DESCEND '99Proceedings To download a copy of the DESCEND Report, click here vIV. Infrastructure and Funding vAppendix I: Summary of Specific Technological Recommendations vAppendix III: Steering Committee vAppendix IV: Workshop Participants vAppendix V: Abstracts submitted by Participants vAppendix VI: Related Website Links
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photo by Craig Cary An
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UNOLS Workshop |
DESCEND
DEveloping Submergence
SCiencE for the Next Decade
The Executive Summary of the DESCEND Workshop has been
published into an 8-page brochure. The
brochure can be downloaded by clicking on “Executive Summary”
below. Copies of the brochure
can be obtained from the UNOLS Office, office@unols.org.
Discovering the Oceans
DESCEND
DEveloping Submergence SCiencE for the Next Decade
DESCEND
Steering
Committee:
Keir Becker, University of Miami
Jim Bellingham, MBARI
Craig Cary, Univ. Delaware
Patty Fryer, Chair, Univ. Hawaii
Lisa Levin, SIO
Marv Lilley, PMEL
I. Background
The DESCEND workshop, held on October 25-27, 1999 in Arlington, VA, was prompted by the need to define both the critical scientific goals for the submergence community and the technological directions that will be required to take submergence research into new realms of discovery in the coming decades.
In order to accomplish its goals the DESCEND Workshop involved both scientists and technology experts. The scientists utilized creatively the face-to-face interaction with the engineers and technicians to articulate the types of research that will need new tools and innovative technological approaches in submergence science. The attendees were charged to think in terms of (1) multidisciplinary and multi-institutional use of multi-purpose platforms distributed globally and (2) in terms of developing infrastructure and specialized tools as appropriate for particular initiatives.
The spectrum of scientific problems and environments that must be investigated require access to a broad scope of ocean environments with a range of safe, reliable, multi-faceted, high-resolution vehicles, sensors and samplers operated from support ships with global reach and station-keeping capabilities in all weather. The marine science community requires the right complement of deep submergence vehicles and versatile support ships from which they can operate. The attendees agree that submersibles, which provide the cognitive presence of humans and heavy payload capabilities, will be critical to future observational, time-series, and observatory-based research in the coming decades. Fiber-optic-based remotely-operated vehicles (ROVs) and tethered systems, especially when used in closely-timed, nested investigations offer unparalleled maneuverability, mapping and sampling capabilities with long bottom times and without the limitation of human/vehicle endurance. The community strongly encourages development of autonomous underwater vehicles (AUVs) of various designs to provide unprecedented access to the global ocean, deep ocean and sea floor without dedicated support from a surface ship.
There are serious impediments to funding for multi-disciplinary science and for global, time-series, or long-term observatory work. Education of the public, our fellow scientists and assisting the funding agencies in education of the appropriate science advisory groups with regard to the advances in and potential from submergence research will be critical to implementing the recommendations from this workshop.
Follow-up to this workshop, by both the deep submergence community and federal agencies is also a critical component to the future success and health of deep submergence facilities and science in the US. The funding agencies have discussed the possibility for a follow-up engineering and technology workshop to discuss details of the priorities of technology research and development that have been recommended at this meeting.
The workshop science sessions were based on the types of environments in
which submergence science is pursued, i.e., mid-ocean ridge environments, the
abyss and open ocean, plate margin environments, polar and coastal regions. The
objectives were to 1) define the critical scientific research themes to be
emphasized in the next decade, 2) to specify the scientific questions to be
addressed and to define strategies needed to approach answers to these
questions, and 3) to define what technological approaches are needed to carry
out these objectives. The objective is to help to direct future strategies for
upgrades to vehicles, science sensors, sampling techniques, and imaging
capabilities of submersible vehicle systems funded by the federal agencies.
A. Mid-Ocean Ridge Processes.
There are a host of fundamental, interdisciplinary questions requiring deep submergence technology that need to be answered in order to understand the Earth’s complex geochemical, biological and geological processes at mid-ocean ridges.
The Biosphere. The biological, chemical and physical processes that have controlled the origin and development of life on Earth can be studied in situ in the ocean crust and upper mantle beneath the global mid-ocean ridge system.
Crustal Architecture. Mid-ocean ridges are the locus of the Earth's greatest mass, chemical, and energy fluxes from the deep interior to the surface; as such, they provide the best windows into their associated processes. The magmatism and tectonism that create oceanic crust are neither steady state nor periodic nor well understood.
