Unit 1 - El Nino/La Nina , Climate

How are the Ocean and atmosphere connected

They exchange heat, moisture and energy

Does it take longer for water or air to absorb/rid heat

Water

What are Gyres

Wind cycles over oceans

What drives the normal conditions in the tropical Pacific

Trade winds create uneven distribution of ocean temperature

Order of events under “normal conditions‘ in the tropical Pacific

1. Trade winds push warm surface water from East to West (South America —> Australia)

2. Warm water accumulates near Australia

3. Western Pacific becomes warmer than Eastern

4. Cold, nutrient-rich deep water rises along west coast of pacific ocean (upwelling)

What is upwelling

1. Deep, cold ocean water rises to the surface

2. Contains nutrients to support marin ecosystems

3. Occurs when surface winds push warm water away from an area, cold water fills in

4. Creates some of the world’s most productive fishing regions

5. As marine life dies, it sinks to the bottom taking the bodies' nutrients with it

When does upwelling occur

Occurs when surface winds push warm water away from an area, cold water fills in

Walker Circulation

 East-West atmospheric circulation caused by temp difference across Pacific (what affects the US during El Nino/Nina)

How does the walker Circulation work

1. Warm ocean water heats air above

2. Warm, moist air rises over Western Pacific

3. Air moves East, high in atmosphere

4. Cooler, drier air sinks over Eastern Pacific

5. Surface trade winds complete circulation

Difference between Walker and Hadley cell

Hadley Cell → Moves air North and South between equator and 30^o latitude

Walker Cell → Moves air East and West along equator

El Nino

Warm surface water shifts eastward

What happens to South America and SE Asia/Australia during El Nino

South America: More rainfall, less fish

SE Asia and Australia: Drought, wildfires, loss of crop

What happens to North America during El Nino

North America: Wetter South, milder north winter, fewer Atlantic hurricanes

La Nina

More warm water pushed westward

What happens to South America and SE Asia/Australia during La Nina

South America: Drier, more fish

SE Asia and Australia: More rainfall

What happens to North America during La Nina

North America: Drier South, wetter Northwest, more Atlantic hurricanes

Trade winds during El Nino

weaker

walker Circulation during El Nino

weakens

pressure over Australia+SE Asia during El Nino

Higher

Pressure over South America during El Nino

Lower

Sea surface temps near Australia + SE Asia during El Nino

Cooler

Sea surface temps near South America during El Nino

Warmer

Upwelling near South Ameria during El Nino

Weaker

Trade winds during La Nina

Stronger

Walker Circulation during La Nina

Stronger

Pressure over Australia + SE Asia during La Nina

Lower

Pressure over South America during La Nina

Higher

Sea surface temps near Australia + SE Asia during La Nina

Warmer

Sea surface temps near South America during La NIna

Cooler

Upwelling near South America during La Nina

Stronger

El Nino Winter

El Nino messes up the jet stream between Hadley + Ferrell Cells causing changes in US weather (polar vortex)

Surface Currents

• Driven by global winds

• Moves warm and cold water across ocean surface

• Influences coastal climates

Deep currents (ocean conveyor belt)

• Driven by differences in water density, temperature + salinity

• Moves heat through deep ocean

Deep Currents Arctic Waters

More dense (cold + salty)

Deep Currents Equatorial Waters

Less dense (warm water)

Conveyor Belt Significance

• Redistributes heat around globe

• Moderates regional climates

• Circulates oxygen through deep oceans

• Transports nutrients that support marine ecosystems

What increases Salinity

• Evaporation (leaves salt behind)

• Sea Ice Formation (leaves salt in surrounding water)

Decreases Salinity

• Precipitation adds freshwater

• River runoff carries freshwater

• Melting glaciers + ice sheets

Warm Currents and nearby land

warms nearby land, increases precip + evap

Cold currents and nearby land

cools nearby land, reduces precip + evap

What happens to precipitation in a watershed

1. Runoff

2. Infiltrate soil

3. Percolate thru deep soil + rock

4. Flow through saturated rock/sediment

5. Evaporate

6. Transpire