Novel online digital video and high-speed data broadcasting via standard coaxial cable onboard marine operating vessels

A recently developed deep-sea telemetry (DST), based on the digital subscriber line technology, has been successfully used to equip various remotely operated underwater devices with online video control, high-speed data transmission, and power supply via standard coaxial cables with a length of up to 8,000 m. The system has been applied to study and sample the extreme saline and high-temperature conditions of the Red Sea brines and to detect gas emissions at abandoned wells in the North Sea. In both applications, it has been integrated into a water sampler rosette, providing live video streaming and internal recording from commercial high-definition and analog cameras as well as simultaneous data transmission from a suite of sensors to record and sample the distribution of dissolved gases (e.g., methane and CO2) and oceanographic parameters. This combination makes an ideal survey and monitoring tool for leak detection even in harsh subsea environments. The DST has also been used to deploy landers at selected spots at the seafloor. In combination with remotely operated vehicle (ROV) deployments, this technique can be used to increase significantly the efficiency of ROV bottom time during deep-water operations. The high quality of the video transmission, ease of operation, and versatile application make this novel system superior to existing conventional analog transmission systems

Modelling sub-surface dynamics in the Black Sea

Dependency of major hydrophysical/chemical features of highly stratified basins on density surfaces in the vertical makes isopycnic models an attractive tool for simulating the dynamics of marginal marine environments such as the Black Sea because of the ability of these models to restrict vertical transport to some desirable degree. In the present work the seasonal variations of the subsurface dynamics of the Black Sea are investigated using an isopycnic model. Particular attention is given to the interfaces of the Cold inter-mediate layer and Suboxic layer and finally, the deep layer circulation in the basin is studied. It appears that although the depth range of the base of the Cold intermediate layer and the lower Soboxic layer interface do not change seasonally, their horizontal distribution is defined by the upper layer dynamics of the basin. Cyclonic surface circulation diminishes with increasing depth and the deep layer circulation is characterised by an anti-cyclonic rim current driven by density gradients created from river runoff and the influx of Mediterranean water. (C) 2002 Ifremer/CNRS/IRD/Editions scientifiques et medicales Elsevier SAS. All rights reserved.La liaison entre les facteurs hydrologiques et chimiques et les densités de surface dans les mers stratifiées rend attractive lˈutilisation de modèles isopycnaux pour simuler la dynamique de mers comme la mer Noire. Ce modèle réduit en effet le transport vertical à un niveau acceptable. Les variations saisonnières de la dynamique de sub-surface de la Mer Noire ont été simulées en se servant dˈun modèle isopycne. Une attention particulière a été portée aux interfaces entre la couche intermédiaire froide et la couche faiblement oxygénée. Finalement, la circulation profonde du bassin est étudiée. Alors que le niveau dˈimmersion de la base intermédiaire et de lˈinterface inférieure de la couche sous- oxygénée ne présentent pas de fluctuations saisonnières, leur répartition horizontale dépend de la dynamique de la couche de surface. La circulation cyclonique superficielle diminue quand la profondeur augmente et la circulation profonde est caractérisée par un courant annulaire anticyclonique entraîné par le gradient de densité crée par lˈapport dˈeau douce et lˈentrée d’eau méditerranéenne