HOT-31: Chief Scientist Report
Chief Scientist: E. FIRING
Personnel List:
---------------
Eric Firing Chief Scientist UH
WOCE group:
Jefrey J. Snyder Technician UH
Patrick C. Caldwell Technician NODC
Sheryl A. McCarthy Student UH
GOFS group:
Dale V. W. Hebel Research Assoc. UH
Omar Calvario-Martinez Scientist ICMyL-UNAM (Mexico)
Daniel W. Sadler Student UH
Luis M. Tupas Post-Doc UH
Christopher J. Carrillo Technician UH
Terrence Houlihan Technician UH
James R. Christian Student UH
John E. Dore Student UH
Ricardo M. Letelier Student UH
Mike Landry's group:
John Constantinou Student UH
Julie D. Kirshtein Technician UH
OSU Marine Tech:
Brian Wendler
Itinerary (local times):
------------------------
Saturday, Oct. 19
1000 left Snug Harbor for fuel pier
1327 left fuel pier
1618 arrived at Kahe Pt. Station, 21-20.62N, 158-16.45W
2230 left Kahe Pt.
Sunday, Oct. 20
0517 arrived at Aloha center position
Wednesday, Oct. 23
1028 recovered the sediment traps about 8 miles NE of
Aloha
1350 arrived at station 3, 23-25.0N, 158-00.0W
Thursday, Oct. 24
0010 station 4, 21-57.8N, 157-59.9W
0340 station 5, 21-46.64N, 158-00.0W
0510 left station 5 for Snug Harbor
1010 arrived at Snug Harbor
Narrative:
----------
After a delay of about 3 hours for fueling and another half hour to
retrieve a missing piece of equipment (the 12-place rosette), the ship
got underway. The Kahe point station took over 6 hours because of
problems with the CTD and with the level wind on the winch. The latter
was fixed on the way to Aloha.
Work at Aloha proceeded at a good pace with no major problems. After
the WOCE and GOFS casts had been completed, the CTD was moved to the
12-place rosette and 4 LADCP casts were made: 1 to 4600 m and 3 to 2000
m. Good data quality was obtained on all.
The sediment traps drifted north and east, consistent with the
prevailing currents measured with the shipboard ADCP. The spar buoy
was sighted before dawn and recovered after breakfast. The recovery
was delayed by an hour for discussion of recovery strategy with the
Wecoma's bosun and the Marine Tech, but otherwise proceeded well. The
traps were in the water more than 72 hours.
A new element was added on this cruise: CTD stations on 158W at 23-25N,
21-57.8N, and 21-46.6N. The first of these, station 3, is 40 miles
north of Aloha. Station 4 is about 10 miles offshore of the 400-m
isobath at Kahuku, and station 5 is near that isobath. Each of these
stations was conducted with the 24-place rosette and with sampling like
that at Kahe Pt. The 100-mile section to Kahuku on 158W was filled in
with T-7 XBTs at 10-mile intervals from station 3 to 22-35N, and at
5-mile intervals from there to 21-50N. Including one failure, this
required 16 probes (15 T-7 and 1 T-4). The last probe was launched
slightly later than intended and hit bottom at 500 m; a T-4 would have
sufficed.
After leaving station 5, the ship proceeded along the North Shore
approximately following the 300-m isobath so as to provide bottom-track
calibration of the shipboard ADCP and gyrocompass. This causes a
negligible lengthening of the cruise track.
Wecoma returned at unusually high speed in order to arrive close to
10AM. This should not be necessary on future cruises, given that the
fueling and Kahe Pt. delays can be avoided.
Weather:
--------
Weather was good throughout the cruise. Winds were light easterlies
for the first part and increased to moderate east-northeasterlies at
the end. On the last day we felt a swell from stronger trades to the
northeast of us. There were only a few brief showers.
Equipment and methods:
----------------------
The CTD was equipped with Marlin Atkinson's Morita O2 sensor for the
first time. At Marlin's request, the CTD was therefore kept powered up
almost continuously, and an effort was made to keep the Morita flushed
with seawater and the rest of the Seabird plumbing flushed with
freshwater. However, because of leaks in the plumbing, sensors were
frequently exposed to air. Improved flushing systems and/or better
plumbing will be needed in the future if the sensors are to be kept wet
at all times.
The CTD was deployed using the Wecoma's non-articulated crane. This
was a somewhat slow and awkward procedure, although it improved during
the cruise as the crew became more practiced. Still, it seems inferior
to using an A-frame. A light A-frame is available here, and we may
want to consider using it in the future. With the crane, we needed two
people on CTD tag lines, one on a tag line for the headache ball, and
typically one more to handle the CTD wire and give signals. The latter
is probably not essential and could be replaced by one of the tag line
handlers, but still it seems that crane deployment requires more deck
hands than using an A-frame. Also, the whip is typically much longer,
and there is great latitude for the package to swing around from the
time it leaves the deck to the time it hits the water. In bad weather
this could become a serious problem.
The wire on the Wecoma's winch was moderately rusty on the top wrap.
With full agreement from the ship's engineers and the Marine Tech, 100
m was cut off before the wire was terminated. Toward the bottom of the
deep WOCE cast, the wire was absolutely pristine: new and shiny. This
was the first time that part of the wire had been used. The wire as a
whole is in excellent condition.
The shipboard ADCP was the standard VM-150 on the Wecoma. For
navigation I brought my own MX4200 receiver, and mounted the antenna on
a pole clamped to a stanchion on the 01 deck, port side, above the aft
end of the dry lab. This worked very well.
One potential problem arose during the recovery of the sediment trap
spar buoy. At the bosun's direction, the top of the spar was held down
while it was hoisted with the bridle. It bent alarmingly under its own
weight, but did not break. This can be avoided in the future by making
the recovery plans with the bosun and Marine Tech earlier, and letting
them know that the spar is not built for this kind of handling.
Another tense moment was when the spar was lifted by the grapnel
(supplied by the Wecoma) and one of the three polypro strands of the
grapnel line broke. The failure was due to melting of the strand at
the splice when the loose end of the strand was heat-sealed.
One Happy Hooker was broken. These are essential for safe and
efficient recovery of the CTD on the Wecoma. The plastic ones are not
very strong, so we should simply ensure that we have an adequate supply
on hand.
Tag lines supplied by the ship were plentiful but not very good
quality. I suggest that WOCE/GOFS invest in a good set of our own tag
lines.
Ancillary programs:
-------------------
Investigator Project
------------ -------
Marlin Atkinson Test of a new oxygen sensor
Omar Calvario-Martinez Dissolved oxygen as measure
of primary productivity
Mike Landry Tests prior to equatorial
JGOFS cruise
student samples: John Dore, Jim Christian, Ricardo Letelier
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