Impacts of the Cryosphere and Atmosphere on Observed Microseisms Generated in the Southern Ocean
Authors:Turner, Ross J. Gal, Martin Hemer, Mark A. Reading, Anya M.
Volume:125
Published:2020
Document Type:Article
Abstract:The Southern Ocean (in the region 60-180 degrees 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.
Author Information
Corresponding Author:Turner, RJ (通讯作者)，Univ Tasmania, Sch Nat Sci, Hobart, Tas, Australia.;Turner, RJ (通讯作者)，Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia.
Reprint Address:Turner, RJ (通讯作者)，Univ Tasmania, Sch Nat Sci, Hobart, Tas, Australia.;Turner, RJ (通讯作者)，Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia.
Addresses:[Turner, Ross J.; Gal, Martin; Reading, Anya M.] Univ Tasmania, Sch Nat Sci, Hobart, Tas, Australia; [Turner, Ross J.; Reading, Anya M.] Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia; [Gal, Martin] Inst Mine Seismol, Huntingfield, Tas, Australia; [Hemer, Mark A.] CSIRO Oceans & Atmosphere Flagship, Hobart, Tas, Australia
E-mail Addresses:turner.rj@icloud.com