<p>So because of Ekman transport, the middle of a gyre is slightly elevated. As a result water starts flowing down the pressure gradient. As it does so it is deflected by the coriolis force until the pressure gradient force and the coriolis effect balance each other out: this is called the geostrophic current.</p>
<p>I'm reading in the book &quot;The Earth System&quot; by Kump et al. (2010) on p. 88 that this geostrophic current spirals <em>inwards</em>. To be precise, Kump et al. say:</p>
<blockquote>
<p>&quot;In practice, the flow is a little less than 90° to the slope, so in fact the water tends to spiral inward as it moves around the gyre and the convergence in the gyre results in downwelling.&quot;</p>
</blockquote>
<p>My question: why does the geostrophic current spiral inwards?</p>
<p>I know that geostrophic wind, when it experiences friction at the surface, also does not perfectly follow the isobars, but in this case the result is an effective flow <em>in the the same direction as the pressure gradient force</em>, not in the opposite direction, as is suggested here.</p>

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2023-09-29T11:00:16.043Z
Yes good point. But I just checked and the third edition says the same thing. Do you have other sources stating the opposite? 

I do believe that there is downwelling in the middle of the gyre, but I don't understand how this could be the result of an inward spiraling geostrophic current.
shamiv
<ocean-currents>
Why does the geostrophic current spiraling around the slightly elevated middle of an oceanic gyre spiral inward?
shamiv
# Why does the geostrophic current spiraling around the slightly elevated middle of an oceanic gyre spiral inward?

(Asked by: username_0 on 2023-09-28)

So because of Ekman transport, the middle of a gyre is slightly elevated. As a result water starts flowing down the pressure gradient. As it does so it is deflected by the coriolis force until the pressure gradient force and the coriolis effect balance each other out: this is called the geostrophic current.

I'm reading in the book "The Earth System" by Kump et al. (2010) on p. 88 that this geostrophic current spirals *inwards*. To be precise, Kump et al. say:

> "In practice, the flow is a little less than 90° to the slope, so in fact the water tends to spiral inward as it moves around the gyre and the convergence in the gyre results in downwelling."

My question: why does the geostrophic current spiral inwards?

I know that geostrophic wind, when it experiences friction at the surface, also does not perfectly follow the isobars, but in this case the result is an effective flow *in the the same direction as the pressure gradient force*, not in the opposite direction, as is suggested here.

**Tags:** ocean-currents

> **Comments:**
> **username_0**: Yes good point. But I just checked and the third edition says the same thing. Do you have other sources stating the opposite?   I do believe that there is downwelling in the middle of the gyre, but I don't understand how this could be the result of an inward spiraling geostrophic current.  

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