The impact of El Nino and La Nina weather patterns on Canterbury ...
El nino and La nina
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El Nino La Nina
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Transcript of El nino and La nina
El Nino
La Nina
Normal Conditions
Sea Surface Temperature (SST)
Normal Conditions
Garrison 8-15b
Green = coldRed = warm
SeaSurface Temperature(SST)
“NORMAL” CONDITIONS
HOTPOOL
COLDTONGUE
NORMALUPWELLING
Normal Conditions
Garrison’s Oceanography text, 8-15a
Normal Conditions
Cold water
Warm water
Thermocline
SOUTHAMERICA
Warm waterspushed westward
AUSTRALIA
EQUATOR
Surface windsblow westward
Normal Trade Winds cause
Deep, cold &nutrient rich
waters
Causes cold
tongue toextend west
NORMAL CONDITIONSSUPPORT COASTAL
UPWELLING.
ONLY UPWELLING CANRETURN THE FERTILIZING
NUTRIENTS TO THE PHOTICZONE
PHOTIC ZONE
SUNLIGHT
NORMAL CONDITIONSSUPPORT COASTAL
UPWELLING.
El nino conditions
Normally, temperatures of surface waters in the western Pacific are 6 to 8 degrees Celsius (10 to 15 degrees Fahrenheit) warmer than in the east. But during an El Niño, the temperature differential reverses.
The nutrient-poor warm water forces the fish that normally thrive off the west coast of South America to go elsewhere to find food. Birds that would feed on the fish die off, and the local fishing economy suffers.
El Niño causes far-reaching weather events as well, including drought and heatwaves across Australia, torrential rainfall in Central and South America, and heavy winter snows and floods in the southern United States -- all of which affect water resources and food supply.
El Niño Conditions
Comparison
Normal El Nino
El Niño Conditions
Sea Surface Temperature
El Niño Conditions
From NOAA website (see KKC 15-13b)
El Nino: El Nino Development
El NINO
EL NINO CONDITIONS
HOTPOOL
SHIFTSEAST
NOCOLD
TONGUE
NOUPWELLING
El Niño Conditions
• Weakening of Walker • Decreased pressure gradient• Weaken Trade winds• Stronger Eq Counter Current• Migration of warm pool• Reduced upwelling (east)• Shallower thermocline (west)• Shift in rainfall to the east
El Niño Conditions
Cold water
Thermocline
Warm waterWarm water deepens offSouth America
SOUTHAMERICA
Warm waterflow stoppedor reversed
AUSTRALIA
EQUATOR
Drought inAustralia andSoutheast Asia
Winds weaken,causing updraftsand storms
EL NINO SUPRESSES COASTALUPWELLING, REDUCES NUTRIENTS& CAUSES SURFACE POPULATIONS
TO DISAPPEAR.
Comparison- SST Anomaly
Normal
El Nino
• Weakens Indian Monsoon. • Causes drought in central North America.
El Niño plays havoc with world weather
Fires in the Amazon
Worsening drought in Sahel
1983 El Niño causedsevere drought, heat waves and
Bushfires in Australia. Flames devour farmland in Victoria, Australia.
El Niño triggered prolonged drought of 1983 made fire a constant hazard. In 1983, winds whipped fires from Adelaide to Melbourne, destroying seven towns and several thousand homes.
EN
EN
Approximately 25% of the 23,000 pups born in June 1997 at San Miguel Island died.
El Niño
• During an El Niño year– normally strong trade winds weaken, and sometimes even
reverse direction– warm water of the western Pacific Ocean moves eastward,
keeping deep cold water from rising to the surface off the west coast of South America.
– Jet stream brings warm, moist air to the US– causes
• Storms in California• Heavier than normal precipitation in much of the US• Droughts in Africa and Australia• Monsoon rains in Indonesia
El Niño’s Effects
La Niña’s Effects
La Niña• During a La Niña year
– Trade winds increase in strength and blow even stronger than normal from east to west• water in the western Pacific Ocean becomes
warmer• water in the Eastern Pacific near the coast of South
America becomes colder• Warm ocean waters, clouds and moisture are
pushed away from North America– Causes:
• Hot, dry weather with droughts in the southern US• Cool weather and excess rainfall in the
northeastern US
El Niño / La Niña
• El Niño and La Niña change worldwide weather patterns in complex ways.
• Scientists do not yet understand what triggers these events.
• An El Niño or La Niña event lasts 1 to 2 years, and occurs every 3 to 6 years, but some events are mild while others are severe.
• The most severe recent El Niño events occurred in 1982-83 and 1998.
• An El Niño generally causes more disruption in global weather patterns than La Niña, but severe drought occurs in the southern U.S. during a La Niña.
El Niño and La Niña
SST = Sea Surface Temperature
LA N
INA
CO
ND
ITIO
NS
HUGEUPWELLING
HOTPOOL
SHIFTSWEST
EXTENDEDCOLD
TONGUE
Nutrients
Normal Conditions and La Nina = more productive
El Nino Conditions = less productive
El Niño La Niña impacts ocean productivity
