THE DYNAMIC OCEAN Earth Science 11/9/10

16.1- Ocean Circulation #1- Surface Circulation- – Surface currents- movements of water that flow horizontally in the upper part of the ocean’s surface Develop from friction between the ocean and wind that blows across its surface – Gyres- huge circular-moving current systems Coriolis effect- deflection of currents away from their original course as a result of Earth’s rotation Currents are deflected to the left in the Southern hemisphere and the right in the Northern hemisphere.

Gyres

16.1 (cont.) – Ocean Currents and Climate- When currents from low-latitude regions move into higher latitudes, 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. – Upwelling- rising of cold water from deeper layers to replace warmer surface water. Brings greater concentrations of dissolved nutrients, such as nitrates and phosphates, to the ocean surface.

16.1 (cont.) #2- Deep Ocean Circulation- – Density Currents- vertical currents of ocean water that result from density differences among water masses An increase in seawater density can be caused by a decrease in temperature or an increase in salinity – High Latitudes- Surface waters salinity increases as sea ice forms. When it becomes dense enough, it sinks. Deep waters will not reappear at the surface for about years.

16.1 (cont.) – Evaporation- Conditions, such as dry winds and sunny days lead to ocean evaporation. Water that has a higher salinity (due to evaporation) can then sink and form density columns. – Conveyor Belt Warm water flows to the poles where its temperature drops and its salinity increases. This makes it more dense, so it sinks and then moves back towards the equator.

16.2- Waves and Tides #1- Waves – Wave Characteristics- most waves obtain their energy and motion from the wind Wave height- vertical distance between trough (bottom of a wave) and crest (top of a wave) Wavelength- horizontal distance between 2 successive crests or two successive troughs The height, length and period of a wave depend on 1) wind speed, 2) length of time of wind, & 3) fetch (distance wind has traveled on open water)

16.2 (cont.) – Wave motion- Circular orbital motion allows energy to move forward through the water while the individual water particles that transmit the wave move around in a circle. – Breaking Waves- As a wave advances toward the shore, the speed and length of the wave decrease. This causes the wave to grow higher. When the wave is too steep to support itself, it breaks, or collapses, and water move onto the shore. This turbulent water is called surf, and the sheet of water made from collapsing breakers is called swash.

16.2 (cont.) #2- Tides- daily changes in the elevation of the ocean surface. Caused by the gravitational attraction exerted upon Earth by the moon, and, to a lesser extent, the sun. – Tide-Causing Force Force that produces tides is gravity. – Tidal Cycle Tidal range- difference in height between successive high and low tides Spring tides- tides that have the greatest tidal range due to the alignment of the Earth-moon-sun system

16.3 (cont.) – Tidal patterns 3 main tidal patterns- – Diurnal tide- one high tide and one low tide each day – Semidiurnal tide- 2 high tides and 2 low tides each day – Mixed tide- large inequality in high water heights, low water heights or both

16.3- Shoreline Processes & Features Beach- accumulation of sediment found along the shore of a lake or ocean #1- Forces Acting on the Shoreline – Wave Impact Waves are constantly eroding, transporting, and depositing sediment. – Abrasion- sawing and grinding of rock fragments in the water

16.3 (cont.) – Wave Refraction- bending of waves Wave energy is concentrated against the sides and ends of headlands that project into the water – Longshore Transport Longshore current- currents that flow parallel to the shore and move large amounts of sediment Turbulence allows longshore currents to easily move the fine suspended snad and to roll larger sand and gravel particles along the bottom.

16.3 (cont.) #2- Erosional Features – Wave-Cut Cliffs and Platforms Wave-cut cliffs result from the cutting action of the surf against the base of coastal land. Eventually, only a flat, bench-like surface is left. – Sea Arches and Sea Stacks When the arch of a sea arch caves in, only an isolated sea stack is left.

16.3 (cont.) #3- Depositional Features – Spits, Bars, and Tombolos Spit- elongated ridge of sand that projects from the land into the mouth of an adjacent bay Baymouth bar- sandbar that completely crosses a bay and seals it off from the open ocean Tombolo- ridge of sand that connects an island to the mainland or to another island

Barrier Islands Formed from the general rise in sea level following the last glacial period former sand dunes Narrow sand bars parallel to the shore

Stabilizing the Shore 1.Protective structures such as groins, breakwaters, and seawalls 2.Beach nourishment is the addition of large quantities of sand to the beach This increases the water’s turbidity and kills offshore reefs