Lisbeth Langhammer

Last Name

Langhammer

First Name

Lisbeth

ORCID

0000-0003-2168-6737

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Publications 1 - 8 of 8

Helicopter-borne ground-penetrating radar surveying of temperate Alpine glaciers
Langhammer, Lisbeth; Rabenstein, Lasse; Schmid, Lino; et al. (2018)
Ice thickness distribution of all Swiss glaciers based on extended ground-penetrating radar data and glaciological modeling
Grab, Melchior; Mattea, Enrico; Bauder, Andreas; et al. (2021)
Journal of Glaciology
Accurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package.
Determining the ice volume distribution of glaciers using helicopter-borneGPR and glaciological modeling
Grab, Melchior; Langhammer, Lisbeth; Bauder, Andreas; et al. (2019)
Geophysical Research Abstracts
A comprehensive analysis of Swiss Alpine glaciers using helicopter-borne ground-penetrating-radar
Rabenstein, Lasse; Maurer, Hansruedi; Bauder, Andreas; et al. (2014)
AGU Fall Meeting Abstracts
Glacier bed surveying with helicopter-borne dual-polarization ground-penetrating radar
Langhammer, Lisbeth; Rabenstein, Lasse; Schmid, Lino; et al. (2019)
Journal of Glaciology
Traditionally, helicopter-borne ground-penetrating radar (GPR) systems are operated with a single pair of bistatic dipole antennas to measure the thickness of glaciers. We demonstrate numerically that the directivity of the radiation pattern of single airborne dipoles do not correspond to an ideal full-space solution if the antennas are employed at typical flight heights. These directionality effects can degrade the quality of the subsurface images significantly, when the GPR antennas are orientated unfavorably. Since an adjustment of the antenna orientation is impractical during flight, we have developed a novel dual-polarization helicopter-borne GPR system consisting of two orthogonal pairs of commercial antennas in broadside configuration. To overcome the image quality deficits of the individual channels, we apply a pseudo-scalar approach in which we combine the data of both polarizations. Results of helicopter-borne GPR surveys on two alpine glaciers in Switzerland reveal more coherent bedrock reflections in the summed data compared with single dipole pair profiles. Generally, the dual-polarization setup is more suitable than a single antenna systems, because it is more versatile and less prone to directional effects caused by the placement of the dipole antennas in relation to undulating subsurface reflectors.
Glacier thickness estimations of alpine glaciers using data and modeling constraints
Langhammer, Lisbeth; Grab, Melchior; Bauder, Andreas; et al. (2019)
The Cryosphere
Advanced knowledge of the ice thickness distribution within glaciers is of fundamental importance for several purposes, such as water resource management and the study of the impact of climate change. Ice thicknesses can be modeled using ice surface features, but the resulting models can be prone to considerable uncertainties. Alternatively, it is possible to measure ice thicknesses, for example, with ground-penetrating radar (GPR). Such measurements are typically restricted to a few profiles, with which it is not possible to obtain spatially unaliased subsurface images. We developed the Glacier Thickness Estimation algorithm (GlaTE), which optimally combines modeling results and measured ice thicknesses in an inversion procedure to obtain overall thickness distributions. GlaTE offers the flexibility of being able to add any existing modeling algorithm, and any further constraints can be added in a straightforward manner. Furthermore, it accounts for the uncertainties associated with the individual constraints. Properties and benefits of GlaTE are demonstrated with three case studies performed on different types of alpine glaciers. In all three cases, subsurface models could be found that are consistent with glaciological modeling and GPR data constraints. Since acquiring GPR data on glaciers can be an expensive endeavor, we additionally employed elements of sequential optimized experimental design (SOED) for determining cost-optimized GPR survey layouts. The calculated cost–benefit curves indicate that a relatively large amount of data can be acquired before redundant information is collected with any additional profiles, and it becomes increasingly expensive to obtain further information.
Glacier inventory for ice volumes from ice penetrating radar and glaciological modeling
Grab, Melchior; Langhammer, Lisbeth; Hellmann, Sebastian; et al. (2019)
SCCER-SoE Science Report 2019
Helicopter-borne ground-penetrating radar surveying of temperate Alpine glaciers
Langhammer, Lisbeth (2018)

Publications 1 - 8 of 8

Lisbeth Langhammer

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