Report of Activities
on the RVIB N.B. Palmer Cruise 02-02
12 and 13 April 2002
The transit south from
A science meeting was held at 1300 on the 12th and the
different scientific parties on board reviewed their scientific objectives and
outlined what they planned to do at the various stations. There was consensus
that a test station some distance from the first station in the grid was needed
and that was programmed into the schedule.
Just after sunrise (~0800) on the morning of the 13th , the test station began about 100 nm north of Grid Station 1. The sea surface was almost glassy and only a low swell was running. Fog hung over the sea surface, but it was not so thick that the ship needed to slow from its 11 knot pace in reaching the test station. But the skies were a hazy light blue above and the winds light. The air temperature (-1.9ºC) and sea temperature (-0.03ºC) continued to decline. The CTD was quickly deployed. The profile to 500 meters went well and except for a couple of bottles that did not close properly, the cast was successful. This was followed by a BIOMAPER-II deployment to 180 m, an Acoustic Properties of Plankton measurement system deployment, and a MOCNESS tow. A second deployment of BIOMAPER-II late in the afternoon was needed to fine tune the towing configuration.
With the completion of the test station, we again set sail
for Station 1. Sea conditions changed
significantly during the day. By
CTD Group report (John Klinck,
Tim Boyer, Chris Mackay, Julian Ashford, Andres Sepulveda, Kristin Cobb)
The CTD group started sampling early in the morning on April
11 as the Palmer sailed out of the
Argentine EEZ with an XBT cast to 760 meters.
For the next two days (ending in the morning of 13 April), 38 XBT casts
were made to 760 m depth at a station spacing of 10 nm. Of these 38 casts, one probe
failed on load, and four more failed due to spikes or erratic temperatures. The
track followed 65ºW longitude for about a third of the
way across the passage, then turned southwest towards station 1.
A section plot of temperature from these
data reveal that the polar front was located between the first two stations,
just south of the 200 mile limit.
South of this for the next 200 km, the surface waters ranged
from 1 to 2ºC with a thickness of about 80 m. Below the surface layer was a
clear Winter Water (WW) layer about 100 m thick with minimum temperatures from
-0.5 to -1.0ºC. Curiously, one station showed a minimum temperature above +0.5 indicating
an almost complete erosion of the WW.
In the southern 200 km of the section, surface waters were
much colder (-0.5 to 0.5ºC) with a thickness of about 80 m. The WW was thinner
(about 50 m) with temperatures below -1.0ºC. The depth of base of the WW layer
shifted by as much as 100 m over distances of 50 km or so. As we moved
southward, the surface layer becomes cooler and merged with the WW. From the section as a whole, the base of the
WW layer rises from 250 m in the north to about 100 m in the south.
At the southernmost cast, the mixed layer is rather warm
(0.0ºC), 100 m thick with no trace of the WW. The southern 3 casts show almost
no subsurface temperature minimum (WW).
We did a test cast of the CTD at 0830 on 13 April. The low winds and calm sea made it a pleasure. The cast was to 500 m with all sensors on, including the FRRF, but not the microstucture probe. The brackets are still being worked on and we want a minimum of attaching and detaching of this sensor. Due to the deep cast at station 1, we decided to wait until station 2 to use this new sensor. With success, we could leave it on the rosette until the next deep station (12).
The cast was accomplished with the expected delays and
confusion. In the end, the cast was completed successfully. A uniform mixed
layer was observed to about 75 m with a thin (15 m) only slightly cooler (-0.5ºC)
WW layer. The flourometer showed a strong response
(0.2 mg/l) in the surface layer and instrument noise below. The new oxygen
sensor adjusted rapidly and displayed no erratic behavior.
As a test of bottle integrity, all (23) bottles were closed
at 500 m. Three bottles did not trip. We drew 20 oxygen samples as practice and
to start working with the oxygen titrator. We also
drew 8 salinity samples to start working with the salinometer.
Several problems with software were detected which are being
worked on. These have to do with processing and exporting the data as well as
printing the cast plot. It has been a
busy two days, with busier days to come.
