Tidal currents are the only type of current affected by the interactions of the Earth, sun, and moon. The moon’s force is much greater than that of the sun because it is 389 times closer to the Earth than the sun is. Tidal currents, just like tides, are affected by the different phases of the moon.
Full Answer
What are tides and tidal currents?
Tidal currents, as their name suggests, are generated by tides. Tides are essentially long, slow waves created by the gravitational pull of the moon, and to a lesser degree, the sun, on the earth's surface.
What is the source of tidal energy?
Tidal current energy is the result of harnessing the power of flowing water. The gravitational interactions between the earth, sun, and moon cause ocean tides; actually, the moon has 68% control while the sun has only 32% (Elghali, 2009).
How do you predict tidal currents?
Tidal Current Prediction for Reference Stations For each day, the date and day of week are given; current information follows. If the cycle is repeated twice each tidal day, currents are semidiurnal. On most days there are four slack waters and four maximum currents, two floods (F) and two ebbs (E).
What information is included in the tidal current volumes?
The volumes also contain general descriptive information on wind-driven currents, combination currents, and information such as Gulf Stream currents for the east coast and coastal currents on the west coast. 932. Tidal Current Prediction for Reference Stations For each day, the date and day of week are given; current information follows.
Where are tidal currents located?
Rectilinear tidal currents, which typically are found in coastal rivers and estuaries, experience a “slack water” period of no velocity as they move from the ebbing to flooding stage, and vice versa.
How are the tides determined?
They are caused by the gravitational forces exerted on the earth by the moon, and to a lesser extent, the sun. When the highest point in the wave, or the crest, reaches a coast, the coast experiences a high tide. When the lowest point, or the trough, reaches a coast, the coast experiences a low tide.
What factors affect tidal currents?
The relative distances and positions of the sun, moon and Earth all affect the size and magnitude of the Earth's two tidal bulges. At a smaller scale, the magnitude of tides can be strongly influenced by the shape of the shoreline.
How do you determine ocean currents?
How we measure currents. The two main components of currents are speed and direction. To measure a current, toss an object into the water and time how long it takes to get to a certain point a known distance away.
What are tides measured against?
Keep in mind, that all tidal heights are measured against the defined plane of reference, called Chart Datum. Chart Datum is basically an average of low tide heights. Nautical charts use this same reference to measure depth.
What are tides geography?
Tides are very long-period waves that move through the ocean in response to the forces exerted by the moon and sun. Tides originate in the ocean and progress toward the coastlines where they appear as the regular rise and fall of the sea surface.
What determines high tide and low tide?
The moon's gravitational pull on the Earth and the Earth's rotational force are the two main factors that cause high and low tides. The side of the Earth closest to the Moon experiences the Moon's pull the strongest, and this causes the seas to rise, creating high tides.
Why are tides different in different places?
Just as the angles of the sun, moon and Earth affect tidal heights over the course of a lunar month, so do their distances to one another. Because the moon follows an elliptical path around the Earth, the distance between them varies by about 31,000 miles over the course of a month.
What affects tides the most?
The moon, however, influences tides the most. The moon's gravitational pull on the earth is strong enough to tug the oceans into bulge.
Which of these factors control ocean currents?
Four Factors That Create Ocean CurrentsWind. Wind is the single biggest factor in the creation of surface currents. ... Water Density. Another major factor in the creation of currents is water density, caused by the amount of salt in a body of water, and its temperature. ... Ocean Bottom Topography. ... Coriolis Effect.
How do tidal currents perform in the open ocean?
How do tidal currents perform in the open ocean? In the open ocean tidal currents are relatively weak. How do they perform near the entrances to estuaries? Near estuary entrances, narrow straits and inlets, the speed of tidal currents can reach up to several kilometers per hour.
Why are tidal patterns generally predictable?
Tides are the periodic rise and fall of surface water caused by the gravitational force of the moon and the sun and by the rotation of the earth. The movements of the solar system that influence the tides are predictable; therefore changes in tide height and time are predictable.
Why are there 2 high tides per day?
Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes. High tides occur 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the water at the shore to go from high to low, or from low to high.
Why are tides higher in some places?
Tidal highs and lows depend on a lot of different factors. The shape and geometry of a coastline play a major role, as do the locations of the Sun and Moon. Storm systems at sea and on land also shift large quantities of water around and affect the tides.
How do you tell if tide is going in or out?
You can look for visual clues like seaweed or wet sand in dry weather to tell if the tide is coming in or out. If the sand above the waterline is wet, you can usually assume that the tide is on its way out. If everything is dry, the tide is probably on its way in.
How do you determine spring and neap tides?
Rather, the term is derived from the concept of the tide "springing forth." Spring tides occur twice each lunar month all year long without regard to the season. Neap tides, which also occur twice a month, happen when the sun and moon are at right angles to each other.
