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Dynamics of Earth and Ocean Systems

The ocean and earth sciences are on the threshold of a revolution involving new questions and requiring novel technologies. It is no longer sufficient to consider each constituent of the Earth-ocean-atmosphere system in isolation or to study the individual physical, chemical, and biological components of that system alone. To understand the present state of the planet and to determine with increasing accuracy environmental change in all of its aspects, we must observe the Earth's interior, its hydrosphere and biosphere on spatial scales appropriate to each component's pattern of heterogeneity, and multiple scales of interaction with other components.

There is an increasing requirement for such observations to be made continuously rather than intermittently. Many natural processes within the Earth system take place on characteristic timescales spanning hours to decades, whereas others are punctuated by brief episodic outbursts of activity that rise above a less energetic continuum. Since Darwin's voyage on the Beagle, earth and ocean scientists have used ships for expeditions of discovery. Much of our knowledge of the ocean basins comes from such discrete expeditionary visits. By the nature of such work, one can gain an understanding of the different regions of the oceans in the three dimensions of space. This approach does not afford knowledge of temporal variations, aside from episodic visits to stations previously surveyed or relatively brief continuous time-series observations from autonomously recording instrument packages deployed by ships and then subsequently recovered.

This approach has provided society with a broad understanding of the fundamental principles that regulate the physical, chemical, biological, and geological processes in the ocean. However, timely advances in our knowledge of the oceans and the Earth beneath are now limited by the lack of sustained observations over extended periods and over the range of spatial scales now required to address scientific issues of great importance; the complex network of interactions between ocean subsystems must be studied in depth.

The study of change extends across many disciplines, including the dynamics of the lithosphere and mantle, climate, biogeochemical cycles in the upper ocean, and the interrelationships between fluids and life in the crust. A successful observatory network must be, therefore, multidisciplinary in nature, providing physical, meteorological, chemical, biological, and geophysical time-series observations and enabling new understanding of the Earth system. Many processes are characterized by very low signal-to-noise ratios (e.g., seismology, geoelectromagnetic induction, or acoustic thermometry), and only long-term observations can be used to enhance these signals vis-a-vis noise processes. An observatory network requires the establishment of a permanent presence in the oceans; Ocean Drilling Program (ODP) Leg 203 is a critical step in this direction.

The Dynamics of Earth and Ocean Systems (DEOS) planning initiative in the United States (US) and the United Kingdom (UK) in coordination with partners in several member states of the European Union and Japan, represented by the International Association of Seismology and Physics of the Earth's Interior (IASPEI)/International Ocean Network (ION) Consortium, has identified a network of sites for multidisciplinary observatories focused on the atmosphere, ocean, and the Earth beneath it. Whereas for centuries observatories have been commonly used on land for many purposes, long-term continuous observations of natural phenomena in the oceans represent a new frontier for the sciences. A component of DEOS seeks to establish a global network of ocean observatories through the use of moorings (Fig. F1) for power supply and high-bandwidth telemetry. In other locations, generally those closer to land, DEOS calls for the use of direct submarine cable connections to shore. The drilling and establishment of a cased legacy hole (Leg 203, Hole 1243A) at the remote equatorial Pacific ION multidisciplinary observatory site provides an ideal location in the 2004 to 2005 time frame for the initial installation of a moored observatory.

The location of Site 1243 also provided a rare window into the petrology, geochemistry, and paleomagnetic history of fast-spreading 10- to 12-Ma Pacific basement material. During Leg 203, 87 m was cored and logged through basement in Hole 1243B, one of only four Deep Sea Drilling Project (DSDP)/ODP sites in Pacific basement of that age at which >80 m penetration through basement has been achieved. A full suite of shipboard analyses of basement rock cores will be reported in the Leg 203 Initial Reports volume.

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