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

9 August 2002


August 9 was a very different day from the 8th when we were stuck for a good portion of time and wondering if we were going to go anywhere.  On the 9th, we were able to cruise along through the pack ice with no difficulty.  Still we did not go very far because there were sufficient predators out on the ice to make the Marine Mammal and Bird Groups on the Gould want to stop and go to work.  This was part of the plan for the steam to the southern section of the SO GLOBEC grid, so the investigators on the Palmer were ready with a series of tasks that could be undertaken quickly to take advantage of the break in steaming and kept working. The first encounter with penguins happened right after a fire and boat drill. The sea bird observers were allowed to go back to the bridge after signing in and it was a good thing they did. Right at the end of the session in the Palmer's level 3 conference room, the call came that a big group of Adélie penguins had been spotted. It was an exciting morning chasing penguins.  A coordinated effort to capture some of them was mounted by both the Gould and the Palmer.  Chris Ribic and Erik Chapman first spotted about 40 to 50 Adélies in a group on the ice pack ahead of the ship about 0930 hrs and they notified the Gould. Then the Gould moved ahead of the Palmer to get next to the penguins, but the penguins started moving away. So the Palmer moved up to cut the escape route and the penguins moved within a short distance of the Palmer before turning back towards the Gould.  By this time about 10 investigators from the Gould had been put onto the ice using the forward crane and personnel basket. The investigators began to walk over the ice pack to the penguins. They stopped halfway to the Palmer, fanned out, and crouched down when they realized that the penguins were now moving right back to where they were.  When the penguins were within feet of the investigators, the investigators sprang into action capturing with nets quite a number of the penguins.  It was an amazing sight with the sun coming up in the background just behind the Gould, which from our vantage point, was directly in line with the investigators and the penguins. It was a scene right out of a movie.  After the free-for-all, the Palmer was positioned to allow the HTI acoustic system and the CMiPs/CTD to be deployed as our first attempt at a rapid response to get some work done.  Having both pieces of gear in the water turned out not to be good for Kendra Daly's work with the HTI system.  The ship had to keep the propellers going to keep the CMiPS/CTD area clear of ice and this messed up Kendra's ability to keep a calibration ball under the pair of transducers.


The Gould had barely completed the work on the penguins when they spotted four crabeater seals on the ice nearby.  So they again deployed a team on the ice, drugged one of the seals, and then did their physiological/biochemical measurements and satellite tagged it. The HTI system was again deployed for some more calibration work, but ice chunks kept drifting in and interferring, so the ship moved around and a nice hole was formed.  In the end there was only about 45 minutes of measurements, which was not enough to complete the work.


Late in the day, the seal work was completed and we again started to move to the south, but only for a mile or two.  Another set of penguins were seen and the Gould made a bee-line for them. On the third stop, Frank Stewart and Jenny Boc took a group on to the ice to do ice-coring and Scott Gallager did an ROV under ice survey.  Once the Gould finished their work, the work on the Palmer was stopped and the two ships again set off along a trackline headed for the southern sector of the grid at about 5 kts.


The weather on the 9th was ideal for the science activities on both ships because the winds were light (<10 kts) and there was a good bit of sun during the day, after the morning clouds gave way to clearer skies. The air temperature was warmer in the morning (-4.6ºC at 0900) than in the evening (-9ºC at 1900).  The lower portions of the mountains of Adelaide Island to the east were clearly visible during the morning sunrise.  By mid-afternoon, while the sky was still partly cloudy with a high thin overcast, the mountains of Adelaide Island were clearly visible in their entirety.  The barometer continued to fall slowly from 991.9 mb in the morning to 986 mb in the evening. The pack ice continues to be 10/10 with infrequent leads.


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

Throughout 9 August and into the early morning of 10 August we did an XBT survey during the southward transit to escort the Gould to the first process site.  The XBT survey was ended when the decision was made to turn offshore and head for an area that the most recent TerraScan image showed to be less ice-covered.  The track followed by the Palmer after making this turn was not conducive to continuing the XBT survey.


During the southward transit, usable temperature data were obtained from 14 XBT probes, either T-7 or T-4 depending on the depth, spaced at about 10 nm intervals.  Additional probes were dropped, but interference from the extensive sea ice cover caused the wire to break prior to reaching the bottom or the maximum depth of the XBT.  The data from the incomplete XBT drops, however, do provide information on the upper water column.


The XBT transect started north of Adelaide Island, just outside of Crystal Sound, and extended southward along the continental shelf to about survey station 60.  At about 30 nm from the start of the transect, Marguerite Trough was crossed.  This is a deep depression that extends from the shelf break, across the continental shelf, and into Marguerite Bay. This provides a connection between the outer and inner shelf regions.  This bathymetric feature is thought to be the primary pathway that allows intrusions of Circumpolar Deep Water to move onto the west Antarctic Peninsula continental shelf.


