This is the first report 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 "maned" 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, and 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 14°C 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 is at -65° 38.93S; -70° 37.92W) is taking 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 is approximately 900 nm.
Shortly after leaving port, we had our first safety meeting with First Mate David Fahey presiding. This included dawning the survival suits and the exercise of getting the entire science party into a large lifeboat and strapped in. The safety meeting was followed by a science meeting lead by MPC Chris Shepard and Chief Scientist Peter Wiebe. During the evening of 22 July, while steaming through the straits of Magellan, we slowed for a test deployment of BIOMAPER-II. This enabled those who will be handling the launch and recovery of the towed body to become familiar with the procedures in running the winch, slack tensioner, and overboarding sheave and docking mechanism together with the operation of the stern A-frame under good weather and sea conditions. It also provided an in-water test of all of the sensors systems while the system was being towed.
During 23 July, we steamed along the eastern side of the southern tip of South America reaching the straits of Maire just after dusk. Winds were in the 10 to 15 kt range for most of the day with partly cloudy skies and an air temperature around 4°C. It was a very good day to develop one's sea legs and to continue the setup of laboratory and deck based instrument systems. It was also a day for ping editing class. The Seabeam bathymetry data has to be edited manually and all in the science party are expected to share in accomplishing this task. Kathleen Gavahan taught the newcomers how to do the editing on the workstations in the computer lab and a test editing file was used throughout the day to develop ping editing skills.
We are currently (~1200 hrs) on the northern portion of the Drake Passage (-57° 20.6S; -65° 55.0W), still within the 200 mile limit of Argentina (hence there currently are no data being collected). The skies are partly cloudy with some occasional light rain and the air temperature is around 3.5°C. Winds are out of the west (270) with speeds between 20 and 30 kts and the seas are rough. Once we reach the 200 mile limit later today (24 July), we will begin our data collections with a sonabuoy drop and the start of an XBT sections across the polar front.
Cheers, Peter