Project I11: Discrimination of Subglacial Flood Types based on seismological and remote sensing data

Timescale: Oct. 2021 – Sept. 2024

Supervisors:

Prof. Eva Eibl, University of Potsdam

Dr. Sigrid Rössner, GFZ Potsdam

Description

Meltwater, rainwater and geothermal fluids accumulate in subglacial or glacier-dammed lakes and drain in hazardous floods, e.g., in Iceland, the Alps, Greenland and the Andes. These floods are recognized as the most common largely distributed hazard to life, property and economy, costing billions of dollars every year. Early warning of these floods is locally achieved using hydrological instruments in the affected glacial rivers that can however only detect a flood that has already progressed from beneath the ice into the river. Early-warning can be improved by using GPS instruments that are deployed on the ice surface on top of some of the lakes, but their maintenance over the years is challenging (Eibl et al., in review).

The project I11 focuses on seismic signals generated during the propagation of subglacial floods that can be recorded from a safe distance outside the glacier. We will process and interpret recordings from seismic arrays and rotational sensors jointly with the observations made by hydrological and GPS data. Pre-existing data from Greenland and Iceland can be used as a starting point. Further datasets will be collected in the European Alps and maybe in the Himalayas in order to address the following objectives:

1. What are the differences and similarities during floods along different flood paths with respect to flood propagation speed, peak discharge and strength of the seismic signal? Determining the finger-print of floods can help to detect them as early as possible and enhance short-term flood mitigation and long-term flood risk management.
2. Can we detect the trigger of a flood seismically? Floods are triggered by the failure of a seal. We will assess whether this failure is silent or can be detected in seismic data.
3. How do floods propagate? Currently two models are discussed: (i) The flood drains through channels that increase their size through melting. (ii) The flood is preceded by a pressure wave and lifts a wide region of the ice while water flows as a sheet between the ice and bedrock.

We expect to be able to track most subglacial floods with seismic instruments even if they propagate beneath the glacier. We will characterise the spatial and temporal evolution of these floods using seismic data in combination with datasets from other disciplines. This will help us to understand the mechanisms that trigger/ drive a flood and will improve the prediction methods, modelling and forecasting techniques.

Dedicated Regional Cluster: Central Europe / European Alps and Himalayas

Related PhD-projects: I4 (first cohort, Georg Veh) and Q8 (second cohort, Melanie Fischer): the project is linked to I4 and Q8 that were devoted to the detection, frequency, and magnitude of glacial outburst floods (GLOFs) in the Himalayas.

Responsibilities: The PhD-project “Discrimination of Subglacial Flood Types based on Seismological and Remote Sensing Data” aims at defining and differentiating the fingerprints of subglacial floods using a combination of seismological as well as remote sensing tools and observations. The project will start with a dataset of the flood in September-October 2015 in Iceland to quantify the links between the different methods and assess the fingerprint of this event. We will then compare this to other subglacially propagating floods mainly in Iceland from the Skaftá cauldrons and Grímsvötn caldera lake, and in Switzerland at Gornersee and Plaine Morte glaciers. We will assess the link between flood trigger, flood mechanism, tremor amplitude, flood discharge and the possible pressure wave at the beginning of a flood. Methods for this project will involve analyses of seismological data, remote sensing data as well as modelling of lake outburst and flood propagation.

Requirements: We are seeking applications from highly motivated individuals with a strong background in seismology and physics with an interest in remote sensing and interdisciplinary data analysis. Fluency in the English language (speaking and writing) as well as the willingness to work in an interdisciplinary team are essential. Experience with seismological software packages, processing of seismological datasets and remote sensing data or modelling is desirable. We expect a solid background in mathematics, physics, programming skills (e. g. Python) and interest in natural hazards such as subglacial floods. A basic knowledge of glaciology or seismic tremor will be of advantage for this post.