upwelling

what happens as distance from equator increase

progressively more mature communities

Antarctic Divergence

1. 2 major wind-driven currents: a. East Wind Drift travels anti-clockwise around Antarctica b. West Wind Drift travels clockwise around Antarctica 2. both currents diverted to left due to Coriolis Force (as in Southern Hemisphere) 3. results in divergence of the currents and upwelling of nutrient-rich water

productivity of southern ocean: summer

no light limitation and huge peak in production

where are major upwelling regions

1. some coastal areas 2. the Equator and 3. the Southern Ocean

causes of equatorial upwelling

1. westward current called South Equatorial Current 2. Coriolis Force causes current to be deflected to right in northern hemisphere and to left in southern hemisphere 3. divergence of water occurs on Equator, with replacement of water by upwelling

why does large scale upwelling occur

1. wind- driven currents 2. the Coriolis Force 3. the replacement of displaced water by nutrient-rich deep water

the antarctic divergence

2 major wind-driven currents: East Wind Drift travels anti-clockwise around Antarctica West Wind Drift travels clockwise around Antarctica both currents diverted to left due to Coriolis Force (as in Southern Hemisphere) results in divergence of the currents and upwelling of nutrient-rich water

how many areas of coastal upwelling are there

5 major regions (with 4 on western coasts) but lots of other smaller regions do exist haha

coastal upwelling

5 major regions, w ith 4 on w estern coasts numerous, smaller coastal upwelling regions also exist

what are biological consequences of coastal upwelling

Very high production e.g. annual production of: 26 m illion tons of sardines in West African system s >12 m illion tons of anchovies off Peru >5 million tons of anchovy & hake off California total of more than half of world's fish catch from coastal upwelling regions!

upwelling

any upwards movement of water most significant upwelling events are generated by wind-induced stress at the sea surface often carries nutrient-laden water to surface where it enhances primary production

how does upwelling enhance primary production

by carrying nutrient loaded water to surface

what is the displaced water replaced by

cold nutrient rich water at the coast

what happens then

current travels at right angels to the coast and then moves offshore

where is the highest productivity

east

what are biological consequences of equatorial upwelling

high primary production close to Equator progressively more mature communities as distance from Equator increases highest productivity in east

productivity of southern ocean: winter

ice causes light limitation and low production

productivity in southern ocean

in winter, ice causes light limitation and low production in summer, no light limitation and huge peak in production 100 x more productive than Arctic waters - why?

summary of upwelling

large-scale upwelling occurs as a result of wind- driven currents, the Coriolis Force and the replacement of displaced water by nutrient-rich deep water major upwelling regions include some coastal areas, the Equator and the Southern Ocean all of these regions are characterised by high levels of primary production and are among the most productive regions in the oceans

Pulses of Upwelled Water across Continental She

low production during cold, upwelling periods high production during warm, stratified periods

Case example: Canary Current System, Northwest Africa

strong wind increases rate of equatorward current (>30 cm s-1) generates a 2-layer circulation system with: a) off-shore movement at surface b) on-shore movement at depth circulation causes upwelling of cold, nutrient-rich water close to shore and its subsequent movement away from coast

east wind drift

travels anti-clockwise around Antarctica

west wind drift

travels clockwise around Antarctica

what direction does current go in southern hemisphere

turns left

what direction does current go in northern hemisphere

turns right

what is solution with coastal upwelling

upwelling followed by periods of calm & stratification promote primary production

what is problem with coastal upwelling

upwelling provides nutrients, especially nitrate & ammonia, but mixing carries phytoplankton out of euphotic zone

How does upwelling stimulate production?

upwelling provides nutrients, especially nitrate & ammonia, but mixing carries phytoplankton out of euphotic zone Solution upwelling followed by periods of calm & stratification promote primary production NB: gentler, constant Peruvian System is an exception

what causes equatorial upwelling

westward current called the South Equatorial Current (5oS to 5oN) Coriolis Force causes current to be deflected to right in northern hemisphere and to left in southern hemisphere divergence of water occurs on Equator, with replacement of water by upwelling

causes of coastal upwelling

wind drives surface current in same direction

what causes coastal upwelling

wind drives surface current in same direction current turns right in northern hemisphere/left in southern hemisphere due to Coriolis Force current eventually travels at right angles to coast and moves offshore displaced water replaced by cold, nutrient-rich water at coast (i.e. coastal upwelling)

what are most significant upwelling events caused by

wind induced stress at sea surface