The Restless Ocean

The Restless Ocean - The Restless Ocean The Restless Ocean...

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Unformatted text preview: The Restless Ocean The Restless Ocean Ocean Currents Ocean Currents • Masses of water that flow from one place to another • Ocean currents can be either deep or surface Ocean Circulation Patterns Ocean Circulation Patterns • Gyre: Current system within an ocean basin Main types of gyres Main types of gyres • • • • • North Pacific South Pacific Indian Ocean North Atlantic South Atlantic Ocean Circulation patterns (cont.) Ocean Circulation patterns (cont.) • The center of each gyre is about 30oN or 30oS latitude. • These are known as subtropical gyres Subtropical gyres Subtropical gyres • Subtropical gyres move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere • The primary factor that influence the movement of ocean water is called the Coriolus effect • Ocean currents play a major role in maintaining Earth’s heat balance • This is accomplished by transferring heat from the tropics to the poles North Atlantic gyre North Atlantic gyre • • • • Gulf stream North equatorial current North Atlantic current Canary current Upwelling Upwelling • Upwelling is the rising of cold water from deeper layers to replace warmer surface water • Upwelling also brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the surface Deep ocean circulation Deep ocean circulation • Deep ocean circulation accounts for the thorough mixing of deep­water masses • This component of ocean circulation is based on density differences • These density variations can be caused by temperature and salinity • This is referred to as a thermohaline The shoreline The shoreline • The shoreline is the dynamic interface among, land and sea • The shoreline is where continental and oceanic processes converge • The shoreline serves as a transition zone between continental and marine environments • The shoreline is constantly being bombarded by waves Waves Waves • Ocean waves are energy traveling along the interface between ocean and atmosphere • Ocean waves often transfer energy from a storm far out at sea over distances of thousands of miles Wave characteristics Wave characteristics • • • Wave crest: The top of a wave Trough: the bottom of a wave Wave height: distance between the crest and the trough • Wavelength: Horizontal distance from crest to crest or from trough to trough • Wave period: The amount of time for a wave to pass a fixed position • Wave height, wavelength and wave period are dependent upon three factors: 1) wind speed 2) length of time that the wind has blown 3) fetch: the distance the wind has traveled across open water Wave speed and length Wave speed and length • As wave speed and length decreases, the waves eventually grows higher and eventually breaks • The turbulent water caused by breaking waves is called surf Beaches Beaches • Beaches consists of whatever material that is commercially available • On the Florida coast (a low latitude region), beaches have a biological component, such as shell fragments • Waves that crash along the seashore transport material along the beach Shoreline features Shoreline features • Two types of shoreline features: 1) erosional 2) depositional Erosional features Erosional features • Features that owe their origin from erosion • Examples: wave­cut cliffs, wave­cut platforms, marine terraces, sea arches and sea stacks Wave­cut cliffs Wave­cut cliffs • Surfaces produced by the cutting ofthe surf against the base of coastal land. Wave­cut platform Wave­cut platform • A platform that is left behind by a receding cliff Marine terrace Marine terrace • This is when a wave­cut platform is uplifted above sea level by tectonic forces (such as volcanism) Sea arches & sea stacks Sea arches & sea stacks • Sea arch: An arch formed by erosion when opposite sides of a headland unite • Sea stack: An isolated mass of rock standing just offshore produced by wave erosion of a headland Depositional features Depositional features • These are features produced by the deposition of sediment • The sediment is transported along the shore and deposited in areas where wave energy is low • Examples: spits, bars, tombolos, barrier islands Spits, bars, and tombolos Spits, bars, and tombolos • A spit is an elongated ridge of sand that projects from the land into the mouth of an adjacent bay • Bar: this is a sandbar that completely crosses a bay, sealing it off from the open ocean • Tombolo: A ridge of sand that connects an island to the mainland or another island Barrier islands Barrier islands • A low, elongated ridge of sand that parallels the coast • Examples: Padre Island National Seashore (Texas), Cape Hatteras (North Carolina) Barrier Islands (cont.) Barrier Islands (cont.) • Most barrier islands are 1 to 3 miles wide and 2 to 20 miles long • Barrier islands are separated from the main coast by lagoons, which are relatively quiet bodies of water Tides • Periodic changes in the elevation of the ocean’s surface • Caused by the gravitational force of the moon • The sun also effects tides, but a much smaller amount than by the moon • The tidal bulges migrate as the moon revolves around the Earth every 29 ½ days • The tidal cycle is a monthly cycle • Two types of tides: spring tides and neap tides Spring tides Spring tides • The highest tidal range. Occurs between the times of the full and new moons • At this time, the sun and moon are aligned and their forces are added together • The result is larger tidal bulges and larger tidal troughs • Spring tides occur twice a month when the Earth­moon­sun system are aligned Neap tides Neap tides • The lowest tidal range • Occurs twice a month, about the time of the first and third quarters of the moon • The gravitational of the moon and sun act on Earth at right angles • Each month, there are two spring tides and two neap tides, each about one week apart Tidal Patterns Tidal Patterns • Three main tidal patterns worldwide: 1) Diurnal tidal pattern 2) Semi­diurnal tidal pattern 3) Mixed tidal pattern Diurnal tidal pattern Diurnal tidal pattern • Characterized by a single high tide and a single low tide each tidal day • Usually occurs at the Northern shore of the Gulf of Mexico Semidiurnal tidal pattern Semidiurnal tidal pattern • Exhibited by two high tides and two low tides each tidal day • Marked by two high tides of the same height and two low tides of the same height • Very common along the Atlantic coast of the United States Mixed tidal pattern Mixed tidal pattern • Similar to semidiurnal tidal patterns, characterized by large inequalities of high tide height, low tide height or both • Two high tides and two low tides each day, with high tides of different heights and low tides of different heights • This tidal pattern is prevalent along the Pacific coast of the United States ...
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This note was uploaded on 12/25/2010 for the course ESC 1000 taught by Professor Faculty during the Fall '10 term at FAU.

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