if I place both waters into a bucket from where the two oceans meet but don’t mix, why do they mix just fine in the bucket?
Why do you say they don’t mix where they meet?
Temperature plus salinity determine density and dissimilar densities will remain distinct in convective mixing until equilibrium is reached.
This is why there are rivers in the ocean, like the gulf stream. You can actually see the height difference sometimes…
The idea of “two oceans meet but don’t mix” is more or less a myth. Most of the pictures of this you see on the Internet are at rivermouths or headlands, where a sharp contrast between water types is visible … but it mixes away pretty quickly.
Tom Scott did a video on this recently.
I don’t understand the question. Can you rephrase it?