Active Cyclic Processes. The entire volume of the world oceans is cycled through hydrothermal vents at mid-ocean ridges every few thousands years. The oceanic crust represents the fundamental reaction zone between the ocean and the deep mantle, yet we still do not understand how it interacts with chemical and biologic processes along ridges.
Global Variability.
The Mantle Connection. Ultimately it is the heat, volatiles and silicate melts derived from the mantle that drive the magmatic, hydrothermal and biologic processes at ridge crests. Understanding the way in which magma melts and flows beneath ridges to form basaltic magmas is a main goal that can be addressed indirectly through submergence research.
INVESTIGATIVE APPROACHES
We must be able to map and sample, from the seafloor
and at depths, at all appropriate scales, to document the extent and diversity
of biological communities and to define crustal architecture and maturation.
Delicate biological samples must be obtained with precision-controlled
manipulators and the samples must be protected from contamination. In situ
monitoring of biological communities both at the seafloor and down-hole will be
required. Near-bottom magnetic, gravity electromagnetic surveys, and active and
passive seismic studies will help to define interrelations between tectonic
forcing functions and biological and chemical processes.
The study of cyclic processes will require event response sampling of lava, biota and vent/plume fluids, as well as sustained time-series observations. We must anticipate events and map and instrument likely sites. Such activities could be accomplished in the future with a fleet of AUVs that can be air-dropped in a region that has a navigation net in place. Development of sensors will be a critical component of this effort. Optimally, we will deploy extensiometers, tiltmeters, heatflow and geodetic devices, chemical monitors, and seismometers at likely sites of activity in order to monitor cyclicity of various processes.
To address questions regarding global variability we must be able to optimize locating vents therefore we must improve spatial coverage. One way to do this would be to develop smart AUV (e.g., instruments that can detect various water properties). To gain wider spatial coverage we could look toward piggy-backing AUVs on other cruises. The critical need is to map the ridge and near-ridge geology and obtain representative surface and subsurface sampling over segment-scale and larger regions.
To address questions regarding the mantle connection to
ridge processes we must establish long-term seafloor observatories that are
capable of monitoring a variety of chemical and physical processes. We must
accomplish surface and subsurface sampling on a segment scale and engage in
sampling for comparison along several segments. This will require detailed
sampling by submersible or ROV and the capability to drill multiple holes in
ridge environments.
B. The Abyss and Open Ocean
The abyss and open ocean host a complex network of interrelated physical, biological, chemical, and geological systems, often difficult to identify and understand because they are spread out over large volumes and are dynamic over time scales of minutes to millennia.
Mapping the Abyss and Open Ocean. The open ocean hosts one of the largest ecosystems on Earth, but the life cycles, spatial and temporal distribution of organisms remains largely unknown.
Quantifying the Dynamics of Abyssal and Open Ocean Systems. This field includes studying fluxes (in and out), changes in storage of energy and mass, reactions and interactions between components of abyssal and open ocean systems (chemical, physical, biological, geological), and studying the importance of variations over many time scales.
Understanding the Natural History, Behavior, Ecology, and Evolution of Abyssal and Open Ocean Communities. Fundamental questions concerning abyssal and open ocean biological communities revolve around their composition and variability, and the linkages which govern their abundance. Spatial and temporal variability of biological systems appears to be higher than for physical parameters of the ocean.
INVESTIGATIVE APPROACHES
Mapping
the abyss and open ocean regions will require both existing and
yet-to-be-developed sensors on submersibles, ROVs and AUV platforms that give
not only a three-dimensional view of sea floor topography, water column particulate
matter and chemical properties, and the distribution of organisms but provide
the ability to document the 4-D changes over time. Temporal variations in these
processes are key to undertstanding them and their importance. Acoustic,
photographic and laser line-scan imaging of water column and seabed features
can be done in a nested mapping approach as has been done in ridge crest
research. A similar nested scheme will need to be developed for mapping of
organisms within the water column. Repeat surveys will provide the necessary
temporal dimension.Permanent
ocean bottom observatories such as those proposed under several initiatives are
planned to be general-purpose observatories available to the community for
installation of diverse experiments. Such stations will supply fixed sites for
long time-series observations of geophysical, biological, chemical and physical
oceanographic parameters over decadal time frames.
