|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 37
3
Status of Planning for Proposed
Research-Oriented Ocean Observatories
This chapter offers an assessment of the readiness of scientific plan-
ning and technical development for construction and installation of each
the three main infrastructure components of the OOI. A summary of the
scientific and technical readiness for each component is presented after
each section (Box 3-2, Box 3-4, and, Box 3-6~.
GLOBAL OBSERVATORY PLANNING
Global observatory science can be loosely divided into two catego-
ries, according to whether the data are obtained from the seafloor or the
water column and sea surface. Data from the seafloor include geophysical
information about earthquakes and the structure of the Earth, investiga-
tions of volcanic and tectonic activity, and studies of life on or below the
seafloor. The data collected in the water column and at the sea surface are
used for research on weather and climate, interactions between the atmo-
sphere and ocean, and ocean physics, chemistry, and biology.
Global geophysicists are particularly interested in sites far from is-
land-based or other land-based observatories in order to provide more
uniform sampling of the Earth's interior. Oceanographers are more inter-
ested in measuring air-sea fluxes, investigating water mass formation,
measuring transport and variability of major current systems, and study-
ing the variability of the ocean's interior. While the sites of greatest inter-
est to these various disciplines often do not coincide, the cost and limited
availability of observatories in the more remote parts of the world's oceans
37
OCR for page 38
38
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
argue strongly in favor of locating global observatories where many re-
search goals can be concurrently and productively pursued. Studies that
cannot be supported by fixed observatories will likely find support in
Lagrangian and satellite observing systems.
The global observatory component of the OOI will provide important
long-term, interdisciplinary measurements at 15-20 widely separated sites
in all of the world's major oceans. A high priority is occupying sites in the
remote Southern Oceans that are currently not sampled. This network
will complement and enhance other international global observatory ef-
forts (see Chapter 6~. The following discussion summarizes the status of
scientific planning and technical development for the OOI global obser-
vatory network.
Status of Scientific Planning
The scientific rationale for a global network of ocean observatories is
well defined and planning for this network is well advanced, including
the identification of specific sites for these observatories (Table 3-1~. The
primary drivers behind this planning effort are international scientist com-
munities involved in climate, global carbon cycle, biological and bio-
geochemical, and solid earth geophysical research. Major research pro-
grams such as WOCE, IGOFS, CLIVAR, RIDGE, ODP, GSN, the Global
Ocean Ecosystem Dynamics Program (GLOBEC), the Carbon Cycle Sci-
ence Program (CCSP), and the Surface Ocean Lower Atmosphere Study
(SOLAS), have all pointed to the establishment of long time-series sites as
critical elements of their research strategy. International groups provid-
ing guidance on the development of a global observatory network in-
clude the Ocean-Observing System Development Panel (OOSDP), the
Ocean Observations Panel for Climate (OOPC), the CLIVAR Ocean Ob-
servations Panel (COOP), the DEOS steering committee, and the Interna-
tional Ocean Network (ION). Each has laid foundations for developing
global arrays.
These groups recognize the unique attributes of fixed observatories,
which include high temporal and vertical resolution, the ability to ob-
serve from the sea surface to the seafloor, and their presence on site
through episodic events and in conditions difficult for ships. Such groups
have indicated that fixed observatories would be an essential element of
the observational approach needed to address their science foci (see Box
3-1~. In each case, strong arguments have been made to justify the cost of
establishing long-term observatories, using a global reference frame that
applies modeling, remote sensing, and other, already-available sampling
methods to complement the observatory network (National Research
Council, 2000~. It is particularly important to test the success of models at
OCR for page 39
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 39
replicating the variability observed in long time-series collected around
the globe in different characteristic regimes. For example, satellite remote
sensing helps numerical weather prediction models predict the global
pattern of weather systems with greater accuracy, but such models have
biases and error in sea-level meteorology and air-sea fluxes. With only
one OWS (a ship) now operating and few open ocean time-series of sur-
face meteorology available from buoys, there is no way to systematically
address the size of the errors, why the models fail, and how to improve
the model physics and performance in different regimes (such as in stratus
cloud deck regions, in the trade winds, in the tropics, in the Southern
Ocean, etc.~. Global observatories would make available time-series cru-
cial to developing better air-sea flux fields and improving atmospheric
general circulation models.
An international Time-series Science Team (TSST) now coordinates
the planning efforts of many of the groups interested in these scientific
questions. Formed by CLIVAR and GOOS (through the COOP and the
GOOS OOPC), and endorsed by the Partnership for Observation of the
Global Ocean (POGO), the TSST represents the ocean community's di-
verse scientific interests and is developing consensus on the desired loca-
tions for time-series stations. In addition, it is charged with beginning the
implementation of different components of an integrated global ocean-
observing system. The TSST has identified a number of potential sites
located at the intersection of regions of interest for multiple disciplines,
giving priority to those sites where a shared interdisciplinary infrastruc-
ture will provide cost-effective observing systems that should be afford-
able and functional for decades to come.
