Geophysics - Research

We investigate climate-relevant Earth system problems including the stability of ice sheets and processes in the critical zone. Our tools include airborne and ground-based georadar, satellite- and ground-based radar interferometry, LiDAR, GNSS, and numerical modeling.  If you are interested to join this group on a BSc, MSc, Ph.D. or postdoctoral level, do not hesitate to contact us. We have succesfull experience in writing grant proposals, also within the German scholarschip scheme. We believe that we are helpful, supportive and friendly people.

 

Current Research Projects

PhD Project by Leah-Sophie Muhle: "Decoding the basal conditions of the Antarctic Ice Sheet by coupling physical forward models with machine learning"

In my PhD project, I will work on improving the radar simulator from my master thesis to simulate radar data for different thermal regimes, basal conditions (ice frozen to bed vs. thawed ice), and internal structures of the ice. Subsequently, I will use this data within a simulation-based inference framework to disentangle how the different conditions inscribe themselves in radar measurements and to derive temperature profiles and basal reflectivity from radar measurements. This would allow for a better characterization of the basal and thermal state of Antarctica’s ice sheet. My PhD project is funded by a scholarship of the Heinrich-Böll-Stiftung.

DFG project by Christian Wild: “SOS Antarctica – Slipping Or Shearing in the margins of outlet glaciers in Antarctica”

Ice shelves, which are extensions of ice sheets connected to land but floating on the ocean, encompass over 75% of the Antarctic perimeter and act as an ice wall that restrains grounded glaciers. Within ice shelves, shear zones typically occur from grounding zones where fast outlet glaciers encounter slower floating ice for the first time. Here we investigate mechanisms that determine the evolution and strength of shear zones. This includes the seeding of the shear-zones at glacier outlets near the grounding zone, the evolution of the shear-zone in the mid-shelf region, and the role of shear zones in crevasse formation and iceberg calving at the ice-shelf front. Understanding these processes is crucial for refining computer models that predict Antarctica's contribution to global sea-level rise.

DFG project by Alexandra Zuhr: "Is Dronning Maud Land mitigating sea level rise in the 21st century? QUantifying the Anthropogenically induced change in SNOw accumulation in East Antarctica (QUASNO) "

Within the Priority Programme SPP1158 from the German Reserach Foundation, the project QUASNO will investigate changes in snow accumulation and surface mass balance on the plateau of the DML during the last 500 years. It combines new airborne radar measurements, firn core data and statistical techniques to reconstruct spatio-temporal accumulation fields. The outcome will reduce the uncertainty on the role of climate change to global mean sea level rise in the 21st century.

BW Eliteprogramm project by Rebecca Schlegel: "BRISANT - Bodengebundene Radar-Interferometrie zum Schmelzen der Antarktis" - Radardevelopment to infer basal melt rates in Antarctica

In this project, we are developing a new phase-coherent radar system to measure basal melt rates along km-long profiles. Understanding basal melt rates over wide areas is essential for better predictions of the stability of ice shelves and thus sea level rise. Current radar systems do not allow measurements of basal melt along profiles. Therefore, we will develop a new radar system as part of a PhD Project in cooperation with the institute for microwave technology in Ulm. 

MSc project by Julius Konietzko: “Exploring the dynamics of Genzgletscher through terrestrial radar interferometry and comparative analyses”

Predictions of melting glaciers and polar ice sheets require a better understanding of the processes driving their deformation. Here we dive into glacier dynamics by studying Grenzgletscher, Switzerland, using advanced radar technology.

PhD Project by Anne Hermann: „Numerical Modelling of Water Flow Dynamics in Snow and Partially Frozen Soils to Quantify Groundwater Recharge“

My PhD research focuses on modelling groundwater recharge for snow-covered soils along hill slopes. Specifically, I investigate water flow dynamics in snow and the underlying soil layers on the Darcy scale. The goal of my project is to quantify lateral runoff driven by processes such as the formation of ice slabs and the development of capillary barriers. Quantifying groundwater recharge and lateral runoff in alpine regions is crucial for effective water management and to improve our understanding of flooding events triggered by snowmelt.

Research Methods

Ground-Penetrating Radar

Ground-Penetrating Radar uses electromagnetic waves for subsurface imaging across a number of disciplines. In Glaciology it is the number one tool for measuring ice thickness and internal stratigraphy. It is also used to derive key parameters such as ice temperature, ice anisotropy, basal properties (e.g. wet vs dry bed) or crevassing.

Terrestrial Radar Interferometry

Terrestrial Radar Interferometry is a comparatively novel technique using a coherent imaging radar system which scanns surfaces at high temporal and spatial resolution. Interferometric differencing of subsequent aquisitions enables interferometric change detection within the mm range. We use this instrument to detect temporal variations glacier flow. Other applications include geohazard applications, for example in mining, landslide detection/prediction or rockfall. 

Data Analysis and Numerical Modelling

Data analysis and signal processing is at the core of many of our projects. Methods applied include classical time series analysis (e.g., fourier analysis, filtering), statistical methods (e.g., principal component analysis) and various invesion schemes.

We use numerical and analytical models to interpret field data and to better understand ice-sheet dynamics. Tools we use are the finite element, full Stokes model Elmer/Ice together with various radar forward models (raytracing, exploding reflectors, matrix based models,..).

Rover Development

Automated rovers are ideally suited to carry geophysical instruments in hazardous areas (e.g., some parts of Antarctic) or to carry out measurements requiring repetitive sampling of profiles (e.g., inflitration experiments or groundwater monitoring). In collaboration with industry and university partners (here Polar Research Equipment) we aim to implement automated rovers as a standard tool for some geophysical monitoring techniques.

