How to calculate a integral for a 4D array?

I am trying to calculate the depth integrated freshwater content. My dataset (Sal) is 1442 (lon) x 233 (lat) x 65 (depth) x 84 (time). I am trying to calculate the integral from z1 to z2 of [(34.8 - Sal(z))/34.8] dz. z1 is depth = 0, Sal(z) is the salinity at depth z, and z2 is depth level where Sal(z) = 34.8.

[Steven Lord]

Moved from R.N.'s flag:

My question was unclear and I did not receive the help I was looking for. I figured out the answer to my question on my own.

Answer 1

[Andreas Bernatzky]

Hey R.N. I think it makes more sense to make a simple cubic integral and show its value along the time variable?