Quantifying the dynamics ofabyssal and water column processes could take advantage of existing and new chemical sensors that can be deployed on ROVs and AUVs. Since chemical, biochemical and genome-based sensors are becoming smaller and are requiring less power, there will be an increasing demand to place them on AUVs and ROVs. These instrumented submergence platforms in conjunction with acoustic, photographic and laser line-scan imaging will result in a capability for an unprecedented dynamic view of physical, chemical and biological events and processes in the sea. This in turn will lead to obligatory changes in the need for modeling, data management and infrastructure support.
Detailed chemical sampling at particle layers and physical discontinuities will be needed. The mid-water column and seafloor organisms must be sampled and their behavior observed. Manipulative ecological experiments will be required. We must quantify biota in the water column and on the seafloor. The ranges and rates of activity of these organisms and the interactions among them will have to be defined. We must measure or infer rates of fluid flow over broad areas and with depth within the seafloor. We must quantify the mid-water processing of surface ocean biomass during its descent to the seafloor, including the role of anoxic/suboxic microzones within the oxic water column.
In-situ experiments and measurements are necessary to resolve time scales of forcing and responses. Sampling and monitoring rates will also need to be adjusted depending on interest in continuous or pulsed inputs, and will need to occur simultaneously over large areas in order to resolve regional-scale processes.
Although remote sensing can be used to resolve near-surface processes at most time and space scales of interest, we lack a similar capacity for the remainder of the water column and seafloor, and any new methods developed for this purpose will need to be extensively verified and calibrated for accuracy.
Addressing questions regarding the natural history, behavior, ecology, and evolution of abyssal and open ocean communities requires a broad new range of capabilities. Existing vehicle assets are not well suited to studying the mid-water environment in the oceans. Communities may be diffuse, consequently to obtain statistically significant population estimates, a key measurement for the studies outlined above, we must be able to search large volumes of water and large areas of seafloor. This observation capability must be backed up by an ability to detect and identify organisms, ideally autonomously. Sampling and collecting capability is also a requirement, especially the ability to acquire many samples per dive. To establish the context for more intensive experiments with mobile assets, work should be coordinated with deployment of equipment designed to obtain time-series data and samples. Access using both fixed and mobile platforms will be required.
The huge data sets will
be not only of numerical character but will also consist of images. There is a
need to establish a data management infrastructure that minimally catalogs the
metadata and ideally compiles a distributed database. Meta-databases indicating
the availability of such information will be useful.
C. Margins
The active and passive margins of tectonic plates and continental masses present the full range of ocean depths from a few meters in estuaries and coasts to >10 km in deep-sea trenches. Margins also differ characteristically by latitude. At high latitudes there are shelf depressions, fords, and abyssal flood plains whereas low latitudes have carbonate platforms, reefs, and the world's steepest and tallest escarpments. Mid-latitudes have coastal deltas, slope gullies and canyons, and the deep-sea fans with their successions of meandering channels. Margins have extraordinarily high biological productivity and among the greatest human population densities. They are the Earth’s principle loci for production of hydrocarbon and metal resources, as well as earthquake, landslide, volcanic and climate hazards. Extreme environmental conditions are prevalent. Margins have the highest organic loading, lowest oxygen levels and the strongest currents. Escaping fluids can range from alkaline to hypersaline, from the lowest to the highest pH recorded on Earth. Margins are the regions where most major fisheries are centered, the areas where human impacts are greatest, and where known species diversity is highest. Major oceanographic features such as boundary currents and oxygen minimum zones often impinge on continental margins. Despite the scientific, societal, and economic importance of margins, many of the mechanical, fluid, chemical and biological processes that shape them, and the way that margins shape ocean life, are poorly known.
Origins of the Continents, Oceans, and Life. Subduction zones are the birthplaces of continents and are the recycling factories of the earth. Ore deposits, volcaniclastic sedimentation, and submarine calderas are among the principal continent-forming phenomena that are best studied on the seafloor at margins.
Rifting of continents creates new ocean basins. Oceans are formed, in part, by the outgassing of the planet at active plate margins. The geochemistry of fluids and mass balance of fluxes in submarine margin environments are least affected by the crust through which they pass and, therefore, most relevant to the origin of the oceans. These environments are unique to earth and processes unique to margin environments have been essential to life on Earth. How do substrate, depth distribution, and geochemistry of margins create variable life forms? Answers may be essential to understanding the origins of life, on Earth or elsewhere.
Global
Biogeochemical Element Cycling. Plate margins cover about 30% of the oceans where most of
the organic carbon and nutrient cycling occurs, hydrocarbon reservoirs are
vast, and tectonically driven fluids are pervasive.
