Acoustic thermometry of ocean climate (ATOC): acoustic remote sensing of the north pacific ocean

摘要

The Acoustic Thermometry of Ocean Climate (ATOC) project is an international project that seeks to use low frequency underwater sound transmission to measure ocean basin temperatures. It is motivated by the need to provide appropriate observations of ocean temperature to initialize and constrain models that are used to forecast seasonal, annual and decadel climate change. Ocean acoustic thermometry is nearly unique in being able to observe temperature change in the otherwise nearly inaccessible deep ocean interior. It is based on the fact that the ocean is transparent to low frequency sound, and sound speed is a strong function of water temperature. Thus, the travel time from a transmitter to a distant receiver is an integrated measure of ocean temperature along the sound path. Since December, 1995 sound transmissions have taken place from a sound source off the west coast of the US to receivers as far distant as Hawaii, Kiritamati Island and New Zealand, and since January 1998 additional transmissions have taken place from a sound source located North of Kauai. These data show that ocean basin temperatures can be determined with millidegree precision. Travel time variations at tidal frequencies agree well with predicted values. Range and depth averaged temperatures obtained from the low frequency travel time variations are comparable to temperature variations derived from historic ocean data. They also compare favorably to temperatures derive from sea surface height variations measured by satellite altimetry.