The DEOS Steering Committee has used the work of the TSST to
identify preliminary locations for 20 moored-buoy observatories that
could comprise the global network component of the OOI (Figure 3-1,
Table 3-1~. The criteria for selecting these sites are outlined in the DEOS
Global Network Implementation Plan (DEOS Moored Buoy Observatory
Working Group, 2003~. These 20 sites are a subset of a longer list identi-
fied to date by the TSST (Appendix E). Some of the sites on that longer list
are already funded; the OOI contribution of an additional 20 sites would
represent a dramatic increase in capability as well as a major step toward
a global array of ocean observatories.
Status of Technical/Engineering Development and Planning
There are two distinct technological approaches for providing power
and two-way communication to instruments at ocean observatories (1)
moored observatories linked to shore via satellite and (2) observatories
linked to shore by cables. Moored systems presently in use include both
OCR for page 40
40
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
TABLE 3-1 Potential Global Network Sites Proposed by the DEOS
Global Working Group
Latitude/
Longitude Remarks
Atlantic Ocean Sites
36N 70W Gulf Stream extension; flux reference at critical site for air-sea coupling;
exchanges of heat; CO2; freshwater; water column instrumented for
water mass-variability and modification studies.
32N 65W BATS/Station S/BTM; historical time-series record and testbed site;
physical, meteorological, biogeochemical.
30N 42W North Atlantic multi-disciplinary site; instrumented for DEOS;
geophysics, meteorology, physical, biogeochemical.
Multidisciplinary mooring; site now occupied by the Pilot Research
Moored Array in the Tropical Atlantic (PIRATA) surface mooring,
getting surface meteorology and upper-ocean data; upgrade to more
capable full water column and seafloor.
Flux reference site; for Atlantic climate modes; as above, upgrade
existing PIRATA mooring.
35S 15W South Atlantic multidisciplinary site; instrumented for DEOS;
geophysics, meteorology, physical, biogeochemical.
Pacific Ocean Sites
50N 145W Former Ocean Weather Station P ("PAPA"), known today as Site P;
meteorology; physical, biogeochemical.
ON 20W
10S 10W
40N 150E Kuroshio Extension; meteorology and air-sea fluxes, water mass
variability.
48 30N
176 30W
9 50N
04 20W
0 145W
Endeavor segment of Juan de Fuca Ridge; RIDGE Integrated Study Site
(ISS); seafloor biology, hydrothermal vents, geophysics.
East Pacific Rise RIDGE ISS site; tropical air-sea coupling, surface
meteorology, water column, seafloor biology, hydrothermal vents,
geophysics.
Eq. Pacific multidisciplinary site; upgrade Tropical Atmosphere Ocean
Project (TAO) site for flux; biogeochemistry, water column.
40S 115W South Pacific multidisciplinary site; instrumented for DEOS; geophysics,
meteorology, physical, biogeochemical.
35S 150W South Pacific multidisciplinary site; instrumented for DEOS; geophysics,
meteorology, physical, biogeochemical.
Indian Ocean Sites
15N 65E Arabian Sea; meteorology, physical, biogeochemical.
12N 88E Bay of Bengal; meteorology, physical, biogeochemical.
10S 90E 90E ridge multidisciplinary site; surface meteorology, water column,
seafloor.
continued
OCR for page 41
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 41
TABLE 3-1 Continued
Latitude/
Longitude Remarks
25S 97E
Indian Ocean DEOS; geophysics, physical, meteorology,
biogeochemistry.
47.7S 60E Kerguelen Fixed Station (KERFIX), part of the Kerguelen Islands Time-
series Measurement Programme follow-on; physical, meteorological,
biogeochemical.
Initial Southern Ocean Sites
42S 9E SW of Cape Town; meteorology, water column instrumentation
geophysics.
55S 90W Antarctic Intermediate Water (AAIW) water-mass formation region;
meteorological, physical, CO2, geophysical.
47 S 142E South of Tasmania; meteorology, physical, biogeochemical, geophysics.
SOURCES: Modified from Figure 1, DEOS Moored Buoy Observatory Working Group,
2003 and data from R. Weller, Woods Hole Oceanographic Institution, personal communi-
cation, 2003.
OCR for page 42
42
o
be
o
o
au
V)
o
o
5-
o
OCR for page 43
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 43
subsurface and surface moorings, but neither type has a hard-wired power
or data connection to the ocean floor and thus cannot power or control
instruments on the mooring or on the seafloor.
