Report of Activities on the RVIB N.B. Palmer Cruise 02-04  

29 August 2002


We finally arrived at Station 26 at 0400 on 29 August after a two and a half day struggle to steam the 67 nm from station 40.  We made an average 2.5 kts for the last 20 nm of the journey because pack ice conditions improved modestly as we moved farther out onto the continental shelf. A dense fog developed during the late night, however, forcing the bridge to proceed with caution. 


Work at the station began immediately with a two-hour deployment of the ice collecting team onto a floe next to the ship and the ROV to survey the ice under the floe. A pair of CTD casts followed after a period in which the ship maneuvered to create a hole in the ice next to the Baltic room door through which the CTD could be deployed. A Reeve net tow was made right after the CTD came on board in an attempt to capture live krill furcilia, but few were caught in the vertical tow.  The 1-m MOCNESS, which was up next, had a false start when the flow meter failed to work once in the water. It was replaced. The tow, which was made in a partially frozen 3-mile lead, went smoothly to within ~25 m of the bottom in 425 m of water,. A number of krill furcilia were caught in the surface net, but not enough for experimental purposes.  In the early afternoon, the Torres group did a SCUBA dive under an older ridge formation. During the dive, the CTD group did a series of vertical profiles to measure variation in microstructure over short time intervals.


The large lead made it possible to do additional net towing to collect live plankton, especially krill furcilia. Two shallow tows (0-40 m) were made with the Tucker trawl, but the results were disappointing; few furcilia were caught.  A deep Tucker trawl netted more live animals for experimental purposes, but few furcilia.  An alternate strategy for capturing furcilia was tried. The two 1-m ring nets were deployed off the stern on the 9/16 trawl wire with one net positioned several meters above the other.  With the propellers turning enough to produce a gentle current aft, but not enough to move the Palmer forward or to cause ice chunks to sweep down under the hull, the pair of nets were lowered to a few meters below the surface. After an hour, the nets were retrieved and the collections contained a very nice catch of live krill furcilia.


The krill furcilia collection marked the end of work at station 26 and also the completion of the work in the central sector of the Southern Ocean GLOBEC grid.  The fourth rendezvous with the L.M. Gould was scheduled for 30 August and we began steaming to the northeast around 2200 on 29 August. BIOMAPER-II was deployed for the steam toward the Gould, but after about two hours ice conditions became inimical to towing and the towed body was brought on deck.


Working conditions during the day were good. The winds were light (< 10 kts) until noon and then picked up to around 25 to 30 kts by evening. This was preceded by a wind shift just after midnight from southwesterly to northeasterly as a high pressure cell left our area. Barometric pressure, which had been quite high (1012 mb), began falling in mid-morning and was at 1005 by late evening and still falling. Air temperature in the morning dropped from -8 to -11ºC until the barometric pressure began to drop and then rose to -3.7ºC by midnight.  Skies were variably cloudy all day. A band of color appeared at the horizon during sunrise, but that was about all we saw of the sun. A light fog enveloped the area for much of the day making visibility mediocre.


CTD Group report (Eileen Hofmann, Bob Beardsley, Baris Salihoglu, Chris MacKay, Francisco (Chico) Viddi, Sue Beardsley)

Station 26, which is on the outer part of survey transect 5, was a busy station for essentially all groups represented on NBP02-04.  After arrival at station 26, one CTD cast was done to obtain microstructure measurements.  This was followed by a second cast that went to within a few meters of the bottom (426 m). The lowering speed on the second cast was reduced in the upper 100 m to accommodate the FRRF.


On the second cast, two Niskin bottles were closed at the bottom to obtain water samples, as is our usual procedure.  However, no bottles were closed between the bottom sample depth and 150 m so that two Niskin bottles could be closed at each of several depths between 150 m and the surface.  The additional water from the upper water column was for the chlorophyll/primary production group to set up experiments.


Following those two CTD casts, the Torres group did an under-ice dive and during the time that the dive group was away from the ship, we did four CTD casts, each to 300 m, in rapid succession.  Each cast took about 20 minutes from start to finish.  These repeat casts provide measurements that will allow the variability associated with the observed microstructure profiles to be determined.  Water samples were not taken on these casts, except for the last cast, during which 10 Niskin bottles were closed at the surface to obtain water for the Daly group.


Surface temperature and salinity at station 26 were -1.82ºC and 33.90, respectively, and these values extended to about 85 m.  This Winter Water layer is similar to that seen at other station locations throughout the survey grid.


