<p>First, we might want to distinguish between the different <a href="https://en.wikipedia.org/wiki/Upwelling#Types" rel="nofollow noreferrer">types of upwelling</a>:</p>

<ul>
<li>Coastal upwelling: It is the best known form of upwelling. 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 <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. If the wind blows in the opposite direction, then <a href="https://en.wikipedia.org/wiki/Downwelling#Oceanic_downwelling" rel="nofollow noreferrer">downwelling</a> occurs.
The figure from the question refers to coastal upwelling (<a href="https://oceanservice.noaa.gov/education/kits/currents/03coastal4.html" rel="nofollow noreferrer">here</a> in its original website with explaining caption). There is definitely more coastal upwelling in the northern hemisphere because of the abundance of shorelines as a greater amount of landmass is present in that hemisphere. </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>Equatorial upwelling: Winds from the east blow and converge along the equator as part of the Intertropical Convergence Zone (<a href="https://en.wikipedia.org/wiki/Intertropical_Convergence_Zone" rel="nofollow noreferrer">ITCZ</a>). While the magnitude of the Coriolis acceleration is zero along the equator, Ekman transport takes place immediately north and south of the equator resulting in surface ocean divergence that requires a compensating flow of denser (nutrient-rich) water upwelled from below.</li>
</ul>

<p><a href="https://i.sstatic.net/gsSm6.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/gsSm6.gif" alt="Equatorial upwelling"></a> <a href="http://www-das.uwyo.edu/~geerts/cwx/notes/chap11/equat_upwel.html" rel="nofollow noreferrer">Source</a></p>

<ul>
<li>Southern Ocean upwelling: Strong westerly (eastward) winds dominate the atmospheric setting around Antarctica. The strong winds force the <a href="https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current" rel="nofollow noreferrer">Antarctic Circumpolar Current</a>, the strongest current in the ocean. The winds also result in an Ekman balance with northward flow in the upper part of the water column. To compensate that flow, some water flows up from greater depths. The magnitude of the Southern Ocean upwelling is still being studied, but some observations and models propose that it represents the main way for dense water from deeper areas to be reintroduced in the surface circulation. If that were the case, then it represents the largest upwelling system in the world. An alternative explanation proposes <a href="https://en.wikipedia.org/wiki/Eddy_(fluid_dynamics)#Mesoscale_ocean_eddies" rel="nofollow noreferrer">oceanic eddies</a> as the main mechanism for dense water to reconnect with the surface circulation. Additionally, there is coastal upwelling over the Antarctic continental shelf driven by local winds that brings relatively warmer waters to the shelf contributing to local/regional ice melting.
<a href="https://i.sstatic.net/8fqNQ.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8fqNQ.jpg" alt="southern ocean upwelling"></a> <a href="https://www.nap.edu/read/13169/chapter/1" rel="nofollow noreferrer">Source</a></li>
</ul>

<p>The question also mentions downwelling associated with dense water formation. Deep water forms at high latitudes (typically north and south of 60°) in both the southern and northern hemispheres. As mentioned in the question, ice contains almost no salt, so when ice forms, a salty, sub-zero brine is left behind and sinks. In the Antarctic, as the saltier water moves down, it mixes with slightly warmer intermediate water. The mixture becomes <a href="https://en.wikipedia.org/wiki/Antarctic_bottom_water#Formation_and_circulation" rel="nofollow noreferrer">Antarctic Bottom Water</a> (AABW), which flows northwards along the bottom in all the main oceans. In the Arctic, the northward flowing branch of the Gulf Stream (salty and warm) joins the subpolar gyre and enters the Labrador Sea where as it cools, it starts to sink. The eastern branch of the Gulf Stream begins to sink in the Nordic Seas. The resulting water masses combine to form the dense <a href="https://en.wikipedia.org/wiki/North_Atlantic_Deep_Water" rel="nofollow noreferrer">North Atlantic Deep Water</a> (NADW) that flows south at depth. Both the creation of AABW and NADW can be considered downwelling, as there is a net downward flow in the formation areas, but they are not related to wind-driven downwelling in the vicinity of coasts.</p>

