<p>I think you are confusing eddy diffusivity with molecular diffusivity. Whereas the latter increases with temperature, for the former there is no such relationship. Eddy diffusivity describes momentum transport due to eddies. The strength of the eddy diffusivity increases with decreasing buoyancy frequency, which is the case, when moving from the bottom of the mixed layer further downwards in the ocean. </p>

CC BY-SA 4.0
2020-04-01T21:19:50.153Z
2020-04-01T21:19:50.153Z
Basileios
<p>In Talley et al.'s <a href="https://www.sciencedirect.com/book/9780750645522/descriptive-physical-oceanography" rel="nofollow noreferrer">Descriptive Physical Oceanography</a>, figure S7.4, it seems that vertical Eddy diffusivity increases with depth between 0 and 30 degrees latitude. Why is this? I thought that diffusivity increases with increasing temperature, but here the opposite seems to be true.</p>

<p><a href="https://i.sstatic.net/DcEXC.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/DcEXC.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2020-04-16T23:21:01.103Z
To add to @Basileios great answer. Think about what is the effect of stratification on eddy diffusivity and where stratification is strongest in the water column?
Isopycnal Oscillation
<oceanography>
Why does vertical diffusivity increase with depth in the ocean?
Auguste Baudin
# Why does vertical diffusivity increase with depth in the ocean?

(Asked by: username_0 on 2020-02-20)

In Talley et al.'s [Descriptive Physical Oceanography](https://www.sciencedirect.com/book/9780750645522/descriptive-physical-oceanography), figure S7.4, it seems that vertical Eddy diffusivity increases with depth between 0 and 30 degrees latitude. Why is this? I thought that diffusivity increases with increasing temperature, but here the opposite seems to be true.

[![enter image description here](https://i.sstatic.net/DcEXC.png)](https://i.sstatic.net/DcEXC.png)

**Tags:** oceanography

> **Comments:**
> **username_1**: To add to @username_2 great answer. Think about what is the effect of stratification on eddy diffusivity and where stratification is strongest in the water column?  

---

## 1 answers

### Answer by username_2 on 2020-04-01. Score: 1

I think you are confusing eddy diffusivity with molecular diffusivity. Whereas the latter increases with temperature, for the former there is no such relationship. Eddy diffusivity describes momentum transport due to eddies. The strength of the eddy diffusivity increases with decreasing buoyancy frequency, which is the case, when moving from the bottom of the mixed layer further downwards in the ocean.


---

