Please be ready for today by: 1. HW out for a stamp 2. Paper and pencil/pen for notes 3. Be ready to discuss what you know about El Nino after you view the video clip
What is El Nino?
El Nino Basics El Nino- Occurs in tropical waters (Equatorial Pacific) El Nino means The Baby (not necessarily the Nino, but close) because it usually happens around Christmas (connected to the baby Jesus)
First, a review of Solar Intensity and Latitude Low latitudes (near the equator) sun s rays are nearly vertical. High latitudes (near the poles) sun s rays are much less intense because the sun remains close to the horizon From http://capone.mtsu.edu/cdharris/geol100/weather/wthr-sum.htm
Equal amounts of sunlight are spread over a greater area in polar latitudes than in temperate or tropical latitudes. Tropics temperate polar From http://capone.mtsu.edu/cdharris/geol100/weather/wthr-sum.htm
The take-home message Tropical latitudes are the warmest (duh...) Air rises (Low Pressure) This causes convection cells (Hadley Cells) that constantly move air throughout the atmosphere Winds at the surface balance the low and high pressure http://minerva.union.edu/failinge/earths_convection_cells.html
Winds of the World Coriolis Effect also moves air masses Clockwise in the N Hemisphere (and CCW in the S Hem.) Winds move generally Westward off of South America s W. Coast Now back to El Nino...
Normal conditions in Pacific These surface winds move warmer surface water to the west Causes more moisture in form of rainfall in western Pacific
Normal conditions in Pacific (cont.) Movement of warm water into western Pacific forces cold deep water towards the eastern Pacific Causes area of upwelling on South American coast. Water is cold and nutrient-rich; supports strong fishing industry by providing nutrients for the basis of food chains
What do normal Pacific conditions look like?
El Nino Trade winds that move warm water to western Pacific lessen, allowing warm water to move towards eastern Pacific
Effects of El Nino Coastal upwelling halts in eastern Pacific ocean More rainfall with movement of warm water mass to eastern Pacific Droughts in western Pacific What other effects can you think of with el Nino?
La Nina Also known as the anti-el Nino or El Viejo Cold phase of the climate pattern Higher pressure and trade winds increase towards the western Pacific Causes more upwelling in eastern Pacific and more rain in western
Visual comparison between El Nino and La Nina Animation showing ENSO
Checkpoint: Describe the events that cause El Nino conditions and its effects on ocean circulation. Describe the effect of an El Nino year on: The climate of the western coast of South America The climate of Indonesia and Australia What about a La Nina Year?
Current Conditions
SST Anomalies for last winter: November to February of 2013-2014
SST Anomalies for This winter: November to February of 2014-2015
Change our focus from the Pacific to the Atlantic
Major Surface Currents
Ocean water flows horizontally in currents Currents = vast riverlike flows in the oceans Driven by density differences, heating and cooling, gravity, and wind Influence global climate and El Niño and La Niña Transport heat, nutrients, pollution, the larvae of many marine species, and people Some currents such as the Gulf Stream are rapid and powerful The warm water moderates Europe s climate
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Currents affect climate Horizontal and vertical movement of oceans affects global and regional climates The Effect of the Gulf Stream on Northern European Climate Thermohaline circulation = a worldwide current system Warmer, fresher water moves along the surface Cooler, saltier, denser water moves beneath the surface North Atlantic Deep Water (NADW) = one part of the thermohaline conveyor belt Water in the Gulf Stream flows to Europe Released heat keeps Europe warmer that it would be Sinking cooler water creates a region of downwelling
Thermohaline Circulation
What would happen if this stopped? Shutting down of the THC
The North Atlantic Deep Water Interrupting the thermohaline circulation could trigger rapid climate change Melting ice from Greenland will run into the North Atlantic Making surface waters even less dense Stopping NADW formation and shutting down the northward flow of warm water Europe would rapidly cool This circulation is already slowing But Greenland may not have enough runoff to stop it