There are several types of ocean currents. Among them there are those that are directed perpendicular to the shore. The rip current is formed at low tide, when the water in some areas leaves at different speeds. This phenomenon is not universal, but everyone can face it.
Rip current
This process may pose a threat to people at sea. It is worth being afraid of shallow reservoirs with a gently sloping coast, framed by sandy spits and skeletons. Natural obstacles prevent the water from moving smoothly away from the shore.
The fluid pressure on the narrow passage that connects the estuary with the ocean is rapidly increasing. As a result, a rapid is formed, along which the water mass rushes away from the coast at a speed of up to 3 meters per second. On the surface of the water, the rip current resembles a turbulent river.
How to recognize
- Jet of water directed away from the shore.
- The color of the water surface is changing near the coastal zone. For example, in the middle of the blue sea, a white area.
- Foam, algae, air bubbles or something similarmoves in the form of a jet perpendicular to the coastline.
- Cracks in tidal waves, reaching a width of 5 to 10 m.
Every fifth rip current in the ocean reveals itself as one of the above signs. In other cases, it is almost impossible to recognize a spontaneous "rip". Professional lifeguards will cope with this task, but ordinary tourists cannot do this. Swimmers only become aware of the problem after being sucked into a powerful invisible current.
How to stay safe
The rip current is the most dangerous among such phenomena. Once in the stream, beginner swimmers try to overcome it and move towards the shore. They quickly run out of strength as the water continues to carry them further out to sea.
The rip current in the Black Sea has a small extent. The highest flow velocity is observed near the surface, so all objects are not pulled under water, but are kept afloat. After getting into the jet, rescuers recommend not to resist, but to wait for the moment when the flow speed weakens. After that, swim a short distance along the coast and move towards land straight or at an angle. It is not recommended to swim between the spits and islands that enclose the estuaries.
Coastal Currents
Waves directed at an angle to the coastline contribute to the formation of coastal and side currents. Their speed is usually not higher than one knot, but it all depends on the direction and height of the waves in eachspecific case.
The strength of such a current is maximum in the surf zone, it is enough to take the swimmer to dangerous rocks or just to an inconvenient place. Coastal streams of water are capable of making depressions at the bottom.
Rip current is observed when masses of water flow into the sea. Large waves approaching the shore form surges that raise the water level. This current has a length of 30 to 1000 m. The strongest rip current occurs when there are no waves.
With the increase in the width of the surf line, the strength of the movement of water from the coast increases. Rip currents are the cause of most diving accidents. This type of water flow is divided into:
- Continuous, existing for a certain period of time. Most often from a couple of hours to two months. Occur as a result of changes in the relief of the seabed near the coast.
- Permanent, appearing in the presence of incessant conditions (an opening in the rocks, a funnel or a chute).
- Instant, arising spontaneously and just as quickly disappearing.
- Mobile, moving along the coast. Their appearance can be predicted.
Wind currents appear under the influence of powerful air currents above the surface layer of water. The farther away from the surface, the lower their intensity. In addition to the wind, the speed and duration of the current are influenced by water temperature, depth and bottom topography.
Convection currents near the coast are caused by air currents in the direction of the sea. Warm water, heated by the sun, leaves withshallow water. To replace it, a cold one rises from the depths.
Ebb and flow
Ebb and flow - changes in sea level, the cause of which is the mutual attraction of the Sun and the Moon. These phenomena move from east to west. The height depends on many factors, including the depth and characteristics of the coastline. The largest fluctuations are observed in narrow bays.
Record holders for water level difference: Penzhinsky (11 m) and Fandi (16 m) bays. High and low water - the name of the highest and lowest points of the level. The magnitude of the tide is the difference between these extremes.
Classification
Depending on the duration of the cycle, high and low tides are divided into:
- Semi-daily. In 24 hours 50 minutes, 2 high and low waters occur.
- Daily allowance. During the same period, high and low tide occur once.
- Mixed. The previous options in their pure form are extremely rare. In most cases, the frequency changes, approaching either the first or the second option.
If the Sun and the Moon are on the same line, then their forces of attraction add up, forming the maximum magnitude of fluctuations in the water level. At present, this phenomenon is well studied. The patterns of their distribution throughout the oceans are complex. For sailors, special tables have been created to help determine the magnitude of the low tide or high tide at any point in the sea and ocean on a specific day and hour.