CC BY-SA 3.0
2018-03-16T01:17:29.070Z
Thanks! So even though the Southern Ocean upwelling is considered the largest in the world, why is  the productivity of the North hemisphere subpolar water so much higher than the Southern subpolar waters ?
Sid Datta
CC BY-SA 3.0
2018-03-16T14:19:21.157Z
I think you have to distinguish between production and productivity. The production of the Southern Ocean might be much larger as the area where upwelling is occurring is much more extensive. The productivity (production per unit area) might be larger in the Arctic (beware of large seasonal and interannual variabilities, https://www.nasa.gov/centers/goddard/mov/97489main_image6-seawifs_npp_linear_sm.mov), because of the abundance of coastlines.
arkaia
CC BY-SA 3.0
2018-03-16T14:19:47.737Z
The large but relatively unproductive deeper part of the Antarctic Ocean represents about 90% of Southern Ocean production. Meanwhile, if you normalize by area, the productivity rates are smaller than in many continental shelves.
arkaia
CC BY-SA 3.0
2018-03-16T17:32:43.517Z
So what you're saying, if I'm interpreting right: in the Antarctic it's generally small upwelling speeds over a large area rather than rapid speeds in focused areas?
JeopardyTempest
CC BY-SA 3.0
2018-03-16T17:37:32.343Z
That is my point, but there is a lot of research on this matter. Ultimately, when there are no observations and a flux balance calculation was done, a large upwelling transport is needed to compensate the surface divergence. The issue that is being study is whether that flow is homogeneous or focused in specific regions where ocean eddies can enhance that flow.
arkaia
CC BY-SA 3.0
2018-03-16T21:34:10.647Z
Thanks, I guess taking wikipedia images at their face value has their consequence.
Sid Datta
CC BY-SA 3.0
2018-03-15T21:26:18.927Z
2018-03-15T21:26:18.927Z
arkaia
<p>Formation of ice and hence more dense saltwater sinking happens in both polar regions, creating downwellings. Meanwhile, only a few spots in Antarctica have upwellings</p>

<p>I refer to this image:
<a href="https://i.sstatic.net/ZSQOd.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ZSQOd.jpg" alt="Upwelling areas"></a>
<a href="https://en.wikipedia.org/wiki/Upwelling#/media/File:Upwelling_image1.jpg" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Upwelling#/media/File:Upwelling_image1.jpg</a></p>

CC BY-SA 3.0
2018-03-15T08:27:02.793Z
dense salt water sinking should imply downwelling right?
shamalaia
CC BY-SA 3.0
2018-03-15T09:11:02.293Z
the gulfstream flows north to the arctic and do sink there so to say there is upwelling in the arctic is wrong.
trond hansen
CC BY-SA 3.0
2018-03-15T09:19:39.370Z
https://en.wikipedia.org/wiki/Thermohaline_circulation#/media/File:Thermohaline_Circulation_2.png
trond hansen
CC BY-SA 3.0
2018-03-15T13:19:56.033Z
Upwelling happens in both polar regions along the continental shelf depending on wind direction and offshore of the shelf. The image is correct. What the other comments refer to is dense water formation in the downwelling regions along the continental shelf in both Arctic and Antarctic regions, but more predominant in the North.
arkaia
CC BY-SA 3.0
2018-03-15T15:12:16.003Z
@arkaia Good comment. But concerning your edit I feel you erased one of the questions there.
Camilo Rada
CC BY-SA 3.0
2018-03-15T18:38:02.063Z
@arkaia Can we say more upwellings happen in the north hemisphere simply because of the presence of more shorelines (Europe and America)?
Sid Datta
CC BY-SA 3.0
2018-03-15T20:06:05.587Z
@SidDatta, partly true. There is definitely more coastal upwelling in the northern hemisphere because of the abundance of shorelines. But, if we are talking about large-scale upwelling, then the Southern Ocean upwelling might represent the largest upwelling system in the world.
arkaia
CC BY-SA 3.0
2018-03-16T07:35:29.487Z
i think i misunderstand the question,for me upwelling is where cold water rises and gets heated but the area along shorelines where wind moves the water causes mixing of the water.
trond hansen
CC BY-SA 3.0
2018-03-16T14:23:01.353Z
The mixing of the water by wind will be restricted to the upper Ekman depth (10-50m depending on diffusivities). As Ekman transport directs water offshore under the right winds, then a return compensating flow from deeper areas is needed. That return flow is the upwelling.
arkaia
<ocean><ocean-currents><antarctic>
Why don't Antarctic waters have more upwellings, when Arctic waters are so rich in upwellings?
Sid Datta
# Why don't Antarctic waters have more upwellings, when Arctic waters are so rich in upwellings?