Among the most important of these cyclic processes are gas hydrate systems. These dynamic systems, sensitive to subtle changes in pressure and temperature, represent an immense global carbon reservoir. They have the potential to drastically affect the global carbon budget and influence global geochemical change on a very large scale. Correlation between areas of gas hydrate and regions of massive slumps or slides suggests that these systems also are related to significant submarine hazard potential.
Biological Diversity and Productivity Benthic communities in margins are extremely heterogeneous both spatially and temporally. This heterogeneity is driven by variations in currents, nutrient input, oxygen availability, sediment and pore water constituents, topography, sediment dynamics, and substratum type. This complexity results in a wide variety of unanswered questions regarding biological processes at margin environments.
Paleoceanographic Conditions. Understanding of key taxa such as foraminifera, deep-sea corals, coccolithophores and fishes, as well as important processes such as bioturbation and microbial activity in present-day margin systems is necessary for reconstruction of paleoceanographic and climatic conditions. Certain margin environments such as nearshore anoxic basins and deep-water coral reefs are likely to contribute valuable historical information. The original invasion of the deep sea from shallow water faunas presumably took place by movement down continental slope. Therefore, investigations of the physiological and reproductive adaptations of slope species can provide insights into how these invasion and speciation processes have occurred and are presently occurring.
Anthropogenic
Impacts. Over
the coming decades, humans will affect margin environments more significantly
than other oceanic environments. Margins will experience greater pressure from
deep-sea fisheries as shallow stocks are depleted and the demand for seafood
increases with increasing human population. How does fishing modify margin
habitats, ecosystems and trophic linkages on the seabed and in the water
column, and what fishing practices maximize sustainable harvest and conserve
ecosystems? Margins, because of their proximity to human population centers,
will be impacted with higher nutrient input from agricultural drainage, sewage,
land use/abuse, deforestation, as well as various chemical pollutants. Organic
loading can alter the structure of margin ecosystems through eutrophication and
associated hypoxia while non-living resource exploitation has other effects.
Sediment Dynamics (erosion, transport, and deposition). Process-based models of marginal marine deposition and basin-filling remain poorly tested and constrained. The distribution of marine sediments is a primary control on the distribution of marine biological communities. Coarse-grained sediments host significant hydrocarbon accumulation and currently are the most important target reservoirs for the petroleum industry. High energy mass wasting events (debris flows, slumps, turbidity currents) pose considerable hazards to society, to marine engineering facilities, and pose a strategic challenge.
Influences of Deformation Processes. Deformation processes at margins control the largest scale topography, sediment transport and dynamics, and chemical fluxes, which in turn force links between biologic, chemical, and geologic processes, and hence the location and magnitude of resources and geologic hazards. Water/rock/organic-matter interactions during deformation change fluid compositions and, by altering rock porosity and permeability, create a feedback mechanism affecting fluid pathways and flow rates. These must be monitored in situ. These fluid flow and diagenetic processes represent important contributions to the global geochemical inventory. Many of these mechanisms, their rates, and the fluid pathways are still largely unknown.
Geologic Hazards. Subduction earthquakes are the largest energy releases on Earth. Because most of the Earth’s population lives within tens of kilometers of the coast understanding and monitoring forcing functions related to this seismicity is critical. We still do not understand the nature of strain accumulation related to great earthquakes.
Mass wasting events accompany most large earthquakes in margin environments and cause far more damage close to the source region of earthquakes than does ground motion. Mass wasting can also be associated with sector collapse during volcanic eruptions and with large storms.
The massive landslides in margin environments have generated devastating tsunamis. In order to understand and ultimately predict adverse affects accurately, what is needed are accurate models based on observations of phenomena both before and during events. Detailed bathymetry and imagery surveys and studies of physical responses to mass wasting must be carried out.
Volcanic activity on convergent margins itself poses potential hazards for human populations and can have devastating effects on both subaerial and submarine ecosystems. Other hazards of importance on margins include hurricanes, storm surge, and flooding, yet we know very little of how storms and floods affect the biology and geology of margins.
