Lecture 9&10 ENSO: From climate to fish and beyond

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Last updated 12:43 PM on 5/14/26
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30 Terms

1
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How does surface pressure vary?

  • Between longitude (E→W) and latitude (N→S)

  • Seasonally

  • Large spatial variation

<ul><li><p>Between longitude (E→W) and latitude (N→S)</p></li><li><p>Seasonally </p></li><li><p>Large spatial variation </p></li></ul><p></p>
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Which has a more stable temperature range, sea or land?

Sea - the high heat capacity of water buffers temperature fluctuations (thermal damping effect)

<p>Sea - the high heat capacity of water buffers temperature fluctuations (thermal damping effect) </p>
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Heat capacity

Amount of heat energy that can be absorbed by something before it changes temperature/volume

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How do climate zones come about?

Different high and low pressure - heat and water

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How does the location deserts come about?

Prevailing wind patterns

<p>Prevailing wind patterns</p>
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How do the prevailing winds lead to deserts?

  • Air picks up moisture as it goes along

  • Driven because it’s falling from its atmospheric cell and moved in a circular pattern (Coriolis effect)

  • Wind is moved from East to West (can vary)

  • Deposits moisture on one side of the continent

  • By the time the air reaches the other side of the continent, it is much drier

  • Forming deserts

<ul><li><p>Air picks up moisture as it goes along</p></li><li><p>Driven because it’s falling from its atmospheric cell and moved in a circular pattern (Coriolis effect)</p></li><li><p>Wind is moved from East to West (can vary)</p></li><li><p>Deposits moisture on one side of the continent </p></li><li><p>By the time the air reaches the other side of the continent, it is much drier </p></li><li><p>Forming deserts</p></li></ul><p></p>
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How do you identify climate zones?

  • Precipitation patterns

  • Temperature range

  • Prevailing winds

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How do you classify the climate?

  • Moisture

  • High/Low pressure

  • Organisms/vegetation surviving

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What is Koeppen’s Climate Classification?

  • Divides the climate into 5 main groups: Tropical, dry, temperate, cold and polar

  • Then subdivides them into divisions for each group

<ul><li><p>Divides the climate into 5 main groups: Tropical, dry, temperate, cold and polar </p></li><li><p>Then subdivides them into divisions for each group </p></li></ul><p></p>
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What disrupts coastal upwelling systems?

El Nino

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What is El Niño?

Changes in the surface ocean temperature in the Pacific Ocean

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What is the Southern Oscillation?

Changes in atmospheric pressure that occur between East and West in the Pacific Ocean

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How is El Nino and Southern Oscillation linked (ENSO)?

ENSO: Changes in atmospheric pressure and wind patterns drive El-Niño and La Niña

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What are the two parts to ENSO?

  • El Niño: Warmer than average sea surface temperature that happens every few years

  • La-Niña: Cooler than average sea surface temperature that happens every few years

  • ~ 3-7 year cycle

  • Neutral periods in between

<ul><li><p>El Niño: Warmer than average sea surface temperature that happens every few years</p></li><li><p>La-Niña: Cooler than average sea surface temperature that happens every few years</p></li><li><p>~ 3-7 year cycle</p></li><li><p>Neutral periods in between </p></li></ul><p></p>
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What is the ‘average’ system in the Pacific (neutral)?

  • Trade winds (East to West) across the Pacific

  • Air and surface water warmer at the equator - pushed West and bunches up

  • Upwelling of cold, nutrient-rich water in the East

  • Thermocline develops - water at depth moves from West to East (warmer → cooler)

  • Warm, moist air rises in the West - lower pressure area

  • Air cools and falls in the East, giving cool, clear conditions - higher pressure area

  • Productive Eastern waters

<ul><li><p>Trade winds (East to West) across the Pacific</p></li><li><p>Air and surface water warmer at the equator - pushed West and bunches up</p></li><li><p>Upwelling of cold, nutrient-rich water in the East</p></li><li><p>Thermocline develops - water at depth moves from West to East (warmer → cooler)</p></li><li><p>Warm, moist air rises in the West - lower pressure area</p></li><li><p>Air cools and falls in the East, giving cool, clear conditions - higher pressure area</p></li><li><p>Productive Eastern waters</p></li></ul><p></p>
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What are El Niño conditions?

