Why is there a permanent thermocline in the ocean?

Because the oceans need a permanent thermocline.

in order to maintain the stability of ocean temperatures.

The permanent thermocline is due to solar radiation.

Heating, rotation of the earth.

The result of a combination of physical processes such as atmospheric wind stress, ocean upflow and salin-heat circulation. The metaphor of the image is that the density of cold water is high and the density of hot water is low, and if there is no disturbance by external factors, the stratification of cold water below and hot water on top is stable.

Sea temperature. Generally decreasing with depth, the layer of water of a certain thickness at the maximum rate of decline (or temperature gradient) is called the thermocline. The thermocline between the 200 and 1,000 m water layers in the middle and low latitudes of the ocean is called the "permanent thermocline" or "main thermocline" because it does not change with the seasons.

There are obvious regional differences in the internal structure of the main thermocline. Near the boundary between the North Equatorial Current and the Equatorial Countercurrent, the thermocline is not only the shallowest in the equatorial sea, but also has the largest vertical gradient of water temperature in the layer. In the equatorial undercurrent near the equator, the thermocline can be divided into two parts:

At the equator, the upper thermocline is the peak, the lower is the valley, and the middle (the center of the undercurrent) is the water layer with a relatively uniform water temperature. The water temperature gradient in the thermocline tends to decrease from the equatorial countercurrent to the north (or from the south of Japan to the east), but increases again in the black current region. Outside the equatorial seas, another type of thermocline generally appears near the sea surface, which directly reflects the heat budget of the sea surface

It is vigorous in summer and disappears in winter, so it is called the seasonal thermocline. Such as in Hokkaido.

In the southeast tidal sea, a deep upper mixed layer of about 0 will be formed during the winter convection period, but in spring and summer, the heat absorbed by the sea surface accumulates on the surface layer and causes the water temperature near the sea surface to rise significantly. In addition, the low salt water formed by the melting ice further increases the vertical stability of the surface layer, thus preventing the heat from spreading to the lower layer, resulting in a particularly developed seasonal cline.

The formation of the main thermocline in the ocean is mainly due to the combined effects of physical processes such as solar radiation heating, earth rotation, atmospheric wind stress, ocean upflow and halothermal circulation. For example, from the mid-latitudes to the polar region, the thermocline floor is oblique upward, similar to the fronts in the atmosphere, which are also tilted mainly by the rotation of the Earth. For another example, the thermocline bottom boundary in the tropics is shallow in the east and deep in the west, which is mainly due to the accumulation of warm sea water in the west by the easterly trade winds.

Because the ocean needs this to maintain the stability of the ocean.

Because creatures need this, the sea has its own adaptability.

Let's take the example of low latitudes.

Although the seasons change, the temperature of the thermocline does not change much, and it is located below the mixed layer. The heat budget given to seawater by solar radiation, etc., is not enough to cause large changes in the temperature of seawater in the thermocline, so the concept of a permanent thermocline is born.

PS: There are also permanent salinity clines and density clines at low latitudes, if you are interested, you can learn about them).

Because of the laws of nature, the laws do not change because of some uncertain factors.

Mainly because of the laws of nature.

Because the thermocline is the result of geological evolution.

This is a phenomenon that arises from the changes in the ecological environment.

It is mainly environmental change plus natural evolutionary causes.

This is the power of nature, science cannot explain it for the time being.

Because that's what the geological formations are.

Because that's how nature evolves.