el niño. how do ocean currents affect weather and climate? oceans store and transport heat. –...

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El Niño

How do ocean currents affect weather and climate?

• Oceans store and transport heat. – High heat capacity– Stores and transports energy from the sun

• Oceans store liquid water and pump vapor into the air – Key link in the global water and energy cycle.

How do ocean currents affect weather and climate?

• Amount of CO2 that the oceans can hold is inversely proportional to temperature– Colder water holds more CO2 and warmer water holds less

• Major source of oxygen due to photosynthesis of microscopic plants in the ocean.

Feedback between Ocean Currents and Climate

• Since atmospheric winds produce currents, variations in climatological winds can affect ocean currents

Anchovies and Peru?

• Every few years a current of warm water reduced population of anchovies around Christmas– Drastic decline in

fishing industry– Disrupted food web

• Changes in weather– Intense rainfall

increased vegetation growth

– Referred to as “Years of Abundance”

El Niño Southern Oscillation

• Spanish for “The Child”• Periodic alternation between warm and cold

phases• Cause dramatic environmental changes– El Nino – warm phase– La Nino – cool phase

ENSO events

• El Niño warm phase about every 2 to 10 years• Highly irregular• Phases usually last 12 to 18 months

El Niño

• High pressure along coast of South America weakens– Weak pressure gradient

(High Low) causes southeast trade winds to diminish (sometimes reverse direction)

– Western-Pacific warm pool flows towards South America

El Niño

• High pressure along coast of South America weakens– Weak pressure gradient

(High Low) causes southeast trade winds to diminish (sometimes reverse direction)

– Western-Pacific warm pool flows towards South America

El Niño Consequences

• Lower biological productivity– Corals particularly sensitive to

warmer seawater

• Thermal expansion – Sea level rises as much as 20

cm

• Reduced upwelling– Difference between cold and

warm layers decreases

El Niño

Sea Surface Temperature Anomaly

El Nino

La Niña

• New term coined recently to refer to the opposite of an El Nino when the Equatorial Pacific is colder than normal

La Niña

• Increased pressure difference across equatorial Pacific

• Stronger trade winds• Stronger upwelling in

eastern Pacific• Shallower thermocline• Cooler than normal

seawater• Higher biological

productivity

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