Report of Activities
on the RVIB N.B. Palmer Cruise 02-02
8 May 2002
The N.B. Palmer
had reached the most southern portion of the Southern Ocean GLOBEC broad-scale
survey on 8 May and was working on the 12th of 13 survey lines. The work began
well before dawn at station 85 about 20 miles from
The skies on 8 May were crystal clear and the peaks of
The transits to the other two stations of the day were done
for the most part while the sun was above the horizon and provided
unprecedented opportunities to see mammoth icebergs seemingly within arms
reach. One was estimated to be more than
70 m (210') tall. For much of the morning,
the Palmer had to thread its way around the bergs and moved through open
patches of freshly iced over leads interspersed with year old ice floes. As indicated, the weather together with the
scene made it, perhaps, the most beautiful day yet of the cruise. Winds were around 10 kts
out of the south in the morning, picked up into the low 20's in late afternoon,
and then dropped to 10-15 kts in the evening. During the day the barometer fluctuated
between 981 to 989 mlb and the air temperature
hovered between -11ºC and -13ºC. Even with the relatively light winds, the wind
chill was such that when working on the deck, it felt bitterly cold.
On May 7, work was completed at broad-scale survey stations 85, 86, and 87. CTD casts were made at each of these stations. An ROV under ice survey and an ice collection were done at station 85, and a 1-m ring net tow for surface zooplankton was done at 87. BIOMAPER-II was in for transits between the all of the stations. Seabird and marine mammal surveys took place during the daylight period and 2 sonobuoys were deployed during the transit to stations 87 and 88.
CTD Group report (John Klinck, Tim Boyer, Chris Mackay,
Julian Ashford, Andres Sepulveda, Kristin Cobb)
The CTD group did three casts today on the inner and middle
part of the 060 line (survey line 12). Two of the stations were shallow and
barely reached into the pycnocline. The mid-shelf
station was typical of other mid-shelf stations, with cold deep water. This station
retained the Winter Water (WW) layer that had vanished at other recent
stations.
Station 85 (cast 89, 175 m). The
surface layer was uniform to 90 m (-1.8ºC, 33.3 psu,
0.06 ug/l chlorophyll). There was an increase of temperature and
salinity to the bottom with no temperature maximum.
Station 86 (cast 90, 260 m). The surface layer was uniform to 80 m (-1.8ºC, 33.4 psu, 0.05 ug/l chlorophyll). Temperature and salinity increased to the bottom, although slight temperature steps occurred at 115 and 160 m. A 10 m thick uniform layer was at the bottom.
Station 87 (cast 91, 442 m). The
surface layer was uniform to 80 m (-1.8ºC, 33.4 psu,
0.06 ug/l chlorophyll). There was a slight WW layer at 150 m. Some 5 m thick
temperature layers occurred. The deep
temperature was almost uniform (1.2ºC) with no temperature maximum. A 5 m thick slightly warm layer occurred at
10 m depth. Some additional thin salinity
spikes were seen below 200 m, which may have been due to the instrument.
Marine Mammal report (Debra Glasgow)
The marine mammal survey began at 1013 on 8 May. It was a clear morning at a crisp minus 13.9
degrees. The transit to Station 86 was
made in 8-9/10 open pack ice, with many icebergs and large first-year ice floes
exhibiting pressure ridging. Open pools covered in nilas
and some brash ice were common. An ice floe sampled at Station 85 was 276 cm
thick, coated with a 74 cm layer of snow. These ice conditions stayed similar throughout
the day, with occasional areas of rafted pancake. Crabeater seals were thinly
spread along the track line as we continued transit during the day to stations
86 and 87, with a total of 18 seals recorded for the day - mostly in the
water. Five of these seals were in a
tight group seen swimming across the bow under the nilas
to shelter and surface around a growler to port. The nilas
was distorted by their wake and their bodies could just be seen under the
surface of the ice. The survey ended at 1637 in very poor light, the last color
from the sunset draining from the sky as we entered a large nilas
coated polynya surrounded by a necklace of sculpted
icebergs.
