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

31 August 2002


The N.B. Palmer and the L.M. Gould were finally able to rendezvous during the morning of 31 August in the vicinity of station 22. The high winds and white-out conditions that had delayed the meeting of the vessels had abated some by the late evening of 30 August.  While there was still some snow falling, the winds were down in the 20 kt range and a transfer of personnel and equipment was possible prior to beginning the third convoy. This transfer took place by zodiac boat in a large lead about 0930 and was completed by 1100.  Three people from the Gould came over to the Palmer along with their gear and personal effects for the duration of the survey of the northern sector of the Southern Ocean GLOBEC grid.  Two, Heidi Geitz and Bret Pickeral, are part of Bill Fraser's penguin group.  They came to the Palmer in order to enhance their opportunities to deploy the remaining five satellite tags on Adélie penguins encountered during the survey.  The Gould's process stations do not afford as much opportunity.  An extra personnel basket to be deployed from the Palmer's bow for use by the penguin group was also transferred temporarily, since the Gould had two of them. The other person to make the transfer was Chris Fritsen, who works on sea ice microbiota.  He wanted more access to the variety of pack ice types that are likely to be encountered during the survey of sector three.


The convoy got underway for the ~50 nm steam north toward station 4, the intended location for the third process site. Along the trackline at approximately 10 nm intervals, XBT's were dropped to vertical temperature profiles. About an hour and a half into the journey a group of Adélie penguins was sighted swimming in a lead.  One hauled out onto the pack ice, while the others disappeared.  A Zodiac was launched from the Palmer with a group of the seabird specialists and within 45 minutes the penguin had been netted and tagged.  It was a good start for the work in the northern sector.  While the Zodiac was out, the pair of ring nets was deployed off the stern in the upper 5 to 10 m in hopes of collecting more krill furcilia for experimental work, but time was short and few were caught. 


The transit to station 4 went remarkably well primarily because the pack ice was somewhat thinner and there was more open water around the floes. More importantly, the floes themselves were broken up into smaller pieces that were easy to move through.  As we got close to station 4, a long period swell running from the north under the pack ice became evident. Along with the high winds of 30 August, the swell was also playing havoc with the pack ice. In an evening radio communication with the Gould, it was clear that they had not seen pack ice that was suitable for staging a third process station.  The storm on the 30th had broken up all of the big floes and loosened up all of the pack ice to such an extent that it would be hard to put people on the ice and take cores for an extended period of time as required for a time-series station.  Unfortunately, better conditions did not appear to be anywhere close, so the convoy continued on to station 4. We arrived there about midnight on 31 August.


During the evening of 31 August, there was a scientific investigator's meeting to discuss the station work for grid sector three.  There was consensus that after station 4, the work would proceed out to station 1 and then back south along the continental shelf to station 23. The most inshore stations would be approached after that and work at them would be done to the extent possible.


The remnants of the 30 August storm were present through the late night period of 30/31 August. After that winds dropped below 30 kts by 0600, but a light snow persisted. The air temperature, which reached a high of +0.6ºC stayed around 0ºC until mid-afternoon when a wind shift from northeasterly to westerly took place. Then the temperature dropped over several hours down to about -5ºC.  The wind shift and temperature change corresponded with a shift in the barometric pressure from falling to a minimum of 974 mb to rising slowly. By the end of the day, winds were in the 5 to 10 kt range. Surface sea water temperatures during much of the transit to station 4 were above freezing, providing another reason for the thinner pack ice in the region.


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

In the early morning of 31 August the weather conditions cleared sufficiently for the Palmer to resume the transit to meet the Gould and move it to the next process site.  Soon after getting underway, the CTD group began an XBT survey which continued throughout the day and ended in late evening when the site selected for the next process station was reached.  A total of ten XBTs were dropped along the transit at about 10 nm intervals.  Of these, seven were T-7 probes with a nominal depth of 760 m; the remaining three were T-4 probes which have a nominal depth of 460 m.


