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 CO 2 that the oceans can hold is inversely proportional to temperature – Colder water holds more CO 2 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