Introduction to Ocean Coastal Current Types

As you already know, the ocean does not stay still. The ocean is alive and it moves. The movement of the ocean water is known as the ocean current. Coastal currents are primarily driven by local winds. So, what are coastal currents?

What is a Wave?

It is important to understand waves to understand coastal currents. The water's surface is pulled on as winds blow across the ocean. The energy that builds up forms waves. The size of the wave is determined by the distance the wind blows, the speed of the wind, and the length of time it blows. For example, a large wave will form if the wind blows for a long time, blows fast, and for a long distance in the same direction. A wave will break when its base comes into contact with the sea floor and becomes unstable, resulting in it toppling onto the shore.

What are Longshore Currents?

This type of current occurs when waves break on the beach and release energy. When a wave heads toward the beach at an angle, a portion of the wave's energy will be perpendicularly directed to the shore. Another part of the wave will be directed parallel to the shore. The longshore current is generated by the parallel energy, which runs along the shoreline. When you are swimming in the ocean and feel the ocean tug you down the shore, you have experienced this type of current.

What is a Longshore Drift?

As sediment is collected and transported down the beach as currents level, it is known as a longshore drift. These can form spits, which are narrow, long outcroppings of land. They can also form long islands parallel to the coast, known as barrier islands. As longshore currents keep picking up, barrier islands constantly change, moving and redepositing sand.

What are Rip Currents?

This type of current occurs when an underwater land formation stops waves from being able to back out to sea. Spent waves funneling out of a narrow opening with immense force are the cause.

What are Upwelling and Downwelling?

When deeper water rises to replace surface water that was displaced by winds blowing it away, this is known as upwelling. Downwelling is the opposite. The water that accumulates due to wind blowing surface water toward the coastline, or other barrier, forces the water on top to sink. Both of these coastal current types are critical to the cycling of nutrients in our world's oceans.

Resources

University of Southern California: Ocean Currents and Climate