Unit 3: Oceanography - Thermohaline Circulation, Waves, and Tides

This set of flashcards covers vocabulary and key concepts from the oceanography lecture notes on deep ocean circulation, wave mechanics, tidal patterns, and coastal hazards like tsunamis and storm surges.

Thermohaline circulation

The global movement of deep ocean water driven by density differences caused by temperature and salinity.

Density

A measure of how “packed together” molecules are, which determines if water sinks or rises; controlled by temperature and salinity.

Evaporation (in oceanography)

A process where water evaporates and leaves salt behind, increasing salinity and density.

Sea ice formation

A process where ocean water freezes into freshwater ice, leaving salt behind in the surrounding water, making it saltier, denser, and causing it to sink.

North Atlantic Deep Water (NADW)

A water mass formed near Greenland due to cold temperatures and salty water.

Antarctic Bottom Water (AABW)

The densest water on Earth, formed near Antarctica, which sinks deepest in the global conveyor belt.

Upwelling

The process where cold, nutrient-rich deep water rises to the surface, often occurring at the equator and west coasts like Peru and California.

Global Conveyor Belt

A continuous loop of ocean circulation driven by density differences where water sinks, travels along the deep ocean floor for hundreds to over $1000$ years, and eventually rises.

Wave

The transfer of energy through water, where water particles move in a circular motion but do not travel forward with the energy.

Crest

The highest point of a wave.

Trough

The lowest point of a wave.

Wave height (H)

The vertical distance from the crest to the trough.

Wavelength (L)

The horizontal distance between two consecutive crests.

Wave period (T)

The time required for one full wave to pass a fixed point.

Wave frequency (f)

The number of waves per unit of time, calculated as f = rac{1}{T}.

Wave base

The maximum depth at which a water wave causes significant motion, calculated as ext{Wave base} = rac{1}{2} ext{wavelength}.

Fetch

The distance over which the wind blows across the water surface to create waves.

Wave celerity (C)

The speed at which a wave travels, calculated as C = rac{L}{T}.

Deep-water waves

Waves where the water depth is greater than $rac{1}{2}$ the wavelength (D > rac{L}{2}), meaning they do not feel the ocean bottom.

Shallow-water waves

Waves where the water depth is less than $rac{1}{20}$ the wavelength (D < rac{L}{20}), and speed is dependent only on depth.

Wave refraction

The bending of waves as they approach the shore because parts of the wave hit shallow water first and slow down.

Longshore current

A current that moves water and sand along the coast when waves hit the shore at an angle.

Rip currents

Narrow, fast-moving currents that flow away from the shore, formed when water piled up near the shore escapes back to the ocean.

Tsunami

A series of waves with very long wavelengths ($ext{~200 km}$) caused by sudden water displacement, such as from earthquakes (75 ext{%}), landslides, or volcanic eruptions.

Tides

The periodic rise and fall of sea level caused primarily by the Moon's gravity and secondarily by the Sun's gravity.

Spring Tides

The strongest tides with the largest tidal range, occurring during Full or New Moon phases when the Sun and Moon are aligned.

Neap Tides

The weakest tides with the smallest tidal range, occurring during First or Third quarter moon phases when the Sun and Moon are at $90^ ext{o}$.

Diurnal tide

A tidal pattern with one high tide and one low tide per day.

Semi-diurnal tide

A tidal pattern with two equal high tides and two equal low tides per day.

Rogue waves

Extremely tall waves formed by constructive interference as waves combine their energy.

Storm surge

A rise in sea level caused by strong winds and low atmospheric pressure, often associated with hurricanes.