1. SEAWATER PROPERTIES: SALINITY All water, even rain water, has dissolved chemicals called “salts” Salinity = the amount of dissolved salts in the water

2. What Is Seawater Made of?

3. Where Do The Salts Come From? 1. Water on land (rivers & rainwater) erode the salts in the rock & carry them to the sea 2. Volcanoes - release salt into air & underwater

4. How Does It Stay Salty? Evaporation - freshwater leaves, salts stay behind Decomposition - as living things decay in the ocean they add to the salt content  The ocean is constantly fed freshwater, why does it remain salty? FYI - if all the water were to evaporate enough salt would be left behind to build a 180 mile tall, one mile thick wall around the equator!

5. What Is The Salinity Of Seawater? P Salinity is measured in parts per thousand, the symbol = o/oo P Average salinity = 35 o/oo (meaning there are 35 grams of salt for every 1000 grams of water) (Or that the ocean is 3.5% salt) P Salinity varies depending on the amount of: rainfall, runoff, evaporation, ice formation, and current in a given area

6. Salinity Variations Ranges from 39-41 o/oo No rivers enter & hot/dry climate with high evaporation (6ft per year)! FYI: Vast amount of deep water mineral deposits (from volcanic activity) - 30,000x more lead than normal as well as gold, silver & copper A. The Highest:

7. Salinity Variations Ranges Ranges from 5-15 o/oo Huge amount of freshwater inflow (runoff supplies 1/40 of its volume each year) B. The Lowest:

8. Salinity Variations ~ 38 ~ 38 o/oo Water trapped in by sargassum (sea weed) & caught in circular eddy current = warmer, more evap. B. Highest in open ocean:

9. Salinity Variations Arctic ocean - 30 o/oo or less low evaporation & melting ice B. Lowest in open ocean:

10. Salinity Variations

11. Salinity at Different Depths Halocline = layers of water where the water’s salinity changes rapidly with depth Salinity is closely tied to water temperature & density!

12. SEAWATER PROPERTIES: TEMPERATURE Most solar radiation (light & heat) is absorbed in the 1st 50-100 meters - this is the surface layer Waves & turbulence mix this heat evenly throughout the surface layer The temperature of the surface layer varies mainly with latitude

13. SEAWATER PROPERTIES: TEMPERATURE  Thermocline = Boundary between surface & deep layers that are not mixed - where temp drops fast! 90% of ocean water is between 0-3ºC (seawater freezes at ~ -2ºC!)

14. SEAWATER PROPERTIES: DENSITY  Density = a mass/volume ratio  Density of seawater is controlled by salinity & temp Density increases as salinity increases Density increases as temp decreases Density increases as pressure increases  Let’s Watch a Density Demonstration!

15. How to Measure Salinity 1. Hydrometer = an instrument that measures specific gravity (density relative to water) = Use the density & temp graph to find salinity http://www.aquatext.com/tables/hyd1.htm

16. How to Measure Salinity 2. CTD = an instrument that measures conductivity, temperature & pressure at different depths & is the most accurate! = conductivity tells amount of salt ions in the water

17. How to Measure Salinity 3. Refractometer = measures the angle of light refraction, which changes with salt concentration!

18. THE RELATIONSHIP BETWEEN SEAWATER PROPERTIES Temp, Salinity, Density & Circulation  Temperature affects density more than salinity because temp varies more in open ocean, but both drive circulation of the water!  Denser water sinks displacing less dense water  This heat & salt (thermohaline) circulation drives a global current (circulation of water) called the Global Conveyer Belt

19. The Global Conveyor Belt

20. High Salinity, cold water sinks in North Atlantic & in Antarctica Deep water returns to surface in Indian & Pacific (upwelling) It takes ~200 years for water to circulate from N to S Atlantic & ~1000 years to complete the circuit

21. The Global Conveyor Belt  Why is it important? The Global Conveyor Belt is the main way oceans store and transport heat. The ocean stores more heat in the uppermost 3 meters than that of the entire atmosphere and acts as a "global heat engine." The ocean circulation helps drive the water cycle & climate!