East Sound 1998 field Season (June 16)
 

Fig. 5. Profiles of rates of dissipation of turbulent kinetic energy dissipation on 16 June 1998.  Gaps in the record occurred due to sampling by other investigators.	Fig. 6. Density contours (-) and contours of fluorescence (colors) in relative units for the same time period.  The microstructure profiler was on the same instrument package as the CTD and Flash Lamp Fluorometer.

 
Pronounced layering of both marine snow and fluorescence occurred during the morning and afternoon of 16 June (Fig 4, 6).  The wind came up in the afternoon increasing rates of turbulent kinetic energy dissipation (Fig. 5).  The depth of the mixing layer, as indicated by epsilon > 10^-8 m² s^-3 increased from 3 m at 1500 h to 8.5 m at 2230 h.  Except when solitons were present, epsilon in the water above the fluorescence maximum tended to have values less than 10^-9 m² s^-3; epsilon increased slightly at the top of the fluorescence maxima.  When the wind driven mixing reached the pycnocline, fluorescence values had increased in the upper mixing layer.  While the increase could be attributed to entrainment, we noted instead that a layer of warmer water had moved into the upper mixed layer and that currents had shifted from the southeast to the northwest. This water from elsewhere in the basin may have been the source of the increased fluorescence in the upper mixed layer. Fluorescence was not diminished in the pycnocline despite high shear, and at the end of our sampling period, we observed a layer of water with low fluorescence between the upper mixing layer and the pycnocline.  These observations indicate that wind mixing is not necessarily a one-dimensional process.  Instead, as water at different depths circulates in different directions, lateral intrusions induce or maintain distinct layers of fluorescence.
 
 

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last updated: October 28, 1999
Comments: brice@icess.ucsb.edu