Source regions of infragravity waves recorded at the bottom of the equatorial Atlantic Ocean, using OBS of the PI‐LAB experiment
Source regions of infragravity waves recorded at the bottom of the equatorial Atlantic Ocean, using OBS of the PI‐LAB experiment
Infragravity waves are generated along coasts, and some small fraction of their energy escapes to the open oceans and propagates with little attenuation. Due to the scarcity of deep-ocean observations of these waves, the mechanism and the extent of the infragravity waves energy leakage from the coasts remains poorly understood. Understanding the generation and pathways of infragravity wave energy is important among others for understanding the breakup of ice-shelves and the contamination of high-resolution satellite radar altimetry measurements of sea level. We examine data from 37 differential pressure gauges of Ocean Bottom Seismometers (OBS) near the equatorial mid-Atlantic ridge, deployed during the Passive Imaging of the Lithosphere-Asthenosphere Boundary (PI-LAB) experiment. We use the beamforming technique to investigate the incoming directions of infragravity waves. Next, we develop a graph-theory-based global back-projection method of noise cross-correlation function envelopes, which minimizes the effects of array geometry using an adaptive weighting scheme. This approach allows us to locate the sources of the infragravity energy. We assess our observations by comparing to a global model of infragravity wave heights. Our results reveal strong coherent energy from sources and/or reflected phases at the west coast of Africa and some sources from South America. These energy sources are in good agreement with the global infragravity wave model. In addition, we also observe infragravity waves arriving from North America during specific events that mostly occur during October–February 2016. Finally, we find indications of waves that propagate with little attenuation, long distances through sea ice, reflecting off Antarctica.
Africa, Antarctica, Atlantic Ocean, back-projection, beamforming, infragravity waves
Bogiatzis, P.
8fc5767f-51a2-4d3f-aab9-1ee9cfa9272d
Karamitrou, A.
25acd266-3030-4958-b5c5-72d4c6b74caf
Ward Neale, J.
adffc01c-a20f-43ea-a64f-3138a239b9ab
Harmon, N.
10d11a16-b8b0-4132-9354-652e72d8e830
Rychert, C. A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Srokosz, M.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
1 June 2020
Bogiatzis, P.
8fc5767f-51a2-4d3f-aab9-1ee9cfa9272d
Karamitrou, A.
25acd266-3030-4958-b5c5-72d4c6b74caf
Ward Neale, J.
adffc01c-a20f-43ea-a64f-3138a239b9ab
Harmon, N.
10d11a16-b8b0-4132-9354-652e72d8e830
Rychert, C. A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Srokosz, M.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Bogiatzis, P., Karamitrou, A., Ward Neale, J., Harmon, N., Rychert, C. A. and Srokosz, M.
(2020)
Source regions of infragravity waves recorded at the bottom of the equatorial Atlantic Ocean, using OBS of the PI‐LAB experiment.
Journal of Geophysical Research: Oceans, 125 (6), [e2019JC015430].
(doi:10.1029/2019JC015430).
Abstract
Infragravity waves are generated along coasts, and some small fraction of their energy escapes to the open oceans and propagates with little attenuation. Due to the scarcity of deep-ocean observations of these waves, the mechanism and the extent of the infragravity waves energy leakage from the coasts remains poorly understood. Understanding the generation and pathways of infragravity wave energy is important among others for understanding the breakup of ice-shelves and the contamination of high-resolution satellite radar altimetry measurements of sea level. We examine data from 37 differential pressure gauges of Ocean Bottom Seismometers (OBS) near the equatorial mid-Atlantic ridge, deployed during the Passive Imaging of the Lithosphere-Asthenosphere Boundary (PI-LAB) experiment. We use the beamforming technique to investigate the incoming directions of infragravity waves. Next, we develop a graph-theory-based global back-projection method of noise cross-correlation function envelopes, which minimizes the effects of array geometry using an adaptive weighting scheme. This approach allows us to locate the sources of the infragravity energy. We assess our observations by comparing to a global model of infragravity wave heights. Our results reveal strong coherent energy from sources and/or reflected phases at the west coast of Africa and some sources from South America. These energy sources are in good agreement with the global infragravity wave model. In addition, we also observe infragravity waves arriving from North America during specific events that mostly occur during October–February 2016. Finally, we find indications of waves that propagate with little attenuation, long distances through sea ice, reflecting off Antarctica.
Text
Source Regions of Infragravity Waves
- Accepted Manuscript
More information
Accepted/In Press date: 12 May 2020
e-pub ahead of print date: 19 May 2020
Published date: 1 June 2020
Additional Information:
Funding Information:
The authors would like to gratefully acknowledge the editor, Dr Kristopher B. Karnauskas, and three anonymous reviewers for their critical reviews that helped to improve this manuscript. The authors would also like to acknowledge funding from the Natural Environment Research Council (NE/M003507/1 and NE/K010654/1) and the European Research Council (GA 638665). The WAVEWATCH III infragravity wave height models, used in this study, are from the work of Ardhuin et al.?(2014) and downloaded from http://ftp://ftp.ifremer.fr/ifremer/ww3/HINDCAST/GLOBAL_IG, last accessed on October, 2019.
Publisher Copyright:
© 2020. The Authors.
Keywords:
Africa, Antarctica, Atlantic Ocean, back-projection, beamforming, infragravity waves
Identifiers
Local EPrints ID: 441196
URI: http://eprints.soton.ac.uk/id/eprint/441196
ISSN: 2169-9275
PURE UUID: 8fed795e-e264-4755-8b76-7d2509c992b6
Catalogue record
Date deposited: 04 Jun 2020 16:31
Last modified: 17 Mar 2024 04:00
Export record
Altmetrics
Contributors
Author:
P. Bogiatzis
Author:
A. Karamitrou
Author:
J. Ward Neale
Author:
M. Srokosz
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics