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:
- Quasisynoptic survey cruises
- Process oriented cruises
- Remote sensing
- 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:
- 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;
- Vertical distribution and abundance of food (the definition of which
depends upon the species of interest);
- Distribution and abundance of top predators;
- 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:
- Data is particularly required on overwintering physiology and life
history strategies;
- Studies on patch formation, maintenance and dissolution are
particularly required.
- Critical studies require measurements of carbon flux, carbon
mineralization in the sediments, and bioturbation;
- Measurements of physiological rates conducted in conjunction with
environmental conditions.
- More information is required on the effect of temperature on growth
and development rates of early life history stages of fishes;
- 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.