May 10, 2008
The Lone Blog Tides, Currents, and Waves
The rise and fall of our Atlantic Oceans tides involves a great deal of energy. Within a twenty four hour time frame, there are usually two high and two low tides. Each high tide being about twelve hours apart and each low tide spacing the same time frame. Keeping track of the tides in a coastal community is as easy as turning on your radio to listen to the surf report or checking your local paper.
Surf's up basically closer to the full and new moon phases but it varies with the wind. The moons gravitational pull displaces water from both the earth's surface facing the moon and the surface directly behind it. The rise and fall of the tides, wind, and thermohaline circulation (thermo-heat, haline-salt) all drive the oceanic currents.
Tidal currents are the only kind that can readily be predicted. They are created by the sun and moons gravity making a current in the ocean close to the shore and in bays and estuaries and are the only currents affected by the gravitational pulls.
Wind is responsible for driving currents at or close to the ocean surface. Wind currents are generally measured in knots (1 knot is equal to 1.15 miles per hour) and effect a concentrated local area along the shore or larger areas out to sea.
Thermohaline currents are a slower moving current that happens when the difference in water density is occurring because of temperature and saline changes. These currents are found at shallow and greater depths and create a kind of circulation much like boiled water in a pot, but not near as drastic.
When observing the angle of a waves approach to shore, notice the break. A wave begins to break when the depth of the wave is half that of the depth of the floor where the floors grade escalates. A wind driven wave that becomes unstable, having elevated sharp angles is referred to as a breaker. Wave height is dictated by wind speed, direction, and length of time the wind has been blowing in that direction. Waves come in sets or patterns that are countable and somewhat predictable on any given day. Surfers watch the wave sets and choose which wave in the next set they will ride based on the breaking patterns of the previous set. Body surfers can tell which wave to catch by the strength of the undertow preceding the wave.
Tides, currents, and waves all have an impact on beach erosion. The explosion of energy released when a wave crashes the coastline causes sediment to be displaced and taken further out to sea know as longshore drift.
A rip current flows away from and perpendicular to the shore. It generally occurs between two breakers and is no more than eighty feet wide. If the waves are small, the rip currents are more numerous but weaker. If the waves are large, the rip currents are spaced further apart but more powerful. Taking some time to look at the wave patterns before you take a swim is the mark of safety and always stay close the life guard stations.
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Stephanie Haile Aka Wavecritter Google Me