Class #16 Monday, October 4, 2010 Class #16: Monday, October 4 Chapter 8 Oceanography and El Niño/La Niña/ENSO 1

Class #16 Monday, October 4, Sea Surface Temperatures Are highest in the tropics, lowest at the poles. In middle latitudes and subtropics, are higher on east coasts than west coasts. In polar regions, lowest temperatures on east coasts. In tropical regions, highest temperatures on west coasts. Are highest in the equatorial western Pacific in the “warm pool” and the Indian Ocean. Correspond to warm and cold surface ocean currents.

Class #16 Monday, October 4, Major Ocean Currents

Fig. 8-7, p. 214

Fig. 8-8, p. 215

Class #16 Monday, October 4, Surface pressure, surface wind, and ocean currents The subtropical highs are persistent enough to create persistent anti-cyclonic wind flow. These winds create gyres of anti-cyclonic ocean surface currents. Ocean currents are bounded by land.

Class #16 Monday, October 4, Wind and ocean current direction Friction between the air and the sea surface forces the water to move. The Coriolis force turns the water to the right (NH) or left (SH). Moving water influences the layer of water beneath. The entire pattern is called the Ekman spiral. On average, water moves to right (NH) or left (SH) in Ekman transport.

Class #16 Monday, October 4, Cold currents, west coast, and upwelling Ekman transport moves water away from the shore, but that water must be replaced. Replacement water rises from below the thermocline. Mixing and cold water brings nutrients close to the surface and favors sea life.

Class #16 Monday, October 4, El Niño Named “The (boy) child” for the season of most common occurrence. Is a common but short-lived feature, but occasional episodes last for months or a year or more. The episodes are what we call El Niño today. El Niño is a phenomenon that affects the entire Pacific Ocean and weather around the globe.

Class #16 Monday, October 4, Characteristics of El Niño Abnormal warming of the waters off Ecuador and Peru. Upwelling ceases Warm waters come from the western Pacific Trade winds weaken

Class #16 Monday, October 4, La Niña Generally, opposite conditions to El Niño Also described as an enhancement of normal conditions Abnormal cooling of ocean waters in the eastern Pacific Upwelling is enhanced Trade winds are stronger

How to get the latest information about El Niño Google on “ENSO diagnostic discussion” Choose the first entry, the National Climate Prediction Center Look at the latest discussion and the weekly update ENSO is “El Niño Southern Oscillation” Class #16 Monday, October 4,

Current phase of ENSO: La Niña Class #16 Monday, October 4,

Watching the change from El Niño to La Niña Class #16 Monday, October 4,

The heat content of the upper ocean changing with La Niña Class #16 Monday, October 4,

Temperature anomalies extend below the surface Class #16 Monday, October 4,

Outgoing longwave radiation is positive for clear skies Class #16 Monday, October 4,

La Niña is forecast to continue through the winter of Class #16 Monday, October 4,

Class #16 Monday, October 4, Sea level/Eastern Pacific rises in El Niño, sinks in La Niña

Class #16 Monday, October 4, El Niño (red) and La Niña (blue) have irregular cycles of 2-7 years.

Class #16 Monday, October 4, ENSO is the acronym for El Niño Southern Oscillation

Class #16 Monday, October 4,

Class #16 Monday, October 4,

Class #16 Monday, October 4,

Class #16 Monday, October 4,

Class #16 Monday, October 4,

Class #16 Monday, October 4,

Class #16 Monday, October 4, North Atlantic Oscillation (NAO), positive phase, period ~ 10 years