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

• 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

Deep ocean – Temp. is stable

-1 to 4°C

Average Temp. of the world ocean is 3.8°C

200 m

Sinking air

Hadley Cell

0° Latitude

Hot, humid

30° latitude

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

Photosynthesis, CO2

Evapotranspiration

O2 + H2O

Nutrients, soil

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

Ocean (1,350,000) = 97% of the total water

425,000385,000

40,000

Ice

Ground water

8,200,000

27,500,000

Rivers, 40,000

Atmosphere = 13,000

Units - 1000 Km3 : 1m 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)

Trade winds

The Amazon Basin

Bio-enhanced cloud formation, This is a water trap set up by biologic activity

Ocean

Amazon River

The Amazon and Oronoco flow systems are responsible for 20% of Earth’s runoff

Physical Pump

• Summer– Rainy season– Drives major rivers– Monsoons in India

• Winter– The ocean surface

circulation follows wind patterns moving away from land