Report of Activities on the RVIB N.B. Palmer Cruise 02-04
The end of the Southern Ocean
GLOBEC survey of the Western Antarctic Continental Shelf in the vicinity of
The two ships began steaming towards the rendezvous site around dawn and met at 1000. There was enough open water in leads to allow the exchange of personnel to take place by Zodiac. The chief scientist on the Gould, Dan Costa, along with MPC, Karl Newyear, and Captain Roberts came over for a meeting to discuss plans for the remainder of the cruise. The party of three that came over to the Palmer from the Gould just before the start of the survey of the northern sector of the grid returned to the Gould. About 1300, the two ships began the convoy to the northeast.
The Palmer headed for a site off the northern tip of
In the evening of 10 September, King Neptune and his court paid the N.B. Palmer a visit to officiate at a ceremony bringing the polliwogs (those crossing the Antarctic circle for the first time) on board into the ranks of the shellbacks. The polliwogs entertained the King with skits, poetry, and multimedia presentations. It was a good time for those who chose to participate in it.
This was another day in which the sun failed to make an appearance. Low clouds prevailed along with a dense fog and mist that turned to a light snow in the afternoon. The air temperature remained relatively mild rising from around -2ºC to above the freezing mark (+0.6ºC) for the second time since arriving in the GLOBEC study site. Winds on 10 September were moderate to low. In the morning they decreased from around 25 kts to less than 5 kts by and then picked up to between 10 and 15 kts in the afternoon and evening. This corresponded to a gradual shift in wind direction from northeast to northwest and modest change in barometric pressure, which varied between 1006 and 1009 mb.
CTD Group report (Eileen
Hofmann, Bob Beardsley, Baris Salihoglu,
Chris MacKay, Francisco (
In the early hours of 10 September we completed two CTD/Rosette casts at station 5, which is in the inner portion of survey transect 1. This station marked the end of the CTD/Rosette work on the survey grid. The first cast at station 5 was to 350 m for microstructure sampling with CMiPS. The second cast extended to within a few meters of the bottom, which was at 675 m.
The surface water temperature at station 5 was -1.84ºC, which is the coldest observed in the northern part of the survey grid. Surface salinity was 33.99. The cold well-mixed Winter Water layer extended to almost 100 m, which is 20 m to 40 m deeper than observed at other stations in this portion of the survey grid.
Below the Winter Water layer, temperature increased to a maximum of 1.49ºC at 315 m, after which it decreased to 1.29ºC at the bottom. Salinity reached a maximum of 34.72 at 560 m and remained at this value to the bottom. These thermohaline characteristics indicate the presence of Upper and Lower Circumpolar Deep Water.
The presence of these water
masses so far inshore on the continental shelf brings up the issue of how they
got there. The observed thermohaline characteristics suggest little mixing,
exchange, or dilution of the oceanic water with the shelf waters. This in turn implies recent arrival of the
oceanic water on the inner shelf or little exchange of the oceanic water with
the overlying Winter Water and inner shelf water. The pathways by which the oceanic water is
brought to the inner part of the west
MOCNESS Report (Phil Alatalo, Peter Wiebe, Ryan Dorland, Dicky Allison, Scott Gallager, Gareth Lawson)
MOCNESS Tow #16 was a morning
deployment at Station 9 on 9 September, close to shore, northwest of
Copepods were the most abundant taxa in the integrated net, with a large siphonophore and krill contributing to the biomass. Net 1 (300-250 m) hosted a fair amount of copepod biomass, mostly Calanus propinquus and gravid Paraeuchaeta sp. Chaetognaths were numerous here and present throughout the water column. Net 2 (250-200 m) contained mostly copepods, amphipods, and pteropods. All nets above 200 m produced low biomass catches and were composed mostly of krill (Thysanoessa macrura and Euphausia superba) and chaetognaths. Krill furcilia and pteropods were abundant between 75 and 25 m. The surface net contained mostly pteropods, a few large copepods, and some juvenile krill. A few fish larvae were found in the upper 50 m and an 8-cm ctenophore, caught between 150-100 m, was given to K. Scolardi since these creatures preserve very poorly and are usually unrecognizable back in the laboratory.
MOCNESS Tow #17 at Station 5 sampled the shelf waters along the first broad-scale survey line. This tow was conducted near dawn on 10 September in water 670 m deep. Copepods continued to remain dominant in deep water while krill provided most of the biomass above 200 m and below 50 m. Large calanoid copepods joined krill in the upper 50 m as dominant taxa. While not contributing much in biomass, thecosome pteropods were found in increasing numbers at all depths. The scattering layer detected by the ADCP between 0-100 m was likely a result of krill, copepods, and pteropods. The SIMRAD scattering layer between 200-350 m was attributed to high densities of small copepods found in net 2. Net 0 captured nothing due to the cod-end bucket getting into the mouth of the net just after the launch of the system thus fouling the net. The OPC functioned well.
The deepest depths sampled contained high abundances of copepods, chaetognaths, siphonophores, and ostracods. Copepods were much smaller in size between 350-200 m. Here also were found specimens of Euphausia crystallorphias. Biomass decreased considerably above 200 m. Thysanoessa macura provided the bulk of the biomass between 200 and 50 m. All stages were present. E. superba juveniles were found in the top 25 m, along with large Calanus propinquus copepods. Pteropods were found everywhere, especially between 150-100 m and above 50 m. Salps, radiolarians, ostrocods, amphipods, and gymnosome pteropods were noted at several depths.
Current Position and Conditions
The work at the time series