Wecoma daily report, 18 August 2001

Since the last report, Wecoma completed Bigbox 3 at 0000 (local) on 17 August. We followed up by immediately starting a SeaSoar/ADCP/HTI/iron survey on "Smallbox South" which consists of an E-W line along a line halfway between lines 7 and 8 ("line 7.5") heading offshore until the 100 fathom contour. We then follow the 100-fm contour N-NW around the outside of Heceta Bank, quantifying the flow across the shelfbreak. We turn back E on a line between lines 6 and 7 ("line 6.5") and close the circuit by heading back to the east end of line 7.5 along the ~45 m isobath.

The Smallbox South region encompasses the southward jet carrying high chlorophyll off the Bank. The Thompson is sampling the same feature by making short E-W sections from N to S over the Bank within our Smallbox region. We completed our first circuit of Smallbox South at 2030 on 17 August. A southward jet (~30 cm/s) was centered on about 124.8W, carrying high chlorophyll off the Bank.

After the switchover from SeaSoar to MOCNESS operations, we completed 3 MOCNESS stations along 124 48'W, moving upstream onto the Bank from 43 48'N (~500m water depth) to 43 58'N (100m water depth). The goal was to investigate whether zooplankton accompanied the high surface chlorophyll streaming south off the Bank. All MOCNESS were completed at night.

We are now doing a second Smallbox South and anticipate covering the circuit twice. We then plan to do some daytime MOCNESS/vertical net stations on Sunday 19 August. These will repeat the alongjet/along-chl-feature stations we did last night. Our goal is to try and distinguish zooplankton being potentially swept off the Bank versus those that migrate up from the bottom on the slope south of the Bank.

Longer term plans are to complete a Bigbox 4 survey on Monday and Tuesday, 20-21 August.

Submitted at 1130 on 18 August 2001 by Jack Barth, Chief Scientist,
R/V Wecoma.