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

Observing the Ocean in the 2000s: A Strategy for the Role of Acoustic Tomography in Ocean Climate Observation

Abstract- Since it was first proposed about 1977, ocean acoustic tomography has ev olved into a multi-purpose oceanic remote sensing measurement tool that has been employed in a wide variety of physical settings. In the context of long-term oceanic climate change, these acoustic techniques are unique among measuring systems in providing integrals through the mesoscale and other high-wav enumber noise over long distances and with remarkable accuracy and precision. In addi-tion, tomographic measurements may be made without risk of calibration drift. On a regional scale, tomography has produced valuable results by its integrals through regions of active convection, through direct observations of oceanic vor-ticity, its vertical resolution, and filtering of short-spatial scales. The remote sens-ing capability has proven extremely valuable for measurements under ice in the Arctic and in regions such as the Strait of Gibraltar where conventional in situ methods fail. As the community moves into an era of global scale observations (ARGO, 1999), the highest priorities for these acoustic techniques appear to be to (1) exploit the unique remote sensing capabilities for regional programs otherwise difficult to carry out, and (2) to gradually move tow ard deployment on the basin-to-global scales as the acoustic technology becomes more robust, simplified, and inexpensive. 1