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Understanding Tides And Currents

Understanding Tides and Currents

Florida is a peninsula, meaning the state is surrounded by water on 3 of its sides. Just about all coastal surfaces consist of beaches, marinas, water accessible restaurants and hotels and piers. This means, miles and miles of shoreline and open ocean that fluctuates, creating tides and currents.

From deep under the ocean to the surface, currents are lurking. If you don’t know the difference or the danger of these currents, there can sometimes be deadly circumstances. Knowing when high tide and low tide are bound to happen is also important.

Tides

Tides are classified as the rise and retreat of the water throughout the day. The tides are determined by the gravitational pull generated by the sun and moon. Florida’s relation to the moon and sun allow for both coasts to generate 2 high tides and 2 low tides, each day.

Gulf of Mexico Tides

The west coast shores generate mixed tides. Mixed tides reference the idea that the 2 high tides and the 2 low tides are rather different in tide level. The standard tide patterns along Florida’s Gulf of Mexico shores show that the high and low tides during the middle of the night are much closer in tide level and there is less time between fluctuations.

The 2nd round of high and low tides are opposite of their earlier counterparts. During the early afternoon, high tide will be much higher than the 2nd low tide. The distance between the afternoon high tide and the evening low tide is also much greater, spanning quite a few hours.

Atlantic Coast Tides

East coast tides generate steady semidiurnal tides. Semidiurnal tides refer to the time intervals between all 4 tides being relatively regular. Additionally, the height of the tides is similar, meaning both low tides and both high tides will tend to be very similar at each instance.

The average days tides seem to follow the pattern of rising and receding every 5-8 hours. During clear weather, it seems that the east coast tide heights fluctuate with .5 – .9-foot differences, consistently. The open Atlantic coasts seem to offer more stable and consistent changes than the West Coast shores.

Surface Rip Currents

Currents

Oceanic Currents reference the motion of the ocean. These currents are controlled by many factors; the tides, wind and thermohaline circulation. Currents can happen deep underwater or at the surface and can move at rapid speeds or be slow and steady.

Tidal Currents

Tidal currents are the currents that are generated from the rise and fall of the tide. These currents happen close to shore, in bays and within coastal estuaries. The rise and fall of these tides create horizontal movement which creates the actual tidal current. These currents are the only type of currents that can be predicted because the coastal tides have regularly changing patterns. Tidal currents are also the only currents that are affected by the relationships between the Earth, Sun and Moon.

As hightide is directed towards the shore, the horizontal currents generated move towards the shore which makes these tidal currents ‘flood currents’. Low tide generates horizontal movement that brings the water away from the shore, making these currents the ‘ebb currents’.

The strongest currents will happen during the peak of change between the high and low tides. During these times, the tide change can cause up to approx. 15 MPH currents. These are the dangerous currents and why if you are warned of heavy currents, you should stay closer to shore, so you don’t get wrapped up in a fast sweeping current.

Surface Currents

Surface currents are determined based on the wind. Wind moves the surface water, which generates these types of currents. These currents are generally measured in meters per second or knots. 1 knot equals 1.85 kilometers per hour, or for us in the US, 1.15 miles per hour. Surface currents near the coast are driven at a local scale, while open ocean surface currents are on a global scale.

There are 2 forms of local surface currents: longshore currents and rip currents. These currents happen along the shoreline, very close to the coast. If you are an avid boater or beachgoer, you have probably heard of rip currents, and although you may not have heard of longshore currents, once you read our explanation, we have no doubt you will know what we are talking about.

Longshore currents are the local surface currents that move the water, sand, shells and other sediment parallel ‘along’ the shoreline, hence the name ‘longshore’. Have you ever set your belongings on the beach, got into the water, then looked back on shore to find that you have been moved many feet past your mark on shore without noticing? This is your local longshore current in action.

Rip currents are among the most dangerous type of deep or surface current. Many people think rip currents are not considered surface currents because they have been given the name ‘undertow’. However, this is inaccurate; rip currents are channels of water that rapidly pull the surface water from the shore out into the ocean. If caught in one, swim parallel to shore, with a slight angle towards shore until you feel the release of the rip current and only then should you finally swim directly towards shore.

Thermohaline Currents

Thermohaline currents are determined by the differences in density between different parts of the ocean. The density is controlled by the temperature and the salinity of both the surface and the deep waters. Density differences can take place in both the depths and the shallows of the world’s oceans.

These currents occur on a global layer and you are less likely to come across these currents. They travel in a specific pattern from the polar regions then down past south America where they make their way across the pond to Africa, India and Australia, then circle back around. As they warm, they make their way back northward to the polar regions, where the currents will restart.

This path, known as the ‘Global Conveyer Belt’, moves year-round, but can take 1,000 years for a single section of water to move across all the oceans and back to where it began.

Conclusion

Knowing your local tides and currents can help if you are presented with a dangerous situation. Rip currents are especially dangerous, and everyone should know how to escape one; by swimming parallel to the shore, at a slight angle until you feel the current release you.

Unless you travel to the polar regions, recreational anglers and standard beachgoers are likely to not encounter a thermohaline current. They travel through all the worlds oceans to make their way around the world, to simply start all over again.

The Earth and its relationship to the Sun and Moon have a great deal to do with how our world’s oceans work and cycle together to help keep our ecosystem in check. The ocean is a strange, scary, intriguing and marvelous aspect of both our local and global environments.

Safe Boating!

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