Download Chapter 16 The Dynamic Ocean

Chapter 16
The Dynamic Ocean
16.1 Ocean Circulation
Surface Circulation
▶ Ocean currents are masses of ocean
water that flow from one place to
another
▶ Surface currents – movements of water
that flow horizontally in the upper part
of the ocean’s surface
▶ Develop from friction btw the ocean
and the wind that blows across its
surface
Surface Circulation
▶ Oceanographers ID currents by:
▶ 1. studying physical
characteristics
▶ 2. studying chemical
characteristics
▶ 3. mapping the paths of debris
Surface Circulation
▶ Surface currents are controlled by
3 factors:
▶ 1. air currents (aka wind)
▶ 2. Earth’s rotation (aka Coriolis
Effect)
▶ 3. shape of ocean basins
Surface Circulation
▶ Winds are caused by uneven heating of
the atmosphere
▶ Variations in air temp lead to variations
in air density and pressure
▶ Wind has KE that is transferred to the
surface of the ocean
Surface Circulation
The Antarctic Circumpolar Current (aka West Wind
Drift) is the largest current in the world. No continents
interrupt the movement of this current
Gyres
▶ Huge circular moving current systems
dominate the surfaces of the oceans
▶ 5 Main ocean Gyres
▶ N. Pacific Gyre
▶ S. Pacific Gyre
▶ N. Atlantic Gyre
▶ S. Atlantic Gyre
▶ Indian Ocean Gyre
▶ Coriolis effect – deflection of
currents away from their
original course as a result of
Earth’s rotation
▶ Due to Earth’s rotation,
currents are deflected to the
right in the N. Hemisphere &
to the left in the S.
Hemisphere
▶ Wind belts AND Coriolis Effect
cause GYRES
Ocean Currents & Climate
▶ When currents from low latitude
(near equator) regions move into high
latitude (near poles), they transfer
heat from warmer to cooler areas on
Earth
▶ As cold water currents travel toward
the equator, they help moderate the
warm temperatures of adjacent land
areas
▶ Play a big role in maintaining Earth’s
heat balance
Ocean Currents & Climate
See fig 3 pg. 450
Upwelling
▶ Rising of cold water from deeper layers to
replace warmer surface water
▶ Wind-induced vertical movement
▶ Brings greater concentrations of dissolved
nutrients to the ocean surfaces
Deep – Ocean Circulation
▶ Density currents – vertical
currents of ocean H2O that
results from density differences
in the H20 masses
▶ Flow much more slowly than
surface currents
▶ Seawater density if affected by
salinity and temperature
differences
Deep – Ocean Circulation
▶
Most water involved in deep-ocean
currents begins in high latitudes (near
poles) at the surface
▶
Density currents can also result from
increased salinity of ocean water due to
evaporation
A Conveyor Belt
▶ In a simplified model, ocean
circulation is similar to a
conveyor belt that travels
from the Atlantic Ocean
through the Indian and
Pacific Oceans and back
again
A Conveyor Belt
https://www.youtube.com/watch?v=L9zjmC8InKA
A Conveyor Belt
Warm H20
flows toward
poles
Cold, deep
water
upwells
Density
increases
Temperature
drops &
salinity
increases
Dense H20
moves
toward
equator
The cycle
repeats
Upwelled
H20 warms