Cabled observatories can be further subdivided into those utilizing
new cables and those re-using cables retired by the telecommunications
industry. Global observatories based on new-cable infrastructure are
probably beyond the scope of the OOI given the high cost of the cables
needed to reach remote observatory sites. Re-using retired telecommuni-
cations cables for observatories is feasible in some circumstances, and is
already occurring with the retired TPC-1 cable. Other cables are being
used by the Earthquake Research Institute in lapan, the H20, and A Long-
Term Oligotrophic Habitat Assessment (ALOHA) Observatory (Appen-
dix D).
Planning for the OOI global observatory network has thus far focused
primarily on moored buoy systems. The opportunity to re-use retired
telecommunication cables for some of these sites should be thoroughly
investigated, however, as it might offer a cost-effective alternative to
moored buoy systems in some locations.
Moored Buoys
At present, well-instrumented moored observatories using surface
buoys are operational at tropical and mid-latitude sites (e.g., TAO, BATS,
and the Pilot Research Moored Array in the Tropical Atlantic PIRATE.
Surface meteorological sensors are mounted on the buoy and suites of
oceanographic sensors are mounted on the mooring line, spaced as little
as 5 m apart throughout the upper ocean, and extending into the interior
of the ocean at wider spatial intervals (Plate 4~. Those surface moorings
designed to survive strong currents and high seas, as in the Arabian Sea,
have used a scope (the ratio of mooring line length to water depth) close
to 1.4 and have included synthetic rope (often nylon), which stretches and
prevents the anchor from dragging and the surface buoy from submerg-
ing. The basic 3 m discus buoy hull developed at WHOI, used at many
sites for research, has also been used by the National Data Buoy Center
(NDBC) for collecting weather observations at many sites around the U.S.
Exclusive Economic Zone (EEZ).
Many aspects of surface and subsurface mooring technology are very
well developed for surface and water column measurements. Servicing
intervals are dictated primarily by the need to maintain sensor quality in
the face of biofouling and corrosive marine air. While some subsurface
moorings can be installed and left unattended for up to five years, servic-
ing intervals for surface expression moorings are typically six to twelve
months for current generation moorings. Increasingly sophisticated in-
OCR for page 44
44
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
strumentation is also being developed for moorings, including multidisci-
plinary instruments, water samplers, in situ analyzers, and profiling in-
struments that move up and down the mooring line.
Current oceanographic moorings, however, have important limita-
tions that the OOI should address. These moorings have a very limited
capability for telemetering data to shore (samples per minute), since they
rely on very low-bandwidth satellite systems. The buoy systems in use
today also possess very limited power generation capabilities, as they rely
generally on batteries or solar panels. Present-day moored observatories
have no capacity to power or communicate at high data rates with instru-
mentation on the mooring or the seafloor. Inductive coupling of instru-
ments to steel mooring cable and acoustic telemetry have been used to
communicate with underwater instruments, but data rates are low. Sur-
face-to-bottom electro-mechanical (EM) or electro-optical-mechanical
(EOM) cables are as yet unproven and their reliability in this application
is unknown.
Strong ocean currents, high sea states, freezing spray, and floating ice
all challenge the survival of even the most robust surface moorings and
cables available today. The large drag of strong currents can cause anchor
dragging or buoy submersion. High waves lead to large cyclic tensions
and mechanical fatigue, and may affect the performance of directional
satellite antennas unless the surface buoy is large and designed to mini-
mize pitch and roll. To sustain the quality of meteorological and air-sea
flux observations in high sea states, buoy motion and mean tilts will need
to be measured, or meteorological sensors will need to be mounted in
gimbals. In addition, meteorological sensors more resistant to hostile en-
vironments must be developed. Mitigating the effects of freezing spray
requires heated meteorological sensors and, by extension, buoys with
significant power generation capabilities.
Subsurface moorings can survive longer in such hostile environments
as they are not exposed to surface wave motion, can be deployed under-
neath ice cover, and are less likely to be vandalized. However, subsurface
moorings are sometimes damaged by fishing activity. Furthermore, the
lack of surface expression limits data return to using pop-up capsules that
communicate via satellite at relatively low data rates, absent a direct con-
nection to a seafloor cable (e.g., ALOHA observatory).
The DEOS Committee investigated new, more capable moored buoy
systems, and found two particular concepts to be most promising for
further development (Table 3-2) (DEOS Moored Buoy Observatory Work-
ing Group, 2000~. The first option is a cable-linked, high-bandwidth spar
or discus buoy that uses an EOM cable to connect seafloor and moored
instruments to the surface (Figure 3-2~. This system is designed to deliver
approximately 500 W of power to the seafloor and would telemeter data
OCR for page 45
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 45
TABLE 3-2 Technical Specifications of Moored Buoy Systems Under
Development
Low-Bandwidth,
Acoustically-Linked
Low-Bandwidth
EOM Cable-Linked
High-Bandwidth,
EOM Cable-Linked
Buoy type Discus buoy
Mooring design Taut mooring
EOM cable No
Data throughput 2.4 kb/s
Power to sensors None
Junction box No (acoustically-linked)
Discus buoy
S-tether mooring
Yes
9.6 kb/s
20W
Yes
Spar buoy
Tri-moored
Yes
64 kb/s
500W
Yes
NOTE: Data volume delivered to shore will depend on commercial telemetry charges rather
than bandwidth of telemetry link (e.g., Iridium telemetry costs are currently $1/m~nute).
