El Niño. How do ocean currents affect weather and climate? Oceans store and transport heat. –...
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Transcript of El Niño. How do ocean currents affect weather and climate? Oceans store and transport heat. –...
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
