Report of Activities on the RVIB N.B. Palmer Cruise 02-04

31 July to 1 August 2002

This is the first report of the fourth and final broad-scale cruise of the U.S. Southern Ocean GLOBEC Program aboard the Research Vessel Ice Breaker Nathaniel B. Palmer and is designated NBP02-04 (the fourth cruise for the Palmer in 2002). The three previous cruises (NBP01-03, NBP01-04 and NBP02-02) took place in Austral fall and winter of 2001 and fall of 2002. The focus of the SO GLOBEC program is on the biology and physics of a region of the Antarctic continental shelf due south of the tip of South America that extends from the northern tip of Adelaide Island to the southern portion of Alexander Island and includes Marguerite Bay. As with the past three cruises, this is a joint ship operation with the R/V L.M. Gould, which will be conducting process studies in the same geographic region.

The focus of the program is on developing an understanding of the overwintering strategy of krill, principally Euphasuia superba, which are key species in the Antarctic ecosystem. Krill form an essential link between the primary producers and the top marine predators. The site chosen for the study was based on earlier observations that indicated that the area was important for the overwintering of krill and their predators due to unique features in the bathymetry and ocean circulation. Thus the goals of the program are to develop a fundamental understanding of the shelf physical circulation processes and their effect on sea ice formation and Antarctic krill (Euphausia superba) distribution and to examine the factors that govern krill survivorship and availability as food to higher trophic levels, including fish, seals, sea birds, penguins, and whales. The work on this cruise will involve attempting to collect data on a grid of 85 regularly spaced stations positioned nominally at 40 km intervals within the survey area. Due to the pack ice extent and thickness this year, it is likely that some stations sampled previously during the fall cruises will not be accessible during this cruise. The station activities will involve the deployment of the CTD [to measure water column physical properties (temperature, salinity, and microstructure) and to collect water samples for nutrients, phytoplankton, microzooplankton], the towing of a variety of nets [to collect zooplankton (especially krill), and mid-water fish for studies of their distribution and abundance and for studies of their physiology and biochemistry], the deployment of an Remotely Operated Vehicle [ROV - for under ice studies of krill distribution and behavior], and the collection of sea ice [for studies of the resident microflora and fauna] and under ice “manned” dives [to study krill behavior and to collect individuals for experimental studies]. The work on the cruise will also involve collection of data along the survey trackline between the stations. The along track activities will involve the “towyoing” of BIOMAPER-II between the surface and about 250 m [to collect multiple frequency (5) acoustic data from reverberation off water column animals, high resolution video data of individual zooplankton, and environmental data (temperature, salinity, fluorescence, etc.)] and the surveying of sea birds and marine mammals. Throughout the cruise continuous measurements will be made of sea surface water properties, water currents (with ADCP), and meteorological properties. Unfortunately, we will not be collecting sea floor bathymetry with a newly installed Simrad Multibeam system because it failed to pass acceptance tests and could not be put into service. Attempts will be made to collect diet samples from the sea birds, especially Adélie penguins.

The cruise got underway at 1400 on 31 July when we left the port of Punta Arenas, Chile after a week of intense set up of the equipment and laboratory spaces needed for the work at sea. The setup and testing of gear went very smoothly as a result of the superb planning and assistance rendered by the Raytheon Technical Support Group. Although the air temperature was right around freezing, skies were partly cloudy and wind and sea conditions were calm. Thus, it was a smooth start to the cruise.

Shortly after leaving port, we had our first ship orientation and safety meeting with Chief Mate Mike Watson. An integral part of the first meeting on a cruise is the putting on of a survival suit, which is issued to each person, and the exercise of getting the entire science party into a large life boat and strapped in, this time with our survival suits on. The safety meeting was followed by brief orientation comments from MPC Chris Shepard and Chief Scientist Peter Wiebe. Then there was a deck safety briefing led by Stian Alasandrini and an Information Technology orientation [email, networking, computer support in general] led by Paul Huckins. Shortly after dinner while in the embayment between the two narrows in the eastern portion of the Straits of Magellan, a deployment of BIOMAPER-II was done to do allow the MT's and others who will be handling the system get some practice with launch and recovery under good sea conditions. It was also done to test the electronics and sensor systems on the towed body, and to adjust the tail elevator to minimize variation of pitch and roll from horizontal under normal towing conditions. Around 2030 at the pilot drop-off point on the eastern end of the Straits of Magellan, three individuals (Peter Martin of Raytheon, and Terry Hammar and Andy Girard both from WHOI) who were assisting in the port setup of the hardware and software associated with BIOMAPER-II and the ROV, left the ship along with the pilot.

