Fish Effects on Ocean Current Observations in the Cariaco Basin
Digital Object Identifier (DOI)
Multiple years of moored current meter observations from the Cariaco Basin show low-frequency variations along with near-inertial waves and further imply the persistent diurnal movement of fish species known to populate the basin. In agreement with short-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-biased data set is developed with depth-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-Munk spectrum. The net result is a data set appropriate for further analysis. A mean downward velocity of 0.18 cm s(-1) 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(-1). 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.
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Citation / Publisher Attribution
Journal of Geophysical Research - Oceans, v. 114, article C03028.
Scholar Commons Citation
Virmani, Jyotika I. and Weisberg, Robert H., "Fish Effects on Ocean Current Observations in the Cariaco Basin" (2009). Marine Science Faculty Publications. 138.