Thompson Cruise Report Aug 10-11 22:00 Local Time

We completed the 48 h time series at CH-3 (midshelf station) at 14:30 on August 10. This was a very successful sampling with almost continuous data for turbulence, chemistry, fRRF and optics. Ricardo's group did 30 min interval sampling during the day/night transitions for HPLC and absorbance and at 2 h intervals the rest of the time. Amanda also worked in two 14C incubations. We will have a very nice data set to evaluate both the tidal cycles and the light/dark fluoresence repsonses.

Meanwhile we were/are continuing other experiments: Mike Wetz has been conducting 6, 12, and 24 h respiration measurements in light and dark bottles in parallel with Amanda's 14C productivity measurements. He also set up triplicate deck incubations in carboys to simulate a phytoplanton bloom. The first experiment set up at CH-1 "bloomed" within 2 days and we are monitoring changes in nutrients, chl, organics and abundances of phytoplankton and bacteria. We will compared these changes to what we observed during our in situ sampling. We also started to run our extracted chlorophyll samples and will be able to comment some on the levels of extracted chl versus the fluoresence signals.

After the time series, we returned to CH-1 for a pump station, completed a profiling transect from CH-1 to CH-6, and a pump station at CH-6. While approaching CH-1 we crossed a front with a temperature drop from 14.5 to 10.5 C and a chl fluoresence drop from 2.25 to 0.5 v. While sampling at CH-1 Moum's biosonics tracing show a large field of "something" being advected past us, but it did not show up in the ship's flow through system, or in our fixed depth sampling.

We prepared Ricardo's drifters for deployment and luckily found out that the "on" switch meant "off" and the "off" switch meant "on". With the help of Moum's group, all drifters were set up on the fantail and were deployed close to NH-25 in less than 15 minutes in a very nice cluster. Then we headed on to Line 6 off Cape Perpetua. We arrived at CP-12 and started an ADCP transect to CP-1 at 21:00 local time August 11, this should take about 4 h. Then, after an inshore pump station, we will run an profiling transect from CP-1 to CP-11. Last May this took about 34 h. With another pump station at the offshore end, we estimate 2 days profiling and than a two day time series at an interesting midshelf station. Based on SEASOAR data from Aug 8 this would be about 25 km offshore where the cold, dense bottom water extends from the bottom up to about 50 m below the surface.

Our schedule looks roughly like this:
Aug 12-13 profiling transect with pump stations on each end
Aug 14-15 midshelf 48 h time series

After the time series we will need to make some decision about what portion of the CP-line to focus on and whether or not we should do some profiling upstrean and downstream to examine changes in jet characteristics.

Pat Wheeler
Chief Scientist, THOMPSON