text: The global meridional Turner angle distributions at the surface and 300-m depth in different seasons are investigated by Tippins, Duncan & Tomczak, Matthias (2003), which indicates the overall stability of the ocean over a long-time scale. It's worth noting that 300-m depth is deep enough to be beneath the mixed layer during all seasons over most of the subtropics, yet shallow enough to be located entirely in the permanent thermocline, even in the tropics.
  At the surface, as the temperature and salinity increase from the Subpolar Front towards subtropics, the Turner angle is positive, while it becomes negative due to the meridional salinity gradient being reversed on the equatorial side of the subtropical surface salinity maximum. Tu becomes positive again in the Pacific and Atlantic Oceans near the equator. A band of negative Tu in the South Pacific extends westward along 45°S, produced by the low salinities because of plenty of rainfall, off the southern coast of Chile.
  In 300-m depth, it is dominated by positive Tu nearly everywhere except for only narrow bands of negative Turner angles. This reflects the shape of the permanent thermocline, which sinks to its greatest depth in the center of the oceanic gyres and then rises again towards the equator, and which also indicates a vertical structure in temperature and salinity where both decrease with depth.