Sea Birds (Erik Chapman and Matthew Becker)
Seabird surveys were conducted for nearly 5 hours on 8 May
under virtually cloudless skies as the ship traveled between stations 85 and 87
near the northern shore of Charcot Island. The area surveyed was covered with 7 to
9/10ths ice concentration, consisting of large year-old and multi-year floes
interspersed with nilas. The ice was substantial enough to cause the
ship to come to a halt several times, and our cruise track assumed the path of
least resistance in order to follow leads and snake through the countless icebergs
in the vicinity.
Outside of a single Adélie Penguin, Snow Petrels were the
only birds observed today in the ice.
Once again, Snow Petrels seemed to be in lower abundance in the thick,
older ice than further offshore where younger predominated. We saw little sign of recent penguin activity
such as tracks or guano on the snow-covered floes. This suggests that Adélies
have not been active in this area at least over the last several days.
A summary of the species and number of individuals of birds and seals within the 300 m transect during 4 hours,56 minutes of daytime surveys between consecutive stations 85 and 87 is the following:
|
Species (common
name) |
Species (scientific
name) |
Number observed |
|
Snow Petrel |
Pagodroma nivea |
43 |
|
Adélie Penguin |
Pygoscelis adeliae |
1 |
Material Properties of Zooplankton Report (Dezang Chu, Peter Wiebe)
On May 9, the only activity associated with the material
properties measurements of plankton was a Reeve Net tow made at station 88 (68 59.782ºS;
76 21.865ºW). The water depth was around 420 m. There was a light scattering
layer between 300 to 350 meters observed on the Simrad
EK500 38 kHz echogram. Normally an oblique tow with the net deployed from the starborad Waterfall winch is made with the ship moving
forward at about 2 kts. But this was not possible due to pack ice,
which prevented the ship from being able to move sideways or ahead without damaging
the net. So only a vertical Reeve Net
tow was made. The Reeve Net was deployed to 375 m. Many copepods (Calanus) were
caught, but it was not enough to use them to conduct reliable acoustic sound
speed and density measurements with the APOP.
Water Sampling for Microzooplankton
(Phil Alatalo)
As we progressed further to the south, the survey lines
shortened in length as
The large ciliates with a distinctive lumbering swimming motion nearly disappeared. Diatoms were distinctly fewer in number, though all previously seen types were present. Mesodinium showed up at depths other than the surface. General motility of all microplankton decreased notably. Chorophyll, temperature, available light were all in decline; ice cover became more frequent. I believe we have been seeing the seasonal transition to winter conditions that was documented on last year's cruise.
Zooplankton (MOCNESS/BIOMAPER-II) report (Carin Ashjian, Peter Wiebe)
There was no MOCNESS towed during 8 May.
On 8 May, the zooplankton and krill survey of using acoustics, video, and environmental sensors on BIOMAPER-II was done on the transits between stations 84, 85, 86, and 87. The thick pack ice made the towyoing nerve racking because often ice floes and other large chunks of ice would come into the wake region and appear about to hang up on the towing cable. In such a case, the ship would be stopped quickly and the wire cleared, but thus far on this cruise this need has not arisen.
During the initial portion of the run from station 84, at the end of survey line 10, to station 85, the inshore start of line 11, krill-like layers appeared regularly. They were generally near the surface (upper 100 to 150 m) and had horizontal extents of 1000's of meters and vertical extents of 100 m. Towards the end of the run, the bottom shoaled from 300 to 400 m to shallower depths (150 to 250 m) and the krill patches tended then to be close to the bottom. During the daylight run from station 85 to 86, very strong backscattering krill-like patches and layers were present at about180m below surface, but with much tighter horizontal extents (120 to 200 m). Layers and patches of krill were seen acoustically and on the VPR during the transit from station 86 to 87, although on the approach to station 87, the backscattering had diminished and the strong backscattering layers were absent. During the late evening run from Station 87 towards 88, the now typical strong scattering near the bottom with a zone within that layer of somewhat higher scattering was present. The layer extended up about 150 above the bottom. Backscattering was much lower at mid-water depths and then increased moderately in the mixed layer. No intense small patches were observed and no isolated larger targets were in the mid-water or bottom layer depths.
The finding of high backscattering layers on the inner
portions of survey lines 10 and 11 provides additional evidence for the
existence of a band of krill residing along the entire length of the
Cheers, Peter
Alberts, F. G. 1995. Geographic names of the Antarctic. Second Edition.