Ocean and Climate I
http://www.gerhardriessbeck.de/
Physical Characteristics of the Ocean
Surface area: 3.61·1014 m2
Mean depth: 3.7 km
Ocean volume: 3.2·1017 m3
Mean density: 1.035·103 kg/m3
Ocean mass: 1.3·1021 kg
Ocean Development
By Plate Tectonics
Alfred Wegener (1880-1930)
The deeper layers of Earth
Underwater
lava
eruption along the
rift can lead to local
warming of deep
water environment
with heat transport
by Eddy currents to
the surface
Shape of ocean floors
Ocean
Currents
Eddies, Gyres, and Geostrophic flows
Collectors of human garbage: from hundreds of shipwrecks to ten thousands of plastic ducks
More than 10,000 ocean containers are lost each year over the side in the world ocean trades -- the result of high seas perils.
Ocean impact on climate
Heat exchange with atmosphere by condensation and
other processes
Meridional heat transport from tropic to polar regions
Heat capacity of ocean causes the ocean to serve as a
thermal reservoir balancing rapid climate changes
Wind surface water interaction causes ocean currents
Earth rotation couples with ocean current through
Coriolis force
Inertia of dense water flow continues currents even
without wind
Salinity of water affects the flow pattern of ocean
currents
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Difference to Atmosphere
 Atmosphere is vertically structured with high altitude events
impacting climate. The role of ocean is limited to the surface layers
 Atmospheric currents (winds) are largely unbounded. Oceans
are laterally bounded by continents (except for southern ocean
where fluid can pass around the globe)
 Atmosphere is largely transparent to radiation and is heated
from below by convection. Ocean absorbs radiation and surface
region is heated by absorption.
 Wind driven and buoyancy driven circulations of ocean current
provide very fast energy transport.
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The cryosphere
2% of the planetary water is frozen (ice sheets, sea ice, glaziers, permafrost), most of it
is contained in ice sheets over land, Antarctica (89%), Greenland (8%), increasing the
average Albedo. 7% of the ocean is covered by ice. Sea ice regulates heat exchange,
moisture and salinity and insulates “warm ocean water from cold polar atmosphere.
Ice Melting
Ocean parameters
Surface area: 3.61·1014 m2
Ocean volume: 3.2·1017 m3
Mean density: 1.035·103 kg/m3
Ocean mass: 1.3·1021 kg
Vmelt 
M melt

Assume 50% of ice sheet melts, corresponding to
1% of the ocean water mass: Mmelt≈1.3∙1019 kg.
1.3 1019 kg

1.035 103 kg / m 3
Vmelt  1.26 1016 m 3
Vmelt 1.26 1016 m 3
H

 35 m
14
2
S
3.61 10 m
Exploration of the Seas Oceanography
Challenger Expedition 1873-1875
At 360 stations the crew measured the
bottom depth, temperature at different
depths, observed weather and surface
ocean conditions, and collected
seafloor, water, and biota samples.
Sir Charles WyvilleThomson
Sir John Murray
A 68,890-nautical-mile
John Buchanan
(127,580 km) journey
Properties of sea water
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H O
2
kg
 0.999  10 3
m
3
kg
 sea water  1.035  10 3
m
3
At 273 K, variations of density are within few percent only!
   T , S , P 
 Cold water is denser than warm water
 Salty water is denser than fresh water
 Pressure increases density of water
Salinity is defined in practical salinity units psu in terms of electrical conductivity, which is close
to the relative proportion of the dissolved salts in g per kg water (or ‰). Seawater has 34.5 psu.
Sea water composition
Chloride: 18.98‰ (g/kg)
Sodium: 10.568‰ (g/kg)
Sulphate: 2.65‰ (g/kg)
Magnesium: 1.27‰ (g/kg)
Calcium: 1.27‰ (g/kg)
Potassium: 0.38‰ (g/kg)
Bicarbonate: 0.14‰ (g/kg)
Others: 0.11‰ (g/kg)
Salinity: 34.48‰ ≈34.48 psu
Since ocean atmosphere interactions are limited to the surface
region, the pressure dependency of the water density is neglected.
There is, however, sensitive temperature dependencies!
     ref
   T , S 
 ref  1000
Contour plot of seawater
density deviations shown
as function of salinity and
temperature at the ocean
surface. The conditions of
relevance for oceans are
shown at the right hand
side.
 Density increases with temperature and salinity (1psu≈1g/kg=1‰),
 Fresh water has maximum density at 4oC (cooling forms ice)
 At 15oC the water at the ocean surface (S≈36 psu) has ≈26.7 kg/m3
which translates into a lower density =1026.7 kg/m3 compared to a
temperature of 0oC.
kg
m3
Temperature and salinity patterns
Steady Temperature decline
towards the polar regions,
visible is the impact of the
cold North Pacific current
branching down the US
Northwest coast and the
Humboldt current branching
from the West Wind Drifts
northwards along the South
American west coast.
Regions of high salinity in
middle latitude range north
and south of the equator
regions. Polar regions show
low salinity including cold
water currents such as the
North Pacific current in the
American Northwest and the
Humboldt current.
Early exploration of salinity
Georg Wüst
Meteor Expedition 1925-1927
1926
1925
1927
Horizontal salinity patterns
Longitudinal cut across the western (top) and the eastern (bottom) regions of the
Atlantic Ocean showing the horizontal distribution of salinity, based on Meteor
observations.
Modern Results WOCE (1990s)
The Hydrographic Program of the World Ocean Circulation Experiment (WOCE) was a
comprehensive global hydrographic survey of physical and chemical properties of the oceans.
WOCE Oxygen & Salinity
WOCE Nitrates & Salinity
http://woceatlas.ucsd.edu/
Mixed layer and thermocline
mixed layer
thermocline
abyssal layer
Typical temperature & salinity
profile for mid-latitude ocean.
Mixed layer has constant temperature due to wind
and density driven convective motion, balanced by
radiative heating and radiative and/or wind cooling
as well as latent heat effects by evaporation
processes. The thermocline layer represents an
exponential decline of temperature to nearly
constant abyssal sea depth temperatures.