1. Oceanography

2. The Oceans Ocean Facts: Covers 71% of the earth’s surface
Accounts for 97% of the water on earth (rest in land ice, groundwater, lakes & rivers)
Average depth ~ 4,000 meters
Average temp ~ 4oC (only 39oF)
Average salinity ~ 35‰ = 3.5%
(1 meter = 3.3 feet)

3. The Oceans

4. Ocean Zones Horizontal divisions:
coastal
oceanic
Horizontal divisions:
Coastal (neritic) = on/over shelf (shallow)
Oceanic = beyond continental shelf (deep)
benthic
shelf
benthic
abyss

5. Ocean Zones Vertical divisions: Pelagic = open water Epipelagic
coastal
oceanic
Vertical divisions:
Pelagic = open water
Epipelagic
(0-200m)
Mesopelagic
( m)
Bathypelagic+
(1000m+)
Benthic =
ocean bottom
benthic
shelf
benthic
abyss

6. Continental Margins Continental shelf
As narrow as <1 km (0.6 mi) at active margins (tectonic activity)
As wide as >750 km (470 mi) at passive margins (in middle of plates)
Shallow, typically <200 m (600 ft)
Only 8% of ocean surface, but biologically richest part of ocean

7. Continental Shelf
Intertidal zone (between high and low tides) – open, exposed
Sandy shores (Atlantic
– Cape Cod and south)
Rocky shores (most
Pacific, Atlantic – north
of Cape Cod)

8. Continental Shelf
Intertidal zone (between high and low tides) – protected, muddy
Salt marshes (temperate)
Mangrove forests (tropical)

9. Tides Tides are affected by both the moon and the sun
Tidal day = 24 hours, 50 minutes

10. Tides

11. Continental Shelf
Estuaries - any semi-enclosed coastal area where freshwater and seawater meet and mix

12. Long Island
Sound

13. South Shore
Bays

14. Peconic Bay http://www.epa.gov/owow/estuaries/programs/studies/pb.gif

15. Continental Shelf Subtidal zone (always underwater)
Soft-bottom (sand, mud)
Unvegetated
Seagrass beds
NOAA

16. Continental Shelf Subtidal zone (always underwater) Hard-bottom
Seaweed, kelp forests
Coral reefs

17. Continental Margins

18. Deep-Ocean Basins Deep sea floor features:
Averages ~4000m (13,000 ft, 2.5 mi)

19. Deep Ocean Bottom Soft bottom (most common): Abyssal plains
Silt, clay, biogenic oozes (forams, diatoms, radiolarians)

20. Deep Ocean Bottom Hard bottom: Seamounts Ridges Deep coral reefs NOAA

21. Hydrothermal Vents

22. Hydrothermal Vents High temperature High chemical concentrations
High acidity

23. Hydrothermal Vents Chemosynthesis – energy from chemicals, not the sun
Chemosynthetic bacteria, archaea:
Outside on rocks
Inside some
animals (tube worms, mussels, clams)
An oasis of warmth and
food for other animals

24. Cold Seeps Brine pools:
Gulf of Mexico was shallow sea that dried up in Jurassic period
Thick layer of salts covered with sediment when seawater returned
Salt seeps up through cracks in sediment
NOAA

25. Cold Seeps Brine pools: Underwater lakes of super salty water
Methane gases also seep out
depth 700 m
NOAA

26. Cold Seeps Chemosynthetic bacteria in mussels An oasis of food NOAA

27. Water Water is unique and critical for life Viscous, thick medium
Slow to heat up & cool down, regulates climate
Exists in 3 states on earth
Maximum density at 4°C, not 0°C (ice floats, insulates)
Universal solvent

28. Seawater
Seawater is a complex solution of dissolved ions and other dissolved solids and gasses

29. Salinity Salinity = the total amount of dissolved salts in water
Average amount = 35 g salt/1000 g seawater = 3.5% = 35‰ (parts per thousand)
Can be 0‰ at river mouths and >40‰ in parts of Red Sea

30. Salts in Seawater
major
minor

31. Temperature
Gulf Stream
Sargasso
Sea
California Current

32. Density
The density of water is a function of its temperature and salinity
Density increases with lower temperature (until 4°C)
← Cold water (max at 4°C)
← Warm water (958 at 100°C)
← Solid ice (917 at 0°C)
← Water vapor (1.2)

33. Density
The density of water is a function of its temperature and salinity
Density increases with higher salinity
Cold salty water is the densest of all
← Salty water (1027)
← Fresh water (1000)

34. Density, Temperature, and Salinity
3 stratified layers according to density:
Surface mixed layer (epipelagic)
Mixed by wind and waves
Warmer and less dense
Up to 200m deep
Intermediate transition layer (mesopelagic)
Deep stable layer (bathypelagic & beyond)
Colder and denser
Below 1000m

35. Density, Temperature, and Salinity
200 -
pycnocline
halocline

36. Density, Temperature, and Salinity

37. Dissolved Gasses
Most gases easily dissolve in seawater, but ocean proportions differ greatly from atmospheric proportions
Carbon dioxide is very soluble (0.039% of atmosphere, 15% of gases in ocean)
Oxygen is not very soluble (much less than in atmosphere)
Unlike solids, gases dissolve better in cold water, so all gas concentrations are higher in the polar waters than the tropics

38. decomposition of organic matter
Dissolved Gasses
Highest at surface –
mixing with air
Oxygen minimum zone -
decomposition of organic matter
High at bottom –
deep water formed at surface

39. Dissolved Gasses Hypoxia = low oxygen (<3 mg/l) Anoxia = no oxygen
Stressful or deadly for marine life

40. Dissolved Gasses Hypoxia in Long Island Sound every summer

41. Dissolved Gasses Increased CO2 in air → more in the ocean
Increase in H+ ions makes water more acidic, pH 8.2→8.1, expected by 2100

42. Dissolved Gasses “Ocean acidification”
Bad for organisms with calcium carbonate shells

43. Dissolved Gasses

44. Light in the Ocean
Most sunlight does not penetrate very far into the ocean
transparency depends upon suspended matter
deeper in tropics, less in coastal
Blocked by scattering and absorption
Different colors penetrate to different depths
NOAA

45. Light in the Ocean

46. Light in the Ocean Epipelagic = photic zone
(bright light, all plants/algae)
Mesopelagic = twilight zone
(little light, no plants/algae)
Bathypelagic = aphotic zone
(no light, no plants/algae)

47. Pressure in the Ocean Pressure increases with increasing water depth
Water is heavier than air
Pressure increases with increasing water depth
Sea level = 1 atm. of pressure
In ocean, each 10m of depth (33ft) you add another atm. of pressure

48. Pressure in the Ocean Before and after travelling to 2000 ft