Results from Deployment of MBARI Drifter #4

Drifter #4 instrumentation included an osmotically-pumped nitrate analyzer, fluorometer, scatterometer, CTD, and GPS receiver. Figure 1 shows a time series of measurements made by the drifter.

Figure 1: Parameters measured during deployment of Drifter #4

The vertical lines on Figure 1 mark the times of AVHRR sea surface temperature images.

"Backscatter" is approximately proportional to concentration of suspended particles.

The drifter was deployed at the upwelling center near 37N 122.3W. This water was characterized by high nitrate and particulates, and low chlorophyll. The drifter went south, passing very close to MBARI mooring M1; particulates decreased steadily during this phase. The drifter then crossed into warm, high chloropyll, low nutrient Monterey Bay water early on April 22; (AVHRR image #7 and image #8 ).

Several drifters deployed during CoOP '95 exhibited this front-crossing behavior; it is likely related to the subduction of recently-upwelled water under warmer, fresher, more productive waters. These frontal features were studied carefully in the following weeks, and further work is ongoing to confirm or reject this hypothesis.

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