(Asked by: username_0 on 2018-03-15)

Formation of ice and hence more dense saltwater sinking happens in both polar regions, creating downwellings. Meanwhile, only a few spots in Antarctica have upwellings

I refer to this image:
[![Upwelling areas](https://i.sstatic.net/ZSQOd.jpg)](https://i.sstatic.net/ZSQOd.jpg)
<https://en.wikipedia.org/wiki/Upwelling#/media/File:Upwelling_image1.jpg>

**Tags:** ocean, ocean-currents, antarctic

> **Comments:**
> **username_1**: dense salt water sinking should imply downwelling right?  
> **username_2**: the gulfstream flows north to the arctic and do sink there so to say there is upwelling in the arctic is wrong.  
> **username_2**: https://en.wikipedia.org/wiki/Thermohaline_circulation#/media/File:Thermohaline_Circulation_2.png  
> **username_3**: Upwelling happens in both polar regions along the continental shelf depending on wind direction and offshore of the shelf. The image is correct. What the other comments refer to is dense water formation in the downwelling regions along the continental shelf in both Arctic and Antarctic regions, but more predominant in the North.  
> **username_4**: @username_3 Good comment. But concerning your edit I feel you erased one of the questions there.  
> **username_0**: @username_3 Can we say more upwellings happen in the north hemisphere simply because of the presence of more shorelines (Europe and America)?  
> **username_3**: @username_0, partly true. There is definitely more coastal upwelling in the northern hemisphere because of the abundance of shorelines. But, if we are talking about large-scale upwelling, then the Southern Ocean upwelling might represent the largest upwelling system in the world.  
> **username_2**: i think i misunderstand the question,for me upwelling is where cold water rises and gets heated but the area along shorelines where wind moves the water causes mixing of the water.  
> **username_3**: The mixing of the water by wind will be restricted to the upper Ekman depth (10-50m depending on diffusivities). As Ekman transport directs water offshore under the right winds, then a return compensating flow from deeper areas is needed. That return flow is the upwelling.  

---

## 1 answers

### Answer by username_3 on 2018-03-15. Score: 3 | Accepted answer

First, we might want to distinguish between the different [types of upwelling](https://en.wikipedia.org/wiki/Upwelling#Types):

* Coastal upwelling: It is the best known form of upwelling. 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. If the wind blows in the opposite direction, then [downwelling](https://en.wikipedia.org/wiki/Downwelling#Oceanic_downwelling) occurs.
  The figure from the question refers to coastal upwelling ([here](https://oceanservice.noaa.gov/education/kits/currents/03coastal4.html) in its original website with explaining caption). There is definitely more coastal upwelling in the northern hemisphere because of the abundance of shorelines as a greater amount of landmass is present in that hemisphere.

[![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).

* Equatorial upwelling: Winds from the east blow and converge along the equator as part of the Intertropical Convergence Zone ([ITCZ](https://en.wikipedia.org/wiki/Intertropical_Convergence_Zone)). While the magnitude of the Coriolis acceleration is zero along the equator, Ekman transport takes place immediately north and south of the equator resulting in surface ocean divergence that requires a compensating flow of denser (nutrient-rich) water upwelled from below.

