<p>Strong upwelling-favorable winds (like the ones described) cause coastal upwelling in the following manner: </p>

<ul>
<li>Winds in these systems flow parallel to the coast (with the coast to the left in the northern hemisphere or to the right in the southern hemisphere) and generate upwelling dynamics. </li>
<li>Surface <a href="https://en.wikipedia.org/wiki/Ekman_transport" rel="nofollow noreferrer">Ekman balance</a> is setup (in deep enough waters) with water transport being to the right (left) of the wind in the northern (southern) hemisphere. The result is a deficit along the coast that requires a compensating flow in the deeper part of the water column bringing usually colder waters to the surface.</li>
</ul>

<p><a href="https://i.sstatic.net/eihoE.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/eihoE.gif" alt="upwelling animation"></a> Source <a href="https://commons.wikimedia.org/wiki/File:Upwelling_animated.gif" rel="nofollow noreferrer">Commons Wikipedia</a>.</p>

<ul>
<li>The resulting density (mostly controlled by temperature in these systems, but sometimes affected by salinity in areas with river influences) shows a strong horizontal gradient. A strong horizontal gradient in density is the definition of strong baroclinicity. That strong gradient can even be visible in a temperature front when the thermocline reaches the surface (SST image below). </li>
<li>Additionally, the density gradient can establish a <a href="https://en.wikipedia.org/wiki/Thermal_wind" rel="nofollow noreferrer">thermal wind</a> balance that results in a coastal upwelling current jet flowing in the same direction of the wind. The horizontal gradient in density is proportional to the vertical gradient in velocity
<span class="math-container">$\mathrm{{\delta\rho\over\delta x} \propto {\delta v\over\delta z}}$</span> . As velocity is zero at the bottom, this results in a strong velocity near the surface. This is what we understand as "intensifying the baroclinicity in the upper layer".</li>
</ul>

<p><a href="https://i.sstatic.net/Ave5l.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Ave5l.gif" alt="SST upwelling"></a> Source: <a href="https://airsea-www.jpl.nasa.gov/cos/theory/upwelling_dynamics.html" rel="nofollow noreferrer">Satellite image of SST showing multiple upwelling centers and cold filaments off central California</a> (Courtesy of E. Armstrong).</p>

CC BY-SA 4.0
2019-02-12T15:13:58.097Z
2019-02-12T15:13:58.097Z
arkaia
<p>Below is an excerpt from <em>The Biology of the Indian Ocean</em>,  Bernt Zeitzschel, Sebastian A. Gerlach</p>

<blockquote>
  <p>The more vigorous atmospheric and oceanic circulation during the SW
  monsoon causes not only the development of a strong western boundary
  current, the Somali Current, but also intense upwelling in several
  places. The circulation appears to penetrate deeper, affecting the
  movements of water masses below the thermocline. The formation of the
  Somali Current as a strong western boundary current of the monsoon
  gyre causes a strong baroclinic adjustment of the structure along the
  coast of Somalia. This baroclinic structure is noticeable as deep as
  1000 m, but is especially pronounced in the upper 400 m. <strong>The strong
  winds parallel to the coast intensify the baroclinicity</strong> in the upper
  layer and cause, in addition, strong upwelling along the coast.</p>
</blockquote>

<p>Through what mechanism do strong winds cause intensification of baroclinicity in the ocean?</p>

<atmosphere><oceanography><wind>
How to strong winds cause baroclinic intensification in the upper ocean?
Reqbisha
# How to strong winds cause baroclinic intensification in the upper ocean?

(Asked by: username_0 on 2019-02-12)

Below is an excerpt from *The Biology of the Indian Ocean*, Bernt Zeitzschel, Sebastian A. Gerlach

> The more vigorous atmospheric and oceanic circulation during the SW
> monsoon causes not only the development of a strong western boundary
> current, the Somali Current, but also intense upwelling in several
> places. The circulation appears to penetrate deeper, affecting the
> movements of water masses below the thermocline. The formation of the
> Somali Current as a strong western boundary current of the monsoon
> gyre causes a strong baroclinic adjustment of the structure along the
> coast of Somalia. This baroclinic structure is noticeable as deep as
> 1000 m, but is especially pronounced in the upper 400 m. **The strong
> winds parallel to the coast intensify the baroclinicity** in the upper
> layer and cause, in addition, strong upwelling along the coast.

Through what mechanism do strong winds cause intensification of baroclinicity in the ocean?

**Tags:** atmosphere, oceanography, wind


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## 1 answers

### Answer by username_1 on 2019-02-12. Score: 2 | Accepted answer

Strong upwelling-favorable winds (like the ones described) cause coastal upwelling in the following manner:

* Winds in these systems flow parallel to the coast (with the coast to the left in the northern hemisphere or to the right in the southern hemisphere) and generate upwelling dynamics.
* Surface [Ekman balance](https://en.wikipedia.org/wiki/Ekman_transport) is setup (in deep enough waters) with water transport being to the right (left) of the wind in the northern (southern) hemisphere. The result is a deficit along the coast that requires a compensating flow in the deeper part of the water column bringing usually colder waters to the surface.

[![upwelling animation](https://i.sstatic.net/eihoE.gif)](https://i.sstatic.net/eihoE.gif) Source [Commons Wikipedia](https://commons.wikimedia.org/wiki/File:Upwelling_animated.gif).

* The resulting density (mostly controlled by temperature in these systems, but sometimes affected by salinity in areas with river influences) shows a strong horizontal gradient. A strong horizontal gradient in density is the definition of strong baroclinicity. That strong gradient can even be visible in a temperature front when the thermocline reaches the surface (SST image below).
* Additionally, the density gradient can establish a [thermal wind](https://en.wikipedia.org/wiki/Thermal_wind) balance that results in a coastal upwelling current jet flowing in the same direction of the wind. The horizontal gradient in density is proportional to the vertical gradient in velocity
  $\mathrm{{\delta\rho\over\delta x} \propto {\delta v\over\delta z}}$ . As velocity is zero at the bottom, this results in a strong velocity near the surface. This is what we understand as "intensifying the baroclinicity in the upper layer".

[![SST upwelling](https://i.sstatic.net/Ave5l.gif)](https://i.sstatic.net/Ave5l.gif) Source: [Satellite image of SST showing multiple upwelling centers and cold filaments off central California](https://airsea-www.jpl.nasa.gov/cos/theory/upwelling_dynamics.html) (Courtesy of E. Armstrong).


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