Oceans Final

Disrupting forces

Forces that initiate waves such as wind

Restoring forces

Forces that return the water surface to equilibrium including gravity for ocean waves and surface tension for capillary waves

Wave displacement

Transfer of energy without permanent water movement where water particles move and return to their equilibrium position

Wave orbital motion

Circular motion of water particles beneath waves that decreases with depth

Wavelength (L)

Horizontal distance between successive wave crests

Wave height (H)

Vertical distance from crest to trough

Wave period (T)

Time required for two successive crests to pass a fixed point

Wave speed (C)

Rate at which wave energy travels

Wave speed equation

C = L / T

Wave generation factors

Wind speed

Sea

Short-period chaotic waves generated by local winds

Swell

Long-period organized waves generated by distant storms

Surf

Breaking waves in shallow water near the shore

Swell dispersion

Process where longer wavelength deep-water waves travel faster than shorter waves causing organized swell

Deep water wave definition

Water depth greater than one-half the wavelength (d > L/2)

Shallow water wave definition

Water depth less than one-twentieth the wavelength (d < L/20)

Deep water wave speed equation

C = √(gL / 2π)

Shallow water wave speed equation

C = √(gd)

Wave base

Depth equal to one-half the wavelength where wave orbital motion effectively ceases

Nearshore wave behavior

As waves enter shallow water speed decreases wavelength shortens and height increases

Wave breaking condition

Waves break when wave height equals approximately 0.78 times the water depth (H ≈ 0.78d)

Wave refraction

Bending of waves due to changing water depth that concentrates energy on headlands and disperses energy in coves

Coastline straightening

Long-term result of wave refraction that erodes headlands and fills bays

Longshore current

Shore-parallel current generated by waves approaching the coast at an angle

Longshore drift

Transport of sediment along the coast by longshore currents

Wave diffraction

Spreading of wave energy behind obstacles such as islands or breakwaters

Tides

Periodic rise and fall of sea level caused by gravitational interactions with the Moon and Sun

Dominant tidal force

The Moon due to its closer proximity despite the Sun’s larger mass

Gravitational force equation

Force proportional to mass divided by distance squared (F ∝ M / d²)

Two tidal bulges

Result of stronger lunar gravity on the near side of Earth and centrifugal force on the far side

Tidal deviations

Variations caused by continents ocean basin geometry depth and the Coriolis effect

Tidal day

Time between successive high tides approximately 24 hours and 50 minutes due to the Moon’s orbital motion

Amphidromic system

Rotating tidal system around a central point with no vertical tide range

Diurnal tides

One high tide and one low tide per day

Semidiurnal tides

Two equal high tides and two equal low tides per day

Mixed tides

Two unequal high and low tides per day

Spring tide

Maximum tidal range caused by alignment of Sun Moon and Earth

Neap tide

Minimum tidal range caused when Sun and Moon are at right angles

Flood tide

Incoming rising tide moving landward

Ebb tide

Outgoing falling tide moving seaward

Tidal deltas

Sediment deposits formed by flood and ebb tides at coastal inlets

Hurricane formation conditions

Warm ocean water low wind shear Coriolis effect and atmospheric instability

Hurricane eye

Calm low-pressure center of the storm

Eyewall

Region of strongest winds rainfall and storm surge

Rainbands

Spiraling outer bands of storms surrounding the eyewall

Coriolis effect

Apparent deflection due to Earth’s rotation that causes hurricanes to spin

Hurricane formation zone

Occurs between approximately 5° and 30° latitude

Equatorial limitation

Hurricanes do not form at the equator due to lack of Coriolis effect

Hurricane season

June through November in the Atlantic

Climatological peak

September

Saffir-Simpson scale

Classification system based on hurricane wind intensity

Climate change and hurricanes

Expected increase in storm intensity rainfall and storm surge

Storm surge

Abnormal rise of sea level driven by hurricane winds

Storm tide

Combination of storm surge and astronomical tide

Most destructive storm area

Right-front quadrant due to strongest winds and surge in the Northern Hemisphere

Sea level rise short-term causes

Thermal expansion and melting of alpine glaciers and ice sheets

Eustatic sea level change

Global sea level change driven by plate tectonics and greenhouse gas concentrations

Milankovitch cycles

Eccentricity obliquity and precession controlling long-term climate variability

Sea level proxies

Chemical geomorphic and sedimentary indicators of past sea levels

Pleistocene sea level change

Fluctuations of approximately 120 meters due to glacial cycles

Post-glacial sea level rise

Rapid rise since 18

Sea level stabilization implication

Allowed development of modern coastlines and human settlement

Relative sea level change

Local sea level changes influenced by vertical land motion

Glacial isostatic adjustment

Land uplift or subsidence due to past ice loading

Subsidence

Sinking of land due to sediment compaction or fluid extraction

Delta shifting

Local sea level change from sediment redistribution

Infrastructure loading

Subsidence from the weight of buildings and roads

Coastal protection

Engineering structures designed to reduce coastal hazards

Accommodation

Adjusting human activities to tolerate coastal hazards

Planned retreat

Relocation away from high-risk coastal zones

Mitigation

Reducing greenhouse gas emissions to limit climate change impacts