Post on 06-Feb-2016
description
Oceans & El Nino
Ocean-atmosphere coupling matters
Key Points Climate & ocean-atmosphere coupling
– Seasonal heating stored in upper layers of ocean– Evaporation of water to atmosphere increases with
temperature The Ocean Circulation
El Niño, La Niña
Other Fluctuations
Evaporation
Increases with temperature
Schematic Layers in the Ocean
Temperature
3700 m
100 mMixed layer
Deep ocean
0 m
Horel and Geisler: Figure 4.5
Deep water is cold and dense Surface warmed by sunlight and mixed by wind
The Principal Links for Climate
Sea Surface Temperature 9/24/98
Winds
– Courtesy WGBH
Sea Surface Temperature From Geostationary Satellite January, 1999
Key Points Climate & ocean-atmosphere coupling
The Ocean Circulation– Ocean basins 4 - 5 km deep– Filled with cold dense water from polar regions– Warmed from above in tropics and mid latitudes– Surface layers mixed by wind and seasonal cooling– Deep ocean overturns slowly ( ~ 2000 yr)
El Niño, La Niña
Other Fluctuations
Schematic Ocean Circulation
Horel and Geisler: Figure 4.6
Ocean surface
Ocean bottomLow latitudes High latitudes
Mixed layer
Upwelling Downwelling
residence time 2000 years
Conveyor Belt A schematic view of the global ocean circulation
Horel & Geissler after Broecker
Key Points Climate & ocean-atmosphere coupling
The Ocean Circulation
El Niño, La Niña – Fluctuations every few years in equatorial Pacific– Feedback: ocean surface temperature ->atmospheric
convection -> winds ->ocean currents -> temperature– Causes droughts and floods world wide
Other Fluctuations
Equatorial Pacific Sea SurfaceTemperature
El Nino
Normal
La Nina
Dec 97
Dec 90
Dec 88 NOAA/PMEL
El Nino Years
El Nino or La Nina? El Nino:
– Eastern and Central Pacific WARM– Indonesian rain area moves EAST– Coastal Andes:
Ocean: NO UPWELLING Land: F LOODS
La Nina:– Eastern and Central Pacific COLD– Indonesian rain area NORMAL– Coastal Andes:
Ocean: UPWELLING Land: VERY DRY
The El Nino Feedback
Ocean-atmosphere coupling Slackening trade winds cause surge in
upper ocean water along equator Ocean temperature anomalies persist
for many months SST anomalies change atmospheric
circulation and trade winds
Ocean Atmosphere - Normal
– Courtesy NOOAA/PMEL
Ocean Atmosphere - El Nino
– Courtesy NOOAA/PMEL
Associations of El Nino - 1
Associations of El Nino - 2
Consequences Warm/cold winters Floods Droughts
Vegetation Stress
El Nino (top) La Nina (bottom)
A TAO Buoy
Pacific Marine Environmental Laboratory
Current Status 10/11/00 In between. Neither El Niño nor La Niña
TAO Array
Current Status 2/13/00 La Nina persists
National Oceanic and Atmospheric Administration
A historical perspective
Sea SurfaceTemp-erature
Strength of trade winds
PMEL
Key Points Climate & ocean-atmosphere coupling
The Ocean Circulation
El Niño, La Niña
Other Fluctuations– Pacific Decadal Oscillation
Salmon catches, Alaska - California
– North Atlantic Oscillation Rainfall in Sahel Drought in N.E. Brazil
Pacific Decadal Oscillation Warm Cool
Mantua et al
SelectedPacific
Salmon Catches
Mantua et al
Black Warm PDO
Grey Cool PDO
Key Points
Climate & ocean-atmosphere coupling
The Ocean Circulation
El Niño, La Niña
Other Fluctuations
Sources of Information Horel & Geisler Chapter 3, 4 http://www.pmel.noaa.gov/toga-tao/el-nino http://www.sacbee.com/news/projects/
gathering_storm/day1.html http://www.check6.com http://www.iphc.washington.edu:80/PAGES/
IPHC/Staff/hare/html/papers/pdo/PDO.html