Science Plan

The Ridge 2000 Science Plan is the product of five interdisciplinary planning meetings and workshops attended by more than 300 scientists. Attendees strongly endorsed the creation of a Ridge 2000 program to work toward a comprehensive, integrated understanding of the relationships among the geological and geophysical processes of planetary renewal on oceanic spreading centers and the seafloor and subseafloor ecosystems that they support. Studies under the Ridge 2000 program are defined by an integrated, whole-system approach encompassing a wide range of disciplines and a progressive focus within scientifically defined, limited geographic areas.

The Ridge 2000 Science plan is shown below; if you prefer, you can download a 52-page, 2.6MB pdf file (includes pictures).

Contents

Overview

Renewal by aging

A vast volcanic province beneath the deep oceans covers more than half of our planet's surface. Within this province, the oceanic crust is continually renewed by volcanic and hydrothermal activity along the global mid-ocean ridge system. This renewal process determines the shape of the ocean basins, thereby influencing the circulation and composition of our oceans and, indirectly, broad climate patterns. Paradoxically, this renewal is a direct result of planetary aging, as convective cooling transfers energy and material from Earth's deep mantle to the crust and ocean.

Life without sunlight

Volcanic and hydrothermal processes that occur along oceanic spreading centers support a potentially vast, complex ecosystem on and beneath the deep ocean floor. The unique organisms at hydrothermal vents and their extraordinary adaptations to extreme and ephemeral habitats have fascinated academic researchers and the public alike. The discovery of an abundance of microbes in the subseafloor is among the most remarkable scientific findings of the twentieth century and has become a powerful motivation for research and exploration in the opening decade of the twenty-first. Indeed, subseafloor volcanic ecosystems may represent both the cradle of life on Earth and a model for the exploration and discovery of life on other planets.

From mantle to microbes

Seafloor ecosystems are inextricably linked to, and perhaps an inevitable consequence of, the flow of energy and material from Earth's deep mantle, through the volcanic and hydrothermal systems of the oceanic crust to the deep ocean. The direct linkages between life and planetary processes on deep-sea spreading centers can only be understood through tightly integrated studies across a broad range of disciplines in geophysics, geology, chemistry, biology, and oceanography.

Ridge 2000 Program activities fall under two main themes:

Integrated studies-Multidisciplinary studies focused within a small number of preselected "type" areas and designed to characterize these units of the global ridge system as integrated volcanic, hydrothermal, tectonic, and biological systems.

Time-critical studies-A program to enhance detection of volcanic and other transient events on oceanic spreading centers and to facilitate rapid-response missions that can observe, record, and sample critical transient phenomena as they happen.

Within these themes, the Ridge 2000 Science Plan identifies several fundamental questions that need to be answered and recommends methods for addressing them. The plan also outlines technological requirements for making observations and carrying out experiments in the harsh environment of the mid-ocean ridge, as well as infrastructure requirements for meetings, workshops, and enhanced data management.

A third theme, Exploratory Studies, targeted to elucidate biodiversity and biogeography in unexplored regions of the mid-ocean ridges, was originally proposed as part of the Ridge 2000 program. Although the review panel thought this theme was worthy of support, it does not require the infrastructure of a major program like Ridge 2000. As a result, it was recommended that Ridge 2000 support planning activities and workshops for Ridge-related exploratory studies.

Relative to the original RIDGE Program (1989-99), Ridge 2000 has a more focused range of scientific priorities, with a much greater emphasis on hydrothermal ecosystems and, especially, on understanding these systems in the context of regional and local volcanic and tectonic characteristics of specific sites.

In addition to the substantial benefits to the individual scientific fields, Ridge 2000's multidisciplinary, integrated approach is certain to yield major, unanticipated scientific discoveries at the interfaces between the disciplines.

Ridge 2000 and ocean sciences planning documents

The last few years of the millennium saw a flurry of planning activities within the National Science Foundation (NSF), the National Academies, and elsewhere. For NSF's Division of Ocean Sciences, the culmination of this planning process was the release (in December 2000) of "Ocean Sciences at the New Millennium," a report prepared by a special NSF "Decadal" Committee. This committee was asked to identify "the most important and promising opportunities for scientific discovery…in the next decade." Its report will form the basis for long-range planning for the division.

Ridge 2000's scientific objectives are consistent with those of this report and an earlier NSF report on the Future of Marine Geology and Geophysics (FUMAGES). Although the Ridge 2000 Science Plan was produced independently of these other planning documents (there were very few common contributors), Ridge 2000 objectives are integral to three of the five "New Directions" identified in the FUMAGES report, and to two of the seven science themes and three of the key "findings" of the "Millennium Report." Ridge 2000 and the "Millennium Report" both emphasize far-reaching collaboration across disciplines and organizational boundaries within NSF.

In common with virtually all of the recent planning documents in earth and biological sciences, the Ridge 2000 Science Plan focuses on the need for science that will:

  • study natural processes and their variability over a range of temporal and spatial scales;
  • integrate findings across a broad disciplinary spectrum;
  • develop a quantitative, whole system understanding of large-scale natural processes.

Ridge 2000 and broader impacts

A complementary theme of recent NSF planning emphasizes the importance of bringing current research to teachers, students, and the general public (Merit Review Broader Impacts Criterion, NSF Grant Proposal Guide, NSF 02-2). Many RIDGE scientists have recognized the importance of such education and outreach efforts. Interactive Web sites and teacher participation became common adjuncts to RIDGE research cruises (see below). Building upon this, Ridge 2000 encourages scientists to continue to develop quality education and outreach offerings. The Ridge 2000 office employs a full-time education and outreach coordinator to assist Ridge 2000 scientists in their outreach efforts as well as foster coordinated, communitywide education and outreach programs.

The Ridge 2000 Education and Outreach Effort has Three Goals:

  • Promote Ridge 2000 science within the scientific community, helping to recruit new and future research scientists and collaborators and increase awareness of Ridge science at colleges, universities, and research institutions.
  • Increase the awareness and understanding of Ridge 2000 science within the context of science education in the K-12 community and help infuse science learning with the excitement of discovery of the deep sea.
  • Promote Ridge 2000 science to the general public to help make them more aware, excited, and supportive of Ridge science.

Some Ridge 2000 Education/Outreach-Oriented Web Sites:

Ridge 2000 and collaboration with other programs

Ridge 2000 will collaborate closely with several NSF ocean sciences programs, including:

  • MARGINS, a program focused on the characterization of passive continental margins and destructive plate boundaries. Together, Ridge 2000 and MARGINS encompass the study of the creation and destruction of Earth's plates. The programs intersect in back-arc basins and in the Red Sea and Sea of Cortes, where spreading centers occupy narrow continental rifts. MARGINS and Ridge 2000 have common development needs in technology, computational tools, data and sample management, and education. The intellectual benefits to each program of co-located activities will be substantial.
  • The Ocean Drilling Program (ODP) and its successor, the Integrated Ocean Drilling Program (IODP). These drilling programs will interact with Ridge 2000 activities primarily at Integrated Studies Sites where there is strong overlap in objectives related to the formation and aging of the oceanic crust, hydrothermal circulation and its effects, and the nature of life in the subseafloor region. The ODP can provide the Ridge 2000 community with data and samples from a third dimension-depth-that is difficult to obtain using other marine instrumentation.
  • The new Ocean Observatories Initiative, which aims to develop autonomous seafloor observatories. This program evolved from the earlier DEOS program and includes a major effort to establish a regional-scale cabled observatory as well as buoys to supply power and communication to the deep sea floor. Ocean observatories are likely to provide major infrastructure that will greatly enhance monitoring and real-time data collection for at least some Ridge 2000 Integrated Studies Sites. Proposals currently under consideration include a plate-scale cabled observatory in the NE Pacific (NEPTUNE), and locating buoys to supply power and communication to the seafloor at each of the Ridge 2000 Integrated Studies Sites.
  • Ocean Mantle Dynamics, a proposed program to study mantle flow and structure that will potentially incorporate and expand the mantle imaging objectives for at least some Ridge 2000 Integrated Studies Sites.

NSF-wide initiatives such as Biocomplexity (Coupled Biogeochemical Cycles, Genomics-Enabled Environmental Science) and Biogeo-sciences (Exploring the Interface Between Geology and Biology) could substantially enrich and expand efforts at any of the Ridge 2000 Integrated Studies Sites.

Ridge 2000 programs also have substantial overlap with other federal programs. Key among these are:

  • NOAA's Pacific Marine Environmental Laboratory (NOAA/PMEL), a vital partner since the inception of the RIDGE Program. PMEL scientists maintain the NEMO Observatory on the Juan de Fuca Ridge, process real-time seismic data from the northeast Pacific through the U.S. Navy SOSUS hydrophone array, process seismic data from autonomous hydrophone arrays in the equatorial Pacific and northern Atlantic, and conduct a broad range of collaborative mid-ocean ridge research.
  • NOAA's West Coast National Undersea Research Center, which has a strong record of support of instrument development for and fieldwork on mid-ocean ridges, particularly in the northeast Pacific.
  • NASA's Astrobiology Program, which is concerned with the origin and evolution of life on Earth and potentially on other planets. Hydrothermal ecosystems are of particular relevance to this mission.

