Download Ocean circulation

Ocean-Air Interaction
Distribution of Solar Energy
• Concentrated solar
radiation at low
latitudes
• Solar radiation more
diffuse at high latitudes
Oceanic Heat Flow
• High latitudes–more heat lost than gained
• Low latitudes–more heat gained than lost
Density Variations in the Atmosphere
• Convection cell – rising
and sinking air
• Warm air rises
– Less dense
• Cool air sinks
– More dense
• Moist air rises
– Less dense
• Dry air sinks
– More dense
Movement of the Atmosphere
• Thick column of air at sea level
– High surface pressure equal to 1 atmosphere
• Air always flows from high to low pressure.
• Wind – moving air
The Coriolis Effect
• Deflects path of moving object from viewer’s
perspective
– To right in Northern Hemisphere
– To left in Southern Hemisphere
• Due to Earth’s rotation
Merry Go Round CE
Drawn CE
The Coriolis Effect
• Zero at equator
• Greatest at poles
• Change in Earth’s rotating velocity with
latitude
– 0 km/hour at poles
– More than 1600 km/hour (1000 miles/hour)
at equator
The Coriolis Effect
© 2011 Pearson Education,
Inc.
Global Atmospheric Circulation
• High pressure zones – descending air
– Subtropical highs – 30 degrees latitude
– Polar highs –90 degrees latitude
– Clear skies
• Low pressure zones – rising air
– Equatorial low – equator
– Subpolar lows – 60 degrees latitude
– Overcast skies with lots of precipitation
Storms and Air Masses
• Storms – disturbances with strong winds and
precipitation
• Air masses – large volumes of air with distinct
properties
Ocean’s Climate Patterns
• Open ocean’s climate regions are parallel to
latitude lines.
• These regions may be modified by surface
ocean currents.
Ocean’s Climate Zones
• Equatorial
– Rising air
– Weak winds
– Doldrums
• Tropical
– North and south of equatorial zone
– Extend to Tropics of Cancer and Capricorn
– Strong winds, little precipitation, rough seas
• Subtropical
– High pressure, descending air
– Weak winds, sluggish currents
Ocean’s Climate Zones
• Temperate
– Strong westerly winds
– Severe storms common
• Subpolar
– Extensive precipitation
– Summer sea ice
• Polar
– High pressure
– Sea ice most of the year
Ocean Circulation
Fig. CO7
Ocean currents
Moving seawater
Surface ocean currents
Transfer heat from warmer to cooler areas
Similar to pattern of major wind belts
Affect coastal climates
Deep ocean currents
Provide oxygen to deep sea
Affect marine life
Types of ocean currents
Surface currents
Wind-driven
Primarily horizontal motion
Deep currents
Driven by differences in density caused by
differences in temperature and salinity
Vertical and horizontal motions
Ekman spiral
 Surface currents move at angle to wind because of the
coriolos effect.
 Ekman spiral describes speed and direction of seawater
flow at different depths
 Each successive layer moves increasingly to right (N
hemisphere)
Ocean
currents
and
climate
Fig. 7.9
Gulf Stream




Meanders
or loops
Warm-core
rings
Cold-core
rings
Unique
biological
populations
Fig. 7.17b
Climate effects of North Atlantic surface
currents
• Gulf Stream warms East coast of U.S. and
Northern Europe
• North Atlantic and Norwegian Currents
warm northwestern Europe
• Labrador Current cools eastern Canada
• Canary Current cools North Africa coast
Thermohaline circulation
•
•
•
•
Below the pycnocline
90% of all ocean water
Slow velocity
Movement caused by differences in
density (temperature and salinity)
– Cooler seawater denser
– Saltier seawater denser
Thermohaline circulation
• Originates in high latitude surface
ocean
• Cold surface seawater sinks at polar
regions and moves towards the
equator
Thermohaline circulation
Fig. 7.26