SOURCE: Data from DEOS Moored Buoy Observatory Working Group, 2003.
to shore using a 64 kb/s C-Band satellite telemetry system with a stabi-
lized, directional antenna.
The second concept is a low-bandwidth, discus buoy system that
could be implemented using either of two different approaches (Figure
3-2~. One option uses acoustic modems to transfer data intermittently
from instruments on either the seafloor or the mooring to the buoy at
rates of up to 5 kb/s and a low power, omni-directional satellite system to
telemeter data from the buoy to shore at rates of 2.4 kb/s. A second
approach uses an EOM cable to deliver approximately 20 W of power to
instruments on the seafloor and to provide two-way data communication
between the buoy and a benthic node. A low power satellite telemetry
system would then deliver data from the buoy to shore at rates of up to
9.6 kb/s. See Table 3-2 for a summary of the technical specifications of the
systems discussed above.
The following discussion offers an assessment of the technical readi-
ness of each of these systems based on the recent DEOS Global Network
Implementation Plan (DEOS Moored Buoy Observatory Working Group,
2003).
Low-bandwidth, acoustically-linked system
This design builds upon previous successful discus buoy deployments
of up to one year in a variety of locations in the world's oceans. An
acoustically-linked moored observatory has been used successfully by
the NOAA Deep-Ocean Assessment and Reporting of Tsunamis program
(DART) (www.pmel.noua.gov/tsunami/Dart/). While there are no high-risk
OCR for page 46
46
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
RING
BUFFER
ARCHIVE
.......................
:;:
...................................................
:;:
..........................
~9=
RING
BUFFER
AR&HIVE
PIS
..........................
4:~
...................................................
Pl'S
FIGURE 3-2 Two moored-buoy design concepts being examined for the OOI.
Top: A low-bandwidth discus buoy system uses acoustic modems to transfer
data intermittently from instruments on the seafloor or mooring to a surface
buoy and from surface to shore via a low-power, omni-directional satellite sys-
tem. Bottom: a high-bandwidth moored observatory that uses an electro-optical
cable to deliver power and two-way data communication to a seafloor junction
box and is linked to shore via a 64 kb/s C-Band satellite telemetry system. Figure
courtesy of John Orcutt, Scripps Institution of Oceanography.
OCR for page 47
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 47
technologies associated with this system, there are questions associated
with the performance of the acoustic modems under various environ-
mental conditions. The primary issues that need to be resolved are (1) the
reliability of the acoustic communication link; (2) the average data rates
possible, both for instruments directly below the buoy on the mooring
and for instruments placed some distance away on the seafloor or in the
water column on a near-by subsurface mooring; and (3) the maximum
horizontal distance from the surface buoy at which a useful acoustic com-
munication link can be maintained.
Low-bandwidth, EOM-cab/e-/inked system
The primary difference between this design and the other low-band-
width system is that an EOM cable, rather than an acoustic-link, is used
both to provide two-way communication to a seafloor junction box, and
to provide small amounts of power (20 W) to the seafloor. In this design,
the EOM cable moors the buoy. The lack of experience with using an
EOM cable in this way makes the mooring the highest-risk sub-system in
this approach. Conventional mooring designs with a wave-following buoy
use the large scope of the mooring line to accommodate both the hydro-
dynamic forces associated with the mean currents that would otherwise
either submerge the buoy or cause the anchor to drag, and the flexural
fatigue problems associated with surface wave motion. Further, on con-
ventional designs, plasticjacketed wire rope extends down to about 1500
m in depth and then transitions to synthetic line. As the buoy heaves with
surface waves and swell, many cycles of flexing occur, and there is mo-
tion of the stiff steel cable relative to the synthetic line below, which must
have its uppermost section supplemented with a strain relief boot to re-
duce fatigue from bending and wear from chafing. With an EOM moor-
ing cable, however, scopes of close to one times the water depth are
planned in order to avoid slack line that might loop, flex, and bend as
currents and sea state vary, thus causing failure of the optic fibers or
strain hardening of the copper conductors in the EOM cable. In that case,
however, in-line tensions could be high and cyclic variation in load sig-
nificant enough to risk fatigue-related failure of the cable. The expected
operational lifetime of EOM cables in this application, and the way in
which factors such as sea state and currents affect their reliability, is not
well known. Outstanding issues regarding EOM cable include (1) cable
design and selection, (2) EOM termination design (including bending
relief), and (3) design of the junction between the discus buoy and EOM
cable.
