Report of Activities on the RVIB N.B. Palmer Cruise 02-02
The N.B. Palmer reached the first Station in the Southern Ocean GLOBEC survey grid in the early morning hours of 14 April. Thick low clouds and a raw cold air (0.5ºC) driven by a 25 kt wind provided a setting not nearly as pleasant as what we experienced at the test station on 13 April, but typical of what we can expect for this time of year. Air temperature was just above freezing (0.5ºC) and the water temperature was a little colder (-0.12ºC). The barometer was holding steady at 987.1 mlb. In the first light of the day, one could see a magnificent iceberg just a short distance off the starboard bow. This is much earlier in the cruise for such sightings compared to last year’s fall cruise.
Work began immediately with the deployment of the CTD. After a pair of casts, one shallow and one deep as described below, BIOMAPER-II was deployed. But a ground fault in the acoustic system caused the towyo between Stations 1 and 2 to be aborted shortly after the towed body was launched. The ship steamed onto the station 2 at the customary 4 to 6 knots needed for the sea bird and mammal surveys while the fault was tracked down and repaired. At Station 2, another CTD cast to the bottom was made followed by another test of the APOP system to see if a noise problem observed during the first deployment at the test station was still present; it was. The launch of BIOMAPER-II came at the end of station 2 and this time it operated as planned. Towyos between the surface and 250 meters were made during the 40 km transit to Station 3. While BIOMAPER-II remained in the water parked about 25 m below the surface, the station work began. At station 3, the microstructure sensor package was mounted on the CTD frame for the first time and was successfully operated. Also at this station, a 1-meter diameter ring net was obliquely towed in the upper 50 m to collect a plankton sample for comparison with bird survey data. Towyoing with BIOMAPER-II down to 250 m resumed during the transit to station 4, which was reached just after .
All in all, it was a very good start to the work on the survey grid.
CTD Group report (John Klinck, Tim Boyer, Chris Mackay, Julian Ashford, Andres Sepulveda, Kristin Cobb)
The CTD group did four casts at three stations today.
Station 1 (Cast 2, 3) was 3200 m deep. Cast 2 went to 100 m with the Fast Repetition Rate Fluorometer (FRRF) attached. This cast covered the surface mixed layer which had uniform properties to about 80 m. No bottles were closed on this short cast. The FRRF was removed and a normal cast was done. Cast 3 had a surface structure with a new mixed layer (-0.2ºC) over an old warmer layer (0.0ºC) which was over a winter water (WW) layer (-0.8ºC). The main pycnocline had layers throughout with structure in both salinity and temperature. The temperature maximum and oxygen minimum were about 300 m deep. The Lower Circumpolar Deep Water (LCD) salinity maximum was seen at about 800 m.
Station 2 (Cast 4, no FRRF or Microstructure instrument - MS) was 650 m deep. A uniform surface layer extended to 80 m. Below is a clear WW layer (-0.5ºC) above the pycnocline which showed strong temperature layering with salinity structure. Thicker layers (10-20 m thick) were evident between 200 and 400 m. The oxygen minimum was at 200 m, while the deep temperature maximum was at 300 m.
Station 3 (Cast 5, FRRF and MS) was 340 m deep. A uniform surface layer rested on a 20 m thick WW layer. The main pycnocline had small vertical scale, moderately energetic layers. A weak oxygen minimum occurred at 200 m and the temperature maximum at 275 m was associated with a slight oxygen maximum.
In all four casts, chlorophyl was uniformly 0.4 mg/l in the surface mixed layer and decreased below detection level below.
Microstructure report (Chris Mackay)
Work on installing the Microstructure Profiler (CMiPS) on the CTD was completed on 14 April and the instrument was first deployed at station 3. It has been in operation now for two subsequent profiles at stations 4 and 5. This instrument measures micro-scale temperature and conductivity along with their respective scaled derivatives plus pressure and its scaled derivative all at a rate of 512 samples per second. Data from the first 2 profiles have been downloaded from the instrument and stored on the network data drive. An initial quick look at these data has shown the instrument to be operating properly.
Marine Mammal report (Debra Glasgow)
An “On Effort” survey began at 0845 on 14 April in
borderline weather conditions (
The most interesting event for the day was a sighting at 1453 of a very dark, shark-shaped fin approximately 30 meters off the port bow and heading towards the ship -65 52.83ºS; -70 11.52ºW. Although provisionally recorded as an unidentified small cetacean, I am not totally convinced it was a cetacean at all as the fin shape was definitely shark shaped and no blow was seen. The animal was only seen once by myself and Karen Riener, and nothing but the dorsal fin was seen.
Sea Birds (Erik Chapman)
Today, sea birds were surveyed for 7 hours and 4 minutes
between consecutive stations 1, 2 and 3 on the survey grid. It was snowing most of the day, but visibility
was greater than 600 meters throughout the survey. The surveys included the shelf break and
there was high bird abundance and species richness throughout the day. Most of the birds observed were following the
ship, and there appeared to have been a general decrease in abundance of birds
as we crossed onto the continental shelf.
As we moved over the shelf, there was a noticeable shift in the species
assemblage, with Southern Fulmar becoming the dominant species over the shelf,
taking of the place of
Species (common name) Species (scientific name) Number observed
Southern Fulmar Fulmarus glacialoides 120
Antarctic Petrel Thalassoica
Blue Petrel Halobaena caerulea 21
Unidentified Prion 15
Grey-headed Albatross Diomedea chrysostoma 7
unidentified large Skua 2
Southern Giant Petrel Macronectes giganteus 2
Antarctic Fur Seal Arctocephalus gazella 22
Zooplankton (MOCNESS/BIOMAPER-II) report (Carin Ashjian, Peter Wiebe)
As noted above, BIOMAPER-II, which was deployed at station 1, immediately developed a ground fault in the acoustic system. In spite of the fault, the system was sent down to 50 m and it was towed for 20 minutes to see whether adjustments to the nose weight and tail elevator improved the towing configuration. More adjustments were needed. The towyo was aborted and on deck Peter Martin and Andy Girard went to work tracking down the ground fault while others in the party worked on reconfiguring the tail assemble to improve the towing performance. The ground fault was located in the bulkhead connector for the upward looking 43 kHz transducer and it appeared to be due to a manufacturing flaw. The connector was replaced. After completion of the work at station 2, BIOMAPER-II was deployed and all the sensors systems worked well.
Early in the section between station 3 and 4, a sizeable patch of scatterers, probably krill, appeared centered about 180 meters below the surface. About an hour later, another patch was crossed. There was also a elevated layer of scatterers extending up from the sea floor about 60 m, which was present for transects between stations 2 and 3, and 3 and 4. Unfortunately, it resided just below the maximum depth of the towyo and we were only able to graze the top of the layer. VPR images indicated mostly copepods and polychates were present in the bottom layer. The VPR images higher in the water column, especially the mixed layer, were dominated by marine snow particles, algal mats, and other small particles.
No MOCNESS tows were taken at the first three stations.