Ridge 2000 recognizes that most ridges are in international waters and that the scientific objectives and interest transcend any national boundaries. Furthermore, the scope of science that can be addressed can never be met fully by the resources of any one nation. Ridge 2000 activities will all benefit from, and in some cases require, international collaborative efforts, and such collaborations are encouraged.

InterRidge is an international association of national organizations that promotes collaboration and cooperation in spreading center research. There is a history of international collaborative scientific activity at each of the initial Integrated Studies Sites and continued international collaboration will lead to more rapid progress than would be achieved by any single nation. Ridge 2000 will continue to be an active member of InterRidge.

The Endeavour Segment of the Juan de Fuca Ridge lies within the Canadian EEZ and portions have been designated a Marine Protected Area (MPA) as part of the Oceans Act. As a result it is expected that significant Canadian resources will be used in the study and administration of the MPA and numerous collaborative opportunities with Canadian scientists will be available. To ensure that principal investigators (PIs) adhere to the spirit of the MPA, an International Advisory Committee will evaluate all funded proposals as part of the clearance process required to enter Canadian waters. Investigators given access to the Endeavour must follow the Marine Environmental Quality protocols documented in the MPA Management Plan.

Much of the East Lau Spreading Center lies within Tongan territorial waters. All research in the area must incorporate collaborations with Tongan scientists, both in the planning process and as active scientists and observers. Clearance to work in Tongan waters must be obtained from the government of Tonga. The South Pacific Applied Geoscience Commission (SOPAC), headquartered in Suva, Fiji, is a coordinating body for natural resource and environmental issues as they affect the South Pacific island nations. They have been quite helpful in facilitating research in the area. The Ridge 2000 Office will continue to ensure that the Kingdom of Tonga and SOPAC are advised of plans for the Lau ISS and will help coordinate collaborative efforts.

Other nations have long-standing research programs on the East Pacific Rise and Mid-Atlantic Ridge; therefore, close coordination and collaboration with other nations is encouraged. Any future slow-spreading Integrated Studies Site is likely to benefit from close coordination with other nations, since Europe in particular has long-standing interest and ongoing programs on the Mid-Atlantic Ridge.

Ridge 2000 and the RIDGE Program

Ridge 2000 was conceived as a direct successor to the RIDGE Program, a highly successful interdisciplinary effort funded by the NSF, dedicated "to understanding the geophysical, geochemical, and geobiological causes and consequences of energy and material transfer, from the Earth's mantle to the hydrosphere and biosphere, along the globe-encircling mid-ocean ridge system."

The RIDGE Program has been remarkable-perhaps unique-in developing both a culture and an infrastructure for cooperative interdisciplinary research across a broad spectrum of the earth, ocean, and biological sciences. Scientifically, the RIDGE Program has spearheaded a decade of discovery and exploration along the global mid-ocean ridge system, supported comprehensive studies of specific areas, and fostered real-time detection of and rapid response to volcanic eruptions and related "events" such as the formation of hydrothermal plumes.

Highlights of the decade include:

  • exploration, mapping, and basic geological sampling of vast, previously unknown segments of the global mid-ocean ridge system;
  • imaging mantle flow patterns and probing the origin of magmas using geophysical and geochemical techniques;
  • probing the spatial and temporal patterns of magma distribution in the upper and lower crust through geophysical and petrological studies;
  • discovering and documenting active volcanic, hydrothermal, and biological systems;
  • discovering and characterizing diverse macro-and microbiological communities that thrive on the deep seafloor in the absence of sunlight;
  • elucidation of novel physiological pathways and biochemical abilities in vent micro- and macrobiota;
  • detecting several seafloor eruptions and mounting rapid-response visits to the eruption sites;
  • measuring active deformation of the seafloor using in situ instruments;
  • discovering previously unknown subseafloor microbial communities composed of both bacteria and Archaea, including some of the most ancient of extant organisms.

Accompanying these field-based discoveries has been a remarkable technological evolution:

  • Deep-sea mapping and imaging are now possible at resolutions approaching those available on land.
  • Shipboard and ocean-bottom seismic techniques are now used to image magma reservoirs in the oceanic crust.
  • Seafloor seismic and electromagnetic techniques are beginning to delineate solid and melt-flow patterns in the mantle.
  • Physical, chemical, and biological sensors are providing time-series records of active vent systems and seafloor deformation.
  • Long-term seafloor observatories with real-time data links to shore are being established
  • A variety of vent animals and microbes can now be maintained in the laboratory under conditions mimicking their natural habitat.
  • New autonomous and remotely operated undersea vehicles are increasingly providing close-up observations and the ability to monitor and/or manipulate hydrothermal and biological systems.
  • Autonomous hydrophones provide a long-term seismic monitoring capability covering large sections of the mid-ocean ridge.

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Integrated studies

Focused, Whole-System Studies of Oceanic Spreading Center Processes. The Integrated Studies theme of Ridge 2000 addresses the complex, interlinked array of processes that supports life at and beneath the seafloor as a consequence of heat and material transfer from Earth's deep mantle to the crust and overlying ocean.

Overarching Goal: Develop focused, quantitative, whole-system models through coordinated, integrated, and interdisciplinary experiments at a small number of sites.

To achieve this goal requires an understanding of the interactions and linkages among all the components of this complex system. Examples of important linkages include:

  • ocean circulation, hydrothermal plumes, and ridge seafloor topography;
  • hydrothermal plumes, ocean chemistry, and pelagic biological activity;
  • dynamics and distribution of seafloor and subseafloor communities and hydrothermal, volcanic, and tectonic activity;
  • crustal composition, tectonic structure, and hydrothermal distribution and chemistry;
  • ridge morphology, tectonic and magmatic processes, and hydrothermal circulation;
  • hydrothermal activity and volcanic, tectonic, and magmatic processes;
  • mantle flow, melt formation, and segregation, and their impact on all surficial processes.

Fundamental questions

The following seven questions, which are only examples of the broad range of issues to consider, illustrate the breadth and scope of the interactions and linkages that must be addressed to construct reasonable, whole-system models:

  • Question 1. What are the relationships among mantle flow, mantle composition, ridge morphology, and segmentation?
  • Question 2. How is melt transport organized within the mantle and crust?
  • Question 3. How does hydrothermal circulation affect characteristics of the melt zone, crustal structure and composition, and ridge morphology?
  • Question 4. How does biological activity affect vent chemistry and hydrothermal circulation?
  • Question 5. What are the forces and linkages that determine the structure and extent of the hydrothermal biosphere?
  • Question 6. What is the nature and space/time extent of the biosphere from deep in the subseafloor to the overlying water column?
  • Question 7. How and to what extent does hydrothermal flux influence the physical, chemical, and biological characteristics of the overlying ocean?

Q1: What are the relationships among mantle flow, mantle composition, ridge morphology, and segmentation?

Mid-ocean ridges are naturally divided into tectonic segments defined by transform faults and other smaller offsets in the axis of spreading, and into magmatic segments defined by abrupt changes in aspects of lava chemistry that reflect the mantle source. This segmentation divides the mid-ocean ridge system into fundamental units, and there is a long-standing debate as to its origin. Is segmentation created by a mantle flow pattern that is largely passive, responding to a plate geometry that is controlled by stresses in the plates? Or is the segmentation geometry controlled by convective flow patterns in the underlying asthenosphere? We can use seismic tomography and electromagnetic methods to distinguish between these possibilities by mapping structures, such as crystal fabric and melt distribution, that respond to stress, strain, and thermal structure.

Segmentation patterns and axial morphologies vary on a regional scale, primarily in response to spreading rate and/or mantle temperature variations. Comparable variations also occur on more local scales between adjacent segments, or even within individual segments in response to local variations in magma supply. Theoretical models suggest that axial morphology is directly controlled by the thickness and thermal structure of the crust and lithosphere. To refine and test such models, integrated geophysical studies will be required to define the structure of the deeper mantle and its transition through the melt zone to the oceanic crust.

Examples of problems in deep crustal and mantle structure that can readily be addressed through multidisciplinary, integrated studies of crustal and mantle properties include:

  • How do mantle flow patterns, mantle temperature, mantle composition, and distribution of melt in and above the melting region vary with spreading rate and other variables?
  • How are mantle flow patterns, mantle temperature, and other variables reflected in the tectonic and petrologic segmentation patterns of the ridge? Do different segmentation patterns correlate with specific mantle attributes?

On a more local scale, isotopic and trace element anomalies in lavas from a small number of Mid-Atlantic Ridge segments have been interpreted as derived from transient compositional anomalies in the mantle. Are such anomalies physically detectable? Do they physically enhance and concentrate mantle upwelling, or does a more fertile mantle composition yield an increased amount of melt, leaving the pattern of upwelling unchanged?

