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<p>Ocean acoustic tomography was introduced by Munk and Wunsch in the early 80s as the only remote sensing tool capable of measuring the ocean interior properties. The ocean is in fact opaque to electromagnetic radiation but is transparent to sound. Sound waves can into the abyssal depths and cross very quickly the vast ocean expanses, being the sound speed velocity ~ 1500&#xa0;m/sec at its minimum. The objective of this paper is to illustrate the inception of the idea; the first major experiments carried out, focused first on mapping the mesoscale eddy field and monitoring the large scale ocean circulation, most importantly its temperature (density) field. The major difficulty of the technique is that it provides integral averages of the sound speed over the interior acoustic ray paths. The problem is hence to disentangle the acoustic data transforming them into pointwise measurements analogous to those taken by traditional oceanographic instrumentation such as mooring arrays and survey vessels. These is accomplished using mathematical inverse theories introduced in oceanography by Wunsch in the 80s. The methodology however induces very significant errors for which the resulting tomographic maps provide just pattern recognitions. This fundamental drawback was overcome with the emergence of the climate problem. The most important parameter for the assessment of global warming is temperature and the most important measurement is the average temperature increase of the global ocean with respect to previous reference averages. This led to the concept of ATOC, Acoustic Ocean Thermometer, and the tomographic experiments of the 90s were in fact focused on the climate objective. Unfortunately, for reasons discussed in the paper, acoustic tomography did not achieve this goal which would have constituted an epochal landmark in the history of physical oceanography. Here is where my paper stops. I do no cover the tomographic experimental efforts carried out in the years after the 2000s nor the related literature. My objective is to describe the introduction of the tomographic concept, the large scale and global experiments and the excitement they produced in the oceanographic community. Even if they failed, they marked the two decades of 80s and 90s. Their follow-ups do not measure to that excitement.</p> Graphical abstract <p></p>

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Sounding of the ocean surface and interior

  • 期刊论文

  • 发表日期：

    2026年3月18日

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  • Paola Malanotte

摘要

Ocean acoustic tomography was introduced by Munk and Wunsch in the early 80s as the only remote sensing tool capable of measuring the ocean interior properties. The ocean is in fact opaque to electromagnetic radiation but is transparent to sound. Sound waves can into the abyssal depths and cross very quickly the vast ocean expanses, being the sound speed velocity ~ 1500 m/sec at its minimum. The objective of this paper is to illustrate the inception of the idea; the first major experiments carried out, focused first on mapping the mesoscale eddy field and monitoring the large scale ocean circulation, most importantly its temperature (density) field. The major difficulty of the technique is that it provides integral averages of the sound speed over the interior acoustic ray paths. The problem is hence to disentangle the acoustic data transforming them into pointwise measurements analogous to those taken by traditional oceanographic instrumentation such as mooring arrays and survey vessels. These is accomplished using mathematical inverse theories introduced in oceanography by Wunsch in the 80s. The methodology however induces very significant errors for which the resulting tomographic maps provide just pattern recognitions. This fundamental drawback was overcome with the emergence of the climate problem. The most important parameter for the assessment of global warming is temperature and the most important measurement is the average temperature increase of the global ocean with respect to previous reference averages. This led to the concept of ATOC, Acoustic Ocean Thermometer, and the tomographic experiments of the 90s were in fact focused on the climate objective. Unfortunately, for reasons discussed in the paper, acoustic tomography did not achieve this goal which would have constituted an epochal landmark in the history of physical oceanography. Here is where my paper stops. I do no cover the tomographic experimental efforts carried out in the years after the 2000s nor the related literature. My objective is to describe the introduction of the tomographic concept, the large scale and global experiments and the excitement they produced in the oceanographic community. Even if they failed, they marked the two decades of 80s and 90s. Their follow-ups do not measure to that excitement.

Graphical abstract