From: Wecoma Chief Scientist
Subject: Wecoma report for 7-8 Feb '03

COAST R/V Wecoma report 7-8 February 2003

During Friday to Saturday, 7-8 Feb, we completed the following sampling:

-- Fourteen CTD stations along the CH-line and line 1 (45 15'N) including the deep offshore CH-line stations (500-1000m deep) to help with dynamic height calculations and numerical model runs
-- A tow-yo CTD section along the CH line from the 70 to the 150-m isobath
-- a SeaSoar/ADCP/iron survey on the BigBox lines 1-3 grid (6th repeat)
-- a SeaSoar/ADCP/iron survey on the SmallBox North grid (9th repeat)

The winds continue to be upwelling favorable (southward) but relatively weak (< 10 knots). Seas are smooth and skies are clear. During our last CH-line sampling, we verified that all four COAST moorings were present and appeared in good shape. Only the meteorological buoy had the two yellow anchor-line buoys streaming south from it on the surface.

The SeaSoar/ADCP surveys reveal continue upwelling, although perhaps less strong than observed a few days earlier. The bottom front, delineated by about sigma-t of 25.8 kg/m**3, intersects the bottom at 50-60 m. The upwelling jet has slowed down a little to around 30 cm/s with a slight reversal to the north inshore of 50 m bottom depth. Phytoplankton fluorescence, in a subsurface maximum at about 5 m, shows 10-15% growth from the previous few days. The highest phytoplankton concentrations are found just offshore and within the southward coastal upwelling jet.

Tim Cowles has been tracking the colored dissolved organic matter (CDOM) - salinity relationship from surface waters over the course of the cruise. He sees distinct relationships between CDOM and salinity (nearly linear in many cases) that have varied over the cruise. Tim also sees differences in the relationship between water masses along a single east-west cross-shelf section. These could be due to differences in biological processes or photochemical reactions between water masses or simply that the water masses had different origins. Tim thinks we have an excellent data set to sort this out.

We are in the middle of a final ADCP survey out to the west to pin down the location of the edge of the anticyclone that was observed during our previous BigBox surveys.

The accomplishments of this cruise have far exceeded our expectations. We were wary of the tough wintertime weather and the heavy crab fishing before we left the dock. While the southerly winds were indeed strong over the first week of the cruise, we were able to work for the entire cruise except for 16 hours! Due to the outstanding vigilance of the captain, mates and crew of the Wecoma, we were able to tow our gear through the crab pots during daylight hours. We combined this with CTD station and tow-yo work at nights to obtain a really great data set. Of the available daylight hours during the 3-week cruise, we towed SeaSoar for 103% of that time! (We made up the daylight time spent on zooplankton sampling along the CH and CP lines by towing offshore during the night.) This last week's weather with upwelling favorable winds and lots of sunshine has been both a treat and a nice scientific contrast to the strong southerly downwelling favorable winds early in the cruise. This is the first time that a wintertime switch from strong downwelling to significant upwelling has been documented in detail. The contrast from summertime upwelling as measured during our 2001 experiments will be fun to explore over the next year and a half.

We are scheduled to be dockside in Newport at 0700 on Sunday morning.

Jack Barth
Chief Scientist, R/V Wecoma
2230, 8 Feb 2003