September 12

The role of the oceans

All of Earth’s water

Source: Howard Perlman, United States Geological Survey

WHAT ROLES DO THE OCEANS PLAY WITHIN THE CLIMATE SYSTEM?

They absorb and reflect solar radiation. (albedo)

They transport heat. (climate variability)

They are source of water vapor. (greenhouse e!ect, precipitation)

They store heat. (heat capacity, latent heat)

The low-latitude oceans are Earth’s main storage tanks of solar heat.“ ”

Bill RuddimanEarth’s Climate: Past, Present and Future

3Main reasons.

1Physical properties of water

The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.

Water

Ice

Wood, oak

Soil, wet

Tar

Earth, dry

Brick, common

Concrete, light

Clay

Lava

Glass

Granite

Steel

0 0.25 0.5 0.75 1

The specific heat of water is WAY higher than any of Earth’s other surfaces.

cal/g

Source: The Engineering Toolbox

Heat capacity = Density × Specific Heatcal/cm3 g/cm3 cal/g

60 : 5 : 2 : 1water : ice : air : land

HEAT CAPACITIES

The low-latitude oceans are Earth’s main storage tanks of solar heat.“ ”

Bill RuddimanEarth’s Climate: Past, Present and Future

Source: Ruddiman, Earth’s Climate: Past, Present and Future

Sun angle controls heat absorption.

179.5W

90˚S 60˚S 30˚S 0˚ 30˚N 60˚N 90˚NLatitude

020

0040

00D

epth

[m]

Depth-temperature profile at 180°W

Source: Levitus and Boyer, 1994

Source: reefdaddy

2Turbulent mixing

Source: Ruddiman, Earth’s Climate: Past, Present and Future

The mixed layer is uppermost layer of the ocean, where temperature and salinity are relatively constant.

Depth of mixed layer (meters)

Boreal winter

Source: Giorgiogp2

Depth of mixed layer (meters)

Boreal summer

Source: Giorgiogp2

179.5W

90˚S 60˚S 30˚S 0˚ 30˚N 60˚N 90˚NLatitude

020

0040

00D

epth

[m]

Depth-temperature profile at 180°W

Source: Levitus and Boyer, 1994

3The conveyor belt

The thermohaline circulation

Source: Jonathan Cohen

Average annual ocean-atmosphere CO2 flux

Source: NOAA PMEL Carbon Program

The residence time describes the average time a water molecule will spend in a specific reservoir within the hydrological cycle.

Age of ocean waters inferred from radiocarbon observations

Source: Gebbie and Huybers, Journal of Physical Oceanography, 2012

1 day 100,000 years

1 week

1 month

1 year

10 years

100 years

1,000 years

10,000 years

Antarctica and Greenland20,000 yr

Groundwater10,000 yr

Oceans3,200 yr

Lakes50 to 100 yr

Glaciers20 to 100 yr

Snow2 to 6 months

Soil1 to 2 months

Atmosphere9 days

The thermal inertia describes the resistance of a component of the climate system to temperature change.

Source: Ruddiman, Earth’s Climate: Past, Present and Future

Sensitivity to solar heating (land vs. ocean)

Source: Ruddiman, Earth’s Climate: Past, Present and Future

Pacific Decadal Oscillation index

1900 1920 1940 1960 1980 2000-3

-2

-1

0

1

2

3

Atlantic Multidecadal Oscillation index

Source: Franklin Hunting

September 20

Impacts on terrestrial climates

GEOG8280NEXT CLASS