A striking feature in the temperature section is the presence of Circumpolar Deep Water in Marguerite Trough.  This water mass extends from 300 m to 500 m and is found along the northern side of the Trough.  Maximum temperature associated with the water mass is 1.54ºC. During the April-May 2002 U.S. SO GLOBEC survey cruise (NBP02-02), water temperature at the same location and depth was 1.4ºC.  The hydrographic data collected in the northern part of the survey grid at the end of NBP02-02 suggested that an intrusion may have been starting.  Thus, it may be that during the two months separating this cruise and NBP02-02, Circumpolar Deep Water moved into Marguerite Trough and onto the west Antarctic Peninsula continental shelf.  This will be examined more extensively once the survey grid is started.


The vertical temperature distribution shows a thick, 80 m to 100 m, Winter Water layer (minimum temperatures of -1.8ºC) in the upper water column over most of the transect.  At two locations the -1.8ºC isotherm breaks the sea surface and upper water column temperatures are between -1.75ºC and -1.78ºC.  The locations at which this occurs are where the northern and southern edges of Marguerite Trough were crossed.  A potential (very speculative) explanation for this structure in the temperature distribution is that the abrupt change in bottom topography results in enhanced local mixing that allows Circumpolar Deep Water to mix with the surface waters.  The input of the warmer water from depth would then warm the surface waters. Understanding the dynamics of how mixing occurs on the west Antarctic Peninsula continental shelf is the focus of several research groups involved in the U.S. SO GLOBEC field effort.


Sea Ice Studies (Frank Stewart and Jenny Boc)

Sea ice biota samples were collected at three ice stations during the period 6 to 9 August: two near the west entrance to Crystal Sound northeast of Adelaide Island (6 August, -66º 33.98′S, -67º 32.45′W; 7 August, -66º 31.92′S, -67º 37.84′W) and one west of Adelaide Island in the immediate vicinity of the L.M. Gould penguin/seal sampling (8/9, -67º 13.38′S; -70º 38.52′W).  Sea ice at stations covered 9 to 10/10th of sea surface area and was dominated primarily by consolidated first-year (FY) floes ranging in thickness from ~0.5 m in west Crystal Sound (7 August) to ~1.4 m in rafted/ridged ice (20 to 30% areal ridge coverage) west of Adelaide Island (9 August).  Consolidated ice cores and interstitial water (brine) were collected at each station and processed aboard ship for algal and bacterial biomass and for bacterial community composition (preliminary data not available).  In conjunction with field sampling, members of the ice collection group, with the generous help of F. Viddi, R. Beardsley, and S. Beardsley, have taken shipboard sea ice observations (according to ASPECT protocol) on an hourly basis beginning at the northern ice edge (~ 60S).  Ice conditions along the transit route have varied considerably, ranging from <1/10th areal coverage in the Gerlache Strait to 10/10th coverage by FY floes (some >1.0 m thick) in regions of Crystal Sound and the survey grid.  Ice surface topography has varied as well, ranging from flat FY cake ice north of Gerlache Strait and over regions of relatively warm (-1.4 to-1.6ºC) surface water west of Crystal Sound to heavily ridged and brashy ice fields that hindered westward transit by the Gould out of Crystal Sound on 8 August.  Concurrent with sea ice observations, the group has made daily recordings (light-time hours only) of the presence or absence of algal coloration in overturned ice floes.  Sea ice algae has been observed, on average, in ~25% of floes >0.2 m in thickness.  These data are in stark contrast to anecdotal observations made during the SO GLOBEC II survey cruise (NBP01-04, July-Aug. 2001), when algae was visible in overturned floes on less than five occasions.  


Sea Birds (Chris Ribic and Erik Chapman)

Today (9 August) the ship traveled with the L.M. Gould, following in its wake off the western shore of Adelaide Island.  Observers on both ships were looking specifically for Adélie Penguins and Crabeater Seals that could be fixed with satellite transmitters by researchers on the L.M. Gould.  After less than an hour of observations, during which a single Emperor Penguin and Snow Petrel were observed, the N.B. Palmer came upon a group of 53 Adélie Penguins approximately 1 km off the port side of the ship.  The L.M. Gould moved as close to the birds as possible before lowering 10 people onto the ice in a personnel basket.  The group of Adélies began to string into a line and move away from the people on the ice in a direction that would take them a few hundred yards off the bow of the N.B. Palmer.  We then used the N.B. Palmer to head the penguins off in hopes that this would turn them back toward the people waiting with nets on the ice.  Sure enough, the group changed direction and began to walk directly toward the L.M. Gould.  The birds walked to within 10 feet of the people, who promptly sprang on the birds capturing 10 of them.  Transmitters were placed on four of the captured birds, and a Crabeater Seal that was captured in the same area. 


