Glaciological controls on debriscover formation are investigated from the perspective of primary dispersal of supraglacial debris across a melting ice surface. This involves the migration of angled debris septa outcrops across a melting, thinning
glacier ablation zone. First, simple geometric relations between englacial septa and the supraglacial debris load are outlined to elucidate the role of glaciological variables (gradient, ice motion, ablation, rate of glacier thinning) on debriscover
formation. Second, these relations are quantified at a small alpine glacier (Glacier d'Estelette, Italian Alps) to present an explanatory model of why certain parts of the glacier are becoming more rapidly debris-covered than others. Finally
, the implications of the model for the debris-cover transition are discussed in relation to the sensitivity of different glacier terminus types to debris-cover formation.
Wash erosion on a debriscovered slope in a semi-arid climate
Ablation spécifique ; Afrique du Sud ; Domaine aride ; Domaine semi-aride ; Eboulis ; Erosion des sols ; Erosion par ruissellement ; Expérimentation de terrain ; Géographie physique ; Orange Free State ; Versant ; Versant de débris
Field experimentation on a steep debris slope. The rate of denudation in terms of rock density was found to be 17.8 mm per thousand years. This rather low figure results from several factors : e.g. good canopy and basal cover of vegetation, cover
by rock debris, very little disturbance by man or grazing animals and the lack of available material suitable for transport.
A rock glacier/debris-covered glacier system at Galena Creek, Absaroka Mountains, Wyoming
At Galena Creek, the ice/debris system has alternated between rock glacier and debris-covered glacier modes due to changes in the size of the accumulation area. These results have important implications for paleoclimatic studies of the ice
The ablation rate under a debris layer is very difficult to measure directly at debris-covered glaciers, because the surface is highly heterogeneous, and the ablation rate varies tremendously from place to place. This paper describes previous works
on the ablation process, and a test result of a proposed method to estimate the ablation rate under a debris layer is presented for the Lirung Glacier in Langtang Valley, Nepal Himalaya.
Properties of natural supraglacial debris in relation to modelling sub-debris ice ablation
Albedo ; Debriscover ; Glacial ablation ; Glacial features ; Glacier ; Glacier mass balance ; Himalaya ; Model ; Nepal ; Seasonal variability ; Thermal conductivity
require consideration in annual or multi-annual distributed modelling of debris-covered glacier surface energy and mass balance.
The AA. report measurements of vertical temperature profiles in debris on the Ngozumpa glacier in the Khumbu Himal region,Nepal, that show : 1) conductive processes dominate during the ablation season in matrix-supported diamict; 2) ventilation may
be possible in coarse surface layers; 3) phase changes associated with seasonal change have a marked effect on the effective thermal diffusivity of the debris. Effective thermal conductivity determined from vertical temperature profiles in the debris
is generally higher in summer than in winter, but values depend on the volume and phase of water in the debris. Surface albedo can vary widely over small spatial scales, as does the debris thickness. The findings from Ngozumpa glacier indicate
that the probability distribution of debris thickness changes from positively skewed in the upper glacier towards a more normal distribution nearer the terminus. These observations highlight aspects of spatial and temporal variability in supraglacial debris that may
Debris-covered glaciers and rock glaciers in the Nanga Parbat Himalaya, Pakistan
The origin and mobilization of the extensive debriscover associated with the glaciers of the Nanga Parbat Himalaya is complex. The AA. propose a mechanism by which glaciers can form rock glaciers through inefficiency of sediment transfer from
A discussion regarding weathering in the western Cape mountains, South Africa : implications for pleistocene cryoclastic debris production
The extensive angular Pleistocene debriscovers of the western Cape have been attributed to cryoclastic origin. However, evidence of chemical weathering and lichen growth is presented suggesting further research is necessary. - (AJC)
La trasformazione dei ghiacciai bianche (debris free glaciers) in ghiacciai neri (debriscovered glaciers) per un approccio didattico applicato
La transformation des glaciers blancs (sans débris) en des glaciers noirs (avec débris) au travers d'une approche didactique appliquée
The Alpine landscape is changing in relation to global warming. Glaciers are progressively covering their tongues by a layer of debris protecting them from the ablation processes. The “clean” glacier changes into a debriscovered glaciers, passing
Distribution of large woody debris along the outer bend of meanders in the Ain River, France
Ain ; Cours d'eau ; Débris ligneux ; Forêt ; France ; Géométrie hydraulique ; Méandre ; Piedmont ; Plaine d'inondation ; Statistique ; Végétation ripicole
The distribution of large woody debris (LWD) was studied along the concave outer bend of 3 meanders in the Ain River. The Ain River is a sixth-order channel dominated by a gravel-cobble bed substrate that meanders through a floodplain covered
The ablation experiments with artificial debriscover were performed on the middle tongue of Vernagtferner, a temperate glacier in the Ötztal Alps, Austria. Ten test plots were established with different debris grain sizes and debris thicknesses
layer thicknesses of the local mica schist. However, the analysis of thermal diffusivities demonstrated that the vertical moisture distribution of the debriscover must be taken into consideration, with the diffusivity values being significantly lower
consisting of different natural material. For each plot, values of thermal conductivity were determined. The observations revealed a clear dependence of the sub-debris ice melt on the layer thickness, grain size, porosity and moisture content. For the sand
The response of partially debris-covered valley glaciers to climate change : the example of the Pasterze Glacier (Austria) in the period 1964 to 2006
Alpes ; Années 1964-2006 ; Autriche ; Bilan de masse ; Changement climatique ; Climat ; Couverture de débris ; Distribution spatiale ; Glacier ; Modèle numérique de terrain ; Moraine ; Vallée glaciaire
This study investigates the response to recent climate change of the partially debris-covered Pasterze Glacier, the largest glacier of the Eastern Alps. The study concentrates on behaviour differences between the adjacent debris-covered and clean
temperatures. The findings clearly underline the importance of supra-glacial debris on mass balance and glacier tongue morphology.