Q2: How is melt transport organized within the mantle and crust?

Mantle melting is the fundamental source of the heat and material fluxes that create new ocean floor, drive hydrothermal circulation, and support and nourish unique seafloor and subseafloor ecosystems. The dynamics of the mantle, mechanisms of mantle melting, size and shape of the melting regime, and pathways by which melt accumulates and moves upward from the mantle to the crust and seafloor are understood only in broad outline.

Recent developments in electromagnetics and seismic tomography have produced regional images of mantle properties and more local images of the lower crust. We are now poised to make real progress in understanding melt distribution, from which we can determine transport mechanisms. Examples of problems that can be addressed in the next few years include:

  • How is melt transport organized in the mantle beneath spreading centers? Is melt flow focused toward the ridge axis at depth, or does melt first migrate vertically, converging toward the axis only when it reaches the sloping base of the lithosphere? Is melt transported through a fractal network of channels, or does it percolate through pores or cracks in response to pressure gradients?
  • What are the pathways by which melt passes from the base of the crust to subseafloor magma chambers and seafloor eruption sites?
  • How do the location, size, shape, and longevity of magma chambers vary with tectonic or other variables?
  • How are the plutonic rocks of the lower crust formed? Is the lower crust formed entirely from shallow magma chambers, or are there magma chambers at various levels within the crust?
  • To what extent does melt migrate along-axis? Does migration occur in deep mush zones, shallow melt lenses, or subvolcanic dikes? What is the across-axis width of the zone through which melt reaches eruption sites on the seafloor? Are dikes the dominant means by which magma reaches the seafloor under all conditions of magma supply, spreading rate, or other factors?
  • What is the frequency of individual magmatic events, what proportion of events lead to a seafloor eruption, and how far along-axis do individual events propagate under different conditions?

Do the short-term patterns of short-term variability and/or the longevity of individual vents and hydrothermal fields vary with the distribution of melt? How do specific magmatic events affect hydrothermal circulation patterns? Can circulation patterns be understood in terms of the interactions with magmatic systems or other variables?

Q3. How does hydrothermal circulation affect characteristics of the melt zone, crustal structure and composition, and ridge morphology?

As the dominant cooling mechanism for new lithosphere formed at spreading centers, hydrothermal circulation is strongly linked to magma supply and crustal thermal structure. Cracking and faulting in response to hydrothermal cooling may create new fluid pathways, modifying circulation and thermal structure, and potentially influence the geometry and location of new magma bodies. Hydrothermal circulation may influence the size and distribution of magmatic heat sources, which will in turn influence the geometry and vigor of hydrothermal circulation.

There is also a strong possibility that, in some places, hydrothermal circulation may influence the thermal and rheological properties of the upper mantle where melts are produced. Chemical reactions controlled by hydrothermal circulation may even influence magma composition by introducing water, chlorine, and other seawater-derived components into melts.

Examples of questions that address the problem of how fluids, rocks, and melts interact beneath spreading centers include:

  • How do the geometry and vigor of hydrothermal circulation vary along-axis? Are observed variations reflected by variations in lava composition on comparable scales?
  • Can variations in hydrothermal circulation patterns be interpreted in terms of magma supply rates and the location, size, or shape of magma reservoirs? Can they be interpreted in terms of variations in melting temperature and/or mantle composition?
  • Do variations in the geometry and vigor of hydrothermal circulation reflect variations in crustal structure and morphology? Do such variations reflect hydrothermal cooling effects on buoyancy, strength, or other characteristics of the lithosphere?
  • Do different volcanic or tectonic terrains support different circulation patterns? Do the distributions of diffuse and focused vents vary with geological, tectonic, or magmatic setting? What is the relative importance of permeability structure compared to variations in deep-seated heat sources in determining the distribution of surface discharge?
  • How do fluid compositions vary spatially in relation to variations in hydrothermal circulation? Can these variations be explained in terms of fluid-rock interactions, flow geometry, or depth of fluid penetration?
  • Under what conditions can water, chlorine, or other seawater-derived components be detected in seafloor lavas? Conversely, under what conditions are magmatic volatiles or other components important constituents of hydrothermal fluids? What are the potential impacts of such components on life below or at the seafloor or on ocean compositions?

Q4. How does biological activity affect vent chemistry and hydrothermal circulation?

Hydrothermal fluid flow through cracks and pores within the oceanic crust provides a rich environment for subseafloor biological communities. There is emerging evidence that microbially mediated dissolution and precipitation reactions at fluid-rock surfaces provide strong feedback, modulating hydrothermal fluid flow by changing the surrounding rocks? porosity and permeability. Microorganisms consume inorganic and organic materials from both fluids and rock substrates, returning particulate and colloidal biological materials to the hydrothermal fluids, fundamentally altering fluid composition.

Changes in fluid composition may limit or enhance growth of microbial or metazoan populations in downstream environments, including those at the seafloor and in the water column. Both in the subseafloor and in vent chimneys, constantly shifting flow patterns may both reflect and influence microbial growth patterns. The transient success of microbes in a particular place may inhibit flow, shifting downstream flow patterns and modifying critical nutrient supplies with significant impacts on overlying or downstream macro- and microorganisms. As the ocean crust moves away from the spreading axis, microbes may play an important role in crustal alteration. Microbially mediated dissolution of volcanic glass and minerals, precipitation of secondary minerals, and growth of biomass will interact to continuously modify permeability as the crust cools and ages.

Examples of important problems that can be addressed through focused Integrated Studies programs include:

  • What is the range of thermal and chemical conditions over which microbially mediated reactions occur in the subseafloor? What is the range of possible chemical reactions?
  • How quickly, and in what manner, does the growth and distribution of subseafloor biomass impact permeability?
  • Are particular microbes associated with particular conditions and/or styles of alteration? Do they create a geological record of temporal and spatial changes in flow patterns? If answers to such questions can be obtained from drill holes or by other means, they will enable the development of increasingly realistic models for the evolution of hydrothermal chemistry and fluid circulation in new oceanic crust as it moves away from the axial neovolcanic zone.

Q5. What are the forces and linkages that determine the structure and extent of the hydrothermal biosphere?

Organisms that live in seafloor and subseafloor environments along the global mid-ocean ridge system depend upon chemical transformations that occur in an energy-rich, aqueous environment that ultimately is dependent upon deep-earth processes.

Hydrothermal activity directly affects the type, abundance, and distribution of life beneath, at, and above the seafloor. Hydrothermal energy flux is the dominant control on primary productivity and standing stock biomass, while hydrothermal fluid temperature and composition control species diversity through two opposing effects. Diversity is enhanced by the ability of microbial populations to utilize a startling variety of metabolic pathways based on a variety of reduced elements and compounds, including Mn-Mn oxides, FeS-Fe-FeO, H S-S-SO , and CH -CO-CO . Diversity is limited by high temperatures, toxic heavy-metal concentrations, and (for metazoans) low oxygen. Less obvious physical controls unique to hydrothermal ecosystems include the abundance of steep gradients in temperature and chemistry and the instability of the habitat on scales from seconds to decades.

Biological interactions also play a major role in structuring hydrothermal communities. These interactions include predation, competition, and facilitation, as well as larval and recruitment dynamics. The latter will be strongly influenced by the behavior and characteristics of hydrothermal plumes.

Q6. What is the nature and space/time extent of the biosphere from deep in the subseafloor to the overlying water column?

At a number of well-studied, high-temperature vent sites the dominant faunas are well known, but discovery of new species continues at a rapid rate. Studies of temporal changes in community composition at different vent types are also in their infancy and accurate estimates of biomass have not been made. Microbes have been sampled from a number of vent-related niches, including interiors of chimneys, exposed surfaces, and plumes. Cultures of numerous strains of Archaea and bacteria have been obtained, but it is not known whether these cultures fully represent the genera or even the metabolic motifs of the microbial dominants. Population densities are also virtually unquantified.

The existence of microbial communities in the subseafloor of the mid-ocean ridge has been inferred from four main sources:

  • observation of "snowblower" vents that eject clouds of abundant biogenic material in the immediate aftermath of seafloor eruptions;
  • analysis of DNA collected directly from high-temperature hydrothermal fluids flowing out of the seafloor;
  • microscopic studies of geological samples showing distinctive patterns of microbial degeneration of volcanic glass;
  • cultures of extremophile microorganisms from hydrothermal plume samples that can only be derived from high-temperature subseafloor habitats.

This subseafloor biosphere has not been directly sampled and none of its characteristics is known with confidence. Characteristics of the subseafloor biosphere that require investigation include:

  • its extent, continuity and standing biomass;
  • the dominant metabolic types or genera;
  • outputs to the ocean floor, and the extent to which they may be driven by eruptions or other magmatic and tectonic events;
  • whether snowblower vents represent transient enhanced production or samples of existing subseafloor biota;
  • finally, and provocatively, whether metazoans also exist in the subseafloor.

