Chapter 16 The Dynamic Ocean

16.1 Ocean Circulation

Surface Circulation Ocean currents are masses of ocean water that flow from one place to another Surface currents – movements of water that flow horizontally in the upper part of the ocean’s surface Develop from friction btw the ocean and the wind that blows across its surface

Gyres Huge circular moving current systems dominate the surfaces of the oceans 5 Main ocean Gyres N. Pacific Gyre S. Pacific Gyre N. Atlantic Gyre S. Atlantic Gyre Indian Ocean Gyre

Coriolis effect – deflection of currents away from their original course as a result of Earth’s rotation Due to Earth’s rotation, currents are deflected to the right in the N. Hemisphere & to the left in the S. Hemisphere 4 main currents within each gyre

Ocean Currents & Climate When currents from LL regions move into HL they transfer heat from warmer to cooler areas on Earth As cold water currents travel toward the equator, they help moderate the warm temperatures of adjacent land areas Play a big role in maintaining Earth’s heat balance

Upwelling Rising of cold water from deeper layers to replace warmer surface water Wind-induced vertical movement Brings greater concentrations of dissolved nutrients to the ocean surfaces

Deep – Ocean Circulation Density currents – vertical currents of ocean H2O that results from density differences in the H20 masses Increase in seawater density can be caused by a decrease in temperature or an increase in salinity

A Conveyor Belt Warm H20 flows toward poles Temperature drops & salinity increases Density increases Dense H20 moves toward equator Cold, deep water upwells Upwelled H20 warms The cycle repeats

16.2 Waves & tides

Waves Energy traveling along the boundary btw ocean and atmosphere Most ocean waves obtain their energy & motion from wind Top of wave = crest Trough = separate crests Wave Height = vertical distance btw trough & crest

The height, length, & period depend on 3 factors: Wavelength = horizontal distance btw 2 successive crests (or 2 successive troughs) Wave period = the time it takes one full wave (one wavelength) to pass a particular spot The height, length, & period depend on 3 factors: Wind speed Length of time the wind has blown Fetch (distance that the wind has traveled across open H20)

Circular orbital motion allows energy to move forward through the H20 while the individual water particles that transmit the wave move around in a circle When waves approach shore, H20 becomes shallower & influences wave behavior (“feels the bottom” at depth = to half of its wavelength)

Tides Tide-Causing Forces Tidal Cycle Results from the gravitational attraction exerted upon Earth by the moon (and the sun) Gravity & Inertia produce tides Gravity attracts the Earth & moon Inertia = tendency of moving objects to continue in a straight line (keeps Earth & moon from crashing into each other Tidal range – difference in height btw successive high & low tides Spring tides – tides that have the greatest tidal range due to the alignment of the Earth – moon – sun Neap tides – lowest tidal range Each month = 2 spring tides & 2 neap tides

Tidal Patterns 3 main tidal patterns Diurnal Tides Semidiurnal Tides 1 high tide & 1 low tide each tidal day Semidiurnal Tides 2 high tides & 2 low tides each tidal day Mixed Tides Large inequality in high water heights, low water heights, or both

16.3 Shoreline processes & features

Forces Acting on the Shoreline Waves along the shoreline are constantly eroding, transporting, & depositing sediment Wave Impact Abrasion Wave Refraction Bending of waves Wave energy is concentrated against the sides & ends of headlands that project into the H20, whereas wave action is weakened by bays https://www.youtube.com/watch?v=G1FIBuybN78

Longshore current – near shore current that flows parallel to the shore Turbulence allos longshore currents to easily move the fine suspended sand & to roll larger sand & gravel particles along the bottom

Erosional Features Shoreline features that originate primarily from the work of erosion Sediment that is transported along the shore & deposited in areas where energy is low produce depositional features Wave-Cut Cliffs & Platforms Sea Arches & Sea Stacks

Depositional Features Spits Bars Tombolos Barrier Islands – narrow sandbars parallel to the coast (separate from coast) (3-30 km offshore)

Stabilizing the Shore Groins, breakwaters, & seawalls are some structures built to protect a coast from erosion or to prevent the movement of sand along a beach Can be built parallel to shoreline Beach nourishment is the addition of large quantities of sand to the beach system