Equatorial Upwelling

1
Equatorial Upwelling

• The ocean around the equator receives the most
  sunlight. However, the surface layer of the ocean
  around the equator shows up as a region
  relatively cooler than surface layers of the
  surrounding oceanic regions.
• Around the equator oceanic region there is such a
  concentration of biomass that it can be seen from
  space.
• What can explain these observations?
• !Equatorial Upwelling!

2
The Physics of Equatorial Upwelling

• On the earth there are trade winds that blow in
  towards the equator from the northeast starting
  at 30 N , and there are trade winds which blow
  towards the equator from the southeast starting
  at 30 S.
• When these winds hit the surface of the ocean
  they create an overall Ekman transport of water
  perpendicular to the line of their impact. These
  two trends meet at the equator, in a region
  called the ITCZ (Inter-tropical convergence zone)
  Southwards is the direction of transport
  perpendicular to the South East trade wind, and
  northwards is the direction of transport
  perpendicular to the North West trade wind.
• Therefore a continuous hole that must be filled
  is created in the equatorial regions. The hole is
  filled from below by an upwelling of cool,
  nutrient rich water from the bottom of the ocean.
  This overall effect is called equatorial
  upwelling and it is the reason for the cooling
  observed at the equator.

3
The Chemical Consequences of Equatorial Upwelling

• This transport of water up from the bottom of
  ocean brings with it nutrients which sustain life
  which have sunk down into the ocean.
• Important nutrients brought up and recycled by
  this continuous process of equatorial upwelling
  include carbon, nitrogen, and phosphorus.
• Therefore the surface layer of the equatorial
  oceanic region of the world are especially rich
  in the nutrients utilized by life, and this
  region can support a greater amount of biomass.
  The increase in ability to support life is so
  significant the biological layer created by
  equatorial upwelling can even be seen from space.
  

4
The Biological Consquence of Equatorial Upwelling

• The increase in nutrient availability from the
  effect of equatorial upwelling leads an increased
  diversity of lifeforms, and an increase in the
  total biomass of lifeforms at the equator. This
  increase in biomass in equatorial regions of the
  ocean can even be seen from space.
• Dinoflagellates and coccoid species such as
  Thoracosphaera heimii may be found in regions
  with equatorial upwelling.
• Examples of larger organisms supported by
  equatorial upwelling include sardina Pilchardus.
  Equatorial upwelling allows nations such as
  Morocco to have major worldwide fishing
  industries. Morocco accounts for 86 of the
  worlds sardina Pilchardus production and much of
  the tonnage brought in by Morocco comes from its
  western costal regions.

References 1. Vink, AnnemiekOn the response of
calcareous dinoflagellates to oligotropy and
stratification of the upper water column in the
Equatorial Atlantic 2. Bush, Andrew B.G. The
role of ocean-atmosphere interactions in the
tropical cooling during the last glacial
maximum 3. Benitez-Nelson Claudia R. Inorganic
and organic sinking particulate phosphorus fluxes
across the oxic/anoxic water column of Cariaco
Basin, Venezuela 4. Taoufik, Radi
Dinoflagellate Cysts as indicators of water
quality in British Columbia estuarine
environments 5. Larson, Gary A study on Crater
Lake 6. http//oceanmotion.org/html/background/up
welling-and-downwelling.htm 7. http//www.nationse
ncyclopedia.com/Africa/Morocco-FISHING.html