Tectonic
Forcing of Hydrologic Systems in Margin Settings. Episodic events, possibly associated
with major earthquake rupture and accompanying ground motion, may dominate the
flux of fluids at convergent margins. Variability of fluid fluxes within
different portions of a given margin region may be related to both shallow and
deep margin processes. These could include partitioning of fluid flux within
the shallow outer forearc regions (prism or hard rock) and depths where fluids
contribute to forearc mantle metamorphism or melt production the relative
importance of transient vs. steady state hydrological processes. The presence
of fluids in a margin setting does in itself alter the physical properties of
the sediments and basement of which the margin is composed, therefore there is
a potential feed-back loop between tectonic processes and hydrologic systems in
these settings about which we know very little.
INVESTIGATIVE APPROACHES
A variety of techniques and field/laboratory efforts are needed for studies of
margins because the questions to be addressed are diverse and the areas
encompass large and globally distributed regions at all latitudes. A global
approach is required because the best examples of given margin processes do not
all occur in a single region. Submersible vehicles capable of reaching a wide
range of depths from shelf to trenches will be needed. Studies will require
monitoring capabilities for both short- and long-term phenomena, in situ
observation, sampling, and experiments for study of processes such as formation
and/or dissociation of methane hydrates, fluid venting, and various responses
of biological activity. ROVs and AUVs equipped with standard imaging packages
and new coring devices can respond to individual events. Tethered, hard-wired
observatories can provide time-series data on the magnitude and frequency of a
variety of events.
Additional vehicle assets, which complement submersible, ROV and AUV systems and a new suite of chemical, biological, and geotechnical sensors will be needed to examine and respond to episodic events. Some experiments and observations will require a seafloor observatory approach. Analogous to the Ocean Drilling Program, we must consider the possibility of multi-platform options. For example, there is a need for alternate-type vehicles such as bottom crawlers, with tools optimized for imaging benthic organisms and measuring such phenomena as respiration rates and microbial activities. Portable rock drills for use in both shallow and deep seafloor environments will also be needed to drill shallow holes into the upper ocean crust. Vehicles must be able to work in regions of strong currents, poor visibility, corrosive water, and near vertical slopes. There will be demand for heavy payloads to accommodate sampling in biogenic substrates such as reefs, crusts, and carbonate sands, and amongst biogenic structures (shells, tubes, coral debris). Finally, some critical questions can best be addressed with efficient response to unpredictable events.
Improving our understanding of deformation at margins will require a better understanding of seafloor tectonics at a variety of spatial and temporal scales. Deep submergence assets are critical to address tectonics at smaller temporal and spatial scales, in much the same way as outcrop-scale geology and geophysics requires different tools than global studies.
Some of the technologies are available and rely on deep submergence assets primarily for installation and maintenance of geodetic reference markers and specialized seismometric, geodetic and strain measurement systems, fluid flow experiments and direct sampling and observations. New technologies under development such as ship-deployable drilling and coring rigs, ROV mapping systems, and others not yet devised will be required to advance our knowledge of margin environments.
All of the aspects of
natural hazards that are outlined above are addressable with submersible
technology, particularly geodetic and seismic monitoring, subduction zone
physical properties, and tsunami warning systems. We will need medium to
high-resolution surveys of targeted margins as the backbone of any
comprehensive and multidisciplinary investigation. Submersible investigation of
the 1998 New Guinea slide area proved the link between fluid venting and mass
wasting. Monitoring microseismicity in areas prone to mass wasting events will
facilitate forecasting. We also need detailed maps of venting regions in potential
mass-wasting localities and monitoring of venting flux and composition. The
study of hydrologic systems will require submergence assets to reveal tectonic
processes occurring on smaller spatial scales than possible with surface assets
and surface geophysics. The only way to study these sensitive systems in detail
is by creating -in situ observatories and providing for submersible
vehicles of various types to down-load data, collect samples, and service the
observatories.
D. Polar Regions
For many polar environments, little or no exploration has occurred using submersibles, let alone time-series measurements of key parameters over multiple spatial scales.
Polar Oceans. A great diversity of ocean environments exist in polar seas. They include ice covered seas over shallow continental shelf and slope environments, abyssal plains, mid-ocean ridge systems, seamount chains, and many others. For polar oceans and most ocean systems, the priorities for investigations generally progress from: (1) exploration and discovery, in which the basic elements of the system are identified, 2) characterization of the system, quantifying spatial and temporal variability of physical, chemical, and biological elements of the system over multiple scales, and 3) experimental and theoretical examination of processes expected to influence system dynamics. These studies must be followed by predictive modeling and synthesis of relevant elements of earlier studies, in order to characterize the dominant sources and patterns of variation in the system.
