No wind but also waves: where does the high tide seawater actually come from? Where does the water go after the tide goes out?

Looking out to sea, the sea level seems to be never-ending, and the ocean is never calm.

The ocean brings human feelings that rivers and lakes do not have. For people who have lived by the sea since the beginning, understanding the ocean can certainly help people to live better.

Tides are an important way to understand the movement of the ocean, and they are perhaps the most reliable natural phenomenon in the ocean; few phenomena are more stable than tides.

In contrast, if it were a wave this phenomenon would be more complex, with many influences, and it would be difficult for people to learn about the workings of the waves from it in the first place.

Unlike tides, which change throughout the day almost in response to the Earth's movement, their activity indicates whether the ocean is functioning properly.

But the only different thing is that tidal activity does not have very obvious precursors like waves do.

Tides tend to occur in a fairly natural state, and without a lot of experience, tidal movements can have an impact on all kinds of sea activities and shipping.

Therefore all merchant ships are provided with a set of appropriate high and low tide guidelines to ensure that the ship can navigate the ocean more easily.

Especially when looking for shallow rivers or docking in ports, it is important to know the timing of high and low tides.

In addition, high tides can also play a very subtle role in unexpected places, even when the U.S. Army landed in Normandy, the Allies had to take into account the impact of tides in their planning.

Because for the beach landing, rushing to the beach at the same time means looking for an optimal point of tidal change.

Although there are no obvious signs of tidal change, it has its own very prominent characteristics.

Tidal changes take place through two main phases, low tide, and high tide.

In low tide, the water stops falling and reaches a local minimum; in high tide, the water level stops rising and reaches a local maximum.

In some areas, there are two other possibilities outside the two. Sea level rises within a few hours, covering the intertidal zone is called flood tide.

The sea level drops within a few hours, exposing the intertidal zone, which is called ebb tide.

Tides are usually semi-diurnal, meaning that there are two high water levels and two low tide levels per day, or one tidal cycle per day in the diurnal state.

Also, the two high water levels for a given day are usually not the same height and the daily state is not equal, these are the higher high water levels and lower high water levels in the tidal performance.

Similarly, the two low water levels for each day are the high low water level and the lower low water level, and the daily water level inequalities are not consistent when the Moon is at the equator.

Tidal changes are closely related to the Moon

Who is influencing the tidal changes?

The main factor causing the tidal phenomenon is the activity of the Moon, which is the largest participant in the tidal motion, and the tidal motion is caused by the Sun's gravity.

According to Newton, ocean tides are caused by the Sun's and Moon's gravitational pull on the Earth's oceans.

The law of gravity states that the gravitational force between two objects is proportional to their mass and inversely proportional to the square of the distance between them.

Therefore, the greater the mass of the objects, the closer they will be to each other and the greater the gravitational force between them.

Because of this, the tidal force on Earth is usually more important in the distance between two objects than their masses.

The tidal generating force is inversely proportional to the cube of the distance between the tidal generating objects and the square of the distance between two objects brought about by the influence of gravity.

So when we look at the gravitational tidal relationship between the three, the Sun, the Moon, and the Earth, we can understand that

The Sun is 27 million times larger than the Moon and based on the corresponding mass conversion, the Sun's gravitational force on the Earth is more than 177 times greater than the Moon's on the Earth.

If the tidal force is based on relative mass, then the tidal force of the Sun should be 27 million times greater than that of the Moon.

However, we cannot ignore the difference in distance between the Sun and the Earth. Therefore, the tidal force produced by the Sun on it would be 390³ less.

Due to these conditions, the tidal generating force of the Sun is about half of that of the Moon.

The effect of the celestial distance must be considered

Therefore, it is the Moon that is the most influential factor in the Earth's tides.

During new and full moons, the Earth, the Moon, and the Sun are aligned. This order of alignment allows all the gravitational forces to combine to produce a more powerful tide, such is called a high tide.

This is completely unrelated to spring weather events, as they occur every month.

This state does not last long, however, and the three bodies will soon detach under their orbits.

Seven days after the high tide, the Moon and the Sun are at an angle of 90° to each other, when the gravitational forces change to interact with each other and the tides become weak, which is called a mini-tide.

The tidal force is greatest when the three celestial bodies are in the same frame

The Moon's gravitational force is strongest when the Earth directly faces the side of the Moon.

At this time, the Earth's waters are strongly pulled in the direction of the Moon.

The side farthest away from the Moon, on the other hand, has the weakest lunar gravity, and the center of the Earth is approximately the average value of the Moon's gravitational pull on the entire planet.

This part of the tidal force is obtained by subtracting the average gravitational force on the Earth from the gravitational force at each of the Earth's positions to obtain the corresponding tidal force.

The tidal forces are the result of the stretching and squeezing of the Earth, which is what causes the two tidal bulges.

As the Earth rotates, the Earth's region crosses these two bulges every day. When out of one of them, a high tide is experienced, and vice versa.

This cycle of two high tides and two low tides occurs along most of the world's coastlines most of the time.

It is worth noting, however, that the Earth is not a uniform sphere and is completely uniformly covered with bodies of water.

Because of the influence of land plates, the continents prevent the water from completely following the gravitational pull of the moon, and all in the same situation, the tidal force performance in different areas will be either large or small.

So now we can know that it is due to the gravitational force between the earth and the moon and the performance of the earth's motion that the seawater repeatedly rises and falls throughout the day.

As the tidal force weakens, the water gradually retreats and returns to its original location.

In addition to celestial influences, winds and weather patterns can also affect tidal changes in water levels.

Strong sea winds can blow the water away from the shoreline, which in turn enhances the performance of low tides. Whereas winds on land can push water towards the shore, which in turn makes low tides less pronounced.

Also, high-pressure weather can lower the sea level, resulting in lower tides.

However, low-pressure systems brought about by strong storms and hurricanes can cause tides to be much stronger than the predicted state, so such tides can be very dangerous.

Tides are long-period waves that occur in the Earth's oceans in response to forces exerted by the Moon and the Sun.

Tides begin in the ocean and progress toward the coastline, where they are manifested by a regular rise and fall of the sea surface.

The horizontal movement of water is usually accompanied by the rise and fall of tides, which are called tidal currents.

The strongest flood and ebb tides, which we mentioned earlier, usually occur near the high and low tides, and the weakest currents occur between the flood and ebb tides.

Although this is a very common natural phenomenon, numerous organisms depend on tidal activity, and tidal marine ecology is a special environment brought about by tides.

For example, barnacles and seaweeds in the intertidal region can behave differently depending on the tidal changes.

Other animals that live here are hermit crabs, starfish, sea slugs, and other nudibranchs that live in the low tide area.

For fishermen living on the coast, low tide is a good opportunity to harvest, and the receding waters bring many creatures that can be caught.

Today, however, this change in activity, which is so regular, is suffering changes. As global warming causes the oceans to expand in size.

In many coastal cities, the sea level is higher than ever before and tidal changes will undoubtedly increase the risk of flooding for these coastal cities.

In addition, human activities are correspondingly changing the tidal manifestations of seawater action brought about by the tides, such as changes in river dredging near the coast, which can alter the changes in water flow and thus tidal action.

The increasing number of dikes and piers will lead to more turbulent currents and faster dissipation of tidal capacity, which will inhibit tidal action.

To consider the tidal action, the corresponding engineering and construction must take this into account, which is why tides and human life are so important.