[![Equatorial upwelling](https://i.sstatic.net/gsSm6.gif)](https://i.sstatic.net/gsSm6.gif) [Source](http://www-das.uwyo.edu/~geerts/cwx/notes/chap11/equat_upwel.html)

* Southern Ocean upwelling: Strong westerly (eastward) winds dominate the atmospheric setting around Antarctica. The strong winds force the [Antarctic Circumpolar Current](https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current), the strongest current in the ocean. The winds also result in an Ekman balance with northward flow in the upper part of the water column. To compensate that flow, some water flows up from greater depths. The magnitude of the Southern Ocean upwelling is still being studied, but some observations and models propose that it represents the main way for dense water from deeper areas to be reintroduced in the surface circulation. If that were the case, then it represents the largest upwelling system in the world. An alternative explanation proposes [oceanic eddies](https://en.wikipedia.org/wiki/Eddy_(fluid_dynamics)#Mesoscale_ocean_eddies) as the main mechanism for dense water to reconnect with the surface circulation. Additionally, there is coastal upwelling over the Antarctic continental shelf driven by local winds that brings relatively warmer waters to the shelf contributing to local/regional ice melting.
  [![southern ocean upwelling](https://i.sstatic.net/8fqNQ.jpg)](https://i.sstatic.net/8fqNQ.jpg) [Source](https://www.nap.edu/read/13169/chapter/1)

The question also mentions downwelling associated with dense water formation. Deep water forms at high latitudes (typically north and south of 60°) in both the southern and northern hemispheres. As mentioned in the question, ice contains almost no salt, so when ice forms, a salty, sub-zero brine is left behind and sinks. In the Antarctic, as the saltier water moves down, it mixes with slightly warmer intermediate water. The mixture becomes [Antarctic Bottom Water](https://en.wikipedia.org/wiki/Antarctic_bottom_water#Formation_and_circulation) (AABW), which flows northwards along the bottom in all the main oceans. In the Arctic, the northward flowing branch of the Gulf Stream (salty and warm) joins the subpolar gyre and enters the Labrador Sea where as it cools, it starts to sink. The eastern branch of the Gulf Stream begins to sink in the Nordic Seas. The resulting water masses combine to form the dense [North Atlantic Deep Water](https://en.wikipedia.org/wiki/North_Atlantic_Deep_Water) (NADW) that flows south at depth. Both the creation of AABW and NADW can be considered downwelling, as there is a net downward flow in the formation areas, but they are not related to wind-driven downwelling in the vicinity of coasts.

> **Comments:**
> **username_0**: Thanks! So even though the Southern Ocean upwelling is considered the largest in the world, why is  the productivity of the North hemisphere subpolar water so much higher than the Southern subpolar waters ?  
> **username_3**: I think you have to distinguish between production and productivity. The production of the Southern Ocean might be much larger as the area where upwelling is occurring is much more extensive. The productivity (production per unit area) might be larger in the Arctic (beware of large seasonal and interannual variabilities, https://www.nasa.gov/centers/goddard/mov/97489main_image6-seawifs_npp_linear_sm.mov), because of the abundance of coastlines.  
> **username_3**: The large but relatively unproductive deeper part of the Antarctic Ocean represents about 90% of Southern Ocean production. Meanwhile, if you normalize by area, the productivity rates are smaller than in many continental shelves.  
> **username_5**: So what you're saying, if I'm interpreting right: in the Antarctic it's generally small upwelling speeds over a large area rather than rapid speeds in focused areas?  
> **username_3**: That is my point, but there is a lot of research on this matter. Ultimately, when there are no observations and a flux balance calculation was done, a large upwelling transport is needed to compensate the surface divergence. The issue that is being study is whether that flow is homogeneous or focused in specific regions where ocean eddies can enhance that flow.  
> **username_0**: Thanks, I guess taking wikipedia images at their face value has their consequence.  

---

