S.O.-Logistics

## Chapter 4 - FIELD PROGRAM LOGISTICS

The GLOBEC Southern Ocean Field Study is anticipated to begin in 1995 or 1996 and to continue for a period of approximately three years. In general terms it is recommended that there be four principal and complementary sampling modes:

1. Quasisynoptic survey cruises
2. Process oriented cruises
3. Remote sensing
4. Shore based laboratory studies

Physical oceanographic studies and biological investigations would be carried out in each of these sampling modes. Where possible attempts should be made to coordinate these cruises with ongoing cruises in the region. Cruises should be scheduled so as to provide maximal coverage of the entire annual cycle, with moorings operating continuously for the entire duration of the field program. Field program logistics are described here using the Bellingshausen Sea as an example site. A second site in the Indian Ocean sector may also be favorable and the general field program logistics described below would apply to this area as well. Specifics of the field program appropriate for the chosen site remain to be determined.

### 4.1 Quasisynoptic Survey Cruises

#### 4.1.1 Survey domain and resolution

Survey cruises would cover a grid of approximately 20 km interline spacing extending from the coastal region of the Bellingshausen Sea to well offshore into open ocean regions. In addition, selected transects should be run deep into the circumpolar Antarctic current and occasionally into areas of the more well studied Bransfield Strait region; this will enable better comparative studies of regionally separate populations.

#### 4.1.2 Timing

In any intensive field year, during which coverage of the entire annual cycle is required, a total of six to 10 survey cruises, each of two to three weeks duration, should be conducted. This amount of time is required to sample the region at the appropriate resolution. Cruises of similar duration, but at lower frequency, may be sufficient to characterize the system in nonintensive field sampling years.

#### 4.1.1 Critical measurements

Working groups agreed that the survey sampling procedures of mutual interest would require the following general types of collections:

1. Vertical distribution, abundance and physiological condition of target species; for a number of species depth distributions to a depth of 1000 meters would be necessary;
2. Vertical distribution and abundance of food (the definition of which depends upon the species of interest);
3. Distribution and abundance of top predators;
4. Physical, chemical and biological properties focusing on vertical profiles of salinity, temperature, inorganic nutrients, beam transmission, downwelling irradiance, and current velocities.

Key instrumentation may involve multiple net samplers (e.g. MOCNESS), optical plankton counters, acoustics, towed video systems, box corers, and bottom trawls. Physical, chemical and biological properties could be sampled by a group of instruments including CTD, radiometer, beam transmissometer, ADCP, and chemical analysis of water samples collected by rosette. Innovative methods in biochemistry and biotechnology which are sufficiently developed would also be incorporated for assessing the physiological condition of specimens.

### 4.2 Process Oriented Cruises

#### 4.2.1 Domain and resolution

Location of the process oriented cruises would be determined on the basis of preliminary results gained from initial survey cruises.

#### 4.2.2 Timing

The exact timing of the cruises will depend to a great extent on the determination of which periods are deemed to be critical to understanding population dynamics of the target species being studied. This may be anticipated beforehand to some degree by the application of modeling results, as well as from historical data.

#### 4.2.3 Critical measurements

Measurements should focus primarily on processes at different time and space scales. Certain types of studies are envisioned as essential and can be described as follows:

Zooplankton/krill:

1. Data is particularly required on overwintering physiology and life history strategies;
2. Studies on patch formation, maintenance and dissolution are particularly required.

Benthos:

1. Critical studies require measurements of carbon flux, carbon mineralization in the sediments, and bioturbation;
2. Measurements of physiological rates conducted in conjunction with environmental conditions.

Top predators:

1. More information is required on the effect of temperature on growth and development rates of early life history stages of fishes;
2. Overwintering studies are needed to understand the critical mortality period of higher predators;

Measurements would concentrate particularly on shipboard and in situ estimates of physiological rates such as egg production, growth and feeding, as well as key population dynamics parameters such as mortality. The theme of these cruises would be to attempt to follow localized aggregations of marine animals and to monitor key changes in their demography, physiology, and distribution as they are affected by physical processes and behavior through time. A variety of background physical, chemical and biological measurements made during the process oriented cruises would provide continuity with data generated from the survey cruises.

### 4.3 Remote Sensing

#### 4.3.1 Domain and resolution

Remote sensing here is taken broadly to include techniques ranging from satellite oceanography to moored sampling devices. Therefore, the domain will range from localized point samples to broad coverage of the entire sampling region, and resolution will range from that dictated by the limits of satellite and airborne sensors to the temporal resolution dictated by the limitations of hardware located on bottom moorings.

#### 4.3.2Timing

Moorings could be deployed at the outset of the first field season and be maintained for the entire duration of the sampling study. It is anticipated that moorings would be brought on line at new locations as the field program progresses, but these should presumably be located at sites both on the coastal shelf as well as on the continental slope.

#### 4.3.3 Critical measurements

It is recommended that each mooring site include a heavily instrumented mooring and possibly peripheral moorings with relatively few instruments. The central moorings might include Acoustic Doppler Current Profilets (ADCPs) and a variety of hydrographic, bio-optical and bioacoustical sensors, whereas peripheral moorings would include only current meters.

Local weather and sea surface conditions and ocean color could be detected using either satellite-borne or airborne sensors. These remote sensing devices should be flown in conjunction with either the process oriented or the survey scale cruises. There should be close coordination between GLOBEC and WOCE concerning meteorological and physical oceanographic data for study areas.

Lagrangian drifter studies should also be included to measure components of the near-sttrface circulation, and to assess other parameters pertaining to the biology of local waters, including transmission, fluorescence, and possibly acoustics.

Selected process studies should be conducted in the vicinity of mooring sites; similarly, survey cruise transects should be brought fairly close to these sites.

### 4.4 Shore-based Laboratory Studies

One of the great advantages of a GLOBEC study site in the Bellingshausen Sea is that it is situated close to a very high concentration of shore-based laboratories belonging to a large number of countries. These laboratories would prove useful for both. scientific and logistic reasons. A wide variety of process oriented studies, particularly focused on physiology, could be contemplated at these various laboratories. The existence of such facilities provides the opportunity for continued studies throughout the entire period of the GLOBEC research program, which would focus on experimental evaluations of physiological rates.