1. The Dynamic Ocean

2. The Dynamic Ocean Surface Circulation Deep-Ocean Circulation
Shorelines & Shoreline Features
Waves & Wave Erosion
U.S. Coasts

3. PSCI 131: The Dynamic Ocean
Surface Circulation

4. PSCI 131: The Dynamic Ocean
Surface Circulation
Surface ocean currents are “rivers” with very different temperature and density than surrounding water
Driven by wind blowing across ocean surface
Ultimate energy source: Sun
Carry warm water from tropics to poles and vice versa
Gyres: huge, slow moving circles – 5 of them

5. Surface Current Patterns
PSCI 131: The Dynamic Ocean: Surface Circulation
Surface Current Patterns

6. Currents and climate Warm currents Cool currents Moderate temperatures
Strongest influence in winter
Cool currents
Chill the air
Greatest influence during summer and in tropics

7. Influence on Climate: The Gulf Stream
PSCI 131: The Dynamic Ocean: Surface Circulation
Influence on Climate: The Gulf Stream
Moves warm water north from tropics
Gives British Isles a temperate climate
North America
Water movement

8. Upwelling and Deep-Ocean Circulation
PSCI 131: The Dynamic Ocean
Upwelling and Deep-Ocean Circulation

9. Upwelling Vertical movement of water
PSCI 131: The Dynamic Ocean: Surface Circulation
Upwelling
Vertical movement of water
Deeper water moves up to replace surface water moved away by winds
Depths: 150-1,000 feet
Replenishes nutrients

10. PSCI 131: The Dynamic Ocean: Surface Circulation

11. Deep-Ocean Circulation
PSCI 131: The Dynamic Ocean
Deep-Ocean Circulation
Vertical motion driven by density differences
If upper layers become denser, they sink
Density controlled by temperature and salinity
aka “thermohaline” circulation
Most water involved in deep-ocean currents begins in high latitudes at the surface

12. Deep-Ocean Circulation
PSCI 131: The Dynamic Ocean
Deep-Ocean Circulation

13. Shorelines & Shoreline Features
PSCI 131: The Dynamic Ocean
Shorelines & Shoreline Features

14. Shoreline: Terminology
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline: Terminology
Shoreline: contact between water and land
Coast: area from shoreline inland as far as ocean-related features are found
Coastline

15. Shoreline: Terminology
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline: Terminology
Coastline: Highest line affected by storm waves

16. Shore: low tide line to coastline
PSCI 131: The Dynamic Ocean: Shorelines: Terminology
Shore: low tide line to coastline
Foreshore: low tide line to high tide line
Backshore: high tide line to coastline

17. Nearshore: low tide line to surf line Offshore: beyond surf line
PSCI 131: The Dynamic Ocean: Shorelines: Terminology
Nearshore: low tide line to surf line
Offshore: beyond surf line

18. Shoreline Features: Beaches
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Beaches
Accumulations of sediment along margin of ocean or lake
Berm: level area, usually dry
Beach face: sloping area, usually wet
Berm:

19. Shoreline Features: Beaches
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Beaches
Composition: any locally available sediment type
Quartz sand
Shells
Volcanic material
Etc.
Rocky Great Lakes beach
Shells
Black volcanic sand

20. Shoreline Features: Barrier islands
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Barrier islands
Wide beaches
Separated from mainland by marshes or narrow seaways
Shaped by wave erosion and storms
Wave-cut cliff
(uplifted wave-cut platform)

21. Shoreline Features: Cliffs, Platforms, Terraces
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Cliffs, Platforms, Terraces
Wave-cut cliff
(uplifted wave-cut platform)

22. Shoreline Features: Sea Arches and Sea Stacks
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Sea Arches and Sea Stacks

23. Shoreline Features: Spits, Bars, Tombolos
PSCI 131: The Dynamic Ocean: Shorelines
Shoreline Features: Spits, Bars, Tombolos

24. PSCI 131: The Dynamic Ocean
Waves and Wave Erosion

25. Ocean Waves Created by wind
PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Ocean Waves
Created by wind
Energy propagating along water-air boundary
Waves move differently in deep and shallow ocean
Deep: no net movement of water, circular motion
Shallow: water is displaced, linear motion

26. Ocean waves Wave Characteristics Dependent upon
Wave height—the distance between a trough and a crest
Wavelength—the horizontal distance between successive crests (or troughs)
Wave period—the time interval for one full wave to pass a fixed position
Dependent upon
Wind speed
Length of time the wind blows
Fetch—the distance that the wind travels

27. Ocean Waves PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Wave base
Wave base: depth below which water does not “feel” wave
Wave base = ½ wavelength

28. Deep ocean wave motion is circular
PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Deep ocean wave motion is circular 1 5 2 6 3 7 8 4
Boat returns to starting position

29. Shallow ocean wave movement
PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Shallow ocean wave movement
Wave base

30. Wave Erosion Direct impact of water Abrasion by sediment in the water
PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Wave Erosion
Direct impact of water
Abrasion by sediment in the water
Rocks polished by abrasion
Cliff undercut by wave impacts

31. Movement of sand Perpendicular to shore
Low wave activity: sand moves up the beach, building up a berm. Typical in summer
High wave activity: sand moves away from beach, erosion dominates. Typical in winter

32. Wave refraction Bending of a wave Wave arrives parallel to shore
Results
Wave energy is concentrated against the sides and ends of headland
Wave erosion straightens an irregular shoreline

33. Wave refraction

34. Movement of snd Parallel to shore
Beach drift—sediment moves in a zigzag pattern along the beach face
Longshore current
Current in surf zone
Flows parallel to the shore
Moves substantially more sediment than beach drift

35. Shoreline Sediment Movement
PSCI 131: The Dynamic Ocean: Waves & Wave Erosion
Shoreline Sediment Movement

36. Rip Currents
Concentrated movements of water flowing in opposite direction of breaking waves
Can be hazardous to swimmers

37. PSCI 131: The Dynamic Ocean
U.S. Coasts

38. Pacific Coast Emergent: Steep, geologically active, rugged
PSCI 131: The Dynamic Ocean: U.S. Coastal Problems
Pacific Coast
Emergent: Steep, geologically active, rugged
Cliffs with narrow beaches
Beaches are getting narrower
Natural sand supplies from rivers have been restricted by damming
Since beaches absorb wave energy, narrower beaches means faster wave erosion of cliffs

39. Atlantic and Gulf Coasts
PSCI 131: The Dynamic Ocean: U.S. Coastal Problems
Atlantic and Gulf Coasts
Submergent: Flat, geologically quiet
Wide beaches, barrier islands
Rising sea level is causing more frequent flooding
Gentle slope of coastline amplifies effect of sea level rise
Wetlands and barrier islands
Natural protection for mainland from storms
Draining and development is diminishing this protection
Gulf Coast wetlands

40. Tides Changes in elevation of the ocean surface
Caused by the gravitational forces exerted upon Earth by the
Moon
Sun (lesser extent)

41. Monthly tidal cycle Spring tide Neap tide During new and full moons
Gravitational forces added together
Especially high and low tides
Large daily tidal range
Neap tide
First and third quarters of the Moon
Gravitational forces are offset
Daily tidal range is least

42. Tidal patterns
Influenced by shape of coastline, configuration of ocean basin, and water depth
Main tidal patterns
Diurnal tidal pattern
A single high and low tide each tidal day
Semidiurnal tidal pattern
Two high and two low tides each tidal day
Little difference in the high and low water heights
Mixed tidal pattern
Two high and two low waters each day
Large inequality in high water heights, low water heights, or both

43. End of Chapter