Seismics

Refraction seismics is an ideal tool for shallow sub-surface imaging, e.g., for detecting the depth to bedrock, the extent of the weathering front or identification of aquifer characteristics. On ice, seismics are use to characterice the ice-bed interface (e.g., soft vs. hard bed) or internal ice propeties such as the bulk ice crystal orientation.

LiDAR

Lidar is a tool for measuring 3D point clouds using a high-performance laser beam. We use the instrument in collaboration within the Earth System Dynamics Group (Prof. Ehlers) for change detection (e.g. rock fall) and characterization of exposed fault surfaces. Lidar has extensive applications in other industries such as autonomous driving, robotics, or anywhere else where 3D models are required.

Past Research Projects

BSc Project Sylvia Köppe: Temporal Evolution of Basal Terraces on Antarctic Ice Shelves

My BSc project focuses on basal terraces in the Antarctic which are topographic features found at the base of ice shelves. I am specifically looking at GPR measurements from 2021 and 2022 near the grounding line of Ekström Ice Shelf where basal terraces were detected. My aim is to reconstruct their 3D structure and investigate their changes in this one year interval.

BSc project by Jonas Weiß: "Determine the wave velocity via Simulation-Based-Inference of simulated radardata"

Ground-penetrating radar is a widely utilised method in a number of disciplines, including engineering, archaeology and glaciology. One challenge in analysing radar data is the lack of knowledge about the wave speed. In this study, we employ SBI to determine the wave velocity for a simple structured subsurface.

BSc project by Melissa Zahn: “Spatial variation and temporal change of the surface mass balance in Dronning Maud Land, East Antarctica”

Ice sheets are reacting to the current temperature changes. They are losing mass at the edges, which is contributing to global sea level rise. However, a warmer atmosphere can also hold and transport more water vapor, which can lead to an increase in snowfall, i.e. accumulation, and thus the surface mass balance, especially in East Antarctica. This project will focus on the investigation of accumulation patterns (spatially and temporally) around the German summer station Kohnen on the East Antarctic Plateau using Ground-penetrating radar (GPR) data to illustrate and analyze the near-surface structures and past accumulation rates.

BSc project by Elisa Fast: "Imaging of subglacial drumlins in Iceland using GPR"

The bed of glaciers can be studied using radar data. Here we map the bed of a glacier in iceland with a special focus to map drumlins, which are hills that forms under glaciers as a result of ice-sediment interactions. By analysing such data, we get a better understanding of the past and current glacier dynamics.

MSc Project by Anne Hermann: "Simulation-Based Inference of Surface Mass Balance from Ice Sheet Stratigraphy"

Ice Sheet models used e.g. to project sea level rise are forced by many parameters, some of which are often unknown. One of them is the net mass gain or loss of the ice sheet at the atmospheric boundary condition (surface mass balance). We use the internal layering of the ice sheet to reconstruct the surface mass balance the ice has experienced using a machine learning based method.

PhD project by Falk Oraschewski: "Determining the englacial stratigraphy and ice fabric anisotropy of glaciers and ice shelfs using radarinterferometry and -polarimetry"

Ice crystals are mechanically and dielectrically anisotropic, meaning that their deformation behaviour and capability to transmit electromagnetic waves have a directional dependence. These anisotropic properties transfer to the bulk behaviour of polycrystalline ice in glaciers, ice sheets and ice shelfs. Accordingly, the macroscale flow dynamics of these ice masses depend on the microscale distribution of the orientations of ice crystals (also called 'ice fabric') within them. Thanks to the dielectric anisotropy, ice fabric can be measured with polarimetric radar techniques. In particular, using phase-sensitive radar small differences in the directionally dependent propagation velocities can be observed, allowing to reconstruct the ice fabric. Similarly, the detection of the englacial stratigraphic structure can be improved by applying interferometric techniques to profiles acquired with phase-sensitive radar. This englacial structure again allows to decipher past ice deformation, which is potentially controlled by the ice fabric.

This project is funded by a doctoral scholarship of the German Academic Scholarship Foundation (Studienstiftung des deutschen Volkes).

BSc project by Leonie Neumann: "Validation of a Low-Cost Geoelectric Measurement Tool to Perform Shallow 4-Point Measurements"

This BSc project developed an open-source, self-built geoelectric measurement device suitable to perform vertical electrical soundings and profiling in resistivity mapping. The instrument design is low-cost but competes well with professional resistivity meters at moderate electrode spacings.

BSc project by Greta Flinsbach "Analysis of the Uppermost Layers in the Catchment Area of Ekström Ice Shelf, Derived by Ground Penetrating Radar Measurements"

In this BSc project, ground-penetrating radar data of kinematic waves near the grounding zone of Ekström ice shelf were processed and analyzed. Kinematic waves describe a complex stratigraphic structure caused by the interplay of ice flow and topography controlled spatially variable snow deposition. This structure was extracted to disentangle and better understand the underlying processes that lead to the formation of kinematic waves.

Projects in Summer 2021

In Summer 2021 a group of students has formed for research in the Lauswiesen. There we try to close the water budget for this well instrumented test site. How much of the rain is taken up by ground-water, how much by evapotranspiration and how much is lost by direct run-off? We investigate this with a number of tools such as ground-penetrating radars, seismics,  automatic weather stations and soil moisture sensors. On a good day we hope that all of these tools will eventually tell us a coherent story. If you want to join the Lauswiesen Project contact us or Dr. C. Leven.

Projects in Summer 2020

In 2020 we complemented research of the CAMPOS project with a seismic refraction survey (cf MSc M. Erb). The goal was to image through the critical zone and find at which depth we could identify the bedrock in the hillslopes.