This is the first report to NSF of the second broad-scale cruise of the U.S. Southern Ocean GLOBEC Program aboard the Research Vessel Ice Breaker Nathaniel B. Palmer. The focus of this study is on the biology and physics of a region of the Antarctic shelf due south of tip of South America that extends from the northern tip of Adelaide Island to the southern portion of Alexander Island and includes Marguerite Bay. This cruise is a joint ship operation with the R/V L.M. Gould, which will be conducting process studies in the same geographic region.
We have two primary goals: to elucidate 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 seals, penguins, and whales. The work on this cruise will involve collecting data at a grid of 92 regularly spaced stations positioned nominally at 40 km intervals within the survey area. The station activities will involve the deployment of the CTD [to measure water column physical properties (temperature, salinity, etc.) and collect water samples for nutrients, microzooplankton, phytoplankton etc.]; 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 a HTI two-frequency acoustic system [for studies of zooplankton distribution when net tows are being done]; the deployment on an ROV [for under-ice studies of krill distribution and behavior]; 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 a passive listening device (sonabuoy) will be deployed to listen to marine mammal calls and continuous measurements will be made of sea surface water properties, meteorological properties, and sea floor bathymetry (with Seabeam). Attempts will be made to collect diet samples from the sea birds and to biopsy whales.
We left the port of Punta Arenas, Chile after a week of cruise preparation at 1800 hours on Sunday, 22 July 2001 with a moderate wind and partly cloudy skies. The sailing was delayed a day primarily because during the assembly and testing of the sensor systems on BIOMAPER-II, it was determined that the high frequency echosounder system was not working. Since this instrument system is so important to the along track surveying, it was essential to figure out what was wrong and fix it in port if possible. The failure was finally traced to a new part installed in the echosounder between the previous cruise in April-May 2001 and this one. Once replaced with a backup part, the equipment returned to normal operation. Delaying the sailing also made it possible to receive a late shipment of 14C and the Fast Response Rapid Fluorometer (also out for repair) both needed for the productivity studies and to enable one of the mates on the L.M Gould, who had several airline flights cancelled and missed the Gould's sailing, to sail with us.
The course to the survey area (first station was at -65° 38.93S; -70° 37.92W) took us east from Punta Arenas through the straits of Magellan, then south along the eastern side of South America (Argentina), through the straits of Maire, then nearly straight south to the start of the grid. The distance from Punta Arenas to the work site was approximately 900 nm.
During 23 July, we steamed along the eastern side of the southern tip of South America reaching the straits of Maire just after dusk. It took another four days to reach survey grid station #1. An XBT survey was done during our steaming across the Drake Passage to document the position and hydrographic structure of the polar front. We ran into pack ice two days before reaching our first station. Since beginning the broad-scale survey on 27 July, we have completed work at stations #1 to 18, averaging a little over 3 stations per day. The work has gone reasonably well in spite of the extensive ice pack, which covers the entire survey area. At these stations, we have completed nineteen CTD profiles, five 1-m2 MOCNESS tows, one 10-m2 MOCNESS tow, two ice collection stations, three under-ice dives, three under-ice ROV excursions, and 14 sonabuoy deployments. BIOMAPER-II towyo's were done between the stations up to #12. The towed body sustained major damage while underway to station #13 when the wire was snagged by ice in the wake and towed body rammed the underside of the ice. Repairs have almost been completed. Bird and mammal observations have been made along the transits between station locations during available daylight, which is in short supply. The 1-m2 MOCNESS also sustained serious damage when it too had the towing wire snagged by ice and rapidly rose to the sea surface, hitting the ice pack. Within two days, it had been repaired and returned to service.
Thanks to the very professional and excellent assistance we are getting
from the Raytheon technical support and the ship's officers and crew, repairs
to the equipment have been effective and done on a timely basis. To read
the daily reports, which provide more detail about our work to date, go
to the SO GLOBEC Web site: http://www.ccpo.odu.edu/Research/globec/main_cruisepage/maincruise_menu.html
Peter Wiebe, Chief Scientist