of purposes, a rapid resurvey on the scale completed in the WHP is not anticipated in the immediate future. Indeed, such a resurvey would not
constitute such basic global exploration as was the
case in WOCE. It is difficult to imagine that a
significantly more detailed global survey could
be undertaken without fundamental advances in
technology, especially in the use of autonomous
platforms and sensors.
In the era following the WOCE observational
phase, global observations are now focused on
strategies for sustained observations, and determining variability and change.
3.1.2 CTD and sample measurements
3.1.2.1 Development and planning of the
WOCE Hydrographic Programme
The planning for the WOCE Hydrographic Programme (WHP) officially started with the establishment and first meeting of the WHP Planning
Committee in April 1987. The committee began
thinking of requirements for variables to be measured and their accuracy. Three kinds of hydrography were envisioned for WOCE: one-time survey,
repeat hydrography and time-series stations. The
one-time survey would sample the ocean on a regular grid of lines spaced so as to cover all the major
ocean sub-basins. Repeat hydrography would
include two types of sampling: selected one-time
lines would be repeated to check the representativeness of the one-time survey; and additional individual sections, not necessarily parts of the one-time
survey, would be repeated once or twice yearly
throughout WOCE. Time-series stations were
envisioned to be regular reoccupations of particular sites that were to continue from pre-WOCE
measurements or to be new sites under the aegis of
WOCE and JGOFS; temporal sampling at timeseries sites would be sufficient to resolve the
seasonal signal. Another contribution to observing
the ocean variability was the high-density XBT
programme conducted from Voluntary Observing
Ships. Figure 3.1.2 shows lines occupied in this
programme.
In terms of magnitude of effort, the initial estimates (WCRP, 1988a) indicated that the WHP
was to exceed by more than an order of magnitude
all previous large-scale ocean ‘surveys’ going back
to the Challenger Expedition (Fig. 3.1.3). The plan
called for 7700 small volume stations in the
one-time survey and a further 15 000 for repeat
hydrography: this would require 10 years’ shiptime for the one-time and a further 15 years for
repeat work.
The WHP, which officially began field work in
1990, evolved into a programme in which the bulk
of the one-time survey in the Pacific Ocean was
carried out during 1991–94, the Indian Ocean
in 1995 and the South Atlantic in 1992–95. The
one-time survey of the North Atlantic, however,
had a distributed sampling throughout the WOCE
period and was not concentrated in time. Documented changes in the North Atlantic during
WOCE have shown a significant change in properties of Labrador Sea Water to have occurred during the North Atlantic one-time survey. The sheer
size of the Pacific Basin mitigated against any
SECTION 3 NEW WAYS OF OBSERVING THE OCEAN
102
Fig. 3.1.2 Schematic location of high-density XBT lines. Prepared by N. P. Holliday (WOCE IPO).
constitute such basic global exploration as was the
case in WOCE. It is difficult to imagine that a
significantly more detailed global survey could
be undertaken without fundamental advances in
technology, especially in the use of autonomous
platforms and sensors.
In the era following the WOCE observational
phase, global observations are now focused on
strategies for sustained observations, and determining variability and change.
3.1.2 CTD and sample measurements
3.1.2.1 Development and planning of the
WOCE Hydrographic Programme
The planning for the WOCE Hydrographic Programme (WHP) officially started with the establishment and first meeting of the WHP Planning
Committee in April 1987. The committee began
thinking of requirements for variables to be measured and their accuracy. Three kinds of hydrography were envisioned for WOCE: one-time survey,
repeat hydrography and time-series stations. The
one-time survey would sample the ocean on a regular grid of lines spaced so as to cover all the major
ocean sub-basins. Repeat hydrography would
include two types of sampling: selected one-time
lines would be repeated to check the representativeness of the one-time survey; and additional individual sections, not necessarily parts of the one-time
survey, would be repeated once or twice yearly
throughout WOCE. Time-series stations were
envisioned to be regular reoccupations of particular sites that were to continue from pre-WOCE
measurements or to be new sites under the aegis of
WOCE and JGOFS; temporal sampling at timeseries sites would be sufficient to resolve the
seasonal signal. Another contribution to observing
the ocean variability was the high-density XBT
programme conducted from Voluntary Observing
Ships. Figure 3.1.2 shows lines occupied in this
programme.
In terms of magnitude of effort, the initial estimates (WCRP, 1988a) indicated that the WHP
was to exceed by more than an order of magnitude
all previous large-scale ocean ‘surveys’ going back
to the Challenger Expedition (Fig. 3.1.3). The plan
called for 7700 small volume stations in the
one-time survey and a further 15 000 for repeat
hydrography: this would require 10 years’ shiptime for the one-time and a further 15 years for
repeat work.
The WHP, which officially began field work in
1990, evolved into a programme in which the bulk
of the one-time survey in the Pacific Ocean was
carried out during 1991–94, the Indian Ocean
in 1995 and the South Atlantic in 1992–95. The
one-time survey of the North Atlantic, however,
had a distributed sampling throughout the WOCE
period and was not concentrated in time. Documented changes in the North Atlantic during
WOCE have shown a significant change in properties of Labrador Sea Water to have occurred during the North Atlantic one-time survey. The sheer
size of the Pacific Basin mitigated against any
SECTION 3 NEW WAYS OF OBSERVING THE OCEAN
102
Fig. 3.1.2 Schematic location of high-density XBT lines. Prepared by N. P. Holliday (WOCE IPO).