From: Wecoma Chief Scientist
Subject: Wecoma report for 24-25 Jan '03

COAST R/V Wecoma report
24-25 January 2003

During Thursday and Friday, 23-24 January, we completed the following sampling:

-- a SeaSoar/ADCP/HTI/iron survey on the SmallBox North grid (4th repeat)
-- CTD stations at CH-7,6.5,6,5.5 and L1-1,2,3,4
-- a SeaSoar/ADCP/HTI/iron survey on the BigBox (lines 1-3) grid (2nd repeat) -- an ADCP transect of the CH line all the way from 125 24' W to 20-m depth off Lincoln City

During our BigBox 2 tow along the CH line we passed about 0.4 nautical miles to the south of the R/V Roger Revelle as they sampled inshore with the pumped profiler and the turbulence profiler. The Revelle was pointed into the strong northward current, crabbing toward shore with both lines in the water. Visibility was about 1 nautical mile through the fog. Should be a nice comparison data set between the two vessels.

During the two SeaSoar surveys, the crab pots were being pulled under by the strong northward currents. We had heard this would happen from talking with the crab fishermen. Fortunately, we had the locations of the crab pot strings marked on our navigation computer and we slalomed and hopped our way over the gear with no incidents. We haven't seen any of the fishing fleet out here since the strong winds started. It's just Wecoma and Revelle and lots of wind and waves :) On our last E-W line (line 3) the crab floats started popping to the surface again, right where we had them marked.

During the CTD stations between SeaSoar tows, we replaced the ac-9 bio-optical instrument on top of the SeaSoar because the light absorption channel had failed. The new ac-9 (#222) is working fine on SeaSoar.

Dale Hubbard got the phosphate system running on the underway 5-m flow-through line late on Friday, 24 Jan. So he now has nitrate, phosphate and pCO2 working.

The cross-shelf structure of the water column after the strong downwelling winds is quite amazing. Inshore, out to about the 50-60 m isobath, the water column is fresh and the added buoyancy keeps the water column stratified. There is a strong colored dissolved organic matter (CDOM) signal in the freshwater, consistent with it being runoff. Over the mid shelf (60-110m), the water column is well-mixed from top to bottom where the wind mixing can overcome the weak stratification. From 110 m and deeper, the deep pycnocline intersects the bottom forming a bottom downwelling front. There is considerable mesoscale variability in the front in the alongshore direction. We also still see cold (< 7.5C) water in the deep pycnocline. Offshore of the shelfbreak there is a very deep surface mixed layer, sometimes in excess of 70 m.

On the shallow end of the ADCP transect, the lights of Lincoln City emerged from the fog as we approached on early Saturday morning. We could see the large swell breaking on the beach. On Saturday morning the winds are up to 25 knots and it's raining with low visibility. We moved the SeaSoar out from under the A-frame and rigged the MOCNESS for zooplankton sampling. We plan to sample the CH-line stations with CTDs, vertical zooplankton nets and the Multiple Opening and Closing Net Environmental Sensing System (MOCNESS). This should take us through the night with the hope to get a day-night zooplankton profile at CH-5. We'll follow that up with some more towing on the SmallBox North and the BigBox (lines 1-3).

Jack Barth
Chief Scientist, R/V Wecoma
1130, 25 Jan 2003