Ocean Water Chemistry

Ocean ChemistryGoal:Describe salinity and factors that are affected by changes in salinity levels.

Agenda:1. Wrap up ‘Ocean Profile’ lab2. Warm-up for Chemistry3. Salinity Reading4. Demo./Notes

Warm-upHow is salt added to the ocean?

The Water CycleLife could not exist without the water cycleThe water cycle continuously moves water

between the atmosphere, the land, and the oceans.

The Water CycleWater vapor condenses and falls to the

Earth’s surface as precipitationSome of this water percolates into the soil to

become ground waterSome runs across the surface into lakes,

rivers, and the oceanThe water is heated by the sun and reenters

the atmosphere by evaporation

Precipitation

Evaporation

Condensation

Evaporation

Percolation

Characteristics of Ocean WaterOcean water is

salty!

The salt is called Sodium chlorideWhy???

SalinityThe amount of dissolved

solids in a given amount of liquid is called salinity

Measured in ppt (parts per thousand)

For example: 1000 grams of ocean water can be evaporated and leave 35 grams of solids behind

How did the oceans get salty?Water flows from land into the oceans and

brings minerals as it flows over rocks and slowly wears them down

At the same time, water is evaporating and leaving the minerals behind

Stop and Think Describe three factors that influence salinity and their relationships.

Factors Affecting Salinity: ClimateCoastal waters in places with hotter, drier

climates typically have higher salinity.Why?

Higher rate of EVAPORATION Removes water but leaves salt behind

Coastal waters in cooler, more humid places typically have a lower salinityLower rate of evaporation

Evaporation = Salinity

Evaporation = Salinity

Factors Affecting Salinity: River runoffCoastal waters near an emptying river tend

to have lower salinityWhy?

The freshwater dilutes the saltwater

Coastal waters not near an emptying river tend to have higher salinity

Fresh water = Salinity

Fresh water = Salinity

Factors Affecting Salinity: MovementSome parts of the ocean move less than other

partsBays, gulfs, seas, open ocean where there’s no

currentSlower moving areas of water develop higher

salinity Less circulation (no currents running through them)

so salt settles here

Faster moving areas of water develop lower salinity

Movement = Salinity

Movement = Salinity

Warm-upExchange paragraphs with a partner and discuss the answers.

Temperature ZonesThe temperature of ocean water decreases as

depth increasesThis change is NOT gradualWater in the ocean can be divided into three

layers by temperature Water at the surface is much warmer than

the average water temperature

Ocean Temperature ZonesSurface Zone

Thermocline

Deep Zone

• Warm, mixed by waves—aka “mixed zone”

• Sunlight, plant growth• Temp depends on latitude

• Temperature drops rapidly with depth

• Uniformly cold• 1-3 degrees C• Polar creep—ocean current

Warm-upHow do thermocline graphs differ depending on latitude and seasons? Describe different latitudes and seasons.