Q7. How and to what extent does hydrothermal flux influence the physical, chemical, and biological characteristics of the overlying ocean?

Hydrothermal circulation cools the lithosphere, transferring heat and material to the ocean by way of both high-temperature focused vents and low-temperature diffuse flows.

The compositions of vented fluids are determined by water-rock reactions over a wide range of temperatures and pressures, microbially mediated reactions within the subseafloor biosphere, and mixing of seawater into circulating hydrothermal fluids within the complex subseafloor hydrologic system.

Around diffuse flows, mineral deposits and complex biological communities develop within the volcanic rocks and overlying sediments. The effects of diffuse flows on the chemistry and circulation of the overlying ocean are largely unquantified but may be significant.

Above high-temperature hydrothermal vents, buoyant plumes ascend as high as several hundred meters above the seafloor until they achieve neutral buoyancy. Each plume is an evolving, complex mixture of gas-enriched vent fluid, dissolved and particulate material, microbial biomass, and entrained seawater. Ongoing, commonly microbially mediated chemical transformations precipitate a portion of the material flux as metal sulfides, oxides, and sulfates, removing material from the water column and altering the chemical and biological composition of deep-sea sediments. Dispersal of the remaining hydrothermal products by a range of physical, chemical, and biological processes may have significant impacts on the ocean.

Scope of an integrated studies site

Although the predominant criterion for site selection is suitability for an integrated, multidisciplinary investigation determined on the basis of a suite of questions comparable in scope to those outlined above, each site should be defined to be as representative of its ridge type as possible. Integrated studies at each site will be carried out at relevant spatial scales, nested about a designated focal area. Each Integrated Studies Site can be visualized as a series of expanding bands, which may be elliptical rather than concentric, around the hydrothermally active region that is the focus of the smallest-scale studies. While the term "bulls-eye" has been used for such a region, the term does not refer to a higher-priority level. Ridge 2000 recognizes that different questions require different scales of investigation. It will be up to PIs to justify the scale they wish to investigate on the basis of the problem they wish to address and to demonstrate the relationship to a vertically integrated type-section at the designated focal area.

As far as possible and reasonable, each Ridge 2000 Integrated Studies Site should:

  • encompass a representative variety of micro-and macrofauna, hydrothermal venting styles, fluid and particulate compositions, and rock types and compositions;
  • display a significant hydrothermal signature in the water column;
  • encompass a representative set of ridge offsets and a variety of morphological expressions;
  • be logistically feasible in terms of weather windows, technological constraints, and port availability;
  • have sufficient background data available;
  • display significant potential for magmatic or tectonic events.

The initial integrated studies sites

The RIDGE Steering Committee (STCOM) initiated a site-selection procedure based on the recommendations of the Ridge 2000 Integrated Studies Planning Workshop in July 2000. The procedure began with a call for suggestions of potential Integrated Studies Sites in each of six spreading types (fast, slow, intermediate, back-arc, sedimented, and mantle plume-influenced) followed by a sign-up period for individuals interested in contributing to a site proposal. Site proposals were written by the interested parties and posted for public comment and modification. The finalized proposals were posted and U.S. scientists were invited to vote on the proposals and include a short justification for their choice(s). Finally, an independent panel evaluated the votes, justifications, and proposals and made a written recommendation to the NSF and the RIDGE/Ridge 2000 transition steering committee. The panel's recommendations were accepted and three initial Integrated Studies Site areas were identified: 8° to 11°N on the East Pacific Rise, the Endeavour Segment of the Juan de Fuca Ridge, and a segment ofthe East Lau Spreading Center in the Lau Basin. The panel also recommended that incubation activities be supported to facilitate the establishment of Integrated Studies Sites on the northern Mid-Atlantic Ridge and Galapagos Spreading Center as soon as resources allow. The Site Selection Panel report is available on the Ridge 2000 Web site.

Following the selection of the three initial Integrated Studies Sites, two communitywide workshops were held to facilitate dissemination of previous results from each site and produce implementation plans specific to each site. The implementation plans for the three initial Integrated Studies Sites are available on the Ridge 2000 website. These plans are intended to guide proponents when preparing proposals for integrated studies under the Ridge 2000 program and to assist the Steering Committee and NSF in oversight of activities at the sites.

Complementary studies

In addition to field studies performed at the formal Integrated Studies Sites, a complete Integrated Studies program may include directly relevant analog, modeling, or experimental studies that are partly or entirely performed onshore or at another location.

Analog studies

Implicit in the Integrated Studies concept is a requirement that all field studies be performed at a geographically defined site and that theoretical and experimental studies demonstrate a clearly defined linkage to site-specific data. At certain sites, however, critical information about one or more component(s) of the integrated system will not be physically accessible. In such cases, proposals for directly relevant "analog studies" designed specifically to compensate for such a lack of accessibility are encouraged.

Modeling studies

Modeling should be an integral part of each ISS research program. Modeling programs may be tightly focused or multidisciplinary and should address both large- and small-scale problems. They should enhance our understanding of potential linkages and interactions between data and observed or inferred processes. The models should generate or test hypotheses and help to direct sampling and experimental studies. Examples of modeling targets include (but are not limited to) magma intrusion into the crust, water-rock-magma interactions, regional and local fluid circulation, stability and evolution of hydrothermal vents and vent fields, relationships between focused and diffuse flow venting, two-phase flow and phase segregation, stability and reactivity of aqueous organics, and energetics of microbial metabolism.

Experimental studies

Laboratory studies that provide fundamental data and observations central to the aims of a specific Integrated Studies Site are encouraged. Examples of broad subjects for potential laboratory study include:

  • processes of partial melting and crystallization at high temperature and pressure;
  • magma and eruption dynamics;
  • physical properties of cracked, hot, and molten rocks;
  • fluid-rock-magma interactions and kinetics;
  • chemical (organic and inorganic) and physical properties of fluids;
  • interactions of microbes and other biota with fluids;
  • physiological tolerances and responses of hydrothermal biota.

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Time-critical studies

Capturing Transient Events Along the Mid-Ocean Ridge. The Time-Critical Studies theme of Ridge 2000 focuses on the immediate biological, chemical, and geological consequences of transient "events" on the seafloor, including volcanic eruptions, intrusion of dikes or other magma bodies at the ridge axis, and deformation events related to seafloor spreading. Transient events occur on time scales of seconds to months (or possibly years). Although they are short-lived, transient events may have major biological, chemical, and geological impacts on the mid-ocean ridge system and other parts of the planetary system. If we are to capture critical data from such events, we must be able to detect and locate them, and also rapidly deploy instruments and sampling devices while they are still in progress.

Overarching Goal: To understand the nature, frequency, distribution, and biogeochemical impacts of magmatic and tectonic events along the global mid-ocean ridge system.

In a single decade, magmatic event detection and response efforts on two short-ridge systems (Juan de Fuca and Gorda Ridges) have revolutionized our understanding of these active processes. Each response to a detected event has given us fundamental new information about the linkages among volcanic events, hydrothermal circulation, and vent biota. Some important results from event detection and response efforts to date include:

  • detection and location of mid-ocean ridge eruptions in real time using cabled hydrophone arrays;
  • correlation of the spatial and temporal distribution of earthquakes with seafloor eruption, dike intrusion, and hydrothermal venting;
  • recognition that event plumes form in association with eruptive and/or intrusive events;
  • the discovery that earthquakes can greatly perturb hydrothermal and biological systems;
  • direct measurement of lava inflation and near-bottom water temperature during a seafloor eruption;
  • observation and measurement of dramatic, transient changes in thermal, chemical, and biological output from hydrothermal vents immediately after volcanic and tectonic events;
  • exploitation of event plumes for studies of their physical, geochemical, and microbial evolution;
  • exploitation of zero-age lava surfaces and event-created hydrothermal systems for studies of biological colonization and succession;
  • recognition of temporal and spatial variability in lava chemistry and the size and distribution of lava flows formed during individual eruptive events;
  • observation and sampling of large amounts of microbial biomass and microbial products released from subseafloor reservoirs;
  • recognition that there is an extensive microbial biosphere in the subseafloor at mid-ocean ridges.

Transient events can effect important changes on time scales from seconds to weeks. Magmatic and/or tectonic events at mid-ocean ridges can force rapid changes in hydrothermal circulation and biological activity. Volcanic eruptions create new seafloor, exposing fresh rock for colonization by organisms and creating new pathways for hydrothermal circulation and alteration. The creation of new or modified hydrothermal systems provides new or modified habitats for development of subseafloor and seafloor ecosystems. The ejection of large volumes of hot fluid, known as "event plumes," transports large amounts of heat, inorganic and organic material, and microbial biomass from the subseafloor to the ocean.