The bottom temperature and salinity values of 1.35ºC and 34.71, respectively, are similar to those expected for a shelf location that is not influenced by an intrusion of Upper Circumpolar Deep Water. The bottom temperatures at this station are cooler than those observed during NBP02-02, which took place in April-May 2002.  This may indicate that more shelf water has moved to the outer portion of the continental shelf in this region.  This in turn may be a response to the occurrence of an intrusion of Upper Circumpolar Deep Water farther to the north.  The stations that we occupy during the next week or so will provide the information needed to determine if this is happening.


Seabirds (Chris Ribic and Erik Chapman)

Seabird and Crabeater seal surveying was conducted for almost 9 hours on 28 August, as the ship moved toward station 26 from a position near station 41.  The Palmer backed and rammed through vast floe ice for most of the day, but the ship was able to move well through leads which we began to encounter more regularly in the afternoon. Visibility varied between 300 and 600 m from the ship as snow fell for most of the day. 


Once again, bird densities were low and 8 Snow Petrels and 2 Antarctic Petrels were the only flying birds observed.  A single Adélie penguin was recorded making this the fifth straight day in which this species has been observed.  Fourteen Crabeater Seals were recorded during the survey as well.  Crabeaters have been recorded throughout the study grid, but seem to be in greater numbers in the southern sector than in the central sector.


A summary of the birds and marine mammals observed on 28 August (YD 240) during 8 hours, 57 minutes of survey time as the ship traveled toward station 26 from near station 41 is the following:


Species (common name)

Species (scientific name)

Number observed          

Snow Petrel          

Pagodroma nivea                 


Adélie Penguin     

Pygoscelis adelii                  


Antarctic Petrel       

Thalassoica antarctica         


Crabeater Seal         

Lobodon carcinophagus  




ROV report (Scott Gallager, Phil Alatalo)

Early in the morning of 29 August, we deployed the ROV near Station 26 at 67º 06.827′S; 72º 00.226′W where the bottom depth was 323 m. The area was 10/10 ice covered with small re-frozen floes and extensive ridge fields about 1 m in height. Ice thickness was about 1.2 m with 30 cm snow cover. The ROV was deployed at 0425 local time immediately after the ice team landed on a small floe on the starboard side of the ship. Once in the water, the ROV instrumentation and sensor systems were checked out and a transect was started at a bearing of 90º with the ship’s bow positioned at 47º. A ridge 12 m deep was navigated immediately upon leaving the stern of the ship. Within an additional 50 m, the bottom of the flow where the ice team was working appeared on our screens. The undersurface of the floe was very heterogeneous, rough, and jagged, appearing like re-frozen brash and chunks, rather than the smooth surface characterizing floes of first year ice. Krill furcilia were scattered throughout the area at concentrations between 0.5 and 5 per m3. One to three furcilia were observed every few seconds on the stereo VPR camera system. There were no large aggregations or patches of these animals.  Most larvae were motionless angled sharply forward in a head down position, but a few were swimming slowly at an attack angle of about 30º. Many ctenophores were also observed on order one per m3. Most of the furcilia and ctenophores were relatively deep at the tips of the ridges rather than up against the undersurface of the floes.


MOCNESS Report (Phil Alatalo, Peter Wiebe, Dicky Allison, Ryan Dorland, Scott Gallager, Gareth Lawson)

A large lead at station 26 provided the trackline for the ninth 1-m MOCNESS tow of the cruise.  The tow was the furthest north on the grid to date.  Recurring problems with the flow meter eventually resulted in three replacements before deployment.  Other than a “slow to function” salinity sensor, no other electrical/mechanical problems occurred; the OPC ran flawlessly.  As we sample more to the north, krill are appearing more regularly in our samples.  The samples below 200 m had relatively large biomass, while all nets above 200 m held very few organisms.


The oblique haul (net 0) for genetic studies captured many copepods and a large siphonophore.  Krill, their furcilia, and amphipods were also abundant. Copepods (Metridia, Paraeuchaeta) were most abundant in the deepest net (375-350 m), with siphonophores providing the most biomass.  Chaetognaths, amphipods, ostracods, juvenile Euphausia superba, and a small dark medusa were also notable.  Net 2 (350-200 m) was full of copepods and juvenile krill.  Ostracods and small pteropods showed up here and were present in all nets up to 75 m.  From 200-150 m, ostracods were nearly as numerous as copepods.  Here large copepods (Calanus propinquus, Paraeuchaeta sp.) were present along with all stages of Thysanoessa krill and a large chaetognath.  Radiolarians were very common from 200 m to 75 m.  Although biomass was very low in the upper water column, Thysanoessa furcilia were abundant around 100 m and E. superba furcilia abundant at the surface.  Other organisms present in shallow water were larvaceans, polychaetes, and chaetognaths.  Two small ctenophores were collected for Kerri Scolardi between 75 and 25 m.