The course to the survey area again took us down the eastern side of the tip of South America (Argentina), through the Estrecho de La Maire, and out into the Drake Passage. Because of the extensive ice pack coverage of the survey area and areas substantially to the north and because of the need to closely coordinate our trackline with that of the L.M. Gould, which is dependent upon the Palmer for ice-breaking services, we will be steaming a line that will take us into the inside passage (Gerlache and Bismark straits) and then down to Crystal Sound. Crystal Sound is just north of Adelaide Island and at the northern end of the survey grid and it will be the first site for joint ship operations. The distance from Punta Arenas to Crystal Sound is approximately 1100 nm.

During 1 August, we steamed along the southern Argentina coast in calm seas and light to moderate winds (<20 kts). Skies remained overcast and the barometric pressure dropped slowly from around 1006 mb in the morning to 996 mb in the late evening. Air temperatures were around 5ºC. Taking advantage of the nice sailing weather during the afternoon, a science meeting was held to discuss in more detail the station work plans and also to provide some of the investigators (Bob Beardsley, Eileen Hofmann, Chris MacKay, Erick Chapman, Kendra Daly, and Scott Gallager) with an opportunity to describe findings from previous cruises as a context for work that will occur on this one. The meeting ended with the Palmer just entering Estrecho de La Maire in the last light of the day with the snow-capped peaks of the mountains of Isla de los Estados to the east and those on Peninsula Mitre on the mainland to the west silhouetted against a darkening sky.

In this and future reports from the N.B. Palmer, the investigators from the different programs on this cruise will be providing sections describing their work and progress. Although most data collection cannot start until we reach the 200 mile limit, and most will not start until we reach Crystal Sound, some observations have been made of the marine mammals that were present along the trackline since leaving Punta Arenas. The following was provided by Francisco Viddi.

Upon leaving Punta Arenas, Chile on 31 July, the Palmer headed Northeast toward the eastern mouth of the Magellan Strait and the Atlantic Ocean. Most of the afternoon was dedicated to getting things ready for the sighting effort next day (downloading programs, checking GPS connections, etc.). With the short day length of this time of the year, no effort was performed. Nevertheless, 4 possible Peale's dolphins (Lagenorhynchus australis) were sighted at 1636 at approximately. 52°45′S; 72°45′W about 030° to starboard and 350 meters from the ship. This was an incidental sighting while having a safety meeting on the deck. Dolphins were only seen for a few minutes swimming 180° from the ship. No behaviour was recorded and no records on ship course or velocity were taken. Beaufort scale equaled 2, sky was partly cloudy (75%), and visibility was good.

Even though the weather conditions on 1 August were very good for whale surveys (good visibility, light, Beaufort 2-3, etc.), most of the day was used to fix the software, which is necessary to log the observations. No GPS connection was established until late afternoon. Four and a half hours of effort were made, but there were no cetacean sightings. A group of 4 Southern Sea Lions (Otaria flavescens) were seen at 1300 on a course of 082° to starboard, 250 meters from the vessel. They were moving north in a tight formation, but came close to the ship (less than 30 meters) for a few minutes. Effort ended at 1500 to attend the science meeting.

We are currently steaming at 11 kts on a 170 course out into the Drake Passage. Our position at 2300 on 1 August is -55º 47.01′S; -64º 43.52′W. The air temperature is 5.5ºC, about the same as the sea surface temperature. Winds are out of NW (321) at 10 to 15 kts and the barometer is at 995.7 mb.

Cheers, Peter