Short-lived perturbations caused by such transient events may also make substantial contributions to the overall thermal, chemical, and biological budgets of the mid-ocean ridge. Systematic observations of perturbed systems while events are in progress, and during their subsequent return to "normal" conditions, are essential for a complete understanding of these budgets and of the interrelationships among volcanic, hydrothermal, and biological systems. Such data is also essential for the development of well-constrained, integrative theoretical models of system behavior.

The ability to identify and respond to events is a potentially important component of at least some of the Ridge 2000 Integrated Studies Sites. One criterion for site selection is a high probability of eruptive activity. Although this is impossible to predict with any certainty, the rewards for success will be great. If an event occurs at an established Integrated Studies Site, it is likely that the earliest perturbations will be captured by in situ monitoring instruments, providing data that could be acquired in no other way. Ensuring an active monitoring capability at appropriate sites is a priority of the new program. It should be noted, however, that the Integrated Studies Sites alone will capture very few events. A productive Time-Critical Studies program will necessarily encompass significant (hundreds to thousands of kilometers) sections of mid-ocean ridge.

Because the location and timing of events cannot be predicted, this theme differs from the Integrated Studies theme in that its goals cannot be achieved by an orderly progression of preplanned expeditions. Rather, they must be achieved through the development of appropriate infrastructure for event detection and timely data and sample collection.

Modeling studies

Modeling is an integral part of the TCS research program. Modeling programs may be tightly focused or multidisciplinary, and could address both large- and small-scale problems. They should enhance our understanding of potential linkages and interactions between data and observed or inferred processes. The models should generate or test hypotheses and help to direct TC studies. Examples of modeling targets include (but are not limited to) the formation of event plumes; the chemical, biological, and physical processes active within the buoyant and neutrally buoyant phases of developing event plumes; and other physical, chemical, and biological responses of hydrothermal systems to tectonic and magmatic events.

Fundamental questions

The discrete magmatic and tectonic "events" responsible for the formation of most of the upper oceanic crust are among the very few geological processes that occur on human time scales and are therefore directly observable. Some examples of scientific questions that require real-time event detection of, and rapid response to, events along the global mid-ocean ridge include:

  • Question 1. How and where do events begin, how do they propagate, and what are the coupled deep and shallow tectonic, magmatic, and volcanic components that cause an event?
  • Question 2. What are the size and frequency of events, and how do these relate to tectonic parameters such as spreading rate and crustal thickness?
  • Question 3. How are event plumes formed? How do they sample the subseafloor hydrothermal regimes and microbial communities, and to what extent do they contribute to global hydrothermal fluxes?
  • Question 4. How are event-related thermal and chemical perturbations manifested in the ensuing microbial and macrofaunal response?

Q1. How and where do events begin, how do they propagate, and what are the coupled deep and shallow tectonic, magmatic, and volcanic components that cause an event?

There are multiple possible causes of a volcanic eruption on the seafloor-for example, new injection of magma from the mantle, degassing within the magma reservoir, and faulting or changes in possible melt pathways above the reservoir. All of these are likely to have associated hydrothermal manifestations. Our understanding of the fine-scale spatial and temporal variability of magma genesis and hydrothermal activity relies heavily on the identification and study of recent eruptions. While dike propagation within the shallow oceanic crust has now been observed, it is not clear whether this is a ubiquitous characteristic of ridge eruptions. Melt transfer might occur at greater depth. Small eruptions might occur without significant propagation along strike. Some eruptions may nucleate at segment ends rather than segment centers. There may be relationships with volcanology, hydrothermal activity, and the compositions of erupted rocks that correspond to the specific pathways and causes of eruptive activity. None of these can be known without rapid response to inferred eruptive events, with the hope of having monitoring present to capture an event from its inception at deeper levels to its manifestations at the surface.

Q2. What are the size and frequency of events, and how do these relate to tectonic parameters such as spreading rate and crustal thickness?

No volcanic eruption has been observed in progress on the deep seafloor, but observations of recently active flows can be used in conjunction with geological mapping, on scales comparable to those used in subaerial terrains, to understand how the internal volcanic structure and composition of the upper oceanic crust varies with spreading rate and other key variables. Upper crustal structure strongly affects the distribution of seafloor and subseafloor ecosystems by providing voids, fractures, and other physical habitats and exerting a strong influence on the pathways and mechanisms of hydrothermal fluid flow.

Studies of magmatic events on the Juan de Fuca Ridge and the East Pacific Rise have shown that eruptions along these medium- to fast-spreading axial ridges are accompanied by along-axis dike injections. These events have been quite small and of short duration, but much larger lava flows and lava fields, indicative of larger and possibly longer-lived events, exist elsewhere along the mid-ocean ridge system. At slow-spreading ridges, geological mapping suggests that crustal accretion processes are substantially different from those of faster-spreading ridges. At slow spreading rates, magmatic and tectonic events appear to be cyclical on a longer time scale, mid-crustal magma bodies are absent or ephemeral, and eruptions may be much larger and less frequent. Active event detection and timely observation of ongoing and recent events will yield the first real data on these differences.

Q3. How are event plumes formed? How do they sample the subseafloor hydrothermal regimes and microbial communities, and to what extent do they contribute to global hydrothermal fluxes?

Several event plumes along the Juan de Fuca and Gorda Ridges have been shown to have formed within a few days after the onset of a diking-eruptive event. The heat content of a single event plume may exceed the annual thermal output of a typical seafloor hydrothermal system, and some event plumes have yielded thermophilic microbes derived from subseafloor habitats that have never been collected from normal vent fields. Based on these and other observations, three possible mechanisms have been proposed for the generation of event plumes:

  • seawater circulation through a rapidly cooling lava flow;
  • enhanced circulation due to a shallow magmatic intrusion;
  • the sudden release of fluid from a crustal reservoir.

It is not yet possible to weigh the relative significance of these mechanisms. A fuller understanding of these important phenomena will require further observations on and above the seafloor, at or very close to their time of formation, using creative observational tools. The most effective observations will come from instruments and experiments that are in place prior to an event and from preplanned rapid-response efforts. Long-term monitoring programs at some Ridge 2000 Integrated Studies Sites offer the potential for such observations.

Thermal and chemical fluxes calculated from available event-plume data suggest that event plumes may account for as much as 5-10 percent of the total heat and chemical fluxes produced by hydrothermal systems. To evaluate the global significance of these figures, however, observations must be made at a number of sites covering a range of spreading rates, magma budgets, and other key variables.

Q4. How are event-related thermal and chemical perturbations manifested in the ensuing microbial and macrofaunal response?

Seafloor eruptions and/or dike intrusions may initiate new thermal, chemical, and biological cycles. Fresh hot rock at or beneath the seafloor provides a new source of heat and reduced chemicals, as well as pristine substrates for colonization. Changes in crustal temperature will affect hydrothermal fluid temperature and chemistry and subseafloor habitat, and these effects will evolve as temperatures decline. Time-series observation and sampling of temperature and fluid chemistry during this decline-together with observation of changes in permeability structure, fluid flow, subseafloor habitat, and macrofaunal communities-will enable a much more detailed understanding of the interactions among these phenomena. For example, in the aftermath of two events (Coaxial and 9°N), vapor-rich vent fluids have been succeeded by brines. These observations have led to a fluid evolution model that depends on early, high-temperature phase separation of a NaCl-rich brine from a low-salinity, vapor-rich fluid. Such predictive models can be tested and refined against future events and, as predictive models improve, their scope can be expanded to incorporate the linkages from magmatic activity to hydrothermal chemistry and biological succession.

A strategy for time-critical studies

The Ridge 2000 time-critical studies theme has two distinct components: event detection and rapid response.

Event detection

The low-magnitude seismicity typically produced by tectonic and magmatic activity at mid-ocean ridges is readily detected by hydroacoustic seismic monitoring, which uses hydrophones to record the waterborne T-phase arrivals of seafloor earthquakes.

Real-time detection

Real-time detection is currently limited to the northeast Pacific SOSUS hydrophone array, which should continue to provide long-term records of, and the potential for rapid responses to, events along the intermediate spreading-rate northeast Pacific centers (Juan de Fuca and Gorda Ridges). Ridge 2000 encourages the installation of additional arrays in areas where spreading rate or other key variables differ from those of the northeast Pacific. Priority scientific support for event detection should focus on coverage for most or all of the Integrated Studies Sites where instruments with the ability to capture aspects of transient events, including precursors, will likely be in place. Real-time detection requires either cable access to shore or buoy-based satellite communication and power systems that are hardwired to hydrophones. Deployment costs for such systems are beyond the scope of the Ridge 2000 program, but plans developed under the Ocean Observatories Initiative (OOI and NEPTUNE) include the installation of autonomous surface communication buoys at each Integrated Studies Site. This initiative has been approved by NSF and awaits budget approval.