Global Climate Change. Polar amplification of climate warming (especially in the Arctic), coupled with accelerated climate warming expected in the next century, underscores the need for climate-related research in polar oceans. For example, there is temporal correlation between a fundamental change in the atmospheric circulation of the Northern Hemisphere and (1) the temperature increase of the Arctic Ocean Atlantic water, (2) the increase in the surface air temperature over the Russian Arctic, (3) the Arctic Ocean circulation changes, and (4) the freshening of the upper Beaufort Sea. These observations suggest the recent change in the Arctic is at least a decadal scale phenomenon and has broad implications for changes at lower latitudes. What is needed are long time-series measurements of physical variables, process studies, and modeling to track and understand the changes. We need to understand how changes in sea ice thickness and extent occur, and the consequences of such changes to upper-ocean hydrographic structure (density structure, formation, position, and intensity of oceanic frontal zones and other hydrographic interfaces), and how they affect climate change.
Research priorities include studies of shelf and basin patterns (physical and biological structure) and processes (biogeochemical cycling, physical oceanography, population dynamics), and interactions between the Arctic shelf and basin environments (e.g. carbon export from shelf to basin).
Arctic and Antarctic Ecosystems. Biological diversity can be considered at three levels, genetic, species and ecosystem diversity. The first involves the variety of genetic information contained in individual plants, animals and micro-organisms that inhabit the system. It occurs within and between populations of organisms that comprise individual species as well as among species. Understanding the natural variability of marine ecosystems is the goal. However, there are some fundamental questions for which we do not yet have answers. These must form the basis of our approach to understanding ecosystems in polar regions.
Glaciation. Glaciological research is concerned with the study of the history and dynamics of all naturally occurring forms of snow and ice, including seasonal snow, glaciers, and the ice sheets. Studies of interest to submergence science communities include history of glaciation in the polar regions, ice dynamics, and remote sensing of ice sheets.
INVESTIGATIVE APPROACHES
Certain types of polar research will require new vehicle designs. For example,
sampling of under-ice habitats is presently limited or impossible using
existing submersible vehicles. The study of ecosystems, such as the mechanisms
necessary for maintenance of cell function in fishes and their feeding
behavior, require long-term observations. Such studies are needed to improve
understanding of man-made or natural changes. Advances in instrumentation,
including remote sensing or telemetering of ice type, thickness, motion, and
growth, should enable large scale dynamics of sea ice to be monitored over long
periods. Recent studies indicate that melting of Antarctic ice shelves
progresses largely by melting from below, rather than ablation or melting on
the surface. Monitoring such processes is critical to understanding the
controls over this process. Increased access to sub-shelf cavities using
submergence technology for studies of hydrography and glaciology is a
desirable. Studies of the polar oceans will by necessity require a wide range
of vehicles or systems. OSVs, ROVs, and especially AUVs. AUVs may be required
for synoptic characterization of the Arctic Basin (requiring long range and
long duration AUVs or other unattended vehicles (e.g. rovers). Long-term
installation of sea floor observatories, either cabled to shore stations, or
moored, equipped with sensor packages for water column and sea floor sampling
will also be required. Submersibles will also be needed to support geophysical,
geological, chemical, biological and other studies of polar rift zones. In
addition, capabilities for drilling (core collection), high resolution mapping,
and imaging, and sample collection devices will be needed. A key requirement
for polar science where access is often logistically difficult, will be the
deployment of fleets of AUVs for time-series measurements of various types and
establishment of ocean floor observatories and programmable monitoring arrays
served by AUVs.
E. Coastal
Environment
Coastal zones present challenges to exploration that are different from those of the open ocean and the deep sea. Physical conditions are often harsh, making it difficult to mount ship-based expeditions, yet most of the US population lives within 50 miles of the coast. Thus, there is high interest in coastal oceanographic processes, especially when these have an impact on human activities or welfare.
Coastal Impacts. Events such as harmful algal blooms, storms, introduction of exotic species, upwelling, bottom-water anoxia, oil spills, and other pollutant plumes can result in long-term impacts on coastal processes. The effects of various pollution phenomena have attracted a great deal of attention, but the details of the effects of these on the complex physical, chemical and biological systems in coastal environments are still poorly known.
