Frequency-dependent noise sources in the North Atlantic Ocean

• Published in: Geochemistry, Geophysics, Geosystems
• Main Authors: Sergeant, Amandine, Stutzmann, Eléonore, Maggi, Alessia, Schimmel, Martin, Ardhuin, Fabrice, Obrebski, Mathias
• Other Authors: Institut de Physique du Globe de Paris (IPGP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Sismologie (IPGS) (IPGS-Sismologie), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Earth Sciences Jaume Almera, Consejo Superior de Investigaciones Científicas Madrid (CSIC), Laboratoire d'Océanographie Spatiale (LOS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: polarization; North Atlantic Ocean; secondary microseism; noise sources; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Arctic; North Atlantic; Sea ice
• Online Access: https://hal.archives-ouvertes.fr/hal-00925917; https://hal.archives-ouvertes.fr/hal-00925917/document; https://hal.archives-ouvertes.fr/hal-00925917/file/Sergeant_et_al-2013-Geochemistry,_Geophysics,_Geosystems.pdf; https://doi.org/10.1002/2013GC004905

International audience Secondary microseisms are the most energetic waves in the noise spectra between 3 and 10 s. They are generated by ocean wave interactions and are predominantly Rayleigh waves. We study the associated noise sources in the North Atlantic Ocean by coupling noise polarization analysis and source mapping using an ocean wave model that takes into account coastal reflections. From the Rayleigh wave polarization analysis, we retrieve the back azimuth to the noise sources in the time-frequency domain. Noise source modeling enables us to locate the associated generation areas at different times and frequencies. We analyze the distribution of secondary microseism sources in the North Atlantic Ocean using 20 broadband stations located in the Arctic and around the ocean. To model the noise sources we adjust empirically the ocean wave coastal reflection coefficient as a function of frequency. We find that coastal reflections must be taken into account for accurately modeling 7–10 s noise sources. These reflections can be neglected in the noise modeling for periods shorter than 7 s. We find a strong variability of back azimuths and source locations as a function of frequency. This variability is largely related to the local bathymetry. One direct cause of the time-dependent and frequency-dependent noise sources is the presence of sea-ice that affects the amplitude and polarization of microseisms at stations in the Arctic only at periods shorter than 4 s.