Figure 15 is the standard deviation of pressure anomaly at 1000m depth. In contract with sea level variation, 1000m pressure variation shows less activities in the southern Indian ocean, eastern tropical Pacific ocean, and northern Atlantic ocean. Figure 16 is the standard deviation of pressure at 1000m depth when the cyclo-stationary ocean is forced by monthly varying wind stress, monthly varying turbulent kinetic energy and constant buoyancy flux. Figure 17 is the standard deviation of pressure anomaly at 1000m depth when the cyclo-stationary ocean is forced by monthly varying buoyancy flux, constant wind stress, and constant turbulent kinetic energy. Since wind stress and turbulent kinetic energy are the main factors for vertical transfer of mass flux, large standard deviation of pressure at 1000m depth may be due to such transfer of mass flux from the sea surface to the deep layers. In the southern Indian ocean and in the northen Atlantic ocean, the vertical transfer of stresses between layers may not be responsible for the annual cycle of sea level anomaly because sea level variation is a good indicator of heat storage of the surface ocean (the mixed layer and the second layer in this model.)
Figure 18 is the ratio of Figure 17 to Figure 16. It is noted that the wind stress-sensitive area for 1000m depth pressure in the Indian Ocean, southern Indian Ocean, antarctic circumplolar current area are located in the similar area of wind stress-sensitive area of Figure 14. This means that the wind stress may be the primary reason of 1000m pressure anomaly in these area. However, the Indonesain sea and New Guinea coast, central to eastern equatorial area are heat flux-sensitive in the 1000m depth pressure anomaly, while the entire tropical Pacific sea level anomaly is wind stress-sensitive.
The mixed layer and the second layer velocity in Figure 10c shows semi-annual cycle that indicates responce to solar insolation heat flux in the equatorial ocean. If the solar penetration in these small spots is large enough to warm the large portion of water column, the effect of thermal expansion may leads to annual cycle in the mixed layer and subsurface layer. It is also note that the heat flux sensitive sea surface level anomaly in the southern Indian Ocean and southern Atlantic ocean, northern hemispheric central Pacific, southern hemispheric eastern Pacific are wind stress sensitive in pressure anomaly at 1000m depth. This indicates that ocean surface respond thermally, while 1000m pressure anomaly responds to wind stresses in these area.
The area of heat flux sensitive sea surface level anomaly corresponds with the area of heat flux sensitive pressure anomaly at 100m are North Atlantic ocean, California coast, south east of Australia, south west of Australia, and west of Drake Passage . In these area, both sea surface anomaly and 1000m depth flow are due to thermal expansion. The heat flux variation in these area may be responsible for the annual cycle of the 12th layer flow in Figure 10c.
