Thompson Report for May 29-30 (Written May 31, 00:00; local time)

We did one vertical profiling transect of the Cape Perpetua line from CP-2 to CP-11 which took about 40 h. Sasha has posted the results on the COAST web page. At each end we did fixed depth pump stations. Today we did a partial profiling transect from CP-2 to beyond CP-5. Currently we are doing a day-night time series for Ricardo?s FRRF fluorescence measurements and will follow this with a fixed depth pumping station at CP-4. All systems (and people) are working well and we?ve had very little down time. I collected iron samples for Zanna at CP-4 and CP-5 through the profiling pump and was able to get samples from the bottom boundary layer.

The vertical profiling plots show a very thick turbid layer (scatterometer) at the surface extending down to 10-30 m from CP-1 to about 27 km offshore. At the outer edge (30 km) the turbid max and chl max are deeper in the water column (30-50 m) deepening in the offshore direction. The bottom turbulence and the turbid bottom boundary layer have intensified between the two samplings. Nutrients are low in the surface water and we should have strong vertical gradients in both the upper water column (through the euphotic zone) as well as some associated with the bottom boundary layer. Burke thinks that the nitrate to silicate ratios are showing significant variation.

We discussed several options for sampling schemes for the remaining three days. A single repeat of the CP-line does not seem too productive without a change in the weather or upwelling conditions. We also considered sampling parallel to the jet or along perhaps along the 90 m isobath. The third (and chosen) option is to concentrate on the inshore processes and to increase our spatial resolution of mixing dynamics over the shelf and of the bottom boundary layer.

Our plan is to run four profiling transects from nearshore to the inner edge of the jet (or the outer edge of high chl) along 44 22.5 N, 44 32.4 N, 44 39.1 N, and 44 50.0 with fixed depth pump stations at each end and vertical profiling in between.

Pat