Marine Mammal report (Chico Viddi)

During the last two days (8 and 9 August), the Palmer has been assisting the Gould transit to the southern sector of the survey grid. Due to the thickness and ice coverage (10/10) during most of the day on Thursday, the Gould had a difficult time moving through the ice and slow progress was made. For this reason, and the fact that it was “virus disinfection day”, only an incidental effort was made. Only some crabeater seals (Lobodon carcinophagus) were seen on 8 August. On 9 August, the day was mainly spent tagging, as well as diet sampling, seals and penguins by the Gould team. The bird and marine mammal observer team on Palmer assisted in finding the animals while active counting during the transit periods. While the penguin tagging and diet sampling was being carried out at 1110, a dispersed group of crabeater seals was seen (-67º 11.24′S; 70º 32.94′W). Once the work on penguins was done, the Gould headed to the seal group to start tagging a few animals. After a few hours working on this, and having started back on the track line, the bird team on the Gould decided to work on three more penguins sighted along the way. While this event was happening, a minke whale (Balaenoptera acutorostrata) was observed at 1611, 62º to starboard at 0.16 nm from the ship (-67º 13.39′S; 70º 38.49′W). This whale surfaced for a few times in a very narrow and long lead of open water.


ROV report (Scott Gallager, Phil Alatalo)

The second ROV deployment in Crystal Sound took place at -66º 31.882′S; -67º 37.980′W at CTD Station 4 on 7 August. At 0849, the release pin was pulled between the ROV pick up point and the aft crane used to swing the SeaRover over the starboard quarter. Three transects about 80 m each were conducted radially out from the ship into loosly packed ice and then under a large floe. Krill furcilia were observed in scattered groups near the edges of the 1 m thick floe and in the unconsolidated material, but not within the smooth, interior regions. Furcillia groups ranged in density from tens to hundreds of individuals.  However, this is certainly not the greatest number we have seen. One ctenophore was observed about 1 m from the under surface of the ice in a particularly rough and jagged region of the transect. The ADCP showed strong, 1 kt current to the west out of Crystal Sound, which may be responsible for carrying larval krill off the shelf. The deployment was cut short after 75 minutes, since the Gould was ready to leave and the ice team, working on the large floe to the starboard side of the ship, was back on board.


While waiting for penguins to be captured from the Gould on 9 August, and the ice team to take cores and pump microplankton samples from the Palmer, we had a quick response opportunity for another ROV deployment, ROV 3. At 1659 local time, while parked in ice at -67º 13.369′S; -70º 38.604′W, the SeaRover was deployed over the stern by the starboard crane. The ice was approximately 1 m thick with 50 cm snow cover that blocked the penetration of any remaining ambient light in the late afternoon hours. Four transects were made extending out approximately 100 m from the starboard quarter in a radial pattern. The under ice topography was very rough with ridges and jagged edges jutting down to a depth of 6 m. The ROV traveled about 3 m below the ice under surface scanning with its stereo cameras, ADCP current meter, and sonar system for larval krill (furcilia) and their predators. Furcilia aggregations appeared sporadically along the transects with organism density ranging from 10 to a few hundred individuals per group. The larvae were generally nestled up into the nooks and crannies of the jagged ice, but occasionally appeared in dense aggregations at the bottom tips of an ice projection. Such aggregations are probably caused by an interaction between water flow characteristics around the projection and swimming behavior of the individual furcilia. No furcilia were observed while the ROV traversed regions of smooth ice. Ctenophore predators were observed about 1 to 2 m below the ice under surface with tentacles extended. Body diameters were on the order of 1 to 2 cm, but full quantification of abundance and size must await further data processing. A number of large amphipods swam through the light beam and attached to the ice surface.  They remained attached for 10s of seconds. The entire deployment required 70 minutes from start to finish with 58 minutes of actual surveying time. A photograph was taken from the helicopter deck to qualify the ice conditions. We hope that additional opportunities will present themselves as we transit south toward Station 77 where our grid survey will begin.


Current Position and Conditions

The third day of our steam towards the southern sector of the SO GLOBEC grid with the L.M. Gould continued with deviations from the straight line course to avoid ice pack too thick for the Gould to transit through. Our current position at 2355 on 10 August is -68º 08.672′S; -75º 25.442′W. The ice pack is variable with mostly 10/10 coverage, except along the outer continental shelf.  The air temperature is -11.5ºC and the sea temperature is -1.851ºC.  The barometer (982.6 mb) is rising slowly.  Winds are out of the west (269) at about 10-15 kts. The skies are cloudy.


Cheers, Peter