What are the phases of the moon that affect tides?
Tidal currents, just like tides, are affected by the different phases of the moon. When the moon is at full or new phases, tidal current velocities are strong and are called “spring currents.”. When the moon is at first or third quarter phases, tidal current velocities are weak and are called “neap currents.”.
What causes a tide to move horizontally?
Tidal currents occur in conjunction with the rise and fall of the tide. The vertical motion of the tides near the shore causes the water to move horizontally, creating currents. When a tidal current moves toward the land and away from the sea, it “floods.”.
What happens to tides after a brief slack period?
After a brief slack period, which can range from seconds to several minutes and generally coincides with high or low tide, the current switches direction and increases in velocity. As the tides rise and fall, they create flood and ebb currents. Click the image for a larger view.
What are the interactions between the Earth, the Sun, and the Moon?
Tidal currents are the only type of current affected by the interactions of the Earth, sun, and moon. The moon’s force is much greater than that of the sun because it is 389 times closer to the Earth than the sun is. Tidal currents, just like tides, are affected by the different phases of the moon. When the moon is at full or new phases, tidal ...
When it moves toward the sea away from the land, it “ebbs”.?
When it moves toward the sea away from the land, it “ebbs.”. These tidal currents that ebb and flood in opposite directions are called “rectilinear” or “reversing” currents.
How do tidal currents rotate?
Tidal current vectors at a fixed point rotate clockwise or counterclockwise with advancing tidal phases by the Coriolis force, depending on floor depths. In the coastal sea with depths greater than the bottom Ekman layer thickness where bottom stresses are not effective to tidal currents, tidal current vectors rotate clockwise in the northern hemisphere, drawing a tidal ellipse at the end point of the vectors during the semidiurnal period. Such a clockwise rotation of tidal current vectors has a similarity to surface Ekman spiral, generated in the upper layer by steady surface wind stresses. The direction of rotation is reversed in the southern hemisphere. In the coastal sea with depths smaller than the bottom Ekman layer thickness, the rotation of tidal current vectors become counterclockwise, owing to the effect of bottom stresses working on the seafloor. This rotation of tidal current vectors is also similar to the counterclockwise rotation of current vectors in the bottom Ekman spiral, generated by ocean currents flowing on the seafloor. The Ekman layer thickness is calculated by
What is the viable tidal current energy resource?
The viable tidal current energy resource is the accessible tidal current energy resource constrained by commercial limitations such as costs, scale, grid connection, and resource distribution of a tidal current energy farm. In order to determine the viable tidal current energy resource, an economic model was used to establish the costs for each of the 11 identified sites. This economic model, developed by Marine Current Turbines Ltd. (UK), was used to determine the viable tidal current energy resource around Ireland. The model specifies the size and quantity of turbines for installation at a particular site and outputs the capital cost of the technology at each site. The viable resource is also limited by peak tidal current velocities as only sites with a peak tidal current velocity greater than 2 m/s are considered economically viable. The turbine spacing was assumed to be 65 m apart and the position of each row of turbines was identified so as to enable ships to bypass the tidal current energy farm easily. From this model, the viable tidal current energy resource was estimated at 0.915 TWh/y.
What are the IAS tides?
The tides are typically semi-diurnal on the Atlantic Ocean margin of the IAS (M2 and S 2 constituents usually), and progressively become diurnal in the Gulf of Mexico where the K 1 and O 1 constituents dominate. Estuaries such as the Mississippi Delta are of the salt-wedge category, mostly because the tidal currents and ranges are small and the river flows very large (average for the Mississippi River is about 10 3 km 3 y −1 ≈0.03 Sv). Tidal currents around many IAS islands are similarly weak, with extremes rarely exceeding v → = 1 m s −1 even in passes through the many bar-built barrier island lagoons.
What is the term for the movement of water by out-of-phase tides?
Tidal currents can be defined as the periodic movement of water driven principally, though not necessarily exclusively, by a head difference created by out-of-phase ocean tides at each end of a restriction.
Why do tidal currents rotate counterclockwise?
In the coastal sea with depths smaller than the bottom Ekman layer thickness, the rotation of tidal current vectors become counterclockwise, owing to the effect of bottom stresses working on the seafloor.
What is the period of an inertial current?
Inertial currents are a ubiquitous feature of the ocean, and are characterized by periods = 12 h / sin ϕ. In the northern IAS, inertial currents often have periods equal to the dominant diurnal tidal currents, such as the K 1 or the O 1 because sin ϕ ≈ 0.5.
How high are the waves in a Caribbean tsunami?
