Impact of environmental forcing on the acoustic backscattering strength in the equatorial Pacific : diurnal, lunar, intraseasonal, and interannual variability

Marie-Hélène Radenac 1 P. E. Plimpton 2 Anne Lebourges Dhaussy 3 L. Commien 4 M. J. Mcphaden 2
1 OLVAC LEGOS
LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
2 PMEL - NOAA Pacific Marine Environmental Laboratory [Seattle]
3 ACAPPELLA - Hydro-acoustique appliquée à l'halieutique, à l'écologie et à l'éthologie aquatiques
4 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
Abstract : We analyzed several records of mean volume backscattering strength (S-v) derived from 150 kHz acoustic doppler current profilers (ADCPs) moored along the equator in upwelling mesotrophic conditions and in the warm pool oligotrophic ecosystem of the Pacific Ocean. The ADCPs allow for gathering long time-series of non-intrusive information about zooplankton and micronekton at the same spatial and temporal scales as physical observations. High S-v are found from the surface to the middle of the thermocline between dusk and dawn in the mesotrophic regime. Biological and physical influences modified this classical diel cycle. In oligotrophic conditions observed at 170 degrees W and 140 degrees W during El Nino years, a subsurface S-v maximum characterized nighttime S-v profiles. Variations of the thermocline depth correlated with variations of the base of the high S-v layer and the subsurface maximum closely tracked the thermocline depth from intraseasonal to interannual time-scales. A recurring deepening (20-60 m) of the high S-v layer was observed at a frequency close to the lunar cycle frequency. At 165 degrees E, high day-to-day variations prevailed and our results suggest the influence of moderately mesotrophic waters that would be advected from the western warm pool during westerly wind events. A review of the literature suggests that S-v variations may result from changes in biomass and species assemblages among which myctophids and euphausiids would be the most likely scatterers.
Keywords : Biological-physical interactions Equatorial Pacific Sound scattering Micronekton ADCP moorings
Document type :
Journal articles
Complete list of metadatas

Cited literature [44 references]  Display  Hide  Download
https://hal.ird.fr/ird-00544133
Contributor : Marie-Hélène Radenac <>
Submitted on : Tuesday, December 7, 2010 - 12:38:55 PM
Last modification on : Friday, October 11, 2019 - 8:23:16 PM
Long-term archiving on : Tuesday, March 8, 2011 - 4:15:28 AM

File

draft_ADCP_Pac_eq_accepte.pdf
Publisher files allowed on an open archive

Identifiers

Collections

IRD | INSU | OMP | OMP-LEGOS | OLVAC | UNIV-TLSE3

Citation

Marie-Hélène Radenac, P. E. Plimpton, Anne Lebourges Dhaussy, L. Commien, M. J. Mcphaden. Impact of environmental forcing on the acoustic backscattering strength in the equatorial Pacific : diurnal, lunar, intraseasonal, and interannual variability. Deep Sea Research Part I: Oceanographic Research Papers, Elsevier, 2010, 57 (10), pp.1314-1328. ⟨10.1016/j.dsr.2010.06.004⟩. ⟨ird-00544133⟩

Export

BibTeX TEI DC DCterms EndNote

Share

Metrics

Record views

431

Files downloads

293

Contact

support.ccsd.cnrs.fr
hal.support@ccsd.cnrs.fr
Logo CCSD