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Marine Geophysical Research

, Volume 40, Issue 4, pp 515–523 | Cite as

Monitoring the deep western boundary current in the western North Pacific by echo intensity measured with lowered acoustic Doppler current profiler

  • Kanae Komaki
  • Akira NaganoEmail author
Original Research Paper
  • 138 Downloads

Abstract

Oxidation of iron and manganese ions is predominant in the oxygen-rich deep western boundary current (DWBC) within the Pacific Ocean. By the faster removal of particulate iron hydroxide and manganese oxide, densities of the particulate matters are considered to be lower in the DWBC than the interior region. To detect the density variation of suspended particles between the DWBC and interior regions, we analyzed echo intensity (EI) measured in the western North Pacific by hydrographic casts with a 300 kHz lowered acoustic Doppler current profiler (LADCP) in a whole water column. At depths greater than 3000 m (~ 3000 dbar), EI is almost uniformly low between 12°N and 30°N but peaks sharply from 30°N to 35°N to a maximum north of 35°N. EI is found to be anomalously low in the DWBC compared to the background distribution. The DWBC pathways are identifiable by the low EI and high dissolved oxygen concentration. EI data by LADCPs and other acoustic instruments may be used to observe the temporal variations of the DWBC pathways.

Keywords

LADCP Echo intensity North Pacific Deep circulation Lower circumpolar deep water 

Notes

Acknowledgements

The authors are grateful to the captain and crew of the R/V Hakuho-maru and to the scientists and technical staff who participated in the cruises of KH-99-1 and KH-04-4. A part of this study was performed based on the study when the first author was supervised by late Prof. M. Kawabe (AORI, University of Tokyo). The authors acknowledge Profs. S. Fujio and D. Yanagimoto (AORI, University of Tokyo) for their helpful comments and C. Garcia for editing. This work was partly supported by Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for Scientific Research (15H04228, 17K05660).

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Copyright information

© Springer Science+Business Media B.V., part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Marine and Environmental AffairsUniversity of WashingtonSeattleUSA
  2. 2.Research and Development Center for Global ChangeJapan Agency for Marine-Earth Science and Technology (JAMSTEC)KanagawaJapan

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