Continuous simulation of discharge has become a standard tool for water management in high mounta... more Continuous simulation of discharge has become a standard tool for water management in high mountainous catchments and namely for the prediction of climate and land use change impacts. These precipitation-runoff models are generally calibrated based on historic discharge measurements. However, in glacierized catchments, closing the water balance is a difficult task since on one hand, observed meteorological data is sparse
JSTさきがけ研究集会 環境問題における数理の可能性. 平成20年6月11日~平成20年6月13日. 札幌市 The numerical simulation of the motion of ... more JSTさきがけ研究集会 環境問題における数理の可能性. 平成20年6月11日~平成20年6月13日. 札幌市 The numerical simulation of the motion of Rhone's glacier in the Swiss Alps is performed from 1874 to 2007, and then from 2007 to 2100. Given the shape of the glacier, the velocity of ice u is obtained by solving a 3D nonlinear Stokes problem. Then, the shape of the glacier is updated by computing the volume fraction of ice ϕ, which satisfies the transport equation ∂ϕ/∂t +u · ∇ϕ = bδΓA. Here bδΓA is a source term acting only on the ice-air interface ΓA which accounts for the accumulation or ablation of ice due to snow falls or melting. A decoupling algorithm allows the two above problems to be solved using different numerical techniques. The nonlinear Stokes problem is solved on a fixed, unstructured finite element mesh made of tetrahedrons. The transport equation is solved using a fixed, structured grid made of smaller cells. The numerical simulation is performed between 1874 and 2007. Then, a median climatic scenario is co...
The accumulation area of alpine glaciers contains a record of glacier mass balance in the past. B... more The accumulation area of alpine glaciers contains a record of glacier mass balance in the past. By measuring thickness and density of annual firn layers, past accumulation rates can be retrieved. We discuss such measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using several in-situ firn cores that are analysed with respect to density and thickness of the annual firn layers. Ground-penetrating radar (GPR) has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Conversion to depth or water equivalent requires the radio-wave velocity that is obtained from the in-situ density-depth profiles. The depths of reflectors in the helicopter-borne GPR profiles are in line with the findings from the firn cores. A distributed data set of past accumulation rates can thus be obtained by t...
The ice-albedo feedback plays a crucial role in various glacial processes, but especially inf lue... more The ice-albedo feedback plays a crucial role in various glacial processes, but especially inf luences glacier ablation. Furthermore, glacier surface albedo depends in a complicated way on many factors, such as cryoconite concentration, impurities due to mineral dust and organic matter or ice surface morphology, and is therefore difficult to model or para-meterize. Nevertheless, albedo is one of the most important variables in the energy balance of snow and ice and glacier mass balance modelling, and hence is usually strongly simplified. In the last two decades, several studies focused on glacier surface albedo using in-situ automatic weather stations (e.g. Oerlemans and Knap, 1998; Bühlmann, 2011) or satellite images (e.g. Klok et al., 2003; Paul et al., 2005). Nevertheless, still fairly little is known about the state, changes and impact of glacier surface albedo in the Swiss Alps, although there are obvious changes and variations in glacier surface characteristics on most alpine g...
End-of-winter snow distribution is the key factor for the winter mass balance of alpine glaciers ... more End-of-winter snow distribution is the key factor for the winter mass balance of alpine glaciers and is thus fundamental for understanding and modelling glacier changes. Measuring the winter mass balance using the direct glaciological method provides point measurements only. A better understanding of processes controlling deposition and redistribution of snow, however, requires spatially distributed information on snow depth and its variability. In this study we present simultaneous measurements from 2010 using not only the glaciological method but ground penetrating radar (GPR) and Light detection and ranging (LiDAR) digital elevation models (DEM). Our study site is Findelengletscher, Valais, Switzerland, a large alpine valley glacier (13.4 km 2). The glaciological survey provides snow depth data from 463 soundings and density measurements at 13 snow pits across the glacier (Figure 1). Spatially distributed snow depth and snow water equivalent are gained through extrapolation in th...
