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

22 April 2002

The long anticipated steam into Marguerite Bay along the inner portion of survey line 5 was what we had been hoping for. It was another spectacular dawn and sunrise with the mountains of Adelaide Island just a few miles away. Broken clouds and patches of blue sky allowed the early morning sunlight to highlight the icebergs close at hand and the mountains. The winds had died overnight and were very light. A very large swell was still running, a reminder of yesterday’s storm, and occasionally the water would slosh onto the aft deck, but the sea surface was almost glassy. The excellent weather conditions persisted throughout the day and during the afternoon there were particularly marvelous views of the southern end of Adelaide Island with a bright sun overhead and clouds hanging behind the mountains. The thick Fuchs ice Piedmont was just amazing to see up close.

The evening weather remained subdued with the wind out of the east northeast (070) about 15 kts. The barometer was at 982.2 mlb, and the air temperature was -1.9ºC. Sea surface temperature was -1.19ºC and salinity was 33.197, much fresher than out on the continental shelf or in the Antarctic Circumpolar Current. There were substantially more icebergs around the ship today and many small ice chunks and bergy bits, but no substantial areas of sea ice.

Work was completed during 22 April at stations 28, 29, 30, 31, 33, and part of 34. These stations, except station 34, occurred in the very shallow water regime just below the southern tip of Adelaide Island in water depths that varied from around 100 m to over 300 m along the trackline. There were 6 CTD casts all with the Microstructure and FRRF sensors, 1 MOCNESS tow, 2 Reeve net live animal tows, and a 1-m ring net tow for surface zooplankton. The last of the satellite tracked drogue deployments took place at station 33 on southwestern end of Laubeuf Fjord, a deep 800 m depression in the northern end of Marguerite Bay. Seabird and marine mammal observations were made during daylight transit periods. BIOMAPER-II towyoing occurred between stations 29 to 30 and 31 and 33. It was out of the water for the other transits for re-termination of the towing cable and maintenance/repair of the Video Plankton Recorder. Two sonobuoys were deployed, one each between station 30 and 31, and 31 and 33. Although there is a station 32 in the survey grid plan, because of the shoal waters in the selected area, the N.B. Palmer is not able to get to that location and the station was dropped from the schedule.

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

The CTD group did six stations today, four to depths less than 200 m and two to depths of 500 or more. All stations showed either deep uniform mixed layers or multilayered mixed layers reflecting, I think, the changeable winds (calm to strong). Only one station had a Winter Water (WW) layer; deep mixing from recent strong winds has eroded WW at many stations. Surface temperatures were variable, but tended to be below -1.0ºC. Surface chlorophyll also showed wide variability (from 0.1 to 0.6 ug/l), but very little vertical structure down to the base of the deepest mixed layer (50 to 70 m). The shallow stations (100-150 m) did not have any special deep structure; bottom temperature and salinity character was consistent with adjacent deeper water. Subpycnocline temperatures tended to be below 1.3ºC with no indication of a temperature maximum or oceanic water.

An ad-hoc ADCP observation (I happened to look at the display) at station 29 (SW of the southern tip of Adelaide Island) showed strong flow (50 cm/s) to the south. This observation is consistent with the coastal current along the west coast of the island. A later plot of the ADCP showed a strong, only slightly sheared current in this region.

Station 28 (cast 32, 458 m) Uniform surface layer to 50 m (-1.2ºC, 33.5). Surface chlorophyll was 0.6 ug/l. Thin (3 m), large amplitude layers were just under the mixed layer. Small-scale structure occurred through pycnocline to 200m. There was no temperature maximum, but deep temperature was around 1.3ºC.

Station 29 (cast 33, 155 m) Uniform surface layer to 80 m (-0.9ºC, 33.4). Surface chlorophyll was 0.2 ug/l. There was small scale variability from 100 m to the bottom.

Station 30 (cast 34, 183 m) Thin surface layer to 10 m (-1.2ºC, 33.3) with considerable temperature and salinity structure from 10 to 20 m. Two relic mixed layers occurred from 20 to 50 m then to 120 m, with temperature and salinity jumps between layers of +0.2ºC and 0.15, respectively. Surface chlorophyll was 0.1 ug/l declining to 0.08 at 100 m.

Station 31 (cast 35, 186) Uniform surface layer to 70 m (-1.1ºC, 33.3). Surface chlorophyll was 0.15 ug/l. Temperature and salinity increased linearly to the bottom with persistent layers (2-3 m thickness).

