HOT-38: Chief Scientist Report

Chief Scientist: E. FIRING

                    HOT-38 Cruise Report
                       R/V Moana Wave
                       July 3-7, 1992

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

      Eric Firing             Chief Scientist   UH

      WOCE group:
      Jefrey J. Snyder        Technician        UH
      Sophia Asghar           Student           UH
      Reka Domokos            Student           UH
      Elaine Kotler           Student           UH

      GOFS group:
      Dale V. W. Hebel        Research Assoc.   UH
      Daniel W. Sadler        Student           UH
      Louie M. Tupas          Post-Doc          UH
      Jan Reichelderfer       Student           UH
      Christopher J. Carrillo Technician        UH
      Ricardo M. Letelier     Student           UH
      Hongbin Liu             Student           UH

      Emerson's O2 project:
      Chuck Stump             Technician        UW

      Other BioGeoChem:
      Ariel Anbar             Student           Caltech

      Lowered ADCP testing:
      Doug Wilson             Scientist         AOML
      Mark Bushnell           Scientist         AOML

      REU students:
      James Girton                              Swarthmore
      Anthony Ferrara                           UH


      STAG:
      Dave Gravitt            Deck Tech.
      Ken Shultis             Elect. Tech.


Itinerary (local times):
------------------------
Friday, July 3
   0800 left Snug Harbor
   1045 arrived Kahe Pt. (Station 1)
   0200 left Kahe for ALOHA
Saturday, July 4
   0116 sediment trap deployed
   0250 arrived at Station 1; began CTD time series
Monday, July 6
   0803 left Station 2 for Station 3 (with detour to check traps)
   1420 arrived at Station 3 (23-25N, 158W)
   ~1930 headed back to pick up the traps
Tuesday, July 7
   0242 traps hooked with grapnel
   0405 heading back to Honolulu
   1305 shallow water LADCP test SW of Pearl Harbor
   1445 docked at Snug

Narrative:
----------
The entire cruise went smoothly and stayed on or ahead of schedule.

On arrival at Kahe Pt., a weight cast was made, followed by a PNF cast
and a CTD cast to 1000 m.  There was a short delay in the latter due to
a hardware problem (turned out to be a bad connection in the lab) and a
software problem (incorrect initial setup of the SEASAVE configuration
files).  Time at Kahe was 3 hours 15 minutes.

At ALOHA, the sediment trap deployment was uneventful and the normal
CTD and water sampling time series went smoothly.  After the first CTD
cast, and between many of the other CTDs, the Lowered ADCP was deployed
from the stern A-frame.  This interleaving of CTD and LADCP casts
worked well, causing little if any delay in the CTD casts.  Sixteen CTD
and 12 LADCP casts were made at ALOHA.  The LADCP cast depths varied
from 500 m to the bottom.

After the 36-hour time series at Station 2, including all necessary
water sampling, the ship steamed over to the sediment traps and then
north to Station 3.  There a deep Morita O2 sensor calibration cast was
made.  This was a departure from previous cruise plans, and the first
full-depth cast at Station 3.

Following the CTD cast at Station 3, the sediment traps were recovered
and we headed for Honolulu.  One final LADCP test cast was done in 350
m of water off the south shore of Oahu to test bottom tracking.

Weather:
--------
Weather was good throughout the cruise, with moderate tradewinds and
few showers.

Equipment and methods:
----------------------
With the exception of the new LADCP, most equipment used on this cruise
was standard for the last several cruises.  Problems were few and
minor.  In addition to the initial CTD system problems mentioned above
(bad connection and incorrect setup files), there were a few mysterious
errors in the CTD data stream (that is, the SEASAVE error count at the
bottom of a profile was typically 5-10), and the Morita sensor was
noisy below about 3000 m.  An altimeter was tested on the deep CTD
casts, but no real-time display was available.  Inspection of the
recorded data suggests that it was not working well.

The new LADCP was a 150-kHz Broadband instrument newly bought by AOML.
There are many differences between the new Broadband instruments and
the previous generation of ADCPs, but the most fundamental is the use
of coded pulses.  In principle, the use of coded pulses should lead to
greatly improved accuracy at a small cost in reduced range.  We found,
however, that below 1000 m the backscattering was simply too weak for
the new instrument to get acceptable range.  Hence the test was
successful in the sense that it uncovered a major problem with the new
instrument in this application, but unsuccessful in that we did not get
good velocity profiles below about 1000 m. There is reason to think
that the problems can be solved with some modifications to the
instrument.

Shipboard ADCP data collection was interrupted during most LADCP casts
to prevent interference; early tests showed that the shipboard profiler
does interfere with the 150 kHz BB instrument when it is within about
200 m of the surface.  Otherwise the shipboard ADCP data collection was
normal and trouble-free.  GPS heading data were also collected during
most of the cruise, but more than a day of data from the middle of the
cruise was overwritten due to a mysterious failure of the PC clock to
increment the day.

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

Investigator                   Project
------------                   -------
Doug Wilson                    Test of a new ADCP
Marlin Atkinson                Test of a new oxygen sensor
Ariel Anbar                    Palladium measurements
Steve Emerson                  O2 measurements


student samples: Ricardo Letelier, Hongbin Liu