Physical Oceanographic Interfaces. Fronts and thin layers are common features of the coastal ocean. For instance patterns of turbulence on the shelf during up-welling and down-welling events are influenced by fronts and jets, and the levels of turbulence can reach sufficient intensity to influence the mesoscale circulation. The effects of the dynamics of mid-water circulation patterns on the water sediment interface are poorly known. Interfaces are intrinsically ephemeral and sensitive to physical, chemical, and biological variations on several time scales.
Seafloor Topography and Sediment Properties. Physical forcing from waves, tides, and storms, coupled with the activity of benthic animals, leads to a dynamic seafloor over most of the continental shelf. Seafloor topography (e.g., sand waves, ripples) and sediment geotechnical properties (e.g., shear strength, porosity) are affected. Along-shore topographic variations dictate the relative importance of two-dimensional versus three-dimensional cross-shelf transport processes with respect to wind-driven dynamics. Coastal morphology is affected by these functions and thus societal concerns are important aspects of the study of physical forcing functions in coastal regions. These effects impact biogeochemical processes. For example, most of the organic matter produced in shelf waters appears to be recycled on the shelf, not exported to the slope or deeper water. A significant portion of this organic matter appears to reach the bottom, where it is rapidly removed as water flows through the permeable, sandy sediments found on much of the shelf. The interactions of waves and currents with an uneven, permeable seafloor are responsible for driving this "subtidal pump."
Submerged reefs record the history of eustatic sea level change and the regional dynamics of tectonic uplift or subsidence. Correlations among globally distributed reef deposits will enhance our understanding of global climatic variability. The variability of coastal morphology both near-shore and on the shelf as a function of various forcing phenomena has important implications for military applications (such as object detection).
Lake
Phenomena. Many of
the processes operating in the coastal ocean are also important in lakes. One
of the most critical aspects of lake studies is the record of climatic change
that is preserved in remote locations in lakes throughout the world, including
polar regions. Studies of individual lakes and global comparisons of the
sediment records preserved in them are both essential components of the history
of climate change.
Essential Habitat. Anthropogenic perturbations and natural variation can adversely affect habitats of ecologically, commercially, and recreationally important species. Midwater and benthic fish communities, shellfish, and coral reefs are examples. The diversity of habitats is poorly known even in the shelf and coastal environments. In the 50-300 m depth range globally there are many communities that are poorly understood, particularly those other than sediment hosted communities. These communities have complex interdependencies on the geological framework for ecological niches. Effects of physical and chemical forcing functions on these communities are virtually unknown. These communities are sensitive to disturbance and a silent approach is needed in order to observe normal community behaviors (sole diver with re-breather). A more effective and less hazardous approach would be to employ ROVs or AUVs. We need to understand better the overall effects of anthropogenic perturbations to the natural system. What is required is a quantitative comparison among the responses of various ecosystems to a given perturbation. This necessitates an approach that includes both short-term and long-term monitoring
INVESTIGATIVE
APPROACHES
The need to survey and map the extent of various coastal events would be best met by rapid-response submersible vehicles, such as AUVs. Because these events are often widespread and evolve rapidly, synoptic sampling is required to prevent space/time confounding. Thus, numerous, inexpensive vehicles that can be deployed as a fleet to track these features would be ideal. Sensors capable of measuring basic chemical and physical properties of the water are widely available and should be standard equipment. Additional sensors, which could be used for identification of specific compounds in the water and even specific organisms (e.g., toxic dinoflagellates), should be employed as well. It is likely that such sensors have already been developed for other applications (for example, molecular and genetic probes), and could be used either as-is or adapted for oceanographic use. Navigation networks capable of tracking and controlling such fleets of submersible vehicles will need to be developed.
Interface areas of physical, biological, and chemical discontinuities can be widespread and rapidly changing. Ship-based sampling is usually impractical. Submersible vehicles, either remotely controlled or autonomous and capable of following gradients in water properties, probably represent the best method of studying interfaces.
The problems of
addressing physical forcing functions in coastal environments could be
addressed with submersibles equipped with sensors for measuring porewater
chemistry and sediment physical and acoustic properties. These could be used to
survey spatial patterns of seafloor topography and sediment properties, their
linkage with water column processes, and how these interactions change over
time. The availability of easily mobilized and demobilized AUVs would pay large
dividends in lacustrine research. AUVs, ROVs, and submersibles, equipped with
high resolution visual systems (e.g., laser line scanners) and more
sophisticated, articulate samplers are needed to document spatial and temporal
changes in essential habitat and understand the factors driving such changes.
