15.1 Composition of Seawater

The total amount of solid material dissolved in water

Mass of dissolved substances : Mass of the water sample

Shown in % Most of the salt in seawater is Sodium Chloride

(NaCl), common table salt

Salinity

Chemical weathering of rocks on the continents is a source of elements found in seawater Reach oceans through runoff from rivers and

streams Another source is of elements found in

seawater is from Earth’s interior Through volcanic eruptions, large amounts of

water vapor & other gases have been emitted into the atmosphere

Sources of Sea Salts

Surface salinity varies in the ocean normally from 33% - 38%

Variations in salinity result from changes in the water content of the solution

Processes Affecting Salinity

Add freshwater to saltwater Precipitation Runoff from land Icebergs melting Sea ice melting

Remove freshwater from saltwater Evaporation Formation of sea ice

Continued…

Ocean’s surface water temperature varies with the amount of solar radiation it gets. (Fxn. of latitude)

Surface waters = higher temperatures (in LL) Deeper waters = lower temperatures (in LL) Thermocline is the layer of ocean water btw

300 m – 1000 m where rapid change of temperature is seen with depth Vertical barrier to many types of animals

Ocean Temperature Variation

In HL (high latitude)… Surface water = cooler than in LL Deeper water = similar to the surface

temperature Curve is vertical

CONTINUED…

Density – mass per unit volume Pycnocline – layer of ocean water btw 300 m

– 1000 m where there is a rapid change of density with depth

Saltwater density is influenced by two factors… Salinity Temperature

Most important factor affecting saltwater density Inversely proportional to density

Ocean Density Variation

Layered according to denisty Low density is near the surface Higher density is near the bottom 3 layered structure

Shallow surface mixed zone Transition zone Deep zone

Ocean Layering

Surface Zone Warmest water temperature

Transition Zone Temperature falls quickly Distinctive layer between warm surface layer &

the deep cold layer Deep Zone

Sunlight never reaches this zone Right above freezing

Continued…

What is salinity? Explain how latitude and sea surface

temperature relate. What are the 3 main zones of the ocean? Where would more dense water be found?

Less dense water?

Review Questions