Some Basics about the marine environment brought to you by: Coach Trowbridge

Wind Haikus (or Haiki?) Wind blowing salt mist across the craggy sea cliffs. A lone sea gull dives. Sondra Ball Why does the wind blow? Can anyone tell me why? Hurry. Tell me now. Trow

Why does the wind blow? Sun heats the surface of land or sea Air warms at surface and rises Surrounding air rushes in to fill where the air just left.

How does wind get its “directionality?” The Coriolis Effect- Earth’s rotation causes wind and current to “swirl.” In the Northern Hemisphere winds take an apparent deflection to the right causing a clockwise rotation of winds. In the Southern Hemisphere winds take an apparent deflection to the left causing a counter-clockwise rotation of winds.

How does wind get its “directionality?”

How do ocean currents form? Currents are driven by three main factors Wind: Surface currents Temperature Changes: Upwelling/Down-welling “halinity”: Down-welling

Surface Currents: How they form As trade winds blow toward equator, current is deflected at 45 o angle (coriolis again) such that the currents move parallel to the equator (west in NH and west in SH). When equatorial currents “hit” land they turn (N in NH and S in SH) as the land now becomes the focus of onshore winds (land heats faster than water). Onshore winds keep turning the current (right in NH, left in SH) until you end up with clockwise flow in the NH and counterclockwise flow in the SH.

Surface Currents: Gyres These huge circular currents that form at the surface are called Gyres.

Waves Haiku Up and down again and again and again and again and a gain. -Trow

Wave formation Waves are formed by the blowing wind. Winds blowing for long periods of time causes waves to get bigger Winds blowing faster causes bigger waves Winds blowing over greater distances (fetch) cause bigger waves

Wave features Crest- High point of wave Trough- Low point of wave Wavelength- distance from crest to crest (or trough to trough) Period- time it takes for one full wavelength to pass a specific spot Waves transmit ENERGY not water. Things floating in the waves “bob” in circular patterns.

Types of waves Peaks- area where the wind “whips up” the waves. Swells- Calmer areas where waves are propagated. Surf- Areas where waves break and release their energy.

Wave Interactions Reinforcement- waves combine into larger waves Cancellation- waves interfere with each other to make smaller waves Wave Anomalies Rogue waves- Huge reinforced waves during high seas Tsunami or Tidal Waves- Massive waves caused by earthquakes or landslides

Tides The rhythmic rising and falling of the oceans due to near-Earth gravitational forces. Expose and submerge areas near land Help bays and estuaries circulate Trigger spawning events in some organisms

Causes of Tides Gravitational Forces from the Earth, Moon and Sun system Rotation of the Earth Position of Earth, Moon and Sun system

Gravitational pull Moon and Earth rotate about a common center of gravity creating a “wobble” which makes the water on Earth “Bulge” near and opposite the Moon. As Earth rotates through the bulge, you will experience two high tides-one when the moon is overhead, and the other when it is underfoot (on the other side of the Earth from your location)

Gravitational pull These “bulges” (high tides) will pass a location on Earth twice in a 24 hr. 50 min. period. The low tides will do the same. (the 50 min is “catch up” time to the moon’s rotation around the Earth)

Adding the Sun’s Interaction When the Sun, Earth, and Moon are in line there is a higher than usual high/low tide called a Spring Tide (think of a stretchy spring, not the season). When the Moon, Earth, and Sun are at a right angle, there is a lower than usual high/low tide called a Neap Tide.

Adding the Sun’s Interaction

Types of Tides Semidiurnal- 2 high tides and 2 low tides per day Diurnal- 1 high tide and 1 low tide per day Mixed semidiurnal- Have successive high tides of different heights

Tide Tables Show when tides will be high or low in specific areas.