OCR for page 61
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 61
initial nodes that could be augmented as scientific demand and resources
grow. However, the combination of Ethernet and conventional subma-
rine telecommunications protocols introduce significant additional engi-
neering complexity, and the cost of this alternative system may be signifi-
cantly greater than the original NEPTUNE telecommunications design. A
full comparison of the two options is currently under way, and will evalu-
ate these options based on their life cycle costs, reliability, and flexibility
and expandability by an independent panel of experts. A final decision on
which design to pursue should be made by late 2003.
Data Management and Archiving System
Leadership of the Data Management and Archiving System (DMAS)
planning for the proposed NEPTUNE regional-scale observatory has been
provided by the Canadian National Research Council's Herzberg Insti-
tute of Astrophysics in Victoria, British Columbia, which is one of three
Hubble Space telescope data repositories. A conceptual design study
(www.neptunecanada.ca/about/reports.htm) incorporates key lessons learned
from the astronomical community's experience with large data streams.
These lessons include:
· the DMAS data management and archives must be science-driven;
· instrument and observatory control system design must support
data management;
· collection, packaging, and validation of data and meta-data should
be automatic;
· data must flow simultaneously to both the Principal Investigator
(PI) and the archive;
· automating the process of quality control should be based on prac-
tical experience; and
· data archives should allow both public and privileged access to
various data streams.
Major additional challenges faced by regional cabled observatories lie
in the heterogeneous data types that will be generated from a wide vari-
ety of instrument suites and the need to support simultaneous execution
of many experiments. Valuable experience will be provided by a proto-
type based on this design study and scheduled for implementation dur-
ing 2003-2004 as the DMAS for VENUS, a funded Canadian testbed obser-
vatory. As part of this implementation, Canadian DMAS planners are
working closely with engineers at MBARI, who are developing the Scien-
tific Instrument Interface Modules (SIIMs). These interface modules will
be inserted between scientific instruments and deep-sea cabled nodes and
OCR for page 62
62
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
both will add essential metadata to the data streams and allow the net-
work to recognize and accept data from newly installed instruments.
Testbeds
In addition to the technical issues described above, there are other
major technical challenges involved in making the transition from the
current oceanographic research techniques to effective use of a regional
cabled observatory. Scientists must learn how to design, install, operate,
and recover complex experiments, while engineers must design, build,
test, and install new hardware in a challenging operating environment.
Information managers must learn how to use huge streams of data (on the
order of 1 Petabyte 10~5 bytes per year) of many different types. Op-
erators must learn how to install instruments, service an array with mini-
mal down time, protect a network from failures in any one of many indi-
vidual instruments, keep a network running with high reliability, restore
service rapidly in the event of a failure, and provide users with the ability
to interact with their experiments as needed. It is widely recognized that
technical challenges are best met through testbed sites, a sequence of
cabled systems that will build the experience necessary to attain the full
potential of a regional cabled observatory.
Two testbed systems are presently under development in support of
the eventual establishment of regional-scale undersea observatories.
Victoria Experimenta/ Network under the Sea
Funded by the Canada Foundation for Innovation and the British
Columbia Knowledge Development Fund for a start in 2003, VENUS will
lay a short single-node cable in Saanich Inlet (an anoxic fjord), a cable
with multiple nodes across the Canadian portion of the Strait of fuan de
Fuca, and another into the middle of the Strait of Georgia south of
Vancouver (Plate 5~. In addition to providing researchers with access to
interesting and very different marine environments, VENUS will enable
early testing of various technologies proposed for a regional observatory
(more information available at: www.venus.uvic.ca/). Cables will be marine
industry standard, with a central core steel tube containing eight optical
fibers surrounded by steel strength wires, a single copper conducting
sheath, and insulation. Installation will use commercial entities with ex-
tensive local experience in submarine telecommunications. As planned,
VENUS will use the major components of the power system proposed for
NEPTUNE. The VENUS communication system will connect each science
node directly to shore, using dedicated fibers and commercial off-the-
shelf hardware. Where possible, science nodes and SIIMs will use designs
OCR for page 63
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 63
and components being developed for NEPTUNE and MARS. The VENUS
Data Management System will be implemented by data managers at the
Herzberg Institute of Astrophysics, based on initial planning carried out
during the NEPTUNE feasibility study.
The VENUS installations placed, in relatively shallow water and us-
ing relatively short cables, will test the following components necessary
for eventual establishment of a regional-scale observatory:
· single-cable multiple nodes;
· power system;
· communications system (simplified version);
· data management system;
· node design;
· SIIMs design; and
· ROV installation and maintenance.
