Seafloor Observatory Science
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SEAFLOOR OBSERVATORY SCIENCE Paolo Favali(1), Roland Person(2), Chris R. Barnes(3), Yoshiyuki Kaneda(4), John R. Delaney(5), Shu-Kun Hsu(6) (1) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via di Vigna Murata, 605, Roma (Italy), Email: [email protected] (2) IFREMER (French Institute for Exploitation of the Sea/Institut Français de Recherche pour l'Exploitation de la Mer) BP 70, 29280 Plouzané, France, Email: [email protected] (3) University of Victoria, PO Box 1700 STN CSC, Victoria BC V8W 2Y2 Canada, Email: [email protected] (4) Japan Agency for Marine-earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa, 237-0061, Japan, Email: [email protected] (5) University of Washington, 7600 Sand Point Way NE, Seattle, WA 98115, USA, Email: [email protected] (6) Institute of Geophysics, National Central University, No.300, Jhongda Rd., Jhongli City, Taoyuan County 32001, Taiwan (R.O.C.), Email: [email protected] at a fixed site, of instruments, sensors, and command ABSTRACT modules connected to land either acoustically or via a This paper deals with a new emerging science the seafloor junction box to a surface buoy or a fibre-optic “Seafloor Observatory Science”. It is evolved rapidly cable…” [1] The establishment of a global network of over the last two decades by means of new projects and seafloor observatories will provide powerful means to programmes towards the establishment of permanent understand the ocean and the complex physical, underwater networks. The main on-going initiatives at biological, chemical, and geological processes. Many global scale are presented for Canada (NEPTUNE - large-scale projects have been planning to establish North East Pacific Time-series Underwater Networked permanent seafloor networks at International level. Experiments), USA (OOI - Ocean Observatories Canada, USA, Japan, Taiwan and Europe are the major Initiative), Japan (DONET - Dense Oceanfloor Network actors. In Canada the major component of this effort is system for Earthquakes and Tsunamis), Taiwan NEPTUNE (North East Pacific Time-series Underwater (MACHO - Marine Cable Hosted Observatory) and Networked Experiments) [2] and VENUS (Victoria Europe (through ESONET-NoE - European Seas Experimental Network Under the Sea) [3]. In the United Observatory NETwork-Network of Excellence and States, the OOI (Ocean Observatories Initiative) a NSF recently with the infrastructure project EMSO - (National Science Foundation) Division of Ocean European Multidisciplinary Seafloor Observatory). Sciences program [4] has launched the RSN (Regional- Moreover, the scientific motivations for seafloor Scale Nodes) [5]. Japan started in 1978 to manage observatories and their main architecture are discussed. cabled seafloor observatories for scientific use, and Finally, the applications and opportunities of cabled particularly for real-time monitoring for seismic and observatories beyond those in ocean science research, tsunami warning. One of the most recent Japanese technology and data services are outlined. It is projects is DONET (Dense Oceanfloor Network system important to recognise that the advent of cabled ocean for Earthquakes and Tsunamis) [6]. In Taiwan the observatories heralds in a new era of ocean exploration project MACHO (Marine Cable Hosted Observatory) and interpretation, which will make profound recently started and is a submarine cabled observatory contributions to socio-economic benefits, public policy offshore of eastern part of the island with the main formulation, and public education and engagement. purpose to establish offshore seismic stations, to provide early warning of earthquakes and tsunamis, and to 1. INTRODUCTION monitor submarine volcanic activity [7]. In Europe the The ocean exerts a pervasive influence on Earth’s effort to build a seafloor observation infrastructure have environment. It is therefore important that we learn how been supported by the EC (European Commission) first this system operates. Understanding the ocean, and the through ESONET-NoE (European Seas Observatory complex physical, biological, chemical, and geological NETwork-Network of Excellence), aimed at gathering systems operating within it, is a challenge for the together the community interested in multidisciplinary opening decades of the 21st century. The establishment ocean observatories [8], and more recently with the of a global network of seafloor observatories will help EMSO-PP project (European Multidisciplinary Seafloor to provide the means to accomplish this goal. A fully Observatory-Preparatory Phase), aimed at establishing comprehensive definition of the term “seafloor the legal entity charged of the construction and observatories” was given for the first time by the NRC management of the EMSO infrastructure. The (National Research Council) report “Illuminating the European-scale network of seafloor observatories Hidden Planet. The future of Seafloor Observatory widely distributed for long-term monitoring of Science”, where we can read: “…an unmanned system, environmental processes related to ecosystem life and Biogeochemistry: global carbon cycle and elemental evolution, global changes and geo-hazards [9]. cycling within the ocean through both physical and biological processes, and ocean acidification. 