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

11 May 2002

With the grid completed and a new work plan in place that called for most of the scientific activities to take place at least 120 nm northeast of the last grid station (92), a good portion of 11 May was spent steaming to get to the first of the new locations (survey station 51) under gorgeous picture taking conditions. The trackline chosen for the run to station 51 followed the inner shelf to the west of the Wilkins Ice shelf, Rothschild Island, and Alexander Island. The nighttime portion of the steam took the Palmer through the same set of icebergs that we traveled through a few days earlier. They were massive, sculptured, and shadowy in the bright search lights used to look ahead that illuminated them. Occasionally, we steamed through small pools of open water on their down wind sides, presumably a result of the ice pack moving faster than the icebergs themselves, which may have been grounded.

First light came about 0830, although the sun did not rise for another 2 hours. The brilliant red on the horizon silhouetted the mountains of Alexander Island and also the icebergs ahead of the ship that rose as black forms above the pack ice. During the morning, SeaBeam bathymetry data were collected over a deep (>1200 m) uncharted portion of a canyon, which was about 5 nm across and lay offshore of Lazarev Bay (the bay lies between Rothschild Island and Alexander Island). The steep sides of the canyon rose on northeast side to depths of around 140 m.

The trackline went over ocean areas that only a week or so ago were ice free and were now completely iced over. Knowledgeable ice observers on board gave credit for the rapid sea ice build up to the remarkably clear, cold, and relatively windless period that we have been experiencing for the past week. The process may also been assisted by the fact that the winds that did exist were from the south/southwest and these were pushing exiting pack ice to the northeast. During the day, the winds were again out of the south (200º) and stayed below about 12 kts. Air temperature stayed down around -11ºC and the barometer continued to rise slowly; for most of the day it was above 1001 mlb.

Late in the afternoon, the Palmer reached station 51 and BIOMAPER-II was deployed for a “pickup” run to station 50. This portion of survey line 7 and a portion of line 6 were not sampled because of equipment problems. Thus, part of the post-grid work plan involved collecting data on some of the missed survey line sections. At station 50 around 2130, BIOMAPER-II was recovered and the Palmer began the steam to another missed section beginning at station 43 and running to station 41. During the daylight transiting, seabird and mammal observations were made and 1 sonobuoy was deployed along the trackline. There was no over-the-side CTD work for the first time in a number of weeks.

Marine Mammal report (Debra Glasgow)

May 10 dawned to another near cloudless sky and an endless field of ice flowers on nilas and young white ice with the mountains of Alexander Island rising to starboard. The sun rose at 1010, gilding the ice flowers and staining the tips of the mountains a soft pink. The “green flash” was seen by many people at sunrise this morning. The marine mammal survey began at 0957 for a day that turned out to be filled with seals and mostly young ice. Forty-one Crabeater seals and 3 Weddell seals were counted and at 1327 and 1418 two rarely seen Ross seals were recorded at around 68.25.20ºS 71.59.24ºW. The first was on an ice floe and the second was in the water. Several seals could also be seen in the distance with binoculars, but were too far away to identify. There were few birds throughout the day, but a small number of Adélie penguins were recorded.

Earlier in the morning, Vladimir Repin saw the blow of an unidentified whale 50-60 meters ahead of the ship in the spotlights while traveling through the ice in darkness from Station 92 to Station 51 between 0600 and 0700.

At 1440, a minke blew and then spy-hopped from a crack in the ice between floes bearing 010º, 0.2 nautical miles ahead of the ship at 68 18.11ºS; 71 51.64ºW. We were in open pack ice with 60% 1st year medium size floes, 25% consolidated pancake and a few icebergs. Many small pools, often coated with nilas, were common. There were also many sightings of seals in that area. The whale was not sighted again.

The survey ended at 1610 in poor light after a beautiful sunny day with a balmy air temperature of around -10.8ºC and only10 knots of wind for most of the day.

