Upwelling in the World Ocean
Mechanisms that create ocean upwelling
Types of upwelling
Identifying upwelling on satellite-derived
Ecological and economic effects of
Mechanisms that create
Upwelling refers to deep water
that is brought to the surface.
Areas of upwelling are created by surface winds
that pull water away from an area. This deficit of
water on the surface invites water to come up
from deeper regions.
To understand upwelling, you must be familiar with how
the Coriolis Force affects ocean surface currents. The
Coriolis Effect acts on moving water, because it is not
attached to the rotating Earth. As water flows over the
rotating earth, it appears to deflect to the right in the
Northern Hemisphere and the left in the Southern.
Due to friction between the layers of water in the ocean
and the Coriolis Effect, the net result of wind blowing
across the surface of the water is transportation of a
layer of water 90 degrees to the direction of the wind.
This is known as Ekman Transport.
Types of Upwelling
1. Equatorial Upwelling
Look at the equator in the
2. Coastal Upwelling
(follow the black arrows)
What’s the difference between
Peru(A) and Columbia (B)?
3. Seasonal upwelling
Onshore winds pile Offshore winds take
water up on shore, water away from
thus surface water will shore, thus water
be forced downward. from depth will
This is ‘downwelling’. upwell to the surface.
The Monsoonal wind shifts in
Oman create very different
April, 1999 August, 1999
Onshore winds: Downwelling Offshore winds: Upwelling
Identifying upwelling on
The deep water that surfaces in upwelling is
cold; by looking at Sea Surface Temperature
maps we can identify cool upwelled water
versus hotter surface water.
Upwelled water also contains nutrients
(nitrate, phosphate, silicate) and dissolved
gases (oxygen and carbon dioxide) that
are not utilized at depth because of a lack
Now on the surface, these nutrients and
gases help to fuel photosynthesis by
small algae called phytoplankton.
Phytoplankton photosynthesize using
specialized color pigments called chlorophyll.
Thus, “Ocean Color” maps are another way to
identify areas of upwelling. Where on this
ocean color map are high phytoplankton
Ecological and Economic
effects of upwelling:
Upwelling leads to more phytoplankton
More phytoplankton leads to more fish
More fish lead to commercial fishing jobs
and to more seafood
Phytoplankton come in many shapes
and forms. Collectively they form the
base of oceanic food webs.
Without upwelling many of the
world’s fisheries would not thrive.
Some climatic events can reduce
El Nino ~
Along Peru’s coast, an El Nino event decreases
the coastal winds. Thus the upwelling from
below is slowed.
An El Nino condition results from weakened trade winds in the western Pacific
Ocean near Indonesia, allowing piled-up warm water to flow toward South America.
Even though upwelling areas
account for only 1% of the ocean
surface, they support 50% of the
Productivity (phytoplankton growth)
of an area is determined by the rate
and the duration of upwelling.
Rate of upwelling Duration of upwelling
determines determines the total
phytoplankton cell amount of
small vs. large few vs. many
Classification of upwelling systems in terms of
rate and duration:
Low Medium High
After Thurman, H.V. (1994)
•Moderate rates of upwelling for long
duration (8 months or longer) provide the
ultimate combination for a large fishery.
•With too low or too high a rate,
phytoplankton are small, so there is a
trophic level between the algae and the
fish….therefore the fish receive less
Upwelling and Fisheries
Using this series of Sea Surface Temperature Maps from 1999, can
you determine areas/times for possible fisheries?
(Hint: Look at Peru’s coast in January and April. Look at the northwestern tip of Africa in
July and October.)