from the shape of the sound speed profile in figure 1, one can see the effect of the order of importance of temperature and depth on sound speed. near the surface, where temperatures are generally highest, the sound speed is often highest because the effect of temperature on sound speed dominates. further down the water column, as temperature decreases in the ocean thermocline, sound speed also decreases. at a certain point, however, the effect of depth, i.e., pressure, begins to dominate, and the sound speed increases to the ocean floor. also visible in figure 1 is a common feature in sound speed profiles: the sofar channel. the axis of this channel is found at the depth of minimum sound speed. sounds emitted at or near the axis of this channel propagate for very long horizontal distances, owing to the refraction of the sound back to the channel's center.