Seasonality of microseismic signal in Antarctica, and its link to sea ice

Analyses of seismic spectra ubiquitously show broad energetic peaks over a 1-20 s period band, primarily composed of Rayleigh waves, and commonly referred to as primary (10-20 s) and secondary (1-9 s) microseisms. These microseisms are due to ocean gravity wave interactions that cause pressure oscillations which in turn generate seismic waves at the ocean floor. In Antarctica, the microseismic signal is weaker in winter than in summer due to the presence of sea ice, which prevents incoming swells from reaching the coast, thereby impeding both direct coupling at the coast (responsible for primary microseisms) and swell reflection (responsible for secondary microseisms). We present the result of a systematic study of microseism spectra for seismic stations in coastal Antarctica. We show that, to first order, microseism power is anti-correlated with ice presence, which invites the possibility of recovering past trends in average ice-duration. To second order, the link between microseism power and sea ice is highly dependent on local conditions. Therefore, the coast-masking effect of sea ice gives insights into the detailed mechanisms of microseism generation.