SiPLABoratory

Acoustic Tomography Monitoring System (ATOMS)

The ATOMS project (POCTI/P/MAR/15296/1999) aims at developing an integrated system for large-scale ocean monitoring, using acoustic tomography. In order to demonstrate the feasibility of the approach, an experimental test will be performed to characterize the upwelling filament structure off the Cape São Vicente. This project is financed under the POCTI programme of FCT with 364 keuros for 4 years. Starting date: October 1st, 2000.

It has been shown that OAT can estimate water column temperature and sea currents in deep water. In shallow water, say in the continental platform, OAT has been slowly appearing in the literature as a potential candidate for efficient assesment of environmental parameters. Therefore, the development of an integrated monitoring system that will take advantage of the classical methods of OAT in deep water and will merge simultaneous observations of satellite, in-situ temperature and currents in a coherent tomographic "picture" of a 3D area is at hand. The tomography network will be studied on the basis of temperature/salinity/ bathymetry data from archives, together with the intensive recourse to acoustic propagation models and tomographic inversion techniques. Regarding the characterization of the cold filament feature, and for the sake of data validation, a set of standard in-situ measurements (i.e., CTDs, XBTs, ADCP, thermistor chains, biological and chemical parameters, etc.) within the target region of Cape São Vicente will be performed. Satellite data concerning this region, acquired during the sea trials will be integrated into the inversion process.

The objectives of the ATOMS project can be summarized as follows:

• to study the feasibility of a tomographic acoustic network to monitor the entire Portuguese EEZ. That network will be composed of 4/5 acoustic emitters/receivers located in the Azores, continental Portugal and Goringe bank and/or Madeira island. The modeled network will use archived data of temperature/salinity profiles (from NODC and BODC data bases). The main characteristics of the network will be determined in order to achieve a given performance in terms of temperature and current resolution.
• To develop an integrated system for Ocean Acoustic Tomography (OAT) and perform a test at sea.
• To develop a preliminary application of the integrated system to monitor a particular area off the Portuguese EEZ. The test target will be the Cape São Vicente filament area, which is one of the most developed and recurrent filaments observed and has important implications in the biological and chemical exchanges between the coastal and offshore ocean.