Using Seismic Noise Generated by Ocean Waves to Monitor Seasonal and Secular Changes in Antarctic Sea Ice

Abstract:

The Earth’s background seismic noise between ~1-30 seconds period is commonly dominated by microseisms that arise when oceanic wave energy and swell are converted to ground displacement as the waves crash and interact with the continental shelf. Peak power in the microseism bands at high-latitude stations typically coincides with large-scale extratropical cyclonic winter storm activity. However, due to the seasonal formation of sea ice around the continental shelves of polar regions, oceanic waves are impeded from efficiently exciting seismic energy, and annual peak microseism power thus occurs prior to the midwinter storm peak. We utilize recently collected seismic data from across the continent to show that power in three distinct microseism bands is found to be strongly anti-correlated with sea ice extent, with the shorter period signals being exceptionally sensitive to local conditions. Particular focus is given to the Antarctic Peninsula, the strongest source of microseism energy on the continent, where we note a significant increase in primary microseism power attributable to near coastal sources from 1993-2012. This increase correlates with regional sea ice loss driven by large-scale wind changes associated with strengthening of the Southern Annular Mode. Additionally, we use microseism analysis to explore changes in sea ice strength and extent relative to wave state and storminess in the Southern Oceans. Investigation of microseism seasonality, power, and decadal-scale trends in the Antarctic shows promise as a spatially integrated tool for monitoring and interpreting such sea ice strength and extent metrics through time.