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, Annemiek”On 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/upwelling-and-downwelling.htm 7. http://www.nationsencyclopedia.com/Africa/Morocco-FISHING.html