Transcript Heat Transfer in Earth’s Oceans

Heat Transfer in Earth’s
Oceans
WOW!,
3 meters of ocean water can hold as much
energy as all other Earth Systems combined!
Tropical air rising
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Warming air = lower density+increasing volume
Rising air = lower pressure, lower temperature
Condensation = warming
Result: tremendous rainfall along the equator
Surface Ocean – Temp. is variable
-2 to 30°C
200 m
Average
Temp. of
the world
ocean is
3.8°C
Deep ocean – Temp. is stable
-1 to 4°C
Sinking air
Hadley Cell
0° Latitude
30° latitude
Hot, humid
Hot, dry (desert belt)
Surface ocean circulation
• Solar radiation
• Large heat capacity
• Heat variations lead to changes in
pressures
• Air circulation (wind)
– Gyres
Tropical Gyre
• Driven by wind
– Trade winds
– Westerly movement
– Counter clockwise (CCW) direction (northern
hemisphere)
Subtropical Gyre
• Very active evaporation
– A product of warm/dry air moving over the
oceans and land masses
• Results in a warm and salty Gulf Stream
• The gyre moves in a clockwise (CW)
direction in this region.
Sub Polar Gyre
• Tremendous transfer of heat from the
ocean to the atmosphere.
– This warms the rising air that travels northeast
and through northern Europe.
– The Erbinger Current (Norwegian/Greenland
Sea)
General surface current
movements
• Winds mix and transport warm waters
through the Earth’s oceans
– Depth of 100 m
– Average depth of 4000 m
• Warm water is circulated from the tropics
towards the poles
• Coriolis force
Movement beneath the surface
• Coriolis force
– Pushes the underlying water
– Through a depth of 100 m
– Friction drives the downward spiralling water
further to the right (Nh) or left (Sh)
Subpolar sink
• Water becomes cold and salty (increase in
density) to the north of Greenland.
• This cold dense water sinks creating
vertical movement
– Supplies the deep ocean with circulating
water
Northern sub polar gyre
Southern Hemisphere
• This vertical movement also occurs in the
southern hemisphere
– Weddell Sea
– Both movements (north and south) occur in
the Atlantic ocean
Polar water/ice
• Ice is fresh water
• Circum-Antarctic Current: Flows around
Antarctica
– Circulates from west to east
– 4000 cubic meters of water
– Insulates Antarctica (keeps it cold)
• This circulation pattern has a huge effect
on global climate.
Deep Water Circulation
• Deep water goes from the North Atlantic to
the North Pacific.
• Surface water flows opposite of the deep
water pattern
• The deep cycle is about 800 to 1000
years.
• Surface water cycles occur on the order of
decades.
Water and The Global Water Cycle
• Largest bulk chemical transfer on Earth
• Important to heat transfer from the Equator
(evaporation)
• Patterns control regional distribution rainfall in
terrestrial environments
• Movement of water is a function of evaporation
and precipitation of two pumps.
– Biologic
– Physical
The Biological Pump
• Operates on feedback
• Nutrients + H20 +CO2 →
organic matter + O2
Evapotranspiration
O2 + H2O
Nutrients, soil
Photosynthesis,
CO2
Biologic Pump, negative feedback
• When there is ample water the inner cell is
enlarged and promotes evapotranspiration
• When water is short the inner cell is closed
allowing for the absence of
evapotranspiration
Water budget
27,500,000
40,000
Rivers,
40,000
Ice
Atmosphere = 13,000
385,000
425,000
Ground
water
8,200,000
Units - 1000 Km3 : 1m
Ocean (1,350,000) = 97% of the total water
water = metric tons, 50 * 1000 Km3 = 1018
Longer residence time for the land
system
• Stock / flux
– Residence time of water in the atmosphere
– 13,000 (atmosphere) / 425,000 (evaporation)
= 0.3 years × 52 weeks
• Residence time in the oceans
– 1,350,000,000/425,000 = 3176 years
Calculate the residence time of
land.
• Add the stocks and divide by the flux
• 357,040,000/425,000 = 840 years
• There are more stocks than listed here so
the value of 840 years will be an
underestimate.
Calculating the average
evaporation and precipitation
• Ocean:
– 100 cm/yr, evaporation
– 70 cm/yr, precipitation
• Tropics
– 4mm/day (precipitation is skewed to the tropics
because this zone account for 50% of the runoff on
Earth
• Poles
– X≤1mm/day, Desert belt 0% rain leads to little to no
runoff.
The Jungle effect (Tropics)
The Amazon and Oronoco flow systems are
responsible for 20% of Earth’s runoff
Trade winds
Amazon River
The Amazon Basin
Ocean
Bio-enhanced cloud formation,
This is a water trap set up by
biologic activity
Physical Pump
• Summer
– Rainy season
– Drives major rivers
– Monsoons in India
• Winter
– The ocean surface
circulation follows wind
patterns moving away
from land