Report of Activities
on the RVIB N.B. Palmer Cruise 02-02
The vistas from inside George VI sound are supposed to be
grand with the ice shelves and mountains surrounding the sound on three sides,
but on 30 April, the first light of day was a sliver on the northern horizon
and a thick cloud layer was over head. The clouds stayed the day, shrouding the
mountain peaks. Only the slopes of some
of the western peninsula mountains to the east were showing. To the west, the clouds lay down nearly to
the sea surface, so that the mountains
The weather remained quite calm. Wind speeds for most of the day were in the
7-10 kt range, out of the south southeast (153). The
barometer held steady around 986 mlb, and the air
temperature varied within narrow limits about -2.0ºC.
The work at the two stations included 2 CTDs,
an ice collection at station 57, and an ROV under ice survey at station
58. A 1-m MOCNESS tow was taken some
distance from 57 when ice conditions had become suitable for towing. This tow
was originally scheduled for station 56, moved to 57, and then delayed again
because of the pack ice was too thick to permit towing. The towyoing of
BIOMAPER-II between these stations was also abbreviated because of the pack
ice, but some portion of all of the transect lines was sampled. Seabirds and
marine mammals were surveyed during daylight periods when the visibility
permitted. One sonobuoy
was deployed.
During the evening, the L.M.
Gould was working in the vicinity of survey grid station 58 and a
rendezvous was arranged to allow for an exchange of scientific supplies and
equipment after the Palmer completed the station work. This included spare nets
for the Palmer’s MOCNESS, live animals
freshly caught by the Gould for
experimental work by Dezhang Chu
on the Palmer, some preserving fluid
in short supply on the Palmer, and a
replacement monitor for the Gould’s scintillation
counter. In addition, with the two ships
positioned bow to stern, the Palmer’s
personnel carrier and crane on the bow was used to transport several
individuals to the Gould, so that an
exchange of information could take place regarding what had been learned by the
two groups thus far and what plans there were for cooperative efforts during
the second portion of the cruise. The two ships parted ways around 2300 when
the Palmer began the transit to
survey station 59.
CTD Group report (John Klinck, Tim Boyer, Chris Mackay,
Julian Ashford, Andres Sepulveda, Kristin Cobb)
The CTD group did two casts on 30 April at stations in
southern
Station 57 (cast 61, 512 m). The
surface layer extended to 40 m with gradually increasing density (-1.8ºC, 33.1 psu, 0.15 ug/l chlorophyll) A second
uniform temperature layer (Winter Water?) extended from 50 to 100 m. Several 10 m thick layers appeared in the pycnocline to 200 m.
The deep water was 1.3ºC with no temperature maximum. At the bottom, chlorophyll increased slightly
(to 0.05 ug/l).
Station 58 (cast 62, 1287 m). The
surface layer was thin (20 m, -1.8ºC, 33.1 psu, 0.15 ug/l chlorophyll). Temperature
and salinity increased from 20 m to 250 m with the same slope. One big
temperature reversal occurred at about 60 m. Some property jumps and layers
occurred throughout the pycnocline. A temperature
maximum occurred at 400 m (1.4ºC) and the temperature below 1000 m was warmer and
saltier by 0.1ºC and 0.02 psu, respectively.
Marine Mammal report (Debra Glasgow)
The marine mammal survey began at 1053 on 30 April in 10/10
close pack ice, which continued all day. Twenty-one seals were counted in the afternoon.
These were 6 Weddell, 6 Crabeater, and 9 unidentified seals (too far away to
identify). At 1452, a group of orcas was seen in the ice bearing 010 to
starboard, 3.5 n miles away. A group of 4-6 whales surfaced,
their dorsal fins obvious in the ice though they were so far away. One dorsal
fin was obviously male, the others were either
juvenile or female. One whale was seen spyhopping
alongside the others. There was open water approximately 7 n miles to starboard
at the time and several seals were visible lying on ice floes nearby. I saw
these whales only once, and first saw them through my binoculars while scanning.
This was the only cetacean sighting for the day. Survey ended at 1605, as we stopped
at Station 58 with the Gould visible
on the horizon.
Marine Mammal passive listening report (Ana Sirovic)
Nine sonobuyos were deployed over
this period, 1 Difar and 8 omnis. Two of the sonobuoys
failed shortly upon deployment, one most likely due to heavy ice. Blue whale calls were heard on 2 of those
buoys—the ones deployed on the 25th and 26th as we were working our way
offshore on transect line 6. Both of
these sets of calls were fairly loud and clear.
A humpback song was heard on 1 sonobuoy
deployed on April 28th after leaving station 53. Whales were sighted while the station work
was ongoing, but they weren't positively identified (see
Sea Birds (Erik Chapman and Matthew Becker)
The seabird survey continued within the sea ice in George VI
Sound between stations 57 and 58 on 30 April.
Ice and snow coverage in the early morning was the heaviest of the
survey, with depths of 4 meters and one meter respectively. In late afternoon, the survey took us within
about 5 nautical miles of the ice edge and there was a visible swell running
through the pack out of the north. As a
result, floes were more loosely packed with open water and slush between them,
a contrast to what exited further into George VI Sound yesterday. Surveys for birds were conducted throughout
the day as the Palmer traveled about 4 knots through the ice. We also surveyed during a MOCNESS tow;
however, due to the slower ship speed at this time, the requirements of
standard seabird survey methodology were not met, and thus the collected data
will only be used qualitatively.