In order to obtain samples for studies of sediment properties it will be
essential obtain drill samples. These samples must come from below the zone of
bioturbation and below wave base. The optimum types of drills envisioned are
relatively inexpensive portable drill systems that can be used with an ROV (for
use in drilling into submerged coral reefs, for example). Also needed is a
relatively inexpensive coring system that is tethered, but mobile, and equipped
with a real-time video for obtaining precisely located cores on the order of 3
to 20 m deep in the shallow water environment. The study of the geological
framework for ecologies of various types of sensitive biological communities
would require as unobtrusive an approach as possible. Such work is more
suitable for ROVs or possibly AUVs. Both short and long-term monitoring of such
communities might best benefit from arrays of fairly simple sensors serviced by
AUVs.
This portion of the workshop
defines strategies to ensure that the facilities and technologies
needed to address the scientific themes defined in the Science Sessions are
available. Critical
issues, needs, and problems, both technical and infrastructural, were defined.
The objective is to
help to direct future upgrades of science sensors, sampling techniques, and
imaging capabilities of
vehicle systems funded by the federal agencies.
A. Event Response
Occasional or periodic perturbations of ocean systems may have a profound impact on both local and distant integrated physical, geological, geochemical, and biological processes. The time scales from initiation to system recovery vary considerably. Most are unpredictable. Studies of such events pose tremendous scientific opportunities and major technical and logistical challenges. These events evolve rapidly, requiring swift deployment of required observational and sampling systems. Effective event responses are constrained by the availability of personnel and equipment at extremely short notice, funding availability, and weather constraints on over-the-side operations. Because most event response studies can best, or only, be accomplished using a submergence vehicle or tool, the availability and capabilities of submergence assets and their support systems are particularly critical.
The types of phenomena that cause sudden perturbations are diverse, and affect coastal, deep ocean, and lacustrine processes. They can include erosional events, dewatering or hydrocarbon release, volcanic or hypabyssal magmatic events, seasonal biological phenomena, storms, tsunami generation, anthropogenic events, etc. The various types of events commonly require both water column and seafloor response components. The potential for very rapid deployment, transportability, and for truly autonomous operation when weather conditions may preclude over-the-side operations makes AUVs the optimal tool for response efforts. Two separate, task-dedicated vehicles are highly recommended for responses to compound events.
*Water
Column: A water
column response might generally require an AUV capable of performing 2 or
3-dimensional surveys using a CTD and variable arrays of optical, chemical and
bio-sensors. Survey dimensions could require tens of square kilometers of
spatial coverage and depth ranges of over 1000 m. "Smart" AUVs would
be required to locate and survey "event," plumes, etc., by virtue of
optical (e.g., threshold optical backscatter) or chemical tracers. AUVs
equipped with high turbidity sensors would be required for many coastal events
(e.g., storm sediment transport, mass-wasting events). Seeding of event plumes
or other subject water mass (e.g., plankton bloom, oil spill) with Lagrangian
drifters for tracking and relocation would extend the rapid response
observations to time-series studies. The scientific community interested in
event response strongly encourages the submergence engineering community to
examine the practicality of designing a hybrid vehicle (i.e., 3-D Lagrangian
float and AUV) for some of these water column operations.
*Seafloor: A robust AUV would be required for seafloor mapping and sampling. AUVs equipped with an array of mapping sensors can be used during an event-response expedition to efficiently detect and map the extent of anomalous regions on the seafloor. Mapping the environment also could be used as a navigational aide in comparison with previous maps where possible. Responses to dynamic sediment processes also require the capability to measure concentration, turbidity, and velocity through active sediment-gravity flows over the duration of the event using laser, acoustic backscatter, and sub-bottom profiler systems. This technology could be used to map concentration, velocity, and turbidity variations along AUV transects during a storm event on the shelf. High-resolution imaging is a high priority for documenting physical (e.g., vent sources, boulder size) and biological (e.g., vent fauna, microbial mats and "blooms") phenomena.
Optimally, the seafloor response AUV would be capable of limited fluid sampling for chemical and microbiological studies. Fluid sampling should include the use of physical, chemical and bio- (DNA-chip) sensors, and possibly the physical collection of small fluid volumes and their preliminary preservation (e.g., poison, filtration). Shallow sediment and sand cores (up to 1-2 m) collected shortly after a sedimentation event (hours to days) can provide important information on sediment thickness, texture, and structuring. Rock coring capability is also highly desired for both the core sample and the consequent access provided to subsurface fluids and bi