Monterey Accelerated Research System
Funded through MBARI by the NSF and the David and Lucite
Packard Foundation, MARS will involve the installation of a cabled test
bed adjacent to Monterey Canyon in Monterey Bay, California (more in-
formation available at: www.mbari.org/mars/~. Planned for installation in
early 2005, MARS will extend the VENUS experience to longer cable runs
(62 km) and deeper water (1220 m), and test a spur topology involving a
branching node supporting an "extension cord" to instrumentation at a
distance of several kilometers from the backbone cable (Plate 6~. In this
environment, the MARS testbed will further test both the DC power and
communications systems being proposed by the MARS/NEPTUNE engi-
neering group. Finally, successful deployment of MARS will (1) allow
researchers to become accustomed to working with the type of nodes,
SIIMs, and data management systems that will accompany a regional-
scale installation; (2) provide the crucial experience required to develop
operational skills (ROV-based installation and maintenance, system fault
response and repair, and system control) that will be needed by operators
and users of larger regional-scale observatories; and (3) supply education
and outreach organizations with real-time and archived data products
that can be used both immediately and in preparation for the more exten-
sive data streams derived from regional-scale installations. Neither VE-
NUS nor MARS provides in-water testing of the mesh (with branches and
loops) cable topology or the high voltages and currents proposed by NEP-
TUNE for a regional-scale observatory.
OCR for page 64
64
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
COASTAL OBSERVATORY PLANNING
The coastal ocean is chronically under-sampled, which is especially
problematic given mounting evidence that human activity is altering
coastal waters by changing sediment deposition, erosion patterns, nutrient
distributions, microbial food web structure, and fisheries (Hallengraeff,
1993; National Research Council, 1995; Jorgensen and Richardson, 1996;
Rabalais and Turner, 2001~. These human-induced changes will increase
in the coming decades with projected coastal development and will be
compounded by climate change and global sea-level rise. Unfortunately,
research efforts in coastal waters have been hampered by inadequate
infrastructure and logistical limitations for individual or small groups of
scientists who need to measure the full breadth of time (seconds to
decades) and space (cm to km) scales that affect coastal processes. There is
a community consensus that traditional monitoring strategies are inad-
equate for studying many coastal processes of increasing societal rel-
evance (Thornton et al., 2000; Jahnke et al., 2002~.
OCR for page 65
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 65
To overcome these sampling shortcomings, the coastal ocean research
community has been conducting interdisciplinary studies focused on de-
veloping integrated observation techniques. With the enabling technolo-
gies that have evolved from these efforts, the ocean sciences are currently
poised to address pressing questions regarding spatial and temporal het-
erogeneity and change in coastal ecosystems. These technologies expand
the range over which ocean phenomena can be observed and will make it
possible to identify and study processes at previously impossible time
and space scales. In addition, these envisioned systems offer the opportu-
nity of in situ, real-time, interactive observations that cross conventional
disciplinary boundaries, allow for adaptive sampling, and provide useful
information to many marine-related user groups. The coastal community
appreciates that to fully realize the potential of these new observation
systems and to move understanding of the coastal environment to the
next level, the community needs to leverage multi-disciplinary studies,
sharing many of these resources along with the logistic costs.
Status of Scientific Planning
Scientific planning for the coastal component of the OOI has grown
from nearly a decade of integrated research efforts conducted through the
NOPP, the Department of Defense ONR, the NOAA EcoHAB Program
and the NSF CoOP. Many of the central scientific problems for coastal
waters were synthesized in two separate NSF sponsored workshop re-
ports: Coastal Ocean Processes and Observatories: Advancing Coastal Research
(lahnke et al., 2002) and the Scientific Cabled Observatories for Time-series
(Dickey and Glenn, 2003~. In addition, the state of knowledge in near-
shore processes and a community consensus on future near-shore re-
search strategies were detailed in State of Nearshore Processes Research: II,
from a 1998 workshop (Thornton et al., 2000~. Finally, Ocean.US, which is
designing a national operational IOOS, has highlighted many of the tech-
nical issues for coastal observatories in Building Consensus: Toward An
Integrated and Sustained Ocean Observing System (2002) (Box 3-5~.
While all these reports agree the OOI will provide major advances in
our understanding of coastal processes and new tools for observing
coastal processes, no clear consensus has yet emerged on the mix of obser-
vational technologies and approaches that will best address the major
scientific problems identified in these reports. These approaches include
relocatable arrays of moored buoys and radars (Pioneer Arrays), cabled
observatories, and fixed, long-term moorings (lahnke et al., 2002~. These
different technological approaches are discussed below in the context of a
multi-faceted, multi-dimensional approach to interdisciplinary coastal
research.