  • Prevailing winds become West → East (reversed)

  • Opposite to ‘normal’ conditions occur

  • Warm, moist air rises in the East

  • Air cools and falls in the West, giving cool, clear conditions

<ul><li><p>Prevailing winds become West → East (reversed)</p></li><li><p>Opposite to ‘normal’ conditions occur </p></li><li><p>Warm, moist air rises in the East</p></li><li><p>Air cools and falls in the West, giving cool, clear conditions</p></li></ul><p></p>
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What are La Nina conditions?

  • East → West trade winds become stronger

  • ‘Normal’ is amplified

<ul><li><p>East → West trade winds become stronger </p></li><li><p>‘Normal’ is amplified </p></li></ul><p></p>
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What is the ENSO Index?

  • Quantifies El Nino and La Nina

  • Unitless number, describing the deviation of the climate from ‘normal’

<ul><li><p>Quantifies El Nino and La Nina </p></li><li><p>Unitless number, describing the deviation of the climate from ‘normal’</p></li></ul><p></p>
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Changes in sea surface temperature correspond to what?

Changes in sea surface level atmospheric pressure

<p>Changes in sea surface level atmospheric pressure </p>
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How does El Nino affect primary production?

  • Less primary production (chlorophyll) during El-Nino compared to ‘normal’

  • During El Nino = fewer nutrients for the food web

  • More chlorophyll = more phytoplankton = more productivity/nutrients

<ul><li><p>Less primary production (chlorophyll) during El-Nino compared to ‘normal’</p></li><li><p>During El Nino = fewer nutrients for the food web</p></li><li><p>More chlorophyll = more phytoplankton = more productivity/nutrients </p></li></ul><p></p>
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What happens to the fish catch numbers of Anchovey during El Nino?

Decreases

<p>Decreases </p>
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Where do ENSO events affect?

Many parts of the world

<p>Many parts of the world </p>
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What is the Teleconnection?

Significant relationships linking weather phenomena across far-apart areas of the globe, e.g. Droughts in Australia with Flooding in Peru, connected by El Niño

<p>Significant relationships linking weather phenomena across far-apart areas of the globe, e.g. Droughts in Australia with Flooding in Peru, connected by El Niño</p>
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How does ENSO affect places further abroad?

  • Interacts with jet streams

  • Changes in Pacific temperature and precipitation (pressure) affect the location and paths of the atmospheric jet streams

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What are the jet streams?

  • In between cells, very strong wind

  • Strong ribbons of air around the world

  • Subtropical forms: between hadley and ferrel cells, relatively warm

  • Polar: forms between polar and ferrel cells, cooler

<ul><li><p>In between cells, very strong wind</p></li><li><p>Strong ribbons of air around the world </p></li><li><p>Subtropical forms: between hadley and ferrel cells, relatively warm</p></li><li><p>Polar: forms between polar and ferrel cells, cooler</p></li></ul><p></p>
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What happens to the jet stream during El Niño?

Subtropical: More amplified and straighter, takes a more direct path across the United States

<p>Subtropical: More amplified and straighter, takes a more direct path across the United States </p>
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What happens to the jet stream during La Niña?

Polar: Comes further south, bringing wetter/colder weather

<p>Polar: Comes further south, bringing wetter/colder weather </p>
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How does El Nino effect coastal populations?

  • Causes major flooding

  • Impacts crop growth (agriculture)

<ul><li><p>Causes major flooding </p></li><li><p>Impacts crop growth (agriculture)</p></li></ul><p></p>
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How is ENSO forecasted?

Monitoring Sea Surface Temperatures

<p>Monitoring Sea Surface Temperatures </p>
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