Non-real-time detection

Presently, Ridge 2000 will support only Time-Critical Studies supported by real-time detection capabilities. Nevertheless, the usefulness of autonomous monitoring systems is clearly recognized. While unable to provide direct funding, Ridge 2000 may assist such efforts with communication and other logistical support. Non-real- time detection uses autonomous hydrophone arrays to monitor activity along large sections of the mid-ocean ridge system that are not accessible to real-time monitoring. One such array is currently monitoring the equatorial East Pacific Rise and the Galapagos Spreading Center. A second is monitoring part of the northern Mid-Atlantic Ridge. Similar arrays can be deployed and recovered approximately annually almost anywhere in the ocean.

The principal scientific purpose of such monitoring is to determine the size, distribution, and frequency of events in different, complementary parts of the global mid-ocean ridge system. On what time scale and in what size increments is new oceanic crust produced at different spreading and magma supply rates? Time-series monitoring will also serve to identify segments or regions that are currently active and therefore of particular interest as areas for other active-process investigations. For those Integrated Studies Sites that are not subject to real-time monitoring, autonomous hydrophone arrays should be deployed to record any history of tectonic and magmatic activity throughout the region. Such events, although interesting in their own right, may be important triggers, precursors, or complements to activity recorded in more detail at the Integrated Studies Sites.

Rapid response

Rapid-response efforts are intended to obtain data and samples from a transient event, beginning as soon as possible after its onset. The key scientific questions may vary with the event type or location and may require more-or less-rapid response times. The nature of a given response will depend on these factors and available logistical support.

Autonomous responses

Autonomous responses will be possible where instruments can be predeployed. Integrated Studies Sites for which there is a reasonable possibility of an event should be instrumented for real-time detection and, as the technology becomes available, for autonomous response. At an ideal site, an autonomous underwater vehicle (AUV) with two-way communication could be ready to perform preprogrammed surveys with an array of physical, chemical, and biological sensors. Prior to, and in conjunction with, AUV deployment, an array of moored sensors and samplers could be programmed to react to seismic or hydro-thermal signals. Except for short deployments, autonomous instrumentation would require an autonomous buoy or submarine cable for power and communication.

Fast responses

Fast responses to significant events at non-instrumented sites will require preplanning and predeployment of "ready-to-go," portable equipment. Real-time detection is critical. While the initial phases of an event would be missed, for many events critical information can still be collected within a few days or weeks after an event begins. Ridge 2000 also encourages development of new instrumentation that will facilitate and augment rapid-response capabilities. Examples may include new/improved expendable profiling sensors deployable from moving ships, and air-droppable sensors and mooring arrays. As monitoring spreads to other parts of the mid-ocean ridge, there will be an increased probability of detecting larger and/or more long-lived events than those detected to date. Recent studies of volcanic morphology along the MAR suggest that large events may be common at slow spreading centers.

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Technological and infrastructure requirements

By its nature, the deep ocean is remote from and hostile to human presence, and the environments studied by ridge scientists are perhaps the most hostile of any in the deep ocean. Ridge science, therefore, depends heavily for its success on a constantly advancing technological infrastructure. The broad scope and interdisciplinary nature of the Ridge 2000 Program also require a support infrastructure for planning meetings; coordinating or sharing results; data and sample archiving and dissemination; and access to computational tools.

Technology requirements

An impressive array of devices is available for deep-ocean research (Appendix C-Existing and Required Technology), but advances are continually required for optimal progress on some technology-limited fronts. From the perspective of Ridge 2000 objectives, rapid technology development is most important in support of an increased emphasis on phenomena that are transient and evolving on time scales of seconds to decades. Scientific study of these phenomena will increasingly require in situ instrumentation above, below, and on the seafloor. Instruments will be required for measuring a wide range of physical, chemical, and biological variables and for discrete sampling of fluids and biological materials. In some cases, specific instruments exist for low-pressure and moderate-temperature applications, but their adaptation for deep-sea hydrothermal conditions still represents a significant challenge. Proposals for development of technology for Integrated and Time-Critical Studies are encouraged.

Addressing the multidisciplinary questions that are the tenant of Ridge 2000 science will require adequate facilities support-ships, deep-sea vehicles (ROVs, AUVs, HOVs), and related equipment. Recent meetings and deliberations concerning future deep-submergence facility requirements (summarized at the UNOLS Web site) stressed the need for the continued capability to conduct in situ experiments, observation, and sampling in the deep sea. Currently, the U.S. scientific community has at its disposal an array of complementary facilities and high-resolution imaging and mapping capabilities that allow U.S. scientists to enjoy broad and technically sophisticated access to the deep seafloor for their research. However, Ridge 2000 science requirements and other current initiatives at the NSF will place an ever-increasing demand on our current fleet of deep-submergence systems. At the same time, ongoing technological developments will provide significant new capabilities to existing and future systems. It is therefore critical that we continue to support the long-term development of instrumentation, vehicles, and support ships that will be essential for Ridge 2000 studies and the marine science community in general. In general, four types of technology development are under way, but continuing or accelerated development will be required as follows:

  • In situ sensors and samplers of many kinds (physical, chemical, and biological) are needed for time series and discrete data collection in the full range of vent environments, including those with high temperature, high pressure, corrosive fluids, and high levels of biofouling.
  • Autonomous Underwater Vehicles (AUV) show great promise to supplement the capabilities of surface ships and to perform a wide variety of tasks during autonomous deployments. Further development is required to create AUVs that are reliable, flexible, everyday workhorses.
  • Drilling technology for fractured and/or hot rock and for numerous shallow holes must be improved.

Real-time data telemetry and long-term power supplies are required for long-term instrument deployments that can collect detailed time-series data and, ideally, be responsive to real-time events.

Much of the required technical development can and should be collaborative, as the needs of Ridge 2000 science are not unique. Potential collaborators include:

  • ocean science initiatives at NSF, such as the Ocean Drilling Program, International Ocean Drilling Program, MARGINS, Ocean Observatories Initiative, and Ocean Mantle Dynamics programs;
  • broad foundation-wide initiatives such as Biocomplexity and Biogeosciences;
  • international programs including InterRidge, Global Ocean Observing System (GOOS), and the Census of Marine Life;
  • national programs of other countries;
  • NASA planetary and astrobiology programs;
  • commercial and research groups involved with similar endeavors in shallow water;
  • a variety of NOAA programs including the PMEL Vents and NEMO programs, the National Undersea Research Programs, and the Ocean Exploration Program.

Infrastructure requirements

The emphasis on interdisciplinary collaboration as a hallmark of Ridge 2000 investigations requires that they be as open as possible to the widest range of investigators. Data and results must be disseminated in a timely fashion. These requirements will be supported by a formal approach to data, sample, and information management:

  • Timely access to data and samples. Integrated Studies Site proposals and Ridge 2000 science proposals should include explicit plans for data and sample management and an agreement for timely data dissemination and sample distribution. Guidelines are provided in the Ridge 2000 Program and Data Policy (Appendix D)
  • Access to computational tools. Usable versions of data sets and tools developed from modeling and experimental studies should be made available to other investigators in a timely fashion. Investigators seeking funding for experimental and modeling studies should include in proposals a plan for disseminating the products of their work.
  • Ongoing support for data/sample management and archiving. Efficient data and sample distribution and management require a support infrastructure. The Ridge 2000 program has developed a data policy (Appendix D) and will support the development of a data management system and operation of a data management office. All funded Ridge 2000 investigators will be required to adhere to the data policy and cooperate fully with the Data Management Office.
  • Flexible procedures to enable rapid response to transient events.

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Appendix A: budgets and resource distribution

In 2007 NSF rewrote the Ridge 2000 program announcement. Revisions included both minor and more significant changes:

  • updates of program manager and office contact information
  • new annual proposal deadline
  • revised proposal review process
  • updated budget information, based on changes in fiscal picture from that of 2001

NSF Ridge 2000 program announcement

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Appendix B: Ridge 2000 management

Responsibility for managing the Ridge 2000 program rests with the Steering Committee (STCOM), who act as a board of directors to establish policies and set directions and priorities for the program in response to community input.

The Executive Committee (EXCOM) is a subset of the STCOM that supports and advises the chair to ensure the program's smooth functioning and broad representation across the disciplines.

The chair of the STCOM acts in an executive capacity to implement these policies and priorities. The chair is responsible for establishing and managing a Ridge 2000 office to handle communication, logistics, education, outreach, and other activities in support of the program.

The Ridge 2000 office will consist of a chair, program coordinator, education and outreach (E & O) coordinator, and program assistant. The office is responsible for communication via mailing lists and a Web site; organization of community workshops, Ridge 2000 Theoretical Institutes, and Field Schools; promotion of the Ridge 2000 program at conferences and in print; and establishing and coordinating education and outreach activities throughout the community.

The program coordinator is responsible for day-to-day coordination and administration of the Ridge 2000 office. This includes scientific planning and coordination of meetings and workshops; interaction with U.S. and international researchers and federal agency personnel; and communication with the Ridge 2000 community through meetings, the Web site, planning documents, and assorted mailings and newsletters.