OCR for page 66
66
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
Pioneer Arrays
A relocatable observatory system would provide the coastal research
community with a flexible observational capacity for collecting high-
resolution, synoptic-scale measurements in a focused region spanning
100-300 km. The total observatory system, termed a Pioneer Array, would
include an array of autonomous surface and subsurface moorings provid-
ing real-time data, coupled with land-based, multi-static, high-resolution,
surface current radars and integrated with other available remotely-
sensed (land-based, airborne, and satellite) data streams (lahnke et al.,
2002) (Plate 7~. The motivation for such a relocatable observatory is to
provide an infrastructure that is not permanently located at one geo-
graphic site, since coastal processes vary widely with location. For ex-
OCR for page 67
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 67
ample, to address the question of elemental cycling on the continental
shelves, measurements should be acquired on both broad shallow (Mid-
Atlantic-type) and short canyon (Monterey-type) coastal shelves. To in-
crease knowledge of near-shore processes, beaches on both broad and
narrow shelves need to be studied not only because of the differences in
the incident wave and current conditions but also to increase the under-
standing of the dominant processes on different beach genotypes (sandy,
cobble, and muddy bottom material; open coast; and protected pocket).
The participants at the CoOP meeting proposed the Pioneer Array as
a means to entrain the wider coastal scientific community by providing
an asset available to scientists in different geographic locations, thus al-
lowing the research community to identify the best study site for a spe-
cific process through peer-reviewed competitive grants (lahnke et al.,
2002~. The geographic flexibility of the Pioneer Array is analogous to a
ship on station for several years, providing data from an array of 20-40
real-time coastal buoys and multi-static arrays of high-resolution coastal
radars. Coupled with the output of other available remote sensors, the
Pioneer Array would provide continuous coherent data streams that could
be used by data-assimilation models. Finally, the process studies con-
ducted with the Pioneer Array could provide insight on the optimal place-
ment of long-term time-series moorings.
The technology required for the mooring aspect of Pioneer Arrays is
mature, although further work will be required to establish techniques to
counter biofouling and fishing losses. Given that the overall goal is to
provide a well-sampled ocean for interdisciplinary studies, the sensor
arrays on the buoys will include operational and preoperational IOOS
instruments but would also provide the flexibility to integrate more ex-
perimental instruments. This flexibility allows the OOI system to inno-
vate components for the IOOS backbone. The CoOP workshop report
recommended that three Pioneer Arrays be acquired as part of the OOI
for process-oriented studies in the coastal regions of the U.S. (lahnke et
al., 2002~.
Surface-based radar technology for remote sensing of surface current
fields has experienced rapid growth and acceptance within the scientific
community over the last few years. Like satellites, radars provide two-
dimensional maps of surface currents, allowing for spatially focused sam-
pling efforts (Plate 8~. Experimental long-range systems demonstrated at
several locations around the country can measure surface currents over a
200 km area with 6 km resolution. Higher resolution systems provide
estimates for radial current vectors over 40 km areas with a resolution of
1.5 km. Some proposals for IOOS call for a national network of these long-
range radar systems to support science, commercial shipping, and the
U.S. Coast Guard. However, the 6 km resolution of this proposed national
OCR for page 68
68
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
network lacks the resolution necessary to resolve many of the scales that
are relevant for scientific efforts in coastal waters (on the order of 0.5-2
km). Coastal applications will require continued engineering and devel-
opment to optimize the number of radar measurements given cost, foot-
print size, and resolution.
Coastal Cabled Observatories
Cabled observatories have been successfully deployed at several
coastal sites for many years. Some examples are LEO-15, the FRF in Duck,
North Carolina, and the MVCO (Appendix D). These systems offer ultra-
high bandwidth and significant power. Their data acquisition systems
have multiple user ports that allow a variety of instruments to be plugged
into the system. Data are telemetered back to shore via twisted pair or
fiber-optic cable. The MVCO is the most recently deployed coastal cable
system, designed and built by the same group who built the earlier LEO-
15 system. Communication at MVCO occurs through commercial-off-the-
shelf, Gigabit Ethernet network switches that communicate over a pair of
fibers back to shore. The MVCO nodes include support for both serial and
Ethernet connectivity for instrumentation, a guest-port management sys-
tem, and a Gb/s link back to shore. The communications electronics have
worked very reliably for the past two years. Scientists are able to easily
connect to their instruments and collect data from them over the Internet,
and can monitor and control their instruments via privileged services
provided on an observatory website.
The major advantage of cabled coastal systems is the availability of
power for sensors that would have to limit their data acquisition sched-
ules if deployed on autonomous moored buoys. This feature greatly en-
hances the coastal community's ability to acquire synoptic data at the
wide range of temporal scales (from seconds to storm events to decades)
that drive coastal processes. Like a Pioneer Array, cabled observatories
can provide a test-bed for new instrumentation because they are easily
serviced by small vessels and divers. The SCOTS report strongly advo-
cates the use of cabled observatories for coastal research (Dickey and
Glenn, 2003~.