2. SCIENTIFIC MOTIVATION FOR SEAFLOOR OBSERVATORIES Marine ecology: distribution and abundance of sea In recent decades ocean, Earth and planetary sciences life, ocean productivity, biodiversity, ecosystem have been shifting from a discontinuous, expeditionary function, living resources, and climate feedbacks. mode toward a mode of sustained in situ observations. 3. SEAFLOOR OBSERVATORY This change in the mode of investigation stems from the ARCHITECTURE realisation that Earth and its oceans are not static, but are dynamic on many time and space scales, not just the The principal characteristic of a seafloor observatory is short-time scales involved in catastrophic events. A a two-way communication between platforms and scientifically powerful component of the observatory instruments and shore. During the last 30 years deep-sea concept is the long time-series collection of multiple investigations moved from scarce observations to variables at a fixed location. These multidisciplinary continuous measurements of a wide set of parameters in datasets will enable the enhancement of more traditional selected areas. Seafloor observatories are characterised methods, giving strong benefits to many disciplines. by the following basic elements: a) abundant power; b) sensor networks; c) high bandwidth communications; d) Seafloor observatories will thus offer earth and ocean possibility to be remotely reconfigured; e) accurate scientists new opportunities to study multiple, positioning; f) data acquisition procedures compatible interrelated scientific processes over time scales ranging with those of shore observatories. from seconds to decades, such as: a) episodic processes; b) processes with periods from months to several years; Seafloor observatory is an unmanned station, capable of c) global and long-term processes. Episodic processes operating for decades on the seafloor, supporting the include, for instance, deep-ocean convection at high operation of a number of instrumented packages related latitudes, volcanic eruptions, earthquakes, tsunamis, and to various disciplines. According to the capacity of biological, chemical and physical impacts of storm communication, the seafloor observatories can have the events. The establishment of an observatory network, following possible configurations: covering from the surface of the ocean along with the 1) Stand-alone observatory: Observatory in stand-alone water column to the seabed beneath, will be essential to configuration for power, using battery packs, and investigate global processes, such as the dynamics of with limited capacity of connection, using, for the oceanic lithosphere and thermohaline circulation, instance, capsules or an acoustic link from the and their reciprocal interactions. surface, which can transfer either status parameters Much of seafloor observatory research is indeed or a very limited quantity of data. interdisciplinary in nature and has the potential to 2) Platform connected observatory: greatly advance relevant scientific sectors, such as: 1) the role of the ocean in climate; 2) dynamics of oceanic a) Acoustically linked observatory able to lithosphere and imaging the Earth’s interior; 3) fluids communicate by acoustics to an infrastructure, and life in the ocean crust; 4) coastal ocean processes; such as a moored buoy or another observatory; 5) turbulent mixing and biophysical interactions; and 6) b) Tethered observatory constituted of a sea bottom ecosystem dynamics and biodiversity [10]. cabled segment connected to a surface buoy with The Seafloor Observatory Science addresses satellite links capacities. This type is strongly Interdisciplinary research priorities in: depending on the environmental constraints, such as water depth or protected conditions. Physical oceanography: water mass characterisation, water column processes, thermodynamics, ice cover, 3) Cabled Observatory: Observatory having as climatology, and impacts on climate change. infrastructure a submarine cable directly connected to shore for power and real-time data transmission. Geosciences: transfer from Earth’s interior to the The cables to be used can be retired cables, crust, hydrosphere and biosphere, fluid flow and gas dedicated cables or shared cables devoted