Ocean Currents, Tides, and Waves

Vocabulary practice flashcards covering ocean surface currents, gyres, thermohaline circulation, tidal mechanics and cycles, and wave dynamics.

Ocean Currents

Continuous, large-scale movements of seawater that act like vast rivers within the oceans, distributing heat from the equator to the poles, transporting nutrients and marine life, and regulating Earth's climate.

Gulf Stream

A well-known warm surface current in the North Atlantic (coined by Ben Franklin) that warms Western Europe, traveling at an average speed of $4\,\text{mph}$ ($6.4\,\text{kph}$).

California Current

A prominent surface current along the U.S. West Coast that brings cooler water southward toward Baja.

Gyres

Massive, circular rotating systems of surface currents in major ocean basins driven by wind patterns and deflected by the Coriolis Effect; they rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Coriolis Effect

The deflection of moving air and water caused by Earth rotating faster at the equator than at the poles, curving moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Great Pacific Garbage Patch

A massive accumulation of marine debris and plastic trapped within the circulating currents of the North Pacific Gyre.

Thermohaline Circulation

A deep-ocean current system driven by density differences resulting from variations in temperature ('thermo') and salinity ('haline'), flowing at roughly $1\,\text{cm/s}$ and taking about $1{,}000\text{ years}$ to complete a full cycle.

Tides

The periodic rise and fall of sea levels caused primarily by the gravitational pull of the Moon and the Sun, combined with Earth's rotation.

Earth-Moon Barycenter

The common center of mass between the Earth and the Moon; rotation around this point creates centrifugal force that produces a secondary tidal bulge on the side of Earth facing away from the Moon.

Bay of Fundy

A narrow coastal inlet in Canada where local geography amplifies the tidal range up to $16\text{ meters}$.

Semidiurnal Tide

A daily tidal cycle characterized by two high tides and two low tides of approximately equal height each day, typical along the U.S. East Coast.

Diurnal Tide

A daily tidal pattern consisting of only one high tide and one low tide per day, seen in portions of the Gulf of Mexico.

Mixed Semidiurnal Tide

A daily tidal pattern with two high tides and two low tides of unequal heights each day, common along the U.S. West Coast.

Spring Tides

Tides exhibiting the largest tidal range (higher highs and lower lows) that occur roughly twice a month during new and full moons when the Sun, Moon, and Earth align.

Neap Tides

Tides with the smallest tidal range that occur roughly twice a month during first- and third-quarter moons when the Sun and Moon pull at right angles relative to Earth.

Nodal Precession

An $18.6\text{-year}$ astronomical cycle caused by variations in the Moon's orbital tilt that creates long-term fluctuations in tidal extremes.

Waves

Energy moving through the ocean that creates disturbances on the surface or at subsurface density interfaces.

Wind Waves

The most common ocean waves, generated when wind transfers energy to the water's surface; their size depends on wind speed, wind duration, and fetch.

Fetch

The uninterrupted horizontal distance of open water over which wind blows in a constant direction to generate waves.

Swell Waves

Smooth, uniform, long-period waves (typically $10\text{--}20\text{ seconds}$) that have traveled long distances away from their originating storm source.

Tsunamis

Extremely long-wavelength waves triggered by large underwater disturbances such as earthquakes or landslides, capable of traveling at speeds of $500\text{--}800\,\text{km/h}$ ($310\text{--}500\,\text{mph}$) in deep water.

Internal Waves

Subsurface waves that form and propagate along the pycnocline (density interface) between water layers of differing temperature or salinity, often generated by tides over bottom topography.

Shoaling

The physical process where a wave moves into shallow water, causing bottom friction to compress circular orbits into ellipses, increasing wave height while decreasing wavelength and speed.

Spilling Breakers

Breakers that form on gently sloping shorelines, characterized by the wave's crest slowly and gradually tumbling forward down the face, producing foamy water.

Plunging Breakers

Breakers characteristic of steep beaches or sandbars, where the crest outruns the base and curls over forward to trap an air pocket or hollow barrel before collapsing.

Surging Breakers

Breakers that occur on very steep beaches where waves build up and surge rapidly directly onto the shore without forming a significant breaking curl or crest foam.