SynopsisThe water masses, major circulation features and long-term variability of Rockall Channel waters are reviewed in relation to work in recent years. Data collected with modern instruments disclose more detail in the water mass structure than found previously, and the range of water masses present in the Channel is examined.The use of recording current meter moorings has amplified our knowledge of the processes occurring within the Rockall Channel circulation, although net flows remain difficult to evaluate. Eddy motions suggested by current meter records and geostrophic data are confirmed by the trajectories of satellitetracked drogues.Changes in the temperature and salinity of the upper waters of the Rockall Channel from the early years of this century to the present are clearly detectable, and a brief account is given of these.

Development of methods and technologies to characterize sites with underwater military munitions (UWMM) and respond to UWMM where the risks posed to human health or the environment or explosive hazards are unacceptable is underway. Department of Defense Military Munitions Sea Disposal Site Hawaii (HI-06), referred to locally as Ordnance Reef, is off Oahu’s leeward coast. This site has become the focal point for research on UWMM. Past studies found that the site presents no immediate danger to public safety. The location and water depth at this site present advantages for UWMM research and development.Promising technologies demonstrated at Ordnance Reef (HI-06) include those for munitions recovery, at-sea demilitarization, nondestructive testing, and explosives detection. Studies on fate and transport of munitions-related compounds and corrosion are ongoing.Among these technologies are the Remotely Operated Underwater Munitions Recovery System (ROUMRS) and the Explosive Hazard Demilitarization System (EHDS). Both are assemblages of commercial off-the-shelf components, and each is housed in a standard 6-m International Organization for Standardization (ISO) shipping container and can be operated on a barge.ROUMRS consists of a remotely operated vehicle, manipulators, an interface between a precision GPS, and underwater navigation equipment used during recovery of UWMM. The system also transports recovered UWMM for treatment. The EHDS consists of a portable X-ray unit to allow positive identification of recovered munitions, remotely operated wet band saws to cut recovered munitions to expose their explosive fill, and low-temperature ovens to treat the exposed explosives, making the remaining material safe for recycling.

The paper describes the design and use of a tide machine capable of producing near-sinusoidal hydrostatic pressure cycles varying in period from 12 to 999 min and in amplitude from 0·4 to 3·2 m. In conjunction with infra-red detection units and a microprocessor logging system the apparatus can be used to detect and record the response of a variety of organisms to cyclic pressure changes.

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