Ch. 21 Ocean WaterCh. 21 Ocean Water

Ch. 21.1 Properties of Ocean Ch. 21.1 Properties of Ocean WaterWater

• Ocean water has both chemical and Ocean water has both chemical and physical properties.physical properties.

• Chemical properties include Chemical properties include composition, salinity, and the ability composition, salinity, and the ability to dissolve other substances.to dissolve other substances.

• Physical properties include Physical properties include temperature, density, and color.temperature, density, and color.

Composition of Ocean Composition of Ocean WaterWater• Ocean water contains dissolved salts, Ocean water contains dissolved salts,

minerals, and gases.minerals, and gases.• 400 billion kilograms of salts carried to 400 billion kilograms of salts carried to

oceans by rivers each year.oceans by rivers each year.• Salts and minerals remain in ocean Salts and minerals remain in ocean

when water evaporates.when water evaporates.• Amount of dissolved substances has Amount of dissolved substances has

remained constant for millions of remained constant for millions of years.years.

• Processes that add salts and Processes that add salts and minerals are balanced by processes minerals are balanced by processes that remove dissolved material that remove dissolved material (formation of sediments; use by (formation of sediments; use by marine plants and animals).marine plants and animals).

Elements in Ocean WaterElements in Ocean Water

• Ocean water is 96.5 % HOcean water is 96.5 % H220.0.• About 75 chemical elements, mostly in About 75 chemical elements, mostly in

dissolved ionic form.dissolved ionic form.• The 6 most abundant dissolved The 6 most abundant dissolved

elements are chlorine, sodium, elements are chlorine, sodium, magnesium, sulfur, calcium, and magnesium, sulfur, calcium, and potassium.potassium.

• Trace elements include gold, zinc, and Trace elements include gold, zinc, and phosphorus.phosphorus.

Dissolved GasesDissolved Gases• Gases found in the atmosphere are also Gases found in the atmosphere are also

found dissolved in the ocean (Nitrogen, found dissolved in the ocean (Nitrogen, Oxygen, Carbon Dioxide (COOxygen, Carbon Dioxide (CO22)).)).

• Carbon Dioxide dissolves the most Carbon Dioxide dissolves the most easily in ocean water.easily in ocean water.

• Most dissolved oxygen is at the surface, Most dissolved oxygen is at the surface, where the ocean is in contact with the where the ocean is in contact with the air.air.

• Unlike solids, gases dissolve better in Unlike solids, gases dissolve better in coldcold water.water.

• Gases can move back and forth Gases can move back and forth between the ocean and the between the ocean and the atmosphere.atmosphere.

• StopStop

Salinity of Ocean WaterSalinity of Ocean Water

• SalinitySalinity is the amount of dissolved solids is the amount of dissolved solids in ocean water, so named because most in ocean water, so named because most of the solids are in the form of salts.of the solids are in the form of salts.

• Defined as number of grams of dissolved Defined as number of grams of dissolved solids per kilogram of ocean water.solids per kilogram of ocean water.

• If 1 kg of ocean water was evaporated, If 1 kg of ocean water was evaporated, and 35 grams of solids remained, and 35 grams of solids remained, salinity would be 35 (salinity would be 35 (salinity = 35 salinity = 35 00//0000).).

• Both evaporation and freezing Both evaporation and freezing increase salinity.increase salinity.

• In the tropics, where evaporation is In the tropics, where evaporation is high, salinity at the surface is also high, salinity at the surface is also high.high.

• Generally, surface water has higher Generally, surface water has higher salinity than deeper water.salinity than deeper water.

• Average ocean salinity is 34.7, with Average ocean salinity is 34.7, with average range from 33 to 36.average range from 33 to 36.

• There may be extremes due to either There may be extremes due to either very high evaporation, or large very high evaporation, or large additions of fresh water.additions of fresh water.

Temperature of Ocean Temperature of Ocean WaterWater

• Solar heating raises the surface Solar heating raises the surface temperature of the ocean.temperature of the ocean.

• Ocean water movement mixes the Ocean water movement mixes the warm water to a depth of 100-300 m.warm water to a depth of 100-300 m.

• Overall warmer surface temp. near Overall warmer surface temp. near the equator than the poles…it even the equator than the poles…it even freezes at the poles, forming freezes at the poles, forming pack pack iceice..

The ThermoclineThe Thermocline

• The depth below the warm mixing The depth below the warm mixing zone, where the temperature drops zone, where the temperature drops rapidly with depth, is called the rapidly with depth, is called the thermocline.thermocline.

Density of Ocean WaterDensity of Ocean Water

• Density is mass per unit volume.Density is mass per unit volume.

• Pure water has density of 1g/cmPure water has density of 1g/cm33..

• Due to dissolved solids, ocean water Due to dissolved solids, ocean water has a density between 1.026 and has a density between 1.026 and 1.028 g/cm1.028 g/cm33..

• Temperature also affects density, with Temperature also affects density, with dense cold water usually sinking to the dense cold water usually sinking to the ocean floors in the polar regions.ocean floors in the polar regions.

Color of Ocean WaterColor of Ocean Water

• Most wavelengths of light are Most wavelengths of light are absorbedabsorbed by ocean water, except by ocean water, except blue, which is blue, which is reflectedreflected, so the ocean , so the ocean appears blue.appears blue.

• Suspended particles or marine Suspended particles or marine organisms may cause the ocean to organisms may cause the ocean to appear green or brown.appear green or brown.