HOT-46: Chief Scientist Report

Chief Scientist: D. HEBEL

HOT 46 Cruise Report
R/V Wecoma
12-17 April 1993



Personnel List:
---------------

	Dale Hebel		Chief Scientist		UH
	
	WOCE group:
	Jeff Snyder		Technician		UH
	Rich Muller		Technician		UH
	Sophia Asghar		Graduate Student	UH
	Hongbin Liu		Graduate Student	UH
	John Bower		Graduate Student	UH

	JGOFS group:
	Louie Tupas		Scientist		UH
	Ursula Magaard		Technician		UH
	Ricardo Letelier	Graduate Student	UH
	Dan Sadler		Graduate Student	UH
			
	Ancillary projects:
	Hongbin Liu		Graduate Student	UH - L. Campbell
	Maureen Keller		Scientist		Bigelow Labs - 
							B. Bidigare
	Mikel Latasa		Graduate Student	UH - B. Bidigare
	Charles Holloway	Graduate Student	UH - J. Cowen
	John Bower		Graduate Student	UH - D. Young
	Naeem Ahmed		Scientist		NIO



Itinerary (approximate local time):
-----------------------------------

Monday, 12 April 
	1015	Departed Snug Harbor
	1330	Arrived Kahe Pt. (Sta. 1)
	1630	Departed Kahe
Tuesday, 13 April
	0200	Arrived Aloha (Sta. 2) trap deployment site 
	0400	Completed sediment trap array deployment
	0500    Arrived Aloha (center of circle), began CTD time series
	0600	First winch problem
	1130	First cable problem
	1530	Winch problem resolved
	1900	Wire problems persist
Wednesday, 14 April
	0200	Commenced Go-Flo cast
	0300	Aborted Go-Flo cast
	1800	Wire problem resolved
Thursday, 15 April
	0200	Commenced  second Go Flo primary productivity cast
	0400	Continued with 3 hr interval CTD casts
	0630	Deployed primary productivity array
	1900	Retrieved primary productivity array
Friday, 16 April
	0700	Completed Sta. 2 CTD operations
	0900	Commenced dive operations
	1130	Completed dive operations
	1200	Conducted PNF cast and net tows
	1300	Departed station ALOHA
	1530	Recovered sediment traps
Saturday, 17 April
	0700	Arrived Snug Harbor
	



Narrative:
----------

HOT 46 was conducted 12-17 April 1993 aboard the R/V Wecoma (full 5
days at sea) with Capt. Doyle as Master.  HOT 46 was not the typical
Hawaii Ocean Time-series cruise due to persistent equipment problems on
13-14 April 1993.  These were primarily associated with the winch and
conducting cable although we also experienced problems during the
primary productivity cast with HOT-JGOFS equipment.  Additional, short
term problems were also experienced with the CTD pylon, fluorometer
transmissometer signal, leaking Niskin bottles, hung up Niskin
lanyards, broken CTD frame weld, and minor CTD software problems.   In
spite of the recurring problems all "core" samples were collected due
to the combined efforts of the scientific personnel and cooperative
support of the ships crew.  However, we did lose valuable time which
resulted in aborting 2 blue water dives and  the second WOCE deep
cast.  Oddly, we did not experience any equipment problems at our
shake-down station (Kahe Pt.).  Here we conducted a weight cast to 500
m followed by a PNF cast and 1000 m CTD cast.  All equipment functioned
properly and all Kahe Pt. samples were collected.  In addition, we
hosted a visiting Pakistani scientist Mr. Naeem Ahmed from the National
Institute of Oceanography.  His objective was to observe overall
operations in preparation for upcoming Arabian Sea work.

We departed Kahe Pt. on schedule and steamed to the trap drop-off
point.  Upon arrival the ADCP indicated a 10-20 cm/sec northeast
current between 100-300 m.  The current was opposite in direction but
similar in magnitude from 0-100m.  We decided to move to 158 04' W
along the same latitude line assuming the traps would track northeast
as in  HOT 45  (this assumption proved false, the traps drifted almost
due west).  Following deployment we steamed to the center of station
ALOHA and began the WOCE deep cast.  The first equipment problems
developed during this cast.  According to the cruise log the winch
stopped 3 times on the downcast and 4 times on the upcast and took a
total of 6 hrs to complete.  At the beginning of my shift I spoke with
Jeff and he felt the problem was possibly a mismatch between the motor
and gears causing the motor to overspeed on the decent and overheat on
the ascent.  Each time the motor overheated it would take ~15 min. to
cool thereby resetting the thermocouple  I spoke with the el

The twist in the cable persisted causing the cable to kink when the
load was applied.  This resulted in  3 terminations and removal of
approx. ~70 m (?) of cable over the following 24 hr period.  At this
time we switched to a one conductor cable configuration so we could use
the Wecoma's CTD swivel.  This solved the problem.  Due to the
inability to maintain the 3 hr CTD cast interval we extended CTD
operations until 0700 hrs on 16 April 1993 (an additional 36 hrs from
the point of swivel installation).

Another problem which did not involve ship equipment materialized
during the primary productivity cast.  We recently repainted the DSE
winch and installed new Kevlar line.  Although the Go Flo bottles were
tested on the new line the Teflon messengers were not.  During the cast
it was found that the messenger groove was too narrow for the new
line.  Therefore, the cast was aborted and rescheduled for the
following night allowing us an opportunity to enlarge the grooves.
This was done in the ships machine shop and the cast and subsequent in
situ incubation completed without incident on 15 April 1993..

Following CTD operations 2 blue water dives were conducted in addition
to the daily midday PNF cast followed by a short surface net tow.  We
departed station ALOHA at approx. 1300 hrs on 16 April 1993 located and
retrieved the sediment traps returning to Snug Harbor by 0700 hrs 17
April 1993.  Off loading was conducted immediately and completed by
1100 hrs.




Weather:
--------
The weather was good throughout the cruise with light-moderate trades
(10-20 kts), mostly sunny skies and 2-3 m seas.




Equipment and methods:
----------------------
All equipment used on HOT 46 was standard for past HOT cruises.
However, persistent winch and cable problems plagued a significant
portion of the cruise.  The only equipment lost was one Niskin spring
and one (?) broken end cap handle..




Ancillary programs:
-------------------

Investigator:			Project:
-------------			--------
 
Charles Keeling (SIO)		CO2 dynamics and inter calibration
Lisa Campbell (UH)		Picoplankton studies
Maureen Keller (Bigelow Labs)	Phytoplankton pigment studies

Students:	
---------
Ricardo Letelier		Tricodesmium studies 
Dan Sadler			Time series pH measurements
John Bower			Squid population studies
Chuck Holloway                  Th-U disequilibria and marine snow
				dynamics
Mikel Latasa			Phytoplankton pigment distributions
Jinchun Yuan			Trace metal studies

Others:
-------
Ted Walsh (Prj Mgr Anly Svc)	Seawater diluent collection
Taro Takahashi			pCO2 inter calibration  (C. Winn P.I.)