Swell-Associated Microseismicity Near the Edge of the Ross Ice Shelf

Ocean swell incessantly perturbs Antarctic ice shelves throughout the austral summer when periods of low sea ice reduce attenuation. The swell generated by low-pressure systems, both from the Southern Ocean and from as far away as the northern hemisphere, agitates ice shelves with an order of 106 strain cycles per year at periods between about 8 and 30 s. This process creates distinct seismic signatures in data collected by continuously operating seismographs atop the Ross Ice Shelf (RIS), including large numbers of stochastically phase-synchronized micro-icequakes near the ice front that produce prominent swell-fundamental harmonics in sufficiently long-time-widow spectra via a Dirac comb process. We correlate swell-triggered seismicity observations with ocean state parameters to further investigate the controlling mechanism(s) of these signals, which have been hypothesized (Aster et al., 2021) to arise from repeated and progressive swell-induced crevasse fracture occurring within a few kilometers of the ice shelf front. Ocean state parameters such as swell arrival azimuth, dispersion, period, intensity, and duration will be quantified for prominent storms (Hell et al., 2019, 2020) and interpreted in the context of the complete dataset from the 34-station 2015-2017 RIS/DRIS broadband seismographic deployment (Bromirski et al., 2015). Better determination of mechanisms and ice front conditions associated with these seismic events will be interpreted to enhance understanding of near-front ice shelf seismogenic processes.