should be easily observable over about 5 kilometers, while the smaller isopycnal slopes of the 

 summer thermocline, (1 cm/km), will require ten or more kilometer spacing. Vertical spacing 

 of the SEACATS should be no more than 5 meters within the thermocline, while sub-thermocline 

 and winter spacing could probably be about 10 meters, based upon the low vertical modal 

 structure observed during SEEP-II and the thickness of the summer thermocline. ADCPs will be 

 needed to provide adequate precision and vertical resolution for measuring currents. 



2. Biological patchiness is not well defined on the shelf. There are conflicting ideas about 

 whether there are dominant scales of patchiness, that is, peaks in the wavenumber spectra, or 

 whether the spectra is "red". Horizontal spectra of fluorescence from an along-isobath (40 m) 

 TOYO section from the MAY 1993 OMP cruise exhibit generally a "red" character, although 

 there is a significant peak at about 10 km. We do not have any evidence yet on the cross-isobath 

 fluorescence spectra. These results suggest that mooring spacing for biological studies should 

 be no further apart than 5 km, and it would be better if the spacing were half that distance. 



3. In the southern MAB frontal waves and meanders have been observed in satellite figures with 

 alongshore scales 20 to 50 km, while filaments have been observed with alongshore scales of 10 

 to well over 100 km and offshore scales well in excess of 100 km. Vertical scales of these 

 features are generally unknown. Temporal scales vary from a few days to a few weeks. 



METHODS AND PLATFORMS 



1. For examining the low frequency internal pressure field, we will need a three-dimensional 

 array of moorings with sufficient horizontal spacing and vertical resolution to observe the mean 

 tilts of the isopycnals, and with the ability to separate the high from the low frequency 

 fluctuations. A minimum of four to five moorings will be needed although nine moorings would 

 be desirable. The moorings should be in the vicinity of the 35 to 40 m isobath near 36° 30'N. 

 Each mooring should be equipped with an ADCP and four to five SEACATs. Hydrographic 

 surveys and satellite SST and color photos will be needed to bring the array into the larger shelf 

 context and to identify anomalous conditions. 



2. The bio-physical interaction study will also require ADCPs and SEACATs in a 

 three-dimensional array of about five moorings but the spatial scale should be smaller, perhaps 

 one half the size. The moorings will also require fluorometers with about the same vertical 

 spacing as the SEACATs. Calibration net tows will be needed for converting acoustic 

 backscatter intensity to biomass estimates, and to monitor the zooplankton species composition 

 and feeding and growth rates. Productivity measurements from either or both shipboard 

 incubations and fast repetition rate fluorometers will also be needed. The more frequent the 

 shipboard sampling the better. 



3. The study of frontal eddies and filaments will require satellite-guided shipboard surveys. The 

 best alternative is a SEAS OAR since it combines speed with a wide suite of instruments. A 

 TOYO can be used instead, but the slower speed of the ship, 3 kts versus 8 kts, limits the areal 



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