ocean water chemistry

Ocean Water Chemistry

Figure 4.17a

http://www.nhptv.org/

Distribution of Earth’s Water

• Oceans 97.2 %• Ice Caps and Glaciers 2.15 %• Atmosphere 0.001 %• Rivers and Lakes 0.009 %• Inland Seas 0.008 %• Groundwater 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)

Na 60 000 000Cl 80 000 000Mg 10 000 000K 6 000 000SO4 9 000 000Ca 1 000 000Mn 7 000Fe 100

Concentration Crust (%) Ocean (mg/l)2.4 10 7700.013 19 5002.3 1 2902.1 3800.026 9054.1 4120.5 0.00022.4 0.002

Dissolved Gases

Gas Solubility:Decreases with Temp. and SalinityIncreases with Pressure

Gases in Atmosphere & Oceans

Percent Gas Phase by VolumeGas 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)+H2OH2CO3H++HCO32H+

+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

http://www.nhptv.org/

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 WhalesMegaptera novaeangliae

Gray Whale & Sonar Proposal

Eschrichtius robustus

Gray Whale Migration

Acoustic Pollution