Because of the sea ice, the wire for three of the XBTs broke before the probe encountered the bottom or reached its maximum depth.  The data from these casts provided measurements of the upper water column; however, the casts were repeated to obtain a full temperature profile. The remaining seven XBTs returned temperature data from the full depth of the probe or until the bottom was reached.


The start of the XBT survey was near station 13 on survey transect 2 from which it extended in a north-northeast direction towards survey station 4 in the mid-portion of transect one.  As a result, the XBT survey cut across the portion of the northern part of the survey grid where previous SO GLOBEC cruises have observed onshore bottom intrusions of Circumpolar Deep Water.


Temperature profiles from the first 2 to 3 XBTs showed warm water (1.45 C to 1.5ºC) present from about 200 m to the bottom, which was between 450 m and 475 m.  This suggested the presence of a Circumpolar Deep Water intrusion.  This was confirmed by the temperature profiles from subsequent XBTs which showed 1.7 C to 1.8ºC water below 250 m, with the maximum temperature at about 350 m.  Below the maximum, water temperature decreased, which is the expected structure for an intrusion of warm, salty water onto the west Antarctic Peninsula continental shelf.  The temperature profiles show considerable fine scale variability below 250 m that may result from mixing and/or interleaving along the boundary between the intruded oceanic water and the continental shelf water.


The surface temperatures along the XBT survey were above the freezing point, with the warmest temperature of -1.72ºC occurring at the north end of the transect.  The depth of the well-mixed Winter Water layer along the transect was about 60 m.  This is the warmest surface water and shallowest Winter Water layer encountered during the survey. These upper water column characteristics may result from mixing of the surface waters with the warmer water at depth.  This process also likely contributes to the reduced sea ice cover and extensive areas of open water that have been encountered during this transit.


Seabirds (Chris Ribic and Erik Chapman)

On August 31, a seabird and Crabeater seal survey was conducted while the N.B. Palmer traveled toward station 4 in convoy with the L.M. Gould from the starting point near station 22.  This survey 40 to 60 miles offshore brought us to the northern-most section of the grid where ice conditions were dramatically different from those farther south.  Ice concentration varied between 6 and 9/10ths coverage of vast floes and small floes separated by areas of open water.  Sea-ice thickness varied considerably, from 40 cm to more than 1 m.  As noted above, XBT data in this area has indicated the presence of warm water associated with the Antarctic Circumpolar Current, which may be responsible for maintaining the considerable open water and thin ice here.  Through much of the day, a swell of 1.5 to 2 m ran through the pack as a reminder of the storm we've experienced over the last two days and perhaps an indication of our relatively close proximity to the ice edge. The seabird species assemblage here differed dramatically from those in areas of the grid farther inside the pack ice.  We saw more species and birds on 31 August that on any previous day of the survey and we saw species that are typically found in open water and species that are typically associated with sea-ice.  The open water species observed included the Southern Fulmar and Blue Petrel.  We also saw a single adult Kelp Gull, a species that typically remains close to land that may have moved farther offshore toward the ice-edge as the pack ice continued to be compacted inshore.  A single Southern Giant Petrel was also recorded in today's survey.  Satellite telemetry of Southern Giant Petrels on the Antarctic Peninsula indicates that this bird may forage along the ice edge and our current observation may be some indication that we aren't too far from the edge of the pack ice.  Snow Petrels and Antarctic Petrels, species that are typically associated with sea ice, were relatively abundant in the survey and were milling over open water and ice-edges.  Interestingly, Antarctic Petrels were also seen in small groups sitting on the surface of the ice.


A group of at least 30 Adélies was recorded porpoising through a large lead.  One individual from this group hauled out on a floe and we were able to assist birders from Dr. Bill Fraser's group fix this bird with a satellite tag that will record dive-depth and location for this bird over the next several weeks.  An Emperor Penguin was also observed in a separate lead.  No seals were observed in today's survey. 


