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

13 May 2002


On 13 May, the Palmer was working most of the day in the survey grid area off of Adelaide Island. The weather continued to be a minimal factor in the over-the-side operations as a result of the large high pressure system that continued to dominate the regions.  In fact, the barometric pressure, which had already been unusually high, climbed a bit higher. Around 0015, it was 1006.4 mlb and by late evening it was at 1008.6 mlb.  Winds were in the 10 to 15 kts range out of the south before dawn and then during the day increased to around 25 to 30 kts.  In places where there was little sea ice along the trackline, the swell started to build and there was actually some motion to the ship. In the evening, the winds had diminished marginally to between 22 and 25 kts. Air temperature remained in the -8 to -9ºC range all day.


The four principal activities on 13 May were: 1) to do the third “pickup” BIOMAPER-II section between stations 28 and 27, 2) to do a MOCNESS tow at station 26, which was missed due to stormy weather when work on survey line 5 was being done earlier in the cruise, 3) to start a CTD section up the middle of Marguerite Trough, and 4) to survey the bathymetry around mooring location A3.  The BIOMAPER-II towyo took place in the late night period and the MOCNESS tow took place in the early morning after the Palmer steamed from station 27 to 26. After the first three of the five planned CTD stations were completed during the mid-day and evening, the Palmer deviated from the course line along the Marguerite Trough to steam west to circle the A3 mooring site gathering Seabeam bathymetry data just before midnight. The bathymetry data are needed by the physical oceanographers to help interpret and model the current meter and other data acquired by sensors on the mooring during the year long period of data acquisition, which ended in February 2002.  Thus, the third day of the post grid work was completed as scheduled and with no complications. 


CTD Group report (John Klinck, Tim Boyer, Chris Mackay, Julian Ashford, Andres Sepulveda, Kristin Cobb)

Today the CTD group did three of five stations along the axis of Marguerite Trough, from the middle of the shelf northward to the shelf break. Surface conditions were variable reflecting the changing ice cover and recent changes in wind speed. None of these stations showed strong indication of Upper Circumpolar Deep Water (UCDW) influence, although a thin, intruding layer of this water was seen at station 94.  At all stations, the deep (below 350 m) temperature decreased and oxygen increased with depth. These changes were also seen at similar depths off the shelf break in the Antarctic Circumpolar Current, leading to the conclusion that this was Lower CDW in the trough. However, no deep path exists for this water to get from offshore into the trough, without rising about 300 m to get over the shelf break (based on along shelf Seabeam surveys). The path, frequency, and dynamics by which this water gets into the trough remains to be determined. These processes need not be related to those that bring warmer, shallower UCDW onto the shelf.


Station 94 aka MT1 (cast 102, 631 m).  A uniform surface layer extended to 30 m (-1.8ºC, 33.5 psu, 0.1 ug/l chlorophyll).  The pycnocline extended from 50 to 150 m with several strong, thin temperature reversals. A 40 m thick, warm (1.8ºC) layer occurred at 200 m.  A deeper temperature maximum occurred at 350 m.  From 500 m to the bottom, temperature decreased, and O2 increased, with slightly increasing salinity.


Station 95 aka MT2 (cast 103, 642 m).  Uniform surface conditions extended to 50 m (-1.6ºC, 33.6 psu, 0.15 ug/l chlorophyll).  A strong density jump at 60 m indicated the top of the pycnocline. There was weak small-scale temperature and salinity variability to 250 m.  A thick temperature maximum (1.4ºC) extended from 250 to 375 m.  Temperature decreased and O2 increased from 500 to 600 m.  A layer 40 m thick with uniform properties occurred at the bottom.


Station 96 aka MT3 (cast 104, 638 m).  A thin (20 m) uniform surface layer (-1.6ºC, 33.8 psu, 0.1 ug/l chlorlophyll) sat over a deeper zone of increasing temperature and salinity to 40 m. A density jump at 50 m was the top of the pycnocline, which extended to 200 m.  A temperature maximum (1.4ºC) occurred at 250 m.  From 350 m to the bottom, temperature decreased as O2 increased, with a slight salinity increase.


Marine Mammal report (Debra Glasgow) 

Conditions on 13 May when starting the marine mammal survey at 1003 had reverted to those experienced for long periods earlier in the voyage - overcast with fog and very limited visibility. Happily, the fog cleared by 1130 and although the wind stayed around 25-28 knots and an air temperature of -7.7ºC, visibility remained good for the rest of the day.  Between 1030 and 1045, four leopard seals were seen on small floes amidst the variable 7-9/10 young grey ice, shuga, and consolidating pancakes. Many pools and a few icebergs completed the ice mix.  From 1100 to 1300, 17 fur seals were counted - most on small ice floes.  Around 1430, the ice thinned out to <5/10 with large areas of open water streaked with shuga, grease, and ice bits with occasional bands of brash and pancake. The sea state was a Beaufort 4+ with many whitecaps, but little or no swell.