Marine Mammal report (Debra Glasgow)
This report summaries observations
since leaving
On 10 April, at sunrise 0700), conditions for cetacean
survey were not good with the wind speed at 35-40 knots from 220-230 continuing
throughout the day. The increasing swell throughout the day and the worsening
weather conditions precluded any decent cetacean survey.
No watch was kept on 11 April due to high wind and seas
until the weather calmed somewhat to 30 knots around 1600 and the ship picked
up speed to 9.4 knots. In spite of a haze on the horizon and occasional sleet
squalls, an incidental watch was kept on the bridge from 1600 until stopped by encroaching
darkness and poor visibility at 1745. No
cetaceans were sighted.
An overcast and generally foggy day today
especially in the afternoon. Three and a half hours full survey was
achieved on the morning of 12 April, though no cetaceans were sighted by the
observer. Around
An all day incidental watch was conducted on 13 April
beginning at 0730 mainly from the ice tower through variable visibility
conditions. The windows in the ice tower this morning were covered in ice
inside and out and some of the morning's observations were from the bridge
while the windows thawed. Though the wind and sea were slight for most of the
day, fog kept visibility low for most of the time with rare clear patches. During one clear time, one unidentified large
whale was sighted at 1247, but proved difficult to track and identify as we
were often changing direction while we tested various instruments. The ship
traveled at 1-3 knots throughout the day and because of this, the fog, and the
constant changes in direction, a full survey mode was not possible. Incidental
mode observing ceased at 1600 due to rain and fog limiting visibility to less
than 200 meters. Large numbers of birds accompanied the ship throughout the
day, increasingly so as the day wore on.
Marine Mammal passive listening report (Ana Sirovic)
After steaming out of the Argentine 200 mile EEZ, a total of
3 sonobuoys were deployed on 12 and 13 April. Blue whale calls were heard on one sonobuoy and possible fin whale calls were heard on
another. The blue whale appeared to have
been swimming north of the sonobuoy deployment
location. The system seems to be working well and antenna range is
satisfactory.
Sea Birds (Erik Chapman)
On 13 April, incidental observations were made from the
bridge while the BIOMAPER-II and MOCNESS were being towed at the test
station. There were about 170 to 200
birds around the ship, about 70% of which were
Zooplankton (MOCNESS/BIOMAPER-II) report (Carin Ashjian, Peter Wiebe)
The BIOMAPER-II test involved a towyo
in which the towed body was sent to 180 meters and then hauled back towards the
surface while making measurements with the five frequency acoustic system, the
two camera video plankton recorder, and the CTD, fluorometer,
and transmissometer sensors. On the return to the surface, the fish was
held at 80 meters and a noise test of the acoustic system was conducted. All
three sensor system performed well. But the towed body performance was poor and
adjustments to optimize its roll, pitch and yaw characteristics were
needed. During the first part of the
tow, significant numbers of krill larvae were observed near the surface in the
VPR images and then later in the tow, several large patches of scatterers, probably krill, were centered about 180 meters
below the surface. In the pycnocline below the Winter
Water layer at the test station, the echograms of the higher frequencies (200
and 420 kHz) displayed horizontal layers of higher backscattering separated by
lower backscattering that appeared to be associated with the physical structure
of that portion of the water column. The microstructure sensor when used on the
CTD should help determine this. A second
deployment of BIOMAPER-II took place around 1700 after making some adjustments
to tail elevator to see if the towing performance was improved.
The first MOCNESS tow of the cruise was conducted at the
test station on 13 April. The short tow to 200 m, sampling at 25 m intervals,
went very well except for the lack of net response signals; we will adjust the
net response for the next tow. Many salps were collected in the 100-200 m depth intervals. Amphipods were collected in the 200-175 m
depth range. Chaetognaths
were present from 125-75 m. Krill furcilia were present from 100-25 m, along with
copepods. Only copepods were observed in
the upper 25 m; they appeared to be genus Calanus and were much more
abundant at this depth than elsewhere (even though we also filtered more water
with this net). The water column oblique
net was preserved in ethanol for genetic analysis.
Cheers, Peter