Abstract
Abstract. Icequakes are the result of processes occurring within the ice mass or between the ice and its environment. Studying icequakes provides a unique view on ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental or climate changes are reflected in icequakes. Counting and characterizing icequakes is thus essential to monitor them. Most of the icequakes recorded by the seismic station at the Belgian Princess Elisabeth Antarctica Station (PE) have small amplitudes corresponding to maximal displacements of a few nanometres. Their detection threshold is highly variable because of the rapid and strong changes in the local seismic noise level. Therefore, we evaluated the influence of katabatic winds on the noise measured by the well-protected PE surface seismometer. Our purpose is to identify whether the lack of icequake detection during some periods could be associated with variations in the processes generating them or simply with a stronger seismic noise linked to stronger wind conditions. We observed that the wind mainly influences seismic noise at frequencies greater than 1 Hz. The seismic noise power exhibits a bilinear correlation with the wind velocity, with two different slopes at a wind velocity lower and greater than 6 m s−1 and with, for example at a period of 0.26 s, a respective variation of 0.4 dB (m −1 s) and 1.4 dB (m −1 s). These results allowed a synthetic frequency and wind-speed-dependent noise model to be presented that explains the behaviour of the wind-induced seismic noise at PE, which shows that seismic noise amplitude increases exponentially with increasing wind speed. This model enables us to study the influence of the wind on the original seismic dataset, which improves the observation of cryoseismic activity near the PE station.
Highlights
The study of icequakes provides insights into the different processes linked to ice dynamics
Cryoseismology has not been studied thoroughly in all regions of Antarctica, but thanks to the improvement of instrumentation and the increasing number of seismic stations in Antarctica, numerous studies linking seismology to glaciology have been published in the last decade: from linking the microseismicity induced by tides in the grounding line of East Antarctica (Barruol et al, 2013), focusing on tremors from stick-slip motions in the Whillans ice stream (Winberry et al, 2013), studying specific cryoseismic events observed at Ekström Ice Shelf, Antarctica (Hammer et al, 2015), to observing thermally induced icequakes and their origins on blue ice in East Antarctica (Lombardi et al, 2019)
The wind speed used in this study is the 1 h average of the maximum wind speed recorded by the automated weather station (AWS) every 10 min
Summary
The study of icequakes provides insights into the different processes linked to ice dynamics. Cryoseismic catalogues and seismic observations can be correlated with numerical models of eastern Antarctic ice dynamics to constrain subglacial properties of a specific area (Lipovsky and Dunham, 2015; Pattyn, 2010; Smith, 1997, 2006) These icequakes mostly have a very low seismic amplitude (few nanometres of displacement) but can still be detected owing to the very low seismic noise observed in Antarctica. The region is subjected to rough meteorological conditions, composed of katabatic winds with velocities sometimes higher than 25 m s−1 (Pattyn et al, 2010) Such highvelocity winds have been known to affect the seismic data (Johnson et al, 2019; Lott et al, 2017) because the kinetic energy in the wind is converted to mechanical energy on reaching the instrument enclosure, contributing noise to the seismic record (Walker and Hedlin, 2010). As reported in Johnson et al (2019) and Lepore et al (2016), by sorting seismic data
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