The Dynamic Ocean

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

PSCI 131: The Dynamic Ocean Surface Circulation

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

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

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

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 https://goo.gl/Jnpvl2

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

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

PSCI 131: The Dynamic Ocean: Surface Circulation https://goo.gl/Igsqs6

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

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

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

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

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

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

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

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:

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

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)

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

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

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

PSCI 131: The Dynamic Ocean Waves and Wave Erosion

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

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

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

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

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

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

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

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

Wave refraction

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

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

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

PSCI 131: The Dynamic Ocean U.S. Coasts

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

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 https://mediaplayer.pearsoncmg.com/assets/6KWIPpY1E5edFwpwgCkItDj1P0VUf2yx Gulf Coast wetlands

Tides Changes in elevation of the ocean surface Caused by the gravitational forces exerted upon Earth by the Moon Sun (lesser extent) https://mediaplayer.pearsoncmg.com/assets/wLsAmS39HxuAPn3KkMrbyWL_wMFipx_F

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 https://mediaplayer.pearsoncmg.com/assets/_Pf7OvQFuaFme0TZCHIxElwMyEiDggPe

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

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