The E & O coordinator, with guidance from the E & O advisory committee, is responsible for identifying the goals for education and outreach for the Ridge 2000 program, identifying activities that support these goals, and developing and implementing a communitywide plan to achieve them. The coordinator will provide guidance and coordination, when needed, to facilitate individual scientists' efforts to convey their science to a broader audience. The E & O coordinator will also actively seek participation from scientists in communitywide education and outreach programs.

Ridge 2000 steering committee (STCOM)

The Ridge 2000 STCOM represents the broad community of scientists interested in the Ridge 2000 program. It sets directions and priorities for Ridge 2000 activities in response to community input and ensures that scientific and educational and outreach activities are carried out in a timely and effective manner.

The Ridge 2000 STCOM will normally consist of fifteen members in addition to the chair. The members will represent the broad range of disciplines and institutions of the Ridge 2000 community.

Membership will be for three years, with one-third of the membership rotating each fall. Nominations of scientists from U.S. universities or research organizations for STCOM membership will be requested from the community each year. New members will be appointed by the STCOM with the primary objective of maintaining a well-balanced, committed, and active membership.

The Ridge 2000 STCOM will normally meet twice a year, or at the chair's discretion.

The Ridge 2000 STCOM is responsible for:

  • establishing policy and setting directions and priorities for scientific and educational/ outreach activities of the Ridge 2000 program;
  • identifying exciting new directions for Ridge 2000 studies, based on input from the Ridge 2000 scientific community;
  • energizing the Ridge 2000 community to accomplish the goals of the Science Plan and keeping them informed of and involved in Ridge 2000 activities;
  • establishing subcommittees for specific themes or issues of critical importance to Ridge 2000? for example, proposal relevancy review, specific Integrated Studies Sites, time-critical studies, data management, and education and outreach (subcommittee chairs will generally be members of the STCOM);
  • soliciting and approving proposals for workshops and theoretical institutes;
  • facilitating communication between Ridge 2000 and other programs.

Because of the importance of oversight and coordination for the success of each Integrated Studies Site, a site coordinator for each site will be chosen by the STCOM. The site coordinator will serve as an ex officio member, on the appropriate STCOM ISS subcommittee, and will be encouraged to request a modest supplement to support the time spent in coordination activities. The main responsibilities of the ISS site coordinators will be to foster communication and ensure the organization of information and materials in support of research activities conducted at each site. The site coordinator will serve as a liaison for the community, encourage preproposal communication, and keep accounts of active programs and field logistics. Each site coordinator will also work with the Ridge 2000 DMO to ensure that metadata and data for all Ridge 2000 field programs are submitted in a timely manner.

Ridge 2000 executive committee (EXCOM)

The Ridge 2000 EXCOM is a subset of the STCOM. It provides the Ridge 2000 chair with ongoing support and advice in order to effectively implement the Science Plan and ensure broad disciplinary involvement in Ridge 2000 activities.

EXCOM will consist of three members plus the Ridge 2000 chair, who will also be the chair of EXCOM.

EXCOM will meet (in person or electronically) on a regular basis to discuss the status of Ridge 2000, and the chair can call upon members at any time for advice.

Members of the EXCOM will be appointed by consensus of the chair and the STCOM, based on their leadership and vision and on the program's needs. Appointees need not be current members of the STCOM, but they will become members on appointment.

Members of the EXCOM will normally serve for three years, with the terms staggered to ensure continuity during rotation of the Ridge 2000 Office.

The Ridge 2000 EXCOM is responsible for:

  • implementing the Ridge 2000 Science Plan consistent with the priorities and directions set by the Steering Committee;
  • overseeing the progress of Time-Critical Studies and each of the Integrated Studies Sites;
  • promoting exciting new directions for Ridge 2000 studies based on input from the Steering Committee and the community;
  • communicating the activities and progress of the Ridge 2000 program to the community and fostering communication from the community to the chair and the STCOM;
  • implementing and maintaining an active education and outreach program.

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Appendix C: existing and required technology

This compilation illustrates the array of technologies required for mid-ocean ridge research, grouped by data and sample type. In a general way, the listing begins in the mantle and proceeds upward toward the ocean. At the same time, the scale of the measurements in space and time decreases.

Imaging mantle properties

The physical properties of the oceanic mantle and crust and their role in the construction and evolution of the lithosphere can be understood through a combination of high-resolution seismic and electromagnetic imaging and geodynamic modeling. The two required technologies are well developed, but ongoing improvements in instrumentation and data processing will continue to improve data quality and resolution. These technologies are the focus of the proposed new NSF Global Geodynamics initiative.

Broadband seismometers-Broadband recordings of teleseismic events by arrays of ocean bottom seismometers are used to image variations in mantle seismic velocity. These velocity variations reflect variations in temperature, volatile content, crystal fabric developed through dislocation creep, and the presence of melt.

Electromagnetic instruments-Passive electromagnetic observations recorded at the seafloor are sensitive to the presence of interconnected melt and other conductive phases in the upper mantle. They complement seismic observations.

Monitoring seismicity and deformation

Earthquakes and crustal-deformation measurements provide information about active magmatic and tectonic processes and the geometry of subsurface magma bodies. Magmatic and/or tectonic events are characterized by earthquake swarms that can be located using hydrophone arrays moored in the SOFAR channel. Hydrophone technology is well developed, but additional deployments will be needed to provide an effective geographic coverage.

Hydrophone moorings-Both the real-time SOSUS cabled arrays and stand-alone moorings from which data are collected periodically by surface ships can provide continuous hydroacoustic monitoring of earthquakes over large areas. Future development of autonomous buoys with satellite telemetry for data transfer will greatlyenhance this capability.

Ocean bottom seismometers (OBSs)-Seismometers provide information about earthquakes, including hypocenter depths and first motion (slip) directions that cannot be obtained from hydrophones. These additional data provide information on deformation patterns and swarm geometry and may help to distinguish between earthquakes of a magmatic or tectonic origin. Data from OBS arrays can be used to image subsurface structures in three dimensions with resolution of a few hundred meters. OBSs (and hydrophones) can also detect harmonic tremor associated with magma movement, which could, in principle, serve as an eruption predictor if data were available in real time.

Seafloor geodesy instruments-Acoustic/GPS positioning systems, tiltmeters, bottom pressure recorders, and acoustic distance measuring devices provide records of horizontal and vertical displacement due to plate motion, magmatic inflation, or other forms of crustal deformation.

Determining crustal physical properties

Determining crustal physical properties is fundamental to a better understanding of the impacts of melt transport and hydrothermal circulation on the formation, cooling, and alteration of the oceanic crust. Many appropriate technologies exist, but in some cases further development is needed.

Deep drilling at active spreading centers-To date, attempts by the Ocean Drilling Program (ODP) to drill bare rock sites on young oceanic crust have been largely unsuccessful. Deep (200-800m) drill holes at or close to the spreading axis will be necessary to characterize its eruptive history, explore the extent of the subseafloor biosphere, and characterize the active hydrothermal system and its history. Development of this technology is an ongoing priority of the ODP.

Shallow drilling at active spreading centers-Short (1-10m) cores can be recovered from bare rock using self-contained drilling devices deployed to the seafloor from conventional ships. Such devices can potentially provide a cost-effective method for sampling the shallow crust in detail, in pursuit of biological, hydrothermal, and volcanological objectives. These devices could also be used to deploy instruments to monitor shallow subsurface processes. No such device is currently available in the United States, and development or acquisition (with a longer-term goal of drilling to depths up to 100 meters) should be a priority objective for many marine geology programs.

Drill core orientation devices-The development of techniques for recording the original orientation of drill cores will considerably enhance the range of information available from deep and shallow drilling. Oriented cores carry structural information, including records of magnetic field orientation and intensity. They provide data on crustal stress and deformation history.

Electromagnetic instrumentation-Active source electromagnetic surveys can be used to image the distribution of conductive media, including magma and hydrothermal fluids in the ocean crust and upper mantle. Although widely used on land, this is relatively new technology in the oceans and further development will be required.

Heat-flow measurement-Measurements of conductive heat flow through bare rock will clarify our understanding of the shallow thermal structure of the oceanic crust. Heat-flow surveys will help to delineate regions of upflow and downflow, leading to more accurate hydrological models. Accurate measurements of advective heat flow due to diffuse and high-temperature venting are essential if we are to quantify hydrothermal fluxes. A prototype heat-flow blanket has been deployed in the Northeast Pacific and further development will be required for routine bare-rock surveys.

Seismic imaging-Reflection, refraction, and tomography studies can be used to map out the velocity and reflectivity structure of the oceanic crust. Velocities are sensitive to temperature, lithology, porosity, fracture geometry, and crustal alteration, thus these techniques can be used to detect regions of magma and hot rock. In conjunction with appropriate mathematical modeling, they can help constrain other physical properties of the oceanic crust.

