1. Ocean Water & Life

2. Ocean Water & Life Composition of Seawater
Ocean Temperature & Density Variation
Oceanic Biological Productivity

3. Composition of Seawater
PSCI 131: Ocean Water & Life
Composition of Seawater

4. Composition of Average Seawater
PSCI 131: Ocean Water & Life
Composition of Average Seawater

5. Composition of Normal Seawater
PSCI 131: Ocean Water & Life
Composition of Normal Seawater
Salt sources
Minerals from the continents Undersea volcanism

6. Processes Affecting Salinity
PSCI 131: Ocean Water & Life
Processes Affecting Salinity
Total mass of salt in open oceans doesn’t change, but salinity does
Salinity is mass of salt / mass of water
So, water must be added/removed for salinity to change

7. Processes Affecting Salinity
PSCI 131: Ocean Water & Life
Processes Affecting Salinity
Salinity increases if water is removed
Evaporation
Sea ice formation

8. Processes Affecting Salinity
PSCI 131: Ocean Water & Life
Processes Affecting Salinity
Salinity decreases if water is added
Precipitation
Runoff (rivers)
Sea ice melting
Icebergs melting

9. Global Salinity Variation
PSCI 131: Ocean Water & Life
Global Salinity Variation
Salinity vs latitude
Patterns correspond to air pressure belts

10. Ocean Temperature and Density Variations
PSCI 131: Ocean Water & Life
Ocean Temperature and Density Variations

11. Temperature vs Depth Warm latitudes Cold latitudes
PSCI 131: Ocean Water & Life
Temperature vs Depth
Warm latitudes
Cold latitudes

12. Thermocline Rapid decrease in water temperature with increasing depth
PSCI 131: Ocean Water & Life
Thermocline
Rapid decrease in water temperature with increasing depth
Exists year-round in tropics/subtropics
Never appears in subpolar/polar latitudes
Seasonal in temperate latitudes

13. Ocean Water Density Controlled by temperature and salinity
PSCI 131: Ocean Water & Life
Ocean Water Density
Controlled by temperature and salinity
Higher temp = lower density
Higher salinity = higher density

14. Density vs Depth Warm latitudes Cold latitudes
PSCI 131: Ocean Water & Life
Density vs Depth
Warm latitudes
Cold latitudes

15. Pycnocline Rapid increase in water density with increasing depth
PSCI 131: Ocean Water & Life
Pycnocline
Rapid increase in water density with increasing depth
Mirror image of thermocline
Temperature has stronger influence on density than salinity

16. Ocean Water Layering In regions where a thermocline is present
PSCI 131: Ocean Water & Life
Ocean Water Layering
In regions where a thermocline is present
Surface mixed zone: warm, well-circulated
Transition zone: location of thermocline
Deep zone: cold, dark

17. Ocean Water Layering If no thermocline, then no layering
PSCI 131: Ocean Water & Life
Ocean Water Layering
If no thermocline, then no layering
Polar, subpolar, temperate (in winter)

18. PSCI 131: Ocean Water & Life
Oceanic Productivity

19. Controls on Marine Productivity
PSCI 131: Ocean Water & Life
Controls on Marine Productivity
Total biomass varies spatially (from place to place) and temporally (over time)
What determines how much biomass a given place at a given time can support?
Availability of sunlight
Amount of nutrients in the water

20. Controls on Sunlight Availability
PSCI 131: Ocean Water & Life
Controls on Sunlight Availability
Sunlight availability in the ocean depends on sun angle
Sun angle controlled by
Latitude
Season
Relationship of latitude to sun angle.
Relationship of season to sun angle.

21. Nutrients: What are they?
PSCI 131: Ocean Water & Life
Nutrients: What are they?
Nutrients are elements and compounds dissolved in ocean water (sodium, phosphorous, carbonate, etc.)
Needed by phytoplankton to live
Phytoplankton live in surface waters
These waters become depleted in nutrients as phytoplankton use them up

22. Nutrients: How are they replenished?
PSCI 131: Ocean Water & Life
Nutrients: How are they replenished?
Upwelling: movement of deeper, colder, nutrient-rich water up to surface
If upwelling is limited or prevented, surface waters will have low biomass

23. Role of the Thermocline
PSCI 131: Ocean Water & Life
Role of the Thermocline
Thermocline restricts vertical water movement
Regions with strong thermocline have nutrient-poor surface water
Warm latitudes
Cold latitudes

24. Role of Phytoplankton in Productivity
PSCI 131: Ocean Water & Life
Role of Phytoplankton in Productivity
Phytoplankton are the foundation of the marine food web
If phytoplankton biomass changes, total biomass changes
Diatom and zooplankton biomass in the Barents Sea over 12 months. Diatoms are a type of phytoplankton.

25. Annual Marine Productivity by Latitude
PSCI 131: Ocean Water & Life
Annual Marine Productivity by Latitude

26. Marine Productivity: Polar/Subpolar
PSCI 131: Ocean Water & Life
Marine Productivity: Polar/Subpolar
Low productivity except for mid-summer
Surface waters are nutrient-rich
Isothermal (no thermocline) year-round
But, sunlight is scarce for most of the year
In mid-summer, enough sunlight becomes available to cause spike in phytoplankton biomass

27. Marine Productivity: Tropical/subtropical
PSCI 131: Ocean Water & Life
Marine Productivity: Tropical/subtropical
Low productivity year-round
Sunlight is plentiful year-round
But, strong thermocline exists year-round
Surface waters are well-lit, but nutrient-poor

28. Marine Productivity: Temperate latitudes
PSCI 131: Ocean Water & Life
Marine Productivity: Temperate latitudes
Productivity varies by season
Sunlight availability and presence of thermocline change significantly

29. Marine Productivity: Temperate latitudes
PSCI 131: Ocean Water & Life
Marine Productivity: Temperate latitudes
Productivity in the temperate-latitude surface ocean over 12 months.

30. PSCI 131: Ocean Water & Life
End of Chapter