The MOCNESS tow captured adult krill in the top 100 m of the
water column, and once again we saw ice-associated Adélie Penguins and Snow
Petrels in the pack, though at slightly lower densities than were found
yesterday. The Snow Petrels appeared to
be foraging in the area and may have been feeding in small openings in the ice
between floes. Adélies
were seen all within a short period of time, about an hour and a half into the survey
and were likely feeding on the krill swarms similar to those sampled during the
MOCNESS tow. Once again, we didn’t see
large numbers of Adélies, rather they were sparsely distributed and patchy
throughout the pack ice. These
observations are consistent with those of the previous two SO GLOBEC cruises.
We will try to take observations tonight using night vision
goggles as we leave station 58, which should take us out of the ice and into
open water within a few miles.
Predators, including flying birds and penguins, have been found to
concentrate along some ice edges and it will be interesting to see if we
observe this phenomenon tonight.
A summary of the species and number of individuals of birds
and seals within the 600 m transect (the quadrant between 600 m off the bow to
600 m off the port beam) during 5 hours, 27 minutes of daytime surveys between
consecutive stations 57 and 58 is the following:
|
Species (common name) |
Species (scientific name) |
Number observed |
|
Snow Petrel |
Pagodroma nivea |
6 |
|
Adélie Penguin |
Pygoscelis adeliae |
15 |
|
Kelp Gull |
Larus dominicanus |
1 |
Water Sampling for Microzooplankton
(Phil Alatalo)
Despite storms along the shelf and ice in
Survey line 6 of NBP0202 started out in good weather and
brash ice in
ROV Under-Ice Investigations (Andrew Girard, Amy Kukulya, Gaelin Rosenwaks, Philip Alatalo)
The Sea-Rover ROV equipped with a stereo camera VPR system
is yet another platform used by researchers in the Southern Ocean GLOBEC
program to discern the whereabouts of krill.
This system is used primarily for investigating the underside of ice for
krill and other organisms which utilize this important habitat. The ROV-VPR utilizes a SBE37 CTD to measure
depth, temperature, and conductivity, a DVL Navigator 1200 kHz ADCP, to measure
current speed and direction, and an Imagenex 630
kHz-1Mhz scanning sonar to navigate. A
pan and tilt video camera allows forward visual orientation for the
operator. Two video cameras linked to a
strobe are placed along a 1 ½ m long mount, allowing stereoscopic filming of roughly
a 1 cubic meter section of the water column or ice surface.
ROV-01 was deployed on 29 April at 2100 at Station 56. Ice conditions were less than optimal due to
ice thickness. This inhibited the ship's
ability to maneuver as well as the ROV.
Much of the piloting was done in brash ice, chopped up by the ship's
propellers. New improvements for the ROV
systems include a shorter light bar, allowing easier removal from the Baltic
Room hangar and a longer cable (160 m) allowing deployment from the stern. To minimize snagging, a polypropylene web
jacket surrounded the cables for a length of 35 m back from the vehicle. Launch was accomplished using the aft crane
and a new stainless steel pull pin.
Recovery was achieved using a Kevlar sling attached to a snatch-hook on extension
pole. Vertical trim of the ROV was
maintained using the upward thruster; neutral buoyancy of the extra cables is
controlled by varying the number of trawl and syntactic floats. Modifications of the buoyancy will be made in
future deployments to optimize maneuverability by the operator.
Investigation of the underside of ice was as expected:
large, rounded chunks and slabs of ice in pieces of less than 1 to several
cubic meters. The ice surface was smooth
and no diatoms were present underside.
Two large ice/snow banks 20-30 m to starboard were examined. Ice conditions were similar to brash, except
the depth of one bank was 12 meters! No organisms were seen on this first trial.
Zooplankton (MOCNESS/BIOMAPER-II) report (Carin Ashjian, Peter Wiebe)
MOCNESS #15 was conducted in George VI Sound between
stations 57 and 58 during mid-day.
Although ice cover was extensive, we had no trouble conducting the
tow. Less wire was let out than the
total bottom depth, so there was no risk of putting the net on the bottom
should the ship be forced to stop. After
the maximum wire had been extended, the ship was slowed to less than 1 knot, so
that the net fell further through the water
column, sampling greater depths than possible at the normal 1.8 -2 knot towing
speed. The net sampled to 378 m in a water
column of 530 m.
Copepods were abundant from 100-378 m and near the
surface. Biomass in the surface net was
very low. Krill were seen at all depths
above 300 m. No
furcilia were observed. Ctenophores were seen from 25-100 m.
Amphipods were observed at mid depths (100-200 m). Ostracods were collected
in the 100-150 m depth range. A salp was collected in the 200-300 m depth interval.
The thick pack ice and heavy snow pack on top made it
difficult for the Palmer to make
quite a portion of the 17 mile transit from station 56 to 57 without stopping
to back and ram, even though it was retracting the path taken on the station 55
to 56 line before heading west to station 57.
So BIOMAPER-II was not deployed on 30 April until nearly half-way to
station 57. The towyo to station 57 was successful
and intense scattering was observed, principally on the 120 kHz echogram, close
to the surface. Well before reaching the location of station 57, the Palmer ran into pack ice that was again
too massive to move through. The towed
body was recovered and the station made where the ship had stopped around 0730.
Although most of the station 57 work was completed in late morning, BIOMAPER-II
was kept on the deck while the Palmer
steamed towards station 58, so that when the ship was able to move continuously
through the ice pack, a MOCNESS tow could be taken. Following the net tow,
BIOMAPER-II was deployed and then towyoed for the
last two hours of the steam to station 58.
Again, the heaviest volume backscattering occurred near the surface.
Cheers, Peter