Station 33 (cast 36, 198 m) Uniform surface layer to 50 m (-1.0ºC, 33.4). Below was a relic mixed layer to 75 m. Surface chlorophyll was 0.2 ug/l. There was a mainly linear increase in temperature and salinity to the bottom with step increases every 50 m.

Station 34 (cast 37, 657 m) Uniform surface layer to 50 m (-1.4ºC, 33.3). The WW layer was between 50 and 80 m. Surface chlorophyll was 0.1 ug/l. There was weak variability in the pycnocline to 200 m. There was no temperature maximum; deep temperature was 1.3ºC.

Microstructure Profiler (CMiPS) report (Chris Mackay)

Since its installation for station 3, the microstructure instrument has acquired data at all CTD stations with the exception of 12, 21, and 22. For those stations, it was removed from the CTD as the water depth would exceed its pressure limit. These time periods provided the opportunity to make some adjustments to the instrument, replace the mechanical hard disc with a solid state drive, and change a temperature probe. As the instrument is new and, due to the very large amount of data generated, only a small proportion of the data has been analyzed so far, with the objective of evaluating the performance of the instrument. The bulk of the data will be analyzed after the cruise. The instrument is operating as expected and valuable experience is also being obtained in deployment of the instrument in and around floating ice. Procedures for removing and reinstalling the instrument in the CTD frame have been working well, although so far the sea state has been favorable.

Marine Mammal report (Debra Glasgow)

The marine mammal survey began on 22 April at 0815 on Incidental watch in excellent conditions, great visibility, a Beaufort sea state 2, and the snow covered mountains of nearby Adelaide Island cloaked in pastel colors from the sunrise. The full survey began at 0929 when the transit to Station 30 began, as passing waves were breaking on an uncharted shoal approximately 500 meters to starboard. Several fur seals rested on the nearby surface. At 0950, two groups of crabeater seals came over to the ship (approximately a dozen in each group) swimming around the ship and accompanying us for over 20 minutes. At 1011, a leopard seal was sighted 30 meters from the starboard bow and the crabeaters seemed to become very agitated, hiding around passing growlers and using the ship as a shield between themselves and the leopard seal. Two of the crabeaters had very recent wounds and exposed flesh was visible along their backs. This turned out to be the most interesting encounter of the day, no cetaceans were sighted. In all, 6 fur seals, 25 crabeater seals and 1 leopard seal were recorded for the day. Good survey conditions prevailed until 1446 when the wind speed suddenly jumped to 25-30 knots within 5 minutes and to sea state 5-6. The sun set behind cloud at 1830 and survey ended in poor light at 1709.

Sea Birds (Erik Chapman and Matthew Becker)

Seabird survey related work began on April 22 with a net tow for surface zooplankton at station 29 before sunrise. The ring net went to 50 m and little biomass was collected at this station compared with other stations. This station was also different from others, in that there were few, if any, amphipods and very little phytoplankton. We did catch copepods and a few larval krill in the tow. The Palmer was underway and surveying from station 29 by 0930 when BIOMAPER-II was put in the water. We also surveyed between stations 30, 31 and 33 on a course along the southern shore of Adelaide Island. The trackline went through some light bands of brash, interspersed with scattered growlers and bergy bits. The transit took us along about 15 nm offshore along the south western shore of Adelaide in light winds, under mostly sunny skies. Very few of the birds observed followed the ship today. This seems to be the case whenever we travel through an area with any ice at all. Interestingly, Snow Petrels were not seen flying over the bands of brash as was consistently seen last year, but there were Southern Fulmars. During last years fall cruise, Southern Fulmars were seen in good numbers inside Marguerite Bay, but in open water. Also observed this day were Kelp Gulls and Blue-eyed, or Imperial Shags near-shore, two species that are rarely seen more than 15 miles or so from shore. There were a good number of Southern Giant Petrels, probably because of the close proximity to Avian Island where Southern Giant Petrels are still attending their nests. Bird densities declined as we approached station 30, and between 30 and 31 and between stations 31 and 33, few birds were seen at all. This pattern was similar to scattering data from BIOMAPPER-II that apparently also peaked in the top 100 m soon after station 29 and declined from there along the transect.

Three species of seals were observed during the survey; Fur Seals, Crabeater Seals, and Leopard Seals (see today’s mammal observation report). We finished the day with a net tow after dark at station 33. Again, little biomass was collected in the 0 to 70 oblique net tow. Phytoplankton, amphipods, and copepods were present, but overall, biomass from this sample was low.

