<p>In practice in the ocean, density is <a href="https://www.sciencedirect.com/science/article/abs/pii/B9780750645522100034" rel="nofollow noreferrer">dominated by temperature, not salinity</a> because the range of salinity is relatively small compared to the range of temperature.</p>
<p>That wouldn't apply with the addition of fresh water or similar; as far as I can interpret those notes, it looks like that's why a large fresh water flux would shut down the circulation (density gradient large enough to outweigh temperature gradient).</p>
<blockquote>
<p>The sea surface thermal forcing, which acts in the direction of the present thermohaline circulation in the North Atlantic, is opposite to the haline forcing from the freshwater flux. [From <a href="https://journals.ametsoc.org/view/journals/phoc/29/12/1520-0485_1999_029_3101_tsotci_2.0.co_2.xml" rel="nofollow noreferrer">this</a> Introduction section.]</p>
</blockquote>

CC BY-SA 4.0
2024-03-16T21:25:09.053Z
2024-03-16T21:25:09.053Z
damp_civil
<p>I am looking at <a href="https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Thermohaline-circulation/2-THC-Stommel-model-notes.pdf" rel="nofollow noreferrer">Stommel's Two-Box model of ocean circulation</a>.</p>
<p>I get that deep water formation occurs in the polar regions due to cooling of the water and sinking to the bottom. However, just looking at the box model, it looks like the equatorial regions should actually be more dense since salinity has a stronger effect on the density of the water?</p>
<p>I am trying to come up with an intuitive explanation of the two-box model, but it isn't making sense with salinity (only temperature). I want a way to explain this concept to anyone, but, right now, explaining the impact of salinity in polar vs equatorial regions is throwing me off.</p>
<p>Thanks!</p>

<climate-models><ocean-currents>
If salinity affects density more than temperature, why is there a surface current in the N. Atlantic by equatorial regions where the water is saltier?
AAAA
# If salinity affects density more than temperature, why is there a surface current in the N. Atlantic by equatorial regions where the water is saltier?

(Asked by: username_0 on 2024-03-15)

I am looking at [Stommel's Two-Box model of ocean circulation](https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Thermohaline-circulation/2-THC-Stommel-model-notes.pdf).

I get that deep water formation occurs in the polar regions due to cooling of the water and sinking to the bottom. However, just looking at the box model, it looks like the equatorial regions should actually be more dense since salinity has a stronger effect on the density of the water?

I am trying to come up with an intuitive explanation of the two-box model, but it isn't making sense with salinity (only temperature). I want a way to explain this concept to anyone, but, right now, explaining the impact of salinity in polar vs equatorial regions is throwing me off.

Thanks!

**Tags:** climate-models, ocean-currents


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## 1 answers

### Answer by username_1 on 2024-03-16. Score: 2 | Accepted answer

In practice in the ocean, density is [dominated by temperature, not salinity](https://www.sciencedirect.com/science/article/abs/pii/B9780750645522100034) because the range of salinity is relatively small compared to the range of temperature.

That wouldn't apply with the addition of fresh water or similar; as far as I can interpret those notes, it looks like that's why a large fresh water flux would shut down the circulation (density gradient large enough to outweigh temperature gradient).

> The sea surface thermal forcing, which acts in the direction of the present thermohaline circulation in the North Atlantic, is opposite to the haline forcing from the freshwater flux. [From [this](https://journals.ametsoc.org/view/journals/phoc/29/12/1520-0485_1999_029_3101_tsotci_2.0.co_2.xml) Introduction section.]


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