Influence of supraglacial debris on summer ablation and mass balance in the 24K Glacier, southeast Tibetan Plateau
Air temperature ; China ; Debriscover ; Glacial ablation ; Glacier ; Glacier mass balance ; Impact ; Model ; Summer ; Tibet
Many temperate glaciers in the southeast Tibetan Plateau are covered by supraglacial debris in the ablation area. To evaluate the effect of such debris on summer ablation and mass balance, the surface ablation on the 24K Glacier was measured
in the summer of 2008. Mean ablation rates varied from 10 to 52 mm/day, strongly correlated to debris thickness. Synchronous observations of air temperature allowed application of a simple degree-day model to calculate ablation rates. Maximum values of both
ablation rate and degree-day factors appeared in the middle area of the glacier where the debris layer thickness was about 1 cm. The simulated daily ablation obtained from the degree-day approach showed that the debris layers significantly affected
Debris-flow magnitude-frequency relationships for mountainous regions of Central and Northwest Europe
Debris flow ; Europe ; Human impact ; Land use ; Mountain ; Natural hazards ; Northwestern Europe ; Plant cover ; Precipitation ; Slope dynamics ; Statistics
From the viewpoint of hazard assessment the magnitude-frequency characteristics is an essential element of the debris-flow process. For this study, published data specifying both magnitude and frequency were used for the Alps, the Tatra Mountains
patterns and debris availability play a prominent part.
Geomorphic evolution of debris fans in the Du Toit's Kloof, Western Cape mountains
Two debris fans in Du Toit's Kloof are investigated by means of geomorphological mapping and relative-age dating (Schmidt hammer, lichen cover and weathering rinds) of their deposits. The data provide important new insights into footslope dynamics
Air temperature ; Climate ; Debriscover ; Digital elevation model ; Glacial ablation ; Glacial features ; Meltwater ; Moraine ; New Zealand ; Sandur ; South Island
To evaluate the effects of varying debris-cover and climate on ice-melt in a maritime mid-latitude setting, an 11-day ablation stake study was undertaken on ice-cored moraine at Fox Glacier. Ablation rates varied with enhancement of melt-rate under
thin debris-covers. Air temperature from nearby Franz Josef Glacier allowed for a simple degree-day approach to ablation calculations, with regression relationships indicating air temperature is the key climatic control on melt. Digital elevation models
produced from topographic surveys of the ice-cored moraine over the following months indicated that ablation rates progressively decreased over time, probably due to melt-out of englacial debris increasing debris-cover thickness. The morphology
into account the disturbance caused by the vegetation cover on the DEM accuracy is proposed. The results of volumetric budgets of the surveyed sediment source areas derived from the DoD analysis were compared with debris-flow volumes estimated from flow stage
Geomorphic changes caused by 3 debris-flow events in a small mountain catchment (Moscardo Torrent, Eastern Italian Alps) were investigated by means of multitemporal terrestrial laser scanning (TLS) surveys over 3 areas exposed to debris-flow
measurements at the instrumented channel reach, underlining advantages and limitations of TLS surveys over morphologically complex areas such as debris-flow catchments.
Topographic control of periglacial slope covers, Ślęża Massif, southwest Poland : a statistical approach
The slopes of Mt Ślęża, southwest Poland, are covered by debriscovers that consist of gabbro blocks. Six classes of slope covers have been distinguished based on the concentration of blocks. A map of slope covers has been digitized
Cet article analyse la structure sédimentaire et l'origine des coulées de débris proglaciaires sur le flanc nord du Popocatepetl, ainsi que leur relation avec l'éruption d'avril 1995. Les investigations ont montré que les coulées de débris ont pris
Sensitivity of frost weathering and aeolian deposition during genesis of Late Quaternary periglacial slope covers on calcareous rocks of a Muschelkalk landscape, eastern Thuringian Basin, Germany
weathering rates within the debris. The AA. assume that the deposition of loess sediments might be sensitive to both properties and patterns of debriscover and to the amount of pre-existing Braunlehm that resulted from limestone dissolution processes. Soil
The lithological and petrological properties of calcareous rock types are reflected by remarkably different structure, thickness and clast properties of frost shattered debris within the investigated Muschelkalk landscape as well as in chemical
moisture conditions and vegetation cover might have been as crucial factors for loess distribution as luff-/lee-effects of the regional wind system or karst surface morphology. Considering the ecological consequences implied by the structure
and heterogeneity of periglacial loose rock cover, limestone landscapes in general seem to be vulnerable to degradation processes.
This paper describes observations of rockfall activity in Hosozawa Cirque in the Japanese Alps, from 1984 to 1998. The period includes intensive observations of both rockfalls and rock temperatures for 3 years (1993-1995). Rock debris transported
onto snow surfaces was measured during seasonal thawing periods. Discussion is focused on the mechanism of rockfall generation and controls of the dimension of rockfall debris.