Near-bottom seismic sources-Source signals that originate near the seafloor, rather than near the sea surface, are essential for high-resolution seismic refraction surveys of the shallow crust, especially where seafloor terrain is rough. High-resolution surveys constrain the density, orientation, and aspect ratio of cracks, leading to constraints on the geometry of hydrothermal systems and the distribution of hydrothermal alteration and infilling.

Seafloor gravimeters-Near-bottom gravity surveys measure subseafloor mass changes, helping to constrain the porosity of the shallow crust. Used in conjunction with precise pressure measurements, they can also help quantify vertical movement of the seafloor.

Compliance measurements-Compliance is the ratio of seafloor displacement to pressure variations as a function of frequency at periods exceeding about 30 s and is obtained by combining measurements from a differential pressure gauge and seafloor gravimeter. It is sensitive to regions of low shear strength within the crust and thus is useful for imaging melt and highly fractured regions.

Near-bottom magnetometers-Near-bottom magnetic observations contribute to our understanding of the evolution of magnetic properties in young lavas and can constrain magmatic processes when inverted for variations in the thickness of the magnetic lava layer.

Monitoring fluids at or beneath the seafloor

Point source and time-series measurements of fluids at on- and off-axis locations provide data essential to the interpretation of chemical, physical, and biologic interactions and the evolution of subseafloor hydrothermal systems. For example, time-series records of fluid chemistry, temperature, and flow rate can be used to unravel the complex reactions associated with the formation and aging of the oceanic crust. New technologies are urgently needed to improve the resolution and duration of time-series measurements. The most critical of these technologies are:

In situ sensors-Development of a wide range of in situ devices that can monitor chemical, biologic, and physical data in hydrothermal fluids over a range of temperatures is critical to progress in understanding subseafloor hydrothermal systems. Technology already exists for some types of measurement at low pressure and temperature, but adaptation for high pressures and temperatures will require significant development of new materials and techniques.

In situ sampling-Direct sampling of organic and inorganic solids and fluids from high- temperature vents greatly enhances material preservation and reduces or eliminates post-collection changes in sample properties. To obtain crucial time-series data, ongoing development of automated samplers is essential. Sampler development faces many of the same material and technique challenges as sensor development.

Deep drilling on-axis, off-axis, and in analog systems-Drilling both inside and outside the volcanically active region will constrain both high- and low-temperature processes and reactions, including those that characterize hydrothermal recharge zones. Well-designed drilling programs will also constrain the history of magmatic processes. Drilling in analog terrains, potentially including on-land ophiolite terrains, will yield data relevant to the inaccessible regions of the oceanic crust, helping to constrain both the nature of deep-seated igneous processes and the depth and extent of hydrothermal systems.

Drill hole logging and monitoring-When deep drill holes sample the oceanic crust, down-hole techniques can be used to maximize information. Some examples of information that may be obtainable include structural and stress-field data, flow thickness and stratigraphy, and porosity and permeability. Down-hole chemical logs may reveal patterns of hydrothermal alteration and igneous stratigraphy.

Water-column monitoring

Time-series monitoring of the water column can provide vent-field scale measurements of changes in chemical, thermal, and biological output from hydrothermal discharge. Time-series monitoring of water properties and current flow can quantify trends in hydrothermal flux, especially in the aftermath of an eruption or other event. At present, such measurements would be made from fixed moorings, but within a few years it should be possible for longer-term deployments of autonomous underwater vehicles (AUVs) to undertake periodic, repeat surveys and event-response activities.

Current measuring devices-Eulerian measurements using current meters on fixed moorings and Lagrangian measurements using neutrally buoyant drifters are both needed. New drifters are being developed that can carry physical and chemical sensors to monitor the chemical evolution of plume waters. Tracer-release experiments will complement drifter data.

Temperature and optical sensors-Sensitive temperature measuring, light-scattering, and light transmission sensors are inexpensive and effective for mapping hydrothermal plumes.

Chemical sensors-New advances in in situ spectrophotometric techniques will enhance our ability to locate hydrothermal plumes and enable long-term monitoring of plume chemistry.

Telemetry-Effective long-term monitoring and event response will require robust power supplies and, preferably, two-way communications between seafloor instrument arrays and land-based computer networks. High-bandwidth acoustic links that transmit data from deep water to surface buoys for onward transmission by satellite are in an early stage of development. The considerable development still required is a priority of the Ocean Observatories Program.

Monitoring hydrothermal structures and biological communities

Comprehensive studies of the origin and evolution of organisms and communities populating seafloor and subseafloor habitats require real-time monitoring and sampling of the fluid and solid, living and nonliving products of rock-water interaction at and beneath the seafloor. A wide range of technologies will be required to effectively complete such studies.

Long-term video monitoring-Time-series images of biological communities will record their growth evolution and responses to transient events.

Long-term chemical and physical sensors-Time-series records of chemistry, temperature, and other characteristics of fluids are critical to our understanding of the origin and evolution of the biological communities they support.

High-resolution sonar and imaging systems-Fine-scale imaging of seafloor terrain, hydrothermal activity, and biological communities is necessary to an understanding of the relation between organism distribution and ridge-crest volcanic and tectonic features. ROV and AUV-based acquisition on near-bottom multibeam sonar imaging can yield vertical resolution of seafloor terrain on the order of tens of centimeters. Digital still-photographic imaging and high-definition video imaging can provide sub-centimeter-scale resolution of smaller areas for more detailed studies of succession in hydrothermal environments.

Biomarkers-Biochemical indicators that signal a changed physiological state of a biologic system have important applications as a means of monitoring and assessing the conditions affecting hydrothermal organisms.

In situ experiments-Experiments to measure in situ habitat characteristics or introduce and observe small perturbations will be required in natural habitats at or below the seafloor. This will require development of new experimental methods and of delicate manipulators and other devices for underwater vehicles.

Technology for time-critical studies

To quickly take advantage of fast-response opportunities, equipment and supplies must be prepared in advance. In principle, a rapid-response equipment pool should include both ship- and air-deployable components. These include a variety of moorings with the widest feasible variety of detectors and/or samplers, neutrally buoyant floats, sonobuoys for detection of seismic signals, and self-contained camera systems. In the future, an appropriately equipped, air-deployable AUV would be an invaluable resource.

Real-time detection capabilities-The U.S. Navy SOSUS hydrophone array in the northeast Pacific provides real-time detection of seismic events on the Juan de Fuca Ridge, but the future of Navy support is uncertain. In the absence of that support, the system could cease to function in a short time. While reliable autonomous hydrophones are available (and in service), currently they do not provide the real-time data required to initiate a rapid response. Development and deployment of cost-effective cabled or satellite data links are essential if a rapid-response capability is to be extended beyond the northeast Pacific.

Cabled observatories and autonomous buoys-The OOI/NEPTUNE initiative is planning for a plate-scale, cabled observatory that receives power from and relays data to shore stations, and for development of autonomous buoys that can function and communicate unattended for periods of months to years. A prototype observatory, deployed on Axial Seamount (Juan de Fuca Ridge) by NOAA/PMEL, is functioning in non-real time for most instruments with minor, experimental real-time telemetry via a surface buoy.

Deployable and on-site AUVs-Autonomous underwater vehicles will soon be sufficiently developed that could be considered as potential rapid-deployment tools. In the future, an AUV could possibly be tethered to a buoy or cable observatory, programmed to respond in real time, and kept in a state of readiness. An AUV could, for example, be programmed to detect and map hydrothermal plumes, perhaps even track chemical gradients and locate a plume source. Other uses include mapping and imaging the seafloor to detect new lava or other structures and collect water samples, either at predetermined points or in response to onboard sensors for subsequent recovery and analysis.

Airdrop technologies-Experience to date has shown that seismic activity associated with magmatic events is often short lived, ceasing before a ship can reach the site. Specially constructed instruments and moorings-including ocean-bottom hydrophones, sampling devices, and even an AUV-could potentially be deployed from an aircraft within hours of an event.

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Appendix D: Ridge 2000 program and data policy

The Ridge 2000 Data Policy is detailed in the Data Management section of this website

Acknowledgments

This document is the result of the efforts of many scientists over a period of several years. It is modified from the original Ridge 2000 Science Plan that was proposed to the National Science Foundation in 2000. That document was produced by the RIDGE Office at the College of Oceanic and Atmospheric Sciences, Oregon State University. It was the result of three open planning meetings that included more than 300 U.S. scientists, as well as the writing and editing efforts of the 2000-01 RIDGE Steering Committee under the leadership of Dr. David M. Christie. The modifications from the original document reflect the recommendations of the NSF panel that reviewed the Ridge 2000 program proposal, the Integrated Studies Site Selection Panel, and the National Science Foundation. These recommendations were accepted by both the RIDGE and Ridge 2000 Steering Committees, at their last and first meetings respectively, and this Science Plan has been reviewed and edited by the Ridge 2000 Steering Committee.

This material is based upon work supported by the National Science Foundation under grant no. 0116823, which established the Ridge 2000 Program in November 2001. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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