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Impacts of the cryosphere and atmosphere on observed microseisms generated in the Southern Ocean

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Turner, RJ ORCID: 0000-0002-4376-5455, Gal, M ORCID: 0000-0001-6767-8017, Hemer, MA and Reading, AM ORCID: 0000-0002-9316-7605 2020 , 'Impacts of the cryosphere and atmosphere on observed microseisms generated in the Southern Ocean' , Journal of Geophysical Research: Earth Surface, vol. 125, no. 2 , pp. 1-16 , doi: 10.1029/2019JF005354.

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Abstract

The Southern Ocean (in the region 60-180° E) south of the Indian Ocean, Australia, and the West Pacific is noted for the frequent occurrence and severity of its storms. These storms give rise to high-amplitude secondary microseisms from sources, including the deep ocean regions, and primary microseisms where the swells impinge on submarine topographic features. A better understanding of the varying microseism wavefield enables improvements to seismic imaging and development of proxy observables to complement sparse in situ wave observations and hindcast models of the global ocean wave climate. We analyze 12-26 years of seismic data from 11 seismic stations either on the East Antarctic coast or sited in the Indian Ocean, Australia, and New Zealand. The power spectral density of the seismic wavefield is calculated to explore how the time-changing microseism intensity varies with (i) sea ice coverage surrounding Antarctica and (ii) the Southern Annular Mode (SAM) climate index. Variations in sea ice extent are found to be the dominant control on the microseism intensity at Antarctic stations, which exhibit a seasonal pattern phase-shifted by 4-5 months compared to stations in other continents. Peaks in extremal intensity at East Antarctic stations occur in March-April, with the highest peaks for secondary microseisms occurring during negative SAM events. This relationship between microseism intensity and the SAM index is opposite to that observed on the Antarctic Peninsula. This work informs the complexity of microseism amplitudes in the Southern Hemisphere and assists ongoing interdisciplinary investigations of interannual variability and long-term trends.

Item Type: Article
Authors/Creators:Turner, RJ and Gal, M and Hemer, MA and Reading, AM
Keywords: microseisms, southern ocean, sea ice, southern annular mode (SAM)
Journal or Publication Title: Journal of Geophysical Research: Earth Surface
Publisher: Wiley-Blackwell Publishing Ltd
ISSN: 2169-9003
DOI / ID Number: 10.1029/2019JF005354
Copyright Information:

Copyright 2020 American Geophysical Union

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