Abstract
Acoustic Doppler current profiles and water density profiles were measured over the 280 m deep continental slope of the Gulf of California to elucidate the bathymetric effect on zooplankton distribution. These measurements were combined with water velocity and density simulations from the Regional Ocean Model System with and without the influence of Coriolis acceleration. The data revealed an acceleration of the near-bottom flow as it moved toward increasing depths. This acceleration was produced by the adjustment of the isopycnals to bathymetry (hydraulic jump). Zooplankton patches moved downward at the continental slope and then upward, thus exhibiting wave patterns. Model outputs without the effect of Coriolis acceleration also suggested that vertical zooplankton concentration followed a wave pattern. However, when Coriolis acceleration was added to the momentum equation, the horizontal zooplankton distribution was enhanced, which reduced the vertical zooplankton concentration observed over irregular bathymetries. Coriolis acceleration was responsible for horizontal dispersal of up to 20% of the total zooplankton concentration located over the wave trough.
Highlights
An understanding of the stratified flow dynamics over irregular bathymetries is crucial for predicting flow patterns [1], lee wave generation [2], and their interactions with planktonic and organic matter concentration [3,4,5,6,7]
Acoustic Doppler current profiles and water density profiles were measured over the 280 m deep continental slope of the Gulf of California to elucidate the bathymetric effect on zooplankton distribution
When Coriolis acceleration was added to the momentum equation, the horizontal zooplankton distribution was enhanced, which reduced the vertical zooplankton concentration observed over irregular bathymetries
Summary
An understanding of the stratified flow dynamics over irregular bathymetries is crucial for predicting flow patterns [1], lee wave generation [2], and their interactions with planktonic and organic matter concentration [3,4,5,6,7]. Such interactions depend on the degree of stratification and on the strength of tidal forcing [8]. An understanding of current velocities and vertical water density variations induced by internal wave activity is crucial to describe near-surface concentration of planktonic organisms, nutrients, and detritus
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