Continuous simulation of discharge has become a standard tool for water management in high mounta... more Continuous simulation of discharge has become a standard tool for water management in high mountainous catchments and namely for the prediction of climate and land use change impacts. These precipitation-runoff models are generally calibrated based on historic discharge measurements. However, in glacierized catchments, closing the water balance is a difficult task since on one hand, observed meteorological data is sparse
JSTさきがけ研究集会 環境問題における数理の可能性. 平成20年6月11日~平成20年6月13日. 札幌市 The numerical simulation of the motion of ... more JSTさきがけ研究集会 環境問題における数理の可能性. 平成20年6月11日~平成20年6月13日. 札幌市 The numerical simulation of the motion of Rhone's glacier in the Swiss Alps is performed from 1874 to 2007, and then from 2007 to 2100. Given the shape of the glacier, the velocity of ice u is obtained by solving a 3D nonlinear Stokes problem. Then, the shape of the glacier is updated by computing the volume fraction of ice ϕ, which satisfies the transport equation ∂ϕ/∂t +u · ∇ϕ = bδΓA. Here bδΓA is a source term acting only on the ice-air interface ΓA which accounts for the accumulation or ablation of ice due to snow falls or melting. A decoupling algorithm allows the two above problems to be solved using different numerical techniques. The nonlinear Stokes problem is solved on a fixed, unstructured finite element mesh made of tetrahedrons. The transport equation is solved using a fixed, structured grid made of smaller cells. The numerical simulation is performed between 1874 and 2007. Then, a median climatic scenario is co...
The accumulation area of alpine glaciers contains a record of glacier mass balance in the past. B... more The accumulation area of alpine glaciers contains a record of glacier mass balance in the past. By measuring thickness and density of annual firn layers, past accumulation rates can be retrieved. We discuss such measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using several in-situ firn cores that are analysed with respect to density and thickness of the annual firn layers. Ground-penetrating radar (GPR) has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Conversion to depth or water equivalent requires the radio-wave velocity that is obtained from the in-situ density-depth profiles. The depths of reflectors in the helicopter-borne GPR profiles are in line with the findings from the firn cores. A distributed data set of past accumulation rates can thus be obtained by t...
The ice-albedo feedback plays a crucial role in various glacial processes, but especially inf lue... more The ice-albedo feedback plays a crucial role in various glacial processes, but especially inf luences glacier ablation. Furthermore, glacier surface albedo depends in a complicated way on many factors, such as cryoconite concentration, impurities due to mineral dust and organic matter or ice surface morphology, and is therefore difficult to model or para-meterize. Nevertheless, albedo is one of the most important variables in the energy balance of snow and ice and glacier mass balance modelling, and hence is usually strongly simplified. In the last two decades, several studies focused on glacier surface albedo using in-situ automatic weather stations (e.g. Oerlemans and Knap, 1998; Bühlmann, 2011) or satellite images (e.g. Klok et al., 2003; Paul et al., 2005). Nevertheless, still fairly little is known about the state, changes and impact of glacier surface albedo in the Swiss Alps, although there are obvious changes and variations in glacier surface characteristics on most alpine g...
End-of-winter snow distribution is the key factor for the winter mass balance of alpine glaciers ... more End-of-winter snow distribution is the key factor for the winter mass balance of alpine glaciers and is thus fundamental for understanding and modelling glacier changes. Measuring the winter mass balance using the direct glaciological method provides point measurements only. A better understanding of processes controlling deposition and redistribution of snow, however, requires spatially distributed information on snow depth and its variability. In this study we present simultaneous measurements from 2010 using not only the glaciological method but ground penetrating radar (GPR) and Light detection and ranging (LiDAR) digital elevation models (DEM). Our study site is Findelengletscher, Valais, Switzerland, a large alpine valley glacier (13.4 km 2). The glaciological survey provides snow depth data from 463 soundings and density measurements at 13 snow pits across the glacier (Figure 1). Spatially distributed snow depth and snow water equivalent are gained through extrapolation in th...
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