Results from OPC data processed from station 26 showed relatively high counts and biovolume in the 395-m tow.  Count densities reached over 1200 individuals/m3 between 300 and 350 m, corresponding to a scattering layer observed on the Simrad Echosounder at 38 kHz.  A second layer observed by the ADCP was sampled between 100 and 150 m with over 800 individuals/m3.  Background counts ranged from 300 near the surface to 600 individuals/m3 near the bottom.  The normalized OPC counts-spectra showed elevated abundances of larger individuals throughout the tow with estimated spherical diameters between one-half and two mm noticeably higher than previous tows in the region.  Biovolume was highest below 300 m, reaching 200 mm3/m3.  These results were comparable to a Crystal Sound tow at the beginning of the cruise.


Footnote:  At a position near station 40, a vertical 1-m ring net tow was conducted in lieu of a 1-m MOCNESS because the pack ice was not conducive to towing while underway.  Copepods were the most abundant organism, with krill, amphipods, radiolarians, worms, and pteropod larvae present.  The weight on the end of the cable hit the bottom (430 m) and the net caught some benthic animals (i.e., a brittle star and large, red polychaete worm).


BIOMAPER II group report (Gareth Lawson, Peter Wiebe, Scott Gallager, Phil Alatalo Dicky Allison, Alec Scott)

After all other work had been completed at station 26 on August 29, we began an 11 km towyo with the BIOMAPER II as we steamed northeast towards our rendezvous with the Gould. A very diffuse shallow scattering layer was present generally between 50 and 100 m, associated with the top of the pycnocline. Due to our problems with the fraying tow cable, we are presently only able to tow the BIOMAPER II to 125 m, and so can make VPR observations only between this depth and the surface. Those VPR images that we did capture on this towyo suggested that the planktonic community between the surface and 100 m consisted of larvaceans, ostracods, and copepods, including Calanus. At 55 m and then again at 95 m depth, we also saw the tails of what were probably two large krill, suggesting that some adult krill were present in the sparse layer we observed acoustically.


Scattering was low throughout the rest of the water column, except close to the bottom (400 m), where there was a dense layer 100 m high. There was also some evidence of stronger individual targets at the top of this layer. The 1-m MOCNESS tow at station 26 sampled the bottom layer and caught some krill and siphonophores as well as copepods. The former two categories may have contributed significantly to the backscattering and target strengths in the layer.  


It is perhaps interesting to note that we collect our acoustic data in two forms. The first measures the total amount of sound reflected back from all organisms found in the water column at a particular range within the transducer's sound beam. This is the quantity we typically refer to as backscatter, and it is related to the density of organisms. The second form of acoustic data measures the intensity of echoes (or target strengths) of individual targets detected within the sound beam. Target strength is proportional to the size of an organism, and so by measuring this quantity we are able to gain an understanding of the planktonic community's size distribution. Therefore the stronger targets at the top of the bottom layer observed in this towyo are likely to be from fairly large animals. Both forms of data are reported in decibels (dB), or ten times the logarithm of the ratio of the intensity of sound reflected back towards the transducer to the intensity of sound emitted from the transducer. Since the former is always smaller than the latter, our measurements of backscatter in dB are always negative, with more intense backscatter values being less negative.


Current Position and Conditions

A major storm with peak winds 45 to 55 kts descended upon us and for much of 30 August, we have been hove-to waiting for white-out conditions to pass so that we could resume our transit to a rendezvous point with the Gould. Our current position at 2205 on 30 August is -66º 49.356′S; -72º 05.669′W.  The air temperature is a remarkable +0.6ºC, the highest we have seen since crossing the polar front in the Drake Passage at the beginning of the cruise.  The barometric pressure is 981.0 and still falling. Winds have abated somewhat and are running between 30 and 40 kts out of the north-northeast (024). Snow is still falling moderately, but the white-out conditions appear to be lifting.


Cheers, Peter