Sea Birds (Erik Chapman and Matthew Becker)

Surveys were conducted on 11 May for almost 6 hours today as the ship transited north about 30 nautical miles offshore and along the north end of Alexander Island. When the ship was in this area previously, it was in open water and Southern Fulmar, Cape Petrel, Antarctic Petrel, Gray-headed Albatross and Wilson's Storm Petrel were observed. Today, the same area was covered in 8 to 10/10ths concentration ice, with one-year old floes about 5 to 10 m in diameter interspersed with new pancake, new gray and nilas ice. In the ice, Snow Petrels and a small number of Adélie Penguins were now observed in this area. Today, Snow Petrels were observed in low numbers despite plenty of open water leads. We continue to find Snow Petrels in relatively low abundance inside the pack, further away from the interface between new ice and open ocean. These observations support results from previous research that indicate that ice is a first-order habitat variable that structures seabird species assemblage. We will eventually test hypotheses that predict the influence of additional physical and biological variables on the abundance and distribution of seabirds within open water and ice habitats.

A summary of the species and number of individuals of birds within the 300 m transect during 5 hours and 49 minutes of daytime surveys between stations 92 and 51 is the following:

Species (common name)	Species (scientific name)	Number observed
Snow Petrel	Pagodroma nivea	23
Adélie Penguin	Pygoscelis adeliae	2

Water Sampling for Microzooplankton (Phil Alatalo)

As the cruise winds down, so does microzooplankton motility. For both the outbound survey line 12 and the inbound survey line 13, fewer organisms were exhibiting swimming behavior and the general number of particles in the water column diminished. Mesodinium was present at the shallow station 85 down to 50 m, probably due to the extended mixed layer there. It continued to be found in surface waters until the shelf-break at station 89, where it was seen in the thermocline sample (150 m). In the three stations of the last survey line (13), Mesodinium or a similar ciliate was found sporatically at various depths. This may have been its southerly limit, at least along the shelf and in deeper waters.

Particle abundance varied considerably between stations and depths. Stations closer to land, such as stations 85, 86, and 92 had elevated particle levels, typically composed of very small (<25 um) particulate matter. Small diatoms were characteristic of shallow inland stations, while larger diatoms such as Corethron sp. and Chaetoceras sp. Were found almost exclusively in the shelf break region.

Ciliates and flagellates tended to become smaller and less frequent. Larger ciliates were associated with the pycnocline depths at stations 91 and 92. However there existed more diatoms and particulate matter at those depths than at the surface or bottom. It seems likely that we are witnessing the steady decline of microplankton abundance and activity as ice cover increases and daylight, temperature, and phytoplankton production decreases.

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

As noted above, BIOMAPER-II was deployed at station 51 and towyoed to station 50. These two stations are on the southern side of the entrance to Marguerite Bay along a section that was not sampled while the grid survey was underway because of equipment problems described in earlier reports. While the BIOMAPER-II was out of the water on the transit from the southern end of the grid, additional troubleshooting was done by Peter Martin in search for the reason why the 43 kHz frequency was still suffering from intermittent noise. A relay on the 43/120/200 transmitter board was found “welded” in one position and replaced, but the relay failure was not the culprit, and subsequent use of the acoustic system showed the noise was still present. On another front, inspection of the electro-optical cable near the cable termination revealed that several strands of the outer armor were broken. Although this has little effect on the strength of the cable, normally this would call for the re-termination of the wire. But with only a few more hours of towyoing left, the wires were taped to prevent unraveling and the towing went forth. This problem with the cable will be dealt with in Punta Arenas.

Early on during the towyo, there were patches of intense volume backscattering around 40 to 50 m and a well developed near bottom layer from 230 to 400 m depth. Later in the run, surface scattering diminished and there were multiple thin layers in the pycnocline (200 to 50 m). Closer to station 51 where the bottom depth was around 325 m, the bottom layer changed character and instead of a generally dense and fairly uniform layer structure, there were more loosely organized individual scatterers within about 70 m of the bottom. At times they became more discrete and took on a krill-like appearance. Throughout the run, there was an empty mid-water zone with few targets.

Cheers, Peter