Ocean acoustic tomography water formation and the gyre circulation. Other applications include the measurement of ocean tides, and the estimation of ocean mesoscale dynamics by combining tomography, satellite altimetry, and in situ data with ocean dynamical models. In addition to the decade-long measurements obtained in the North Pacific, acoustic thermometry has been employed to measure temperature changes of the upper layers of the Arctic Ocean basins, which continues to be an area of active interest. using data from acoustic pulses sent from one end of the earth to the other. Acoustic thermometry is an idea to observe the world's ocean basins, and the
Origin of water on Earth ocean water removed most CO from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared. Study of zircons has found that liquid water must have existed as long ago as 4.404 ± 0.008 Ga, very soon after the formation of Earth. This requires the presence of an atmosphere. The cool early Earth theory covers a range from about 4.4 Ga to 4.0 Ga. In fact, recent studies of zircons (in the fall of 2008) found in Australian Hadean rock hold minerals that point to the existence of plate tectonics as early as 4 billion years ago.