Mapping glacier internal structure and subglacial flow from seismic noise interferometry

Laboratoire(s) de rattachement : IGE

Encadrant : Florent Gimbert

Co-encadrant : Philippe Roux - ISTerre

Niveau de formation & pré-requis : The candidate should have a solid background in geophysics, and in particular in signal processing. Being familiar with Matlab and/or Python is recommended. Solid kills in solid and fluid mechanics as well as interest in glacier physics are also strongly valuable.

Mots-clés : seismology, glacier dynamics, signal processing, dense array

Place : Institut des Géosciences pour l’Environnement or Institut des Sciences de la Terre - Université Grenoble Alpes – France (to be decided)

Salary : classical internship salary (554€/month)

Supervisors : Florent Gimbert (florent.gimbert@univ-grenoble-alpes.fr) and Philippe Roux (philippe.roux@univ-grenoble-alpes.fr).

Perspective after the internship : possible follow-up for a Ph.D. in the context of the ANR SAUSSURE project (funding acquired).

Abstract

Glacier dynamics governs the advection of ice towards warmer areas with faster melt, and thus exerts key control on glacier mass loss and associated sea level rise under a warming climate. Glacier dynamics is largely set by the internal glacier structure (thickness, bedrock topography, internal ice heterogeneity/anisotropy), as well as by sliding at the ice-bedrock interface, which is itself highly modulated by subglacial hydrology. All of these aspects and processes, however, remain poorly known due to lacking observations. It is thus pressing to develop innovative instrumental techniques in order to overcome these observational lacks. The aim of the RESOLVE project, in which takes place the presently proposed research project, is to do so using seismology.

The internship will consist in inverting glacier structure as well as mapping the wide variety of englacial and subglacial seismic sources (fracturing, basal stick slip and subglacial hydrology) using advanced signal processing applied to seismic records from a dense (100 sensors) array that operated on the Argentière Glacier (Mont Blanc, France) during May 2018. Signal processing will involve (i) building catalogues of noise cross-correlation functions appropriate to retrieve internal glacier structure on one hand and/or internal glacier seismic sources on the other hand ; (ii) conducting tomography and/or beamforming analysis to the different catalogues in order to retrieve glacier structure and/or internal glacier source locations. This seismic analysis will ultimately be put into a glaciological context by comparing results with independent observations of glacier geometry obtained from ground penetrating radar, glacier speed obtained from GPS and radar interferometry analysis, subglacial hydrology measured from in-situ pressure sensors and outlet stream gauging, etc…

This internship takes place prior to the newly funded ANR project SAUSSURE, which aims at a better understanding of glacier sliding by coupling experimental, theoretical and modeling approaches on the Argentière Glacier. In this framework, a PhD will start in October 2019.