In this area at 1500, a lone humpback was sighted on the edge of a band of shuga 0.6 nautical miles away, 330º, at 67 12.34ºS; 70 16.44ºW.  Most blows were small and were sheared off by the wind making the whale hard to track.  At first it was swimming quickly away from us, but our course changed and we came closer to the whale.  When it stopped and logged at the surface briefly, there was a clear view of the body. The dorsal fin was very distinctive and had a white spot on the right hand side. The light was too poor for photos, so video of habitat only was taken as the whale soon disappeared as we were moving at 7-8 knots at the time. Ana Sirovic deployed a sonobuoy and some humpback sounds were heard though not very distinctly. This was the only cetacean sighting for the day. The Survey continued until 1600 when we stopped at Station MT2 for a CTD in very poor light.


Sea Birds (Erik Chapman and Matthew Becker)

Seabird surveys were conducted on 13 May for over 4 hours as the ship traveled offshore of Adelaide Island between stations MT1 and MT2.  A steady wind out of the southeast over the past several days appeared to be opening leads in the pack by pushing patches of ice north.  Ice conditions were characterized by pancake, shuga, nilas, and grease ice varying between 1 and 9/10ths coverage.  The Palmer mainly traveled through open water interspersed with bands of pancake or other young ice types, and according to satellite ice images, was near the edge of the ice.  A single Adélie Penguin, 4 Antarctic Petrels, and a relatively large number of Snow Petrels were observed during the surveys.  The abundance of Snow Petrels appeared to be higher in this area than deeper inside the pack, but similar to that observed in new ice near the ice-edge during prior surveys.


A summary of the species and number of individuals of birds within the 300 m transect during 4 hours and 21 minutes of daytime surveys near stations MT1 and MT2 is the following:


Species (common name) 

Species (scientific name)

Number observed

Snow Petrel                    

Pagodroma nivea                


Antarctic Petrel

Thalassoica Antarctica


Adélie Penguin                  

Pygoscelis adeliae      




ROV Under-Ice Investigations (Andrew Girard, Amy Kukulya, Gaelin Rosenwaks, Philip Alatalo)

On 12 May at Station 28, ROV Deployment #7 collected valuable video footage under moderately difficult weather/ice conditions.  Newly formed pancake ice was present in large patches, separated by leads filled with windrows of slush.  The thin ice and 10 knot wind made it difficult for the Palmer to hold position while the ROV was in the water.  Working from the stern, we were able to make four 50-meter horizontal transects despite the fact that the ship was drifting faster than the ice.


This deployment occurred at night (2253) in deep water (620 m) just southwest of Adelaide Island on May 12th.  The undersurface of the ice was mostly smooth with some structure at the edges of each piece. About 10-20 cm of clear water separated the pancakes. No apparent algae colonization was seen from the ship.  Krill furcilia were present both individually and in small groups, swimming directly below the ice surfaces in higher concentrations than observed in previous deployments.  The beating pleopods of swimming  furcilia were clearly visible.  Salps and amphipods were also present.


Surveying stopped when the Palmer eventually drifted out of the pancake ice patch.  The Sea Rover ROV was retrieved at 2346.  We felt rewarded for our diligence in keeping station as we were able to document early colonization by krill furcilia in newly-formed ice.


Zooplankton (MOCNESS/BIOMAPER-II) report (Carin Ashjian, Peter Wiebe)

The twenty-third MOCNESS tow was conducted early in the morning of 13 May, prior to sunrise, at station #26.  This was a station location which had been missed previously because of bad weather.  The net was towed to 450 m. The deepest depth contained only copepods, perhaps including Euchaeta and large Calanus/Calanoides.  Krill were observed from 150-350 m and again from 100-75 m.  The krill in the 100-75 m interval were Thsyanopoda spp. rather than Euphausia spp.   Copepods were abundant throughout the water column with the exception of the surface depth interval (25-0 m).  Krill furcilia were numerous in the upper 100 m. Diatoms were collected in the upper 50 m.  A few chaetognaths were collected from 150-100 m and from 200-350 m.  Siphonopohres were collected from 200-150 m. Ctenophores and salps both were collected in the water column net (0-450 m) but were not obvious in the discrete depth nets.  Fish were collected (only 2) in the surface net (25-0).


The third BIOMAPER-II “pickup” was a short run from station 28 to 27.  The towyo was started just after midnight on 13 May and finished about 0445.  With water depths around 470 m, the towyed body was sent to its maximum depth of around 250 m on each towyo. In the surface mixed layer for a portion of the tow, the echograms displayed vertical bands of high and low backscattering that changed to horizontal layering at the base of the mixed layer and extended down into the pycnocline.  Most of the time, the mid-water depths were remarkably free of scatterers, except for occurrence of a patch centered about 250m depth that had a ~ 100 m vertical extent and ~ 800 m horizontal extent. A deep bottom associated layer existed with higher backscattering.


Cheers, Peter