Deep Currents
PG.368-371
Deep Currents
• Streamlike movements of water far below the surface
• NOT directly controlled by wind or the Coriolis effect
• Formed by increased density
• Density- ratio of mass to volume
• Temperature, salinity affect ocean water’s density
Form in 3 ways
Decreasing Temperature
• Cold air chills surface water
• Molecules slow down and squish together
• Water becomes denser and sinks to the
ocean floor
Increase in Salinity Through Freezing
• Salinity= amount of
dissolved solids in a liquid
• Ocean freezes at surface
• Ice floats on top (less dense)
• Dissolved liquids are squeezed
out of the ice and enter water
below the ice
• Increases the salinity, water
becomes denser and sinks
Increasing Salinity Through Evaporation
• Water evaporates, leaving behind solids (aka-salts and minerals)
• In what kind of climates is this more common?
• More solids= more density
• What happens to the denser water?
Movement of Deep Currents
• Move at different rates because of different densities
• Which one moves faster???
• More dense currents
• Less dense currents
AABW= Antarctic Bottom Water
NADW= North Atlantic Deep Water
750yrs to get from
Antarctica to the equator
Currents Trading Places
• Surface currents carry warm
water from equator to poles
• Warm water replaces cold
water that sinks to the
ocean floor
• Deep currents carry cold
water away
• Water from deep currents
rises to replace water
leaving in surface currents
Stabilizing Climates
• Surface currents can make colder areas consistently warmer and
warmer areas consistently cooler
• Gulf Stream
• California Current
Upwelling- cold, nutrient-rich water from the deep
ocean rises to the surface to replace warm water
How does this current
effect Europe?
El Niño and La Niña
• complex weather patterns (cause floods, hurricanes, etc.)
• formed from changes in ocean temps. in the Equatorial Pacific
• have the most effect between Dec.-Apr.
• last about 9-12 months (start in summer)
• happen every 3-5yrs.
More common
El Niño and La Niña
warm
cold
The Little Boy, or Christ Child
The Little Girl
also called "a cold event,”
El Viejo, anti-El Niño
El Niño-Southern Oscillation (ENSO) cycle.
What are we in
right now???
New NOAA forecast suggests current El Niño will fade
fast, and be replaced by a strong cooling La Niña this year
Normal
El Nino