Caribbean tsunami waves have been observed to exceed 9 m in height. Since a tsunami is a progressive shallow-water wave with celerity c = gH, the maximum currents come at the wave crest and at the wave trough. These wave-currents probably exceed v → = 10 m s − 1, and have timescales of several minutes.
Where do tides start?
Tides start in the ocean and move towards the coast, where they appear as the regular rise and fall of the sea surface. How much the water level changes over the day varies depending on where you are and what day it is. Currents. Currents put motion in the ocean! Tides involve water moving up and down; currents involve the movement ...
What are the factors that drive currents?
Currents are driven by several factors. Tides are one of these. Wind, the shape of the land, and even water temperature are other facts that drive currents. Related links.
What does the number mean on a nautical chart?
Mean lower low water, or the average of all observed lower low waters (the lower of the two low waters of any tidal day), is known as chart datum in most areas.
What are the two main components of currents?
The two main components of currents are speed and direction . To measure currents, buoys are equipped with Global Positioning System technology or satellite communications that relay data and information.
How do we measure currents?
To measure a current, toss an object into the water and time how long it takes to get to a certain point a known distance away. Granted, technology allows us to be a little more accurate and sophisticated in our measurements.
What happens when water levels change?
A change in water level (due to tides) can leave someone stranded (or flooded). And knowing how fast water is moving—and in what direction—is important for anyone involved in water-related activities.
What is the purpose of the Integrated Ocean Observing System?
Coast Guard conduct search and rescue operations with greater accuracy. The Integrated Ocean Observing System uses high frequency radar systems to develop maps of surface currents for the Coast Guard to use in their operations. These maps may also be used to support other scientific work, such as oil spill response, harmful algal bloom monitoring, and water quality assessments.
Why are tidal currents predictable?
Because the relative positions of the moon, sun and earth change at a known rate, tidal currents are predictable. Currents, whether tidal, surface or deep ocean, profoundly affect the world as we know it. To learn more about the complex systems that drive ocean currents, dive into the links below.
What are the effects of tidal currents?
Fast tidal currents toss sediment around and affect plant and animal life. Currents may, for example, transfer a fish's eggs from an estuary out into the open sea or carry nutrients that the fish needs from the sea into the estuary. The strongest tidal currents occur at or around the peak of high and low tides.
How fast do tides move?
Although tides and tidal currents don't have much impact in the open oceans, they can create a rapid current of up to 15.5 miles (25 kilometers) per hour when they flow in and out of narrower areas like bays, estuaries and harbors [source: Skinner ]. Fast tidal currents toss sediment around and affect plant and animal life.
What causes tides to occur?
Tides are essentially long, slow waves created by the gravitational pull of the moon, and to a lesser degree, the sun, on the earth's surface. Since the moon is so much closer to the earth than the sun, its pull has more influence on the tides. The moon's gravitational pull forces the ocean to bulge outwards on opposite sides of the earth, ...
What causes the ocean to bulge outwards on opposite sides of the Earth?
The moon's gravitational pull forces the ocean to bulge outwards on opposite sides of the earth, which causes a rise in the water level in places that are aligned with the moon and a decrease in water levels halfway between those two places.
When the tide is rising and the flow of the current is directed towards the shore, the tide is called?
When the tide is rising and the flow of the current is directed towards the shore, the tidal current is called the flood current , and when the tide is receding and the current is directed back out to sea, it is called the ebb current. Because the relative positions of the moon, sun and earth change at a known rate, tidal currents are predictable.
Which type of current triggers the weather pattern known as El Nino?
The warm, eastward-flowing, equatorial counter current, for example, can trigger the weather pattern known as El Nino. A colder surface current, the Labrador current, flows along the west coast of Greenland and often sends icebergs into the North Atlantic shipping lanes.
tidal stream
tidal stream The flow of water in and out of estuaries, bays, and other restricted coastal openings associated with the rise and fall of the tide.
tidal stream
tidal stream The flow of water in and out of estuaries, bays, and other restricted coastal openings associated with the rise and fall of the tide. Landward (flood) and seaward (ebb) streams often follow different paths in shallow-water areas, so forming ebb/flood avoidance cells and a braided pattern of sandbanks.
What is the energy of tidal currents?
Tidal Currents. The movement of ocean water volumes, caused by the changing tides, creates tidal current energy. Kinetic energy can be harnessed, usually nearshore and particularly where there are constrictions, such as straits, islands and passes.
What direction do ocean currents go?
Open ocean surface currents are driven by latitudinal distributions of winds (clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere). They tend to operate at shallow depths (<800 m) and are slower but more continuous flows than tidal currents.
What are the effects of tides?
The effects of these tides are complex and most major oceans and seas have internal tidal systems . The rise and fall of the tide (range) offers the opportunity to trap a high tide, delay its fall behind a barrage or fence, and then exhaust the potential energy before the next tidal cycle.