A summary of the birds and marine mammals observed on 31 August (YD 243) during 4 hours, 21 minutes of survey time as the ship traveled near station 4 from near station 22 is the following:


Species (common name)

Species (scientific name)

Number observed          

Snow Petrel            

Pagodroma nivea                         


Antarctic Petrel       

Thalassoica antarctica                 


Southern Fulmar        

Fulmarus glacialoides                  


Blue Petrel            

Haobaena caerulea                      


Kelp Gull              

Laru dominicanus                        


Southern Giant Petrel

Macronectes giganteus                  


Adélie Penguin         

Pygoscelis adelii                      


Emperor Penguin        

Aptenodytes forsteri                   




Krill distribution, physiology, and predation (Kendra Daly, Kerri Scolardi, Emily Yam and Jason Zimmerman)

We deployed the Tucker Trawl three times, towing it repeatedly between the surface and about 30 m in depth.  Although this sampling strategy yielded about 20 larval Euphausia superba per tow, small ice chunks caught in the towed net damaged many of the animals.  We decided instead to deploy the Reeve Net and the Ring Net in tandem (the Reeve Net attached to the cable about 3 m below the Ring Net) at about 10 and 7 m, respectively, below the stern. Using this method we collected a couple of hundred E. superba and E. crystallorophias larvae in excellent condition.  The larvae were furciliae stage 4 to 6, 8.5 to 13 mm in length.  We also collected ctenophores, numerous copepods, small larvaceas, chaetognaths, a few small juvenile krill, fish larvae, and greenish detrital material. 


Based on net collections and diver and ROV observations to date, larval krill appear to be distributed very differently from our last winter GLOBEC cruise.  In contrast to the high densities of larvae concentrated under sea ice last year, this year larvae are scare and may be primarily in the upper water column.  Instead of feeding on sea ice biota, which is present on the undersurface of sea ice thus year, they may be feeding on aggregates in the surface layer.  The chitinous outer exoskeleton of krill is relatively transparent, so we can see food in their stomachs if they have been feeding recently.  Most of the larvae collected had small amounts of material in their guts and intestines, in contrast to larger krill, which seldom had material in their stomachs.


We are currently measuring growth and molting rates on the larval krill.  We completed experiments to measure ingestion and egestion rates of larvae using surface seawater as a food source.  The furcilia produced numerous fecal pellets (egested unassimilated material after feeding) over the time period of the experiment, indicating active feeding.  Although chlorophyll concentrations are relatively low (0.02 g L-1) throughout the water column, sticky aggregates of detrital material and microplankton are present in near surface waters.  These aggregates are composed of varying material.  Many are radiolarians with a silica “lattice” outer framework, remaining from a fall bloom, some are larvacean houses, other aggregates are long setae from a fall bloom of chain diatoms.  Unidentifiable small detrital particles adhere to these aggregates, as well as veliger larvae, small larval worms, and small copepods.  Another ubiquitous component appears to be glacial flour. The small, often colorful, crystalline fragments range in size from a few tens of microns to hundreds of microns in size.  We have observed these particles in samples from the water column and ice and in the guts and fecal pellets of krill on all four GLOBEC cruises.  Although these particles have no nutritional value, they may add additional weight to the fecal pellets thereby increasing their sinking rates into deep water.


We also are continuing to observe diet in ctenophores and to measure their digestion rates.  In addition we are measuring ctenophore respiration and excretion rates in collaboration with Jose Torres.


Current Position and Conditions

Work in the northern sector of the Southern Ocean GLOBEC survey grid is proceeding apace. During the first day of the survey, work at three stations was completed.  We are now at Station 1 located off the continental shelf in 3000 meters of water and work here will be completed shortly.  Our current position at 0741 on 2 September is -65º 37.291′S; -70º 36.241′W.  The air temperature is -7.1ºC and the barometric pressure is 988.5 mb and rising.  Winds are back up into the 30 kt range (30-35 kts) out of the southwest (217). The pack ice is mixed with considerable open water and the Palmer is gently moving in response to a long period swell moving through the area.  High clouds cover the entire region, but visibility is good.


Cheers, Peter