1. Unit 2: Surface Processes and the Hydrosphere Lesson 7: Physical Oceanography Pt. 2 ( Heath Earth Science – Pg. 308-352)

2. Today’s Objectives  Describe features and processes associated with physical oceanography, including:  Identify the physical properties of sea water (temperature, density, salinity, composition)  Explain the general pattern of major currents in oceans

3. Physical Properties of Sea Water  Sea water has several characteristics that differentiate it from fresh water  These characteristics include:  1) Temperature  2) Salinity  3) Density  4) Composition

4. 1) Temperature  The Ocean has three main temperature zones:  Mixed layer (surface):  Warm zone where wind and waves at the surface mix heat evenly throughout the zone  Only layer with seasonal temperature fluctuations  Thermocline:  Layer with rapid temperature change between mixed layer and deep water, usually between 500-1000m below surface  Deep water:  Cold layer beneath the thermocline  Deep ocean water can be as cold as 2˚ C

5. Ocean Temperatures  Note that ocean temperatures only change seasonally in the surface layer

6. 2) Salinity  Salinity is a measure of the dissolved solids in sea water  The main sold is common salt, or sodium chloride  Other salts such as magnesium chloride and calcium sulfate also occur in sea water  Salinity can be determined by evaporating a measured quantity of filtered sea water.  The white crust that remains in the evaporating dish is made up of the salts that were dissolved in the water  The ratio of the mass of salt to the original mass of the water is the salinity

7. Variations in Salinity  Sea water typically has a salinity of 35 parts dissolved salt per 1000 parts sea water, or 35‰  Ocean water ranges from 33 ‰ to 37 ‰ near it’s surface  Salinity is below average where:  Large amounts of fresh water enters the ocean, such as near river deltas  Areas of high rainfall, such as along the equator  Where glaciers enter the ocean  Salinity is above average where:  Climate is hot and dry, where evaporation is high (20-30 degrees latitude)  Polar waters near sea ice (sea water freezes, leaves salt behind in the water)

8. 3) Density  The density of pure water is 1 gram/cm 3 @ 4˚C  The density of sea water is 1.025 gram/cm 3 @ 4˚C  Why do you think sea water is more dense than pure water?  Answer is in the chart on the next page

9. 4) Composition of Sea Water  Dissolved ions are carried by the sea water, thus increasing its density Dissolved IonPercentage Chloride (Cl-)55.04 Sulfate (SO4 2-)7.68 Bicarbonate (HCO3 -)0.41 Bromide (Br -)0.19 Sodium (Na+)30.61 Magnesium (Mg 2+)3.69 Calcium (Ca 2+)1.16 Potassium (K+)1.10 All others0.12 100.00

10. Practice  Topic Questions  Pg. 313, #4,6  Pg. 315, #8-10

11. Ocean Currents  An ocean current can be defined as any continuous flow of water along a broad path in the ocean -  The flow may occur at the surface or far below it  The flow may be up, down, or parallel to the surface  Each water mass is distinct from the water around it because of its identifiable temperature, salinity, and chemical composition  Surface ocean currents are mostly driven by wind, and to some extent the shape of the continents  Sub-surface ocean currents are driven by density

12. Surface Ocean Currents Follow general direction of major wind belts Currents will follow coastline of continents if wind takes them there

13. Sub-Surface Ocean Currents  Sub-surface currents  High salinity = high density, water sinks  Low salinity = low density, water floats  Example (Ocean conveyor belt):  Water near the north Atlantic freezes leaving salt behind in the sea water, increasing the cold water’s density even more. The water then sinks. Warm, less dense water from the equator moves in to replace it.

14. Ocean Conveyor Belt System

15. Practice  Topic Questions  Pg. 347, #1-3,5  Pg. 351, #7-10