Fish Effects on Ocean Current Observations in the Cariaco Basin

Jyotika I. Virmani, Robert H. Weisberg

Research output: Contribution to journalArticlepeer-review

Abstract

<p> Multiple years of moored current meter observations from the Cariaco Basin show low&hyphen;frequency variations along with near&hyphen;inertial waves and further imply the persistent diurnal movement of fish species known to populate the basin. In agreement with short&hyphen;term observations from 1979, the more recent observations with acoustic Doppler current profilers provide evidence of the multidecadal presence and behavior of these species. An unwanted corollary, however, is a bias in both the vertical and horizontal components of velocity due to the fish movements. Removal of this fish bias results in large data loss (approximately 72%); however, an interpolated, non&hyphen;biased data set is developed with depth&hyphen;averaged horizontal velocities comparable to the observations, demonstrating successful elimination of the bias. Further comparisons show that the interpolated data result in minimal variance density loss at low frequencies and a reduction of variance density at high frequencies such that the interpolated data in the internal wave range more closely fit the Garrett&hyphen;Munk spectrum. The net result is a data set appropriate for further analysis. A mean downward velocity of 0.18 cm s <sup> &minus;1 </sup> is a reflection of a biogenic particle flux and some residual fish contamination. The mean settling speed of particles in the Cariaco Basin is calculated, via Stokes law, to be smaller than 0.04 cm s <sup> &minus;1 </sup> . Velocity observations from acoustic current meters at depths greater than 400 m are impacted by the water clarity; therefore alternate methods should be used to make velocity measurements at depth.</p>
Original languageAmerican English
JournalJournal of Geophysical Research - Oceans
Volume114
DOIs
StatePublished - Mar 31 2009

Keywords

  • current meter observations
  • diurnal fish migration
  • Cariaco Basin

Disciplines

  • Life Sciences
  • Marine Biology

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