On the Use of Electromagnetics for Earth Imaging of the Polar Regions

0539443 - GFÚ 2021 RIV NL eng J - Journal Article
Hill, Graham J.
On the Use of Electromagnetics for Earth Imaging of the Polar Regions.
Surveys in Geophysics. Roč. 41, č. 1 (2020), s. 5-45. ISSN 0169-3298. E-ISSN 1573-0956
Institutional support: RVO:67985530
Keywords : electromagnetic methods * magnetotellurics * polar regions * Antarctica * Arctic * source field * instrumentation * tectonics * magmatism * glaciology
OECD category: Geology
Impact factor: 6.673, year: 2020
Method of publishing: Open access
https://link.springer.com/article/10.1007%2Fs10712-019-09570-8

The polar regions are host to fundamental unresolved challenges in Earth studies. The nature of these regions necessitates the use of geophysics to address these issues, with elec-tromagnetic and, in particular, magnetotelluric studies finding favour and being applied over a number of different scales. The unique geography and climatic conditions of the polar regions means collecting magnetotelluric data at high latitudes, which presents chal-lenges not typically encountered and may result in significant measurement errors. (1) The very high contact resistance between electrodes and the surficial snow and ice cover (com-monly MΩ) can interfere with the electric field measurement. This is overcome by using custom-designed amplifiers placed at the active electrodes to buffer their high impedance contacts. (2) The proximity to the geomagnetic poles requires verification of the fundamen-tal assumption in magnetotellurics that the magnetic source field is a vertically propagat-ing, horizontally polarised plane wave. Behaviour of the polar electro-jet must be assessed to identify increased activity (high energy periods) that create strong current systems and may generate non-planar contributions. (3) The generation of ‘blizstatic’, localised random electric fields caused by the spin drift of moving charged snow and ice particles that pro-duce significant noise in the electric fields during periods of strong winds. At wind speeds above ~ 10 m s−1, the effect of the distortion created by the moving snow is broad-band. Station occupation times need to be of sufficient length to ensure data are collected when wind speed is low. (4) Working on glaciated terrain introduces additional safety challenges, e.g., weather, crevasse hazards, etc. Inclusion of a mountaineer in the team, both during the site location planning and onsite operations, allows these hazards to be properly managed.
Permanent Link: http://hdl.handle.net/11104/0317188