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Dynamic Ocean Currents and Coastal Processes

Explore the powerful forces driving ocean currents, from wind friction to density variations, and their impact on marine life and coastal erosion.

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Dynamic Ocean Currents and Coastal Processes

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  1. CH 16 The Dynamic Ocean • Ocean water is in constant motion and powered by many forces • Forces include wind, Coriolis, gravity, density differences • Ocean currents are masses of ocean water that flow from one place to another • Surface or deep

  2. Surface Currents • Movements of water that flow horizontally • Develop from wind friction • Gyres = huge circular moving current systems (5) • Coriolis Effect = the deflection of currents to the right in the NH (& left in the SH) due to earth’s rotation • Warm currents move from the equator to the poles • Cold currents move from polar regions to the equator • Cold currents = west coast; warm currents = east coast

  3. Deep Ocean Circulation • Vertical movement of water • Upwelling = cold water rising from deep layers to replace warm surface water • Brings nutrients to surface(good for fishing) • Density currents = vertical currents of water due to density differences • From temperature(cold) and salinity (high) • Read pages 451 – 453

  4. Waves • Most waves obtain their energy and motion from wind • Big wind = big waves • Crest = top • Trough = bottom • Wave height = distance from trough up to crest • Wavelength = distance from crest to next crest • Wave period = time it takes a full wavelength to pass a fixed position

  5. Height, length, & period of waves depends on 3 factors: • 1. Wind speed • 2. Length of time the wind blows • 3. Fetch (distance across body of water) The only thing that really moves forward in a wave is energy(particles move in circular orbital motion) Breakers--Waves that break (fall forward) when the depth of the water is one-half of the wavelength.

  6. TIDES • Please see other PP

  7. SHORELINE PROCESSES/FEATURES • BEACH = accumulation of sediment along shores. (white,pink,tan,black,green) • SHORELINE (WAVE) FORCES: • Eroding • Transporting • Depositing • Wave impact • Abrasion • Refraction = bending of waves

  8. Wave energy is concentrated at headlands = more erosion • Wave energy is weakened in bays = more deposition • Longshore current = sediments carried along (parallel) to shore due to waves hitting at an angle.

  9. EROSIONAL FEATURES: • Sea Cliff – result from waves cutting at the base • Sea Cave – from softer rock being eroded • Sea Arch – cave all the way through • Sea Stacks – roof of the arch collapses • Wave-cut platform or terrace – from continued wave action causing a flat eroded area

  10. DEPOSITIONAL FEATURES: • Spit – elongated ridge of sand sticking into the bay • Hook – when the spit hooks due to currents • Baymouth Bar – when a sand bar completely crosses the bay • Tombolo – a ridge of sand that connects an island to the mainland • Barrier Islands = (Outer Banks)

  11. Stabilizing/protecting shores: • Jetties or groins –barrier built at right angles to the beach to catch sand • Breakwaters – offshore and parallel to coast • Seawalls – parallel to coast often from the shore • Beach nourishments • Natural protectors: sand bars, sand dunes, fringing reefs, barrier reefs, & atolls

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