El Nino: Causes and Effects

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El Nino Causes and Effects

• Marine Biology
• March 2006

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Climate vs. Weather

• Weather
• Short term properties of the troposphere at a
  particular place at a particular time (short time
  period)
• Temp, pressure, humidity, precipitation, wind
  direction etc
• Climate
• A regions general pattern of weather conditions
  over a long period
• Average temperature/precipitation are two key
  factors determining climate
• Temp/precipitation patterns determined by global
  air circulation patterns

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Another View
Trades blow east to west normally
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Upwelling
BrooksCole Animation 5 Ch6
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Short Term Climate ChangesEL Nino-Southern
Oscillation (ENSO)

• A periodic, global change in climate patterns
• Affects coastal upwelling in Equatorial Pacific
  (specifically off South Americas coast)
• Affects climate world wide but especially in land
  along the Pacific and Indian Oceans
• Causes major ecological and socioeconomic
  problems (stop)
• Flooding brings water borne illnesses like
  Malaria
• Drought causes a range of issues elsewhere

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Normal Conditions
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El Nino Conditions
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ENSO Sequence of Events

• Equatorial Trade winds weaken
• Unusually warm waters develop
• The water piled up in the western pacific sloshes
  back East carrying the warm pool of water with
  itthermocline is depressed and this causes
  upwelling to cease!!!
• food supply for plankton thus begins to dwindle
• The region of rising air moves East with the warm
  pool and the pumping of heat and moisture air
  into the upper atmosphere deflects the normal
  paths of jet streams which causes the changes in
  weather that the rest of the world experiences.
  
• When eastern SST become warm, the east to west
  temperature contrast is small, so the trade winds
  weaken even further, leading to essentially flat
  wind conditions across the entire equatorial
  pacific
• Drought in Indonesia, Asia, and Australia Fires
  Food shortages
• Flooding on West Coast of N and S America
  Malaria Refugees

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Geography of ENSO

• Most severe effects are found close to the
  equatorequatorial tropical pacific
• The usual pattern of deserts in Peru and
  Galapagos and heavy rainfall in Indonesia and the
  Western Pacific reverses.
• Forest fires occur in Indonesia and Australia
• Peru suffers flooding with accompanying epidemics
  of cholera and other sewage and mosquito borne
  diseases
• N US has mild winters,
• SW US has increased rainfall, less Atlantic
  Hurricanes

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Geography of El Nino
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ENSO Cause and Effects

• Warming of Water
• Problems Habitat destruction Increased algal
  blooms coral bleaching disruption of migration,
  disrupt upwelling of nutrient rich waters
  nutrient rich waters not available for fish and
  other species die off of species that cant
  tolerate the warmth lowered water-solubility of
  CO2 increased storms
• Effects Starvation/die-off of species Loss of
  food for higher trophic levels (HUMANS TOO!!)
  Disruption of food webs loss of biodiversity

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ENSO Cause and Effects

• Increased/Decreased Storms Rainfall
• Problems Flooding, mudslides, erosion, nutrient
  leaching from soils contaminated water supplies
  drought, lack of water for life increased risk
  of fires, less plant growth
• Major health issues arise from these
  conditions!!!!
• More mosquitoes! More cholera, more dysentery
• Effects Habitat destruction plants unable to
  grow/loss of food production starvation-die
  offs increased likelihood of infectious diseases

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El Nino and Disease

• Wetter conditions lead to
• Increasing mosquito levels these guys carry
  malaria, dengue fever, yellow fever
• Increased flooding causes major sanitation
  problems (may promote the spread of cholera,
  dysentery, giardia
• Slightly drier conditions lead to
• Streams become more stagnant, resulting in
  standing water that may breed mosquitoes
• Drought conditions lead to
• Deterioration in fresh water supplies
  concentrates pollutants and increases probability
  of cholera and other diarrheal diseases
• Higher land/air temperatures lead to
• Give insects longer window of reproduction times
• Increased breeding and feeding of insects
• Higher water temperatures lead to
• Increased growth of bacteria and other insects

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Animations

• Data as of today (here too)
• SST in 1982-83 Event
• SST in last 4 El Nino events
• Other nice visualizations
• Other still frames and animations
• Nice general resource