Fixed, Long-Term Moorings
A third essential component of a coastal observatory system is an
array of fixed, long-term moorings designed to provide measurements of
key physical, chemical, and biological parameters and their long-term
variability in order to detect subtle but important trends of environmental
change in the coastal ocean in the coming decades (Figure 3-5~. Indeed,
OCR for page 69
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 69
one of the major rationales for establishing a seafloor observatory net-
work for basic research is to advance oceanographic science beyond the
ship-based expeditionary approach, in order to obtain "long time-series
measurements of critical ocean parameters" (National Research Council,
2000~. Such long-term observatories will likely be required at approxi-
mately 20-30 locations in order to cover significant regions of the coastal
ocean and Great Lakes of the U.S. The CoOP Workshop addressed the
issue of long time-series data acquisition and concluded that the coastal
IOOS backbone could provide the necessary long-term observations in
the coastal zone. However, to serve as useful platforms for research, the
IOOS backbone or "Sentinel" moorings may require a broader suite of
instrumentation (e.g., pCO2 sensors, time-series sediment traps) than is
presently envisioned. If the coastal component of the OOI was restricted
to Pioneer Arrays and cabled observatories as recommended by the CoOP
FIGURE 3-5 Launch of fixed, long-term coastal mooring in Monterey Bay. These
buoys have provided detailed information on sea surface temperature, salinity,
chlorophyll concentrations, and other data for more than a decade. The data are
collected from sensors mounted on and suspended from the buoy, and are radi-
oed to shore. Figure courtesy of Victor Kuwahara, C)2001 MBARI.
OCR for page 70
70
ENABLING OCEAN RESEARCH IN THE 2 lST CENTURY
and SCOTS workshop reports, an important opportunity to establish long,
continuous observations on the Atlantic, Pacific and Gulf Coasts and in
the Great Lakes could be missed. There is a clear need for the coastal
research community to determine a minimal list of key parameters and
key sites needed to observe long-term changes in the coastal ocean. In
addition the community should play an active role in the design and
implementation of IOOS in order to ensure that the placement and instru-
mentation of long-term coastal Sentinel moorings meet both the opera-
tional and research needs of the ocean community.
Status of Technical and Engineering Development and Planning
The technologies required for coastal surface and subsurface moor-
ings and cabled coastal observatories are relatively mature and offer the
OOI immediate scientific results. At present, well-instrumented moored
observatories using surface buoys are operational in multiple locations
around the continental U.S. Long-term deployments are possible, but are
not necessarily a cost-effective design criterion as coastal buoys can be
easily serviced. The ease of accessibility is fortunate since biofouling rates
are high in coastal waters. Corrosion rates are also significant and high
wave stresses can dramatically reduce system lifetime. Finally, the prox-
imity to coastal populations leads inevitably to encounters and losses,
most commonly from fishing trawlers.
The ability to cost-effectively service coastal buoys frequently has the
additional benefit of allowing moorings to also serve as platforms for
testing newly developed instrumentation. While data telemetry from
open-ocean sites is often a problem, coastal sites can combine line of sight
radio-frequency modems, cell phone, and Iridium satellite links for real-
time data transmission. Pilot deployments of integrated sensor packages
that have successfully collected physical, biological, and chemical data
have occurred off the coasts of California and Oregon and in the Gulf of
Maine.
Traditional coastal radar sites are monostatic and consist of transmit
and receive antennas. These antennas work together to measure the scat-
ter of the transmitted signal off the ocean surface. Since these systems use
the phase of the transmitted signal to interpret the signal from the re-
ceiver, they require that the transmitter and receiver be physically con-
nected. However, using the GPS satellite-timing signal should make it
possible to synthesize the transmitted signal at the receiver, allowing the
transmitter and receiver to be physically separated and converting the
monostatic backscatter system into a bistatic forward-scatter system. This
synthesis increases the footprint of the system and allows transmitters to
OCR for page 71
STATUS OF PLANNING FOR PROPOSED RESEARCH-OR/ENTED OBSERVATORIES 71
be placed on moorings. Additionally, GPS timing allows the transmitters
and receivers to be simultaneously operated at the same frequency in
monostatic and bistatic mode, forming a multistatic radar array. Multi-
static operation thus increases resolution, decreases the geometric dilu-
tion of precision errors nearshore, and potentially decreases the number
of expensive monostatic systems that need to be purchased. For example,
offshore points within view of multiple sites will experience a significant
decrease in the expected error of the total current vectors because they
contain N2 rather than N component estimates. The greater number of
points available means smaller radii averaging circles in the total vector
calculation used, enabling the network to better resolve fronts. These de-
velopments will be necessary for coastal research efforts where effectively
resolving currents is a key to success. The potential of radar arrays has
been demonstrated over the past five years, and the OOI would allow for
the development and deployment of high-resolution multi-static arrays,
ideal platforms for collecting coherent surface current data in coastal
waters.
Representative terms from entire chapter:
enabling ocean
