Open-ocean deep convection explored in the Mediterranean

Open-ocean deep convection is a littleunderstood process occurring in winter in remote areas under hostile observation conditions, for example, in the Labrador and Greenland Seas and near the Antarctic continent. Deep convection is a crucial link in the “Great Ocean Conveyor Belt” [Broecker, 1991], transforming poleward flowing warm surface waters through atmosphere-oceaninteraction into cold equatorward flowing water masses. Understanding its physics, interannual variations, and role in the global thermohaline circulation is an important objective of climate change research. In convection regions, drastic changes in water mass properties and distribution occur on scales of 10–100 km. These changes occur quickly and are difficult to observe with conventional oceanographic techniques. Apart from observing the development of the deep-mixed patch of homogeneous water itself, processes of interest are convective plumes on scales <1 km and vertical velocities of several cm s−1 [Schott et al., 1994] that quickly mix water masses vertically, and instability processes at the rim of the convection region that expedite horizontal exchanges of convected and background water masses [e.g., Gascard, 1978]

Inversion techniques for ocean acoustic tomography and bottom classification based on normal mode theory

The paper presents a short review of the modal representation and inversion techniques applied to problems of ocean acoustic tomography and geoacoustic inversion. The use of the modal inversion techniques is based on the assumption that the modal component of the acoustic field can be recognized in the recorded acoustic signals. The paper is referred to the main techniques that have been applied so far by the group of the Institute of Applied and Computational Mathematics at FORTH and address their benefits and drawbacks

Inverse problems in underwater acoustics

The paper presents an aver view of the inverse problems associated with applications of underwater acoustics. The problems are classified into four main categories, according to the recoverable quantities: Acoustic source localization, bottom identification; ocean acoustic tomography and target recognition: The paper gives emphasis to the three first categories, and includes methods to solve the inverse problems associated with the appropriate experimental configurations

Time and frequency measurements using scaled laboratory experiments of shallow water acoustic propagation

International audienc

Acoustic observations of heat content across the Mediterranean Sea

The ability to monitor the heat content of oceans over long distances is becoming increasingly important for understanding the role of oceans in climate change, for determining the variability of the state of the oceans, for operational ocean observing systems, and for studying large-scale ocean processes such as water-mass formation. Although the properties of the upper layers of the ocean can be routinely measured on large scales by satellite remote sensing (providing altimetric and infrared data) and with expendable probes dropped from commercial vessels, the deep interior of the ocean is more difficult to monitor. Ocean acoustic tomography1 is a promising technique for such applications, as it has the potential to provide systematic, instantaneous and repeated measurements of the ocean interior over large parts of an ocean basin. Here we demonstrate the capability of this technique for measuring the heat content across an entire (albeit small) ocean basin—the western Mediterranean Sea