Ocean Water Chemistry
Figure 4.17a
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Distribution of Earth’s Water
•
•
•
•
•
•
Oceans
Ice Caps and Glaciers
Atmosphere
Rivers and Lakes
Inland Seas
Groundwater
97.2 %
2.15 %
0.001 %
0.009 %
0.008 %
0.625 %
Ocean Water is SALTY
• Salinity: Total amount of dissolved solids
• Units: o/oo = 1/1000
• Range: 33 – 37 o/oo
• Increase in salinity:
–
–
–
–
Increase in Density
Decrease in Freezing Point
Decrease in Vapor Pressure
Increase in Osmotic Pressure
Origin of Salts in Oceans
• Rivers (largest transport of chemicals to ocean)
– Rain + CO2  H2CO3
– Si, Al, Na, K, Mg
• Volcanoes
– Cl, S, CO2
• Dust / Rain
– Fe, Si
• Anthropogenic
– CO2, P
Example Geochemical Cycle
Concept of Steady State
Example 2 Geochemical Cycle
Residence Time
(T = Ocean amount/Output rate)
• Concentration of elements in seawater is
determined by their removal rate
• Conservative elements:
– Major Elements: Cl, Na, SO4, Mg, Ca, K
- Minor Elements: Br, Sr, B, C, F
• Non Conservative Elements
– Nutrients: N, P, Si
– Dissolved gases: O2, CO2, N2
– Trace Elements: Fe, Al, Mn
– Organic Compounds
Residence Time - Concentration
Element
Res. Time (yrs)
Concentration
Crust (%)
Ocean (mg/l)
Na
Cl
Mg
K
SO4
Ca
Mn
Fe
60 000 000
80 000 000
10 000 000
6 000 000
9 000 000
1 000 000
7 000
100
2.4
0.013
2.3
2.1
0.026
4.1
0.5
2.4
10 770
19 500
1 290
380
905
412
0.0002
0.002
Dissolved Gases
Gas Solubility:
Decreases with Temp. and Salinity
Increases with Pressure
Gases in Atmosphere & Oceans
Percent Gas Phase by Volume
Gas Atmosphere
Surface Ocean
Total Ocean
N2
79%
48%
11%
O2
21%
36%
6%
CO2
0.04%
15%
83%
Seawater pH
• Pure water pH = 7
• Seawater pH = 7.5 – 8.1
• Seawater is very well buffered!
CO2(gas)+H2OH2CO3H++HCO32H++CO32
H2O: Universal Polar Solvent
H20: Temperature and Density
H2O: Frozen & Liquid density
H2O: Heat Capacity
• Heat Capacity: heat needed to change
the temperature of a substance
• Water has higher heat capacity than:
– All solids
– All liquids, except liquid ammonia
• Latent heat of Vaporization: heat
needed to evaporate a liquid
– Water has the highest of all substances
Seawater: Temperature and Density
Seawater: Temperature and salinity
Seawater: Ice Formation
Electromagnetic wave penetration
Open water
(low productivity)
Coastal and Estuarine waters
(high productivity)
Nuclear Missile Submarine
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How do we measure light penetration?
Secchi Disc
Water Refraction
Eschrichtius robustus
Sound Velocity
• Influenced by Salinity, Temperature
and Pressure
– Increases with Salinity
– Increases with Temperature
– Increases with Pressure
• Concept of Midwater Sound Channel
Study in Detail Fig 5-19!
Sound Channel
Humpback Whales
Megaptera novaeangliae
Gray Whale & Sonar Proposal
Eschrichtius robustus
Gray Whale Migration
Acoustic Pollution