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NRL scientists are collaborating with international colleagues in developing a new way of observing water masses in the ocean: seismic oceanography. Using low-frequency seismic systems designed to image sub-seafloor geologic structures, thermohaline contrasts between water masses can be mapped, characterized, and quantified. Seismic oceanography uses the relationship between oceanic temperature contrasts and acoustic reflectivity to generate a quantitative measure of vertical temperature gradient throughout the water column at vertical and lateral resolution of 5 to 10 meters, several orders of magnitude finer than traditional methods. Such resolution opens up a new window on small-scale processes and mixing of the coastal and deep ocean. In 2009, we executed an ambitious field effort in the Adriatic Sea (ADRIASEISMIC-09) to acquire seismic data together with state-of-the-art oceanographic data as a way to compare the datasets and evaluate the limits and capabilities of seismic methods to characterize ocean processes. This was only the third such combined field effort ever performed, and the first in shallow water, thus adding to the useful development of this new approach. Incorporating seismic oceanography into standard oceanographic practice will require integrating field acquisition practices and developing new signal processing algorithms, with the potential benefit of gaining a new view of ocean structure. [ABSTRACT FROM AUTHOR]