A summary of the species and number of individuals of birds and seals observed during 4 hours, 49 minutes of daytime surveys between consecutive stations 29 and 33 is the following:

Species (common name)	Species (scientific name)	Number observed
Cape Petrel (“Pintado Petrel”)	Daption capense	74
Southern Fulmar	Fulmarus glacialoides	112
Blue-eyed Shag	Phalacrocorax atriceps	12
Antarctic Tern	Sterna vittata	2
Wilsons Storm-petrel	Oceanites oceanicus	7
Unidentified Skua		2
Snow Petrel	Pagodroma nivea	1
Southern Giant Petrel	Macronectes giganteus	27
Kelp Gull	Larus dominicanus	76
Leopard Seal	Hydrurga leptonyx	1
Crabeater Seal	Lobodon carcinophagus	26
Antarctic Fur Seal	Arctocephalus gazella	7

Material Properties of Zooplankton Report (Dezang Chu, Peter Wiebe)

Two Reeve net tows to collect live animals for material properties measurements were made at station 29 and station 34. At station 29, the water depth was 170 and a scattering layer was located around 100 m on Simrad EK 500 echo sounder (both 120 and 200 kHz echograms). The Reeve net was deployed almost to the bottom and was towed for about 30 minutes. About a dozen live adult krill (E. superba) and a number of juveniles were caught. Around midnight as we approached Station 34, we saw a scattering layer from 70 m to 120 m on Simrad EK500 120 and 200 kHz echograms. After the CTD cast, the second Reeve net tow of the day was done down to about 150 m. The number of individuals caught was about the same as the tow at station 29 i.e., about 10 adult krill and some juvenile krill. There was no APOP cast, but one is planned for 23 April.

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

MOCNESS Tow # 8 was conducted early in the morning (0300) on 22 April just southwest of Adelaide Island at station 28. The net tow was shallow (260 m) and successful. Very little was collected in the deepest depth interval (200-260 m). Low abundances of copepods, krill furcilia, and amphipods were seen in the 150-200 m range. Krill furcilia were observed from 25-150 m, with high abundances in the 25-50 m range. Algae was seen at 125-150 m and 75-100 m, probably originating as dead diatom chains that agglomerated into diatom mats and were sinking to the bottom (about 300 m). Copepods were seen from 25-100 m. The upper depth interval, 0-25 m, was marked by a high abundance of 2-3 cm long juvenile krill (approximately 1 pint total).

An aftermath of the 21 April storm was the damaged BIOMAPER-II towing cable described in the last report and the effort needed to re-terminate the cable. That effort went through the night and was completed in time for the deployment of BIOMAPER-II at the end of the work at station 29. A superb job was done by the BIOMAPER-II tech group (led at different times in the night by Andy Girard, Mark Dennett, Phil Alatalo and Peter Martin) and the Ratheyon Marine Techs (Jenny While, Steve Tarrent and Stian Alesandrini) in getting the towed body and cable operational. In addition to fixing the wire, repairs were made to the rollers, which fairlead the cable on the over boarding sheave.

Upon leaving station 29, an intense patch of scatterers occurred right near the surface, which may have been krill. Not long after than a few more small krill-like patches were observed near the surface. The extremely variable topography in this area prevented towyos to any substantial depth, but when the bottom dropped off to deeper depths, the down-looking transducers revealed that there was considerable scattering close to the bottom, especially on the 200 kHz echogram. As the day progressed, backscattering in the upper water column became much lower and there were few acoustic targets present. Most of the moderately intense backscattering occurred in the valleys below the peaks in the bottom topography. During the run between station 31 and 33, the strongest backscattering was near the bottom and the surface layer had little.

A side effect of working in very shallow water is that the acoustic noise generated by the ships engines and other machinery reverberates more effectively in the shallow water column. This had a pronounced effect on the 43 kHz echograms, which was dominated by ships noise and to a lesser extent on the 120 kHz record for most of two transits between stations 29 to 30 and 31 to 33.

During the towyo starting at station 29, the VPR camera system stopped working. The towed body was brought on deck at station 30 and trouble shooting of the system began. A retainer ring holding the strobe light lens had come loose inside the pressure case and allowed the lens to move out of alignment. The system was repaired during the transit to station 31 and BIOMAPER-II was re-deployed at the end of station work there. Unfortunately, the one of the two cameras was still not working properly because of an alignment problem, so at the end to the transit to station 33, the towed body was again retrieved and during the short transit station 34, the VPR was worked on again.

Cheers, Peter