. Purdie
Abstract:, Seasonal variations in ablation and surface velocity were investigated on the lower Fox Glacier. Variations occur between summer and winter ablation, with surface velocity also showing marked seasonality. Recent advance has resulted in the glacier gaining around 200 m length since late 2004. Longer term, Fox Glacier appears linked to the Southern Oscillation Index, with positive glacier mass balances associated with negative Southern Oscillation Index (El Niño). An estimated glacier response time of approximately 9,14 years suggests the current terminus advance was linked to mass gains in the mid-1990s. Recent collapses at the terminal face continue to prove a hazard at this busy tourist destination. [source]

Two decades of responses (1986,2006) to climate by the Laurichard rock glacier, French Alps

Geomorphic processes at a snowpatch hollow on Gassan volcano, northern Japan

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2002
Yoshihiko Kariya
Abstract Present-day geomorphic processes, in a snowpatch hollow on an andesitic volcano (Gassan, 1984 m ASL; 38° 38, N, 140° 02, E) where late-lying snow survives nearly 10 months every year, have been measured for several years. Although soil temperature data show a concentration of freeze-thaw activities in autumn, these fluctuations rarely drop to the effective temperature range for frost shattering. Wetting and drying rather than frost action is thought responsible for debris production which ranges from 2.12 to 49.68 g m,2 a,1, equivalent to a rock surface retreat of 0.001 to 0.019 mm a,1. Thawing of seasonal frost and saturation of soils induces frost creep and gelifluction: maximum values of surface velocity and depth of soil movement are 0.9 cm a,1 and 14 cm, respectively. Annually, slope lowering of 0.3 cm occurs in the pro-nival and sub-nival wash-rill zones. In comparison with other snowpatch sites in the world, rates of soil movement and rock surface denudation are considerably lower at the study site, while fluvial action seems important. Copyright © 2002 John Wiley & Sons, Ltd. [source]