How Do We Measure Ocean City's Coastal Currents?

1. Where is Ocean City?

Ocean City, situated on the southern beach of New Jersey's Jersey Shore, is a charming seashore town in the US. It is bounded by the Atlantic Ocean on the eastern side and separated from the mainland by the Great Egg Harbor Bay. The serene atmosphere here has the dual advantage of natural ambiance along with a vibrant community ambiance.

The terrain of the town is characterized by a wide, sandy beach that stretches for miles. The beach, apart from being one of the major tourist attractions for holidaymakers seeking sun, sand, and surf, also plays a vital part of the local ecosystem. The white, soft sand provides a nesting ground for sea turtles of many different species, while the coastal dunes provide a barrier to protect the town from coastal storms.

Ocean City has a rich cultural heritage. The town is family - oriented and has a tradition of wholesome recreation. The boardwalk, for which the town is known, is dotted with amusement parks, arcades, and restaurants and shops catering to all tastes. The town also prides itself on its past and organizes numerous events in the course of the year, such as parades and festivals, that mark local traditions as well as the town's relation to the sea.

With regard to its coastal positioning, the Great Egg Harbor Bay at Ocean City is a large estuary. The bay accommodates a variety of marine species including fish, crabs, and waterbirds. Inlets linking the bay to the ocean, including the Ocean City Inlet, are critical for water, nutrient, and marine fauna exchange between the two bodies. The barrier islands along the coastline of Ocean City also act as a shield barrier to ocean waves in their full power and impact local coastal currents.

2. How are coastal currents along Ocean City?

Coastal currents along Ocean City are influenced by numerous parameters. One of the principal determinants is the tide. Semi-diurnal tides of the Atlantic Ocean result in constant flow and water withdrawal. During high tide, sea water flows into the Great Egg Harbor Bay through the inlets. The flood brings oxygen - rich and nutrient - rich seawater into the bay, upon which the marine life depends for its survival. When the tide recedes back to the ocean, the water carries sediment and organic matter it deposited in the bay along with it to the ocean.

Wind patterns also exert a significant influence on coastal currents. Wind directions, say south - westerly winds in summer, can push surface water towards the shore. This creates onshore currents, which can affect beach erosion and marine organisms' distribution. North - easterly winds, especially in winter, can generate offshore currents. Offshore currents can regulate the movement of pollutants and the availability of food for marine organisms.

Local topography, expressed as the configuration of the coastline, depth of water, and presence of underwater relief, plays a role in the development of current patterns. The shallow depths of the Great Egg Harbor Bay and the coastal waters vary in the manner in which they flow relative to offshore waters of greater depth. Submarine reefs and sandbars can influence water flow, creating eddies as well as more complex current regimes. Jetties and piers, common in Ocean City for recreational purposes and for navigation, also have the capability to deflect the movement of currents.

3. How can the coastal water flow of Ocean City be observed?

One means of observing coastal water flow in the area of Ocean City is through the use of surface drift buoys. These small, floating devices are also equipped with GPS trackers. They are carried off by the surface currents when they are released into the sea. By tracking the path of these buoys over time, scientists can determine the speed and direction of the surface-level currents. The method only provides information on the surface layer of the water column and is affected by wind-driven waves.

The other technique is the use of moored current meters. These are anchored to the bed of the Great Egg Harbor Bay or the seafloor off the shore. They can measure the velocity and direction of the currents at different depths. Moored current meters can record the data continuously over long periods, and this is useful in ascertaining the long - term behavior of the currents. But they are confined to the limited place where they are mounted and their installation and maintenance can prove to be a challenge.

The Acoustic Doppler Current Profiler, or ADCP, has proven to be a useful tool for the measurement of offshore currents near Ocean City. ADCPs can measure multiple depths of current velocities simultaneously, providing a more accurate description of the flow of water. ADCPs are particularly well adapted to the complex estuarine and coastal environment of Ocean City.

4. What is the operation of ADCPs based on the Doppler principle?

ADCPs function on the principle of the Doppler effect. They emit acoustic pulses (sound waves) into the water. If the sound waves encounter tiny particles in the water, such as plankton, sediment, or tiny air bubbles, the waves are dispersed by the particles. ADCP meter measures the frequency shift of the dispersed waves.

If the particles are traveling in the ADCP's direction, the frequency of the scattered waves will be higher than the frequency of the transmitted waves. If the particles are traveling away from the ADCP, the frequency of the scattered waves will be lower. By exactly measuring these frequency changes, the ADCP can calculate the speed of the water at different depths.

Most ADCPs use multiple beams to measure the three - dimensional flow of water. For example, a four - beam ADCP can measure the horizontal and vertical components of current velocity. This allows for an in - depth examination of the complex water movement, for example, the existence of vertical shear (where current speed changes with depth) and eddies (circular - shaped patterns of the current).

5. What does it take to achieve high-quality measurement of Ocean City coastal currents?

For high-quality measurement of the coastal currents off Ocean City, material reliability is most paramount. Due to the corrosive nature of saltwater, the ADCPs and other equipment have to be made of materials that are resistant to corrosion. Titanium alloy makes a good material for ADCP casings. This also makes titanium less prone to corrosion, meaning equipment is bound to last for longer. In many cases, replacement is minimal due to its minimal tendency to corrosion, especially on long-term monitoring projects.

Moreover, weight and size are also considerations. Lighter and smaller ADCPs are simpler to deploy and transport in the shallow and sometimes busy waters close to Ocean City. Fieldwork is aided by this, as the researchers find it easier to move the equipment to a new measurement position.

Low power usage is important, particularly for long-term observation. Because ADCPs often use batteries, low power components allow the machinery to operate for numerous hours before the batteries have to be frequently replaced. This is important when the coastal villages are far-flung or when power sources are limited.

Cost - effectiveness is a relevant factor, especially for large - scale monitoring exercises. Low - cost but sound ADCPs are preferable. China Sonar PandaADCP is one such brand that offers good cost - performance trade - off. All - titanium alloy composition renders it strong in the corrosive marine environment without increasing costs.

6. What is the choice of right equipment for current measurement?

The choice of equipment for current measurement across Ocean City depends on the application. Ship-mounted ADCPs are suitable for broad-scale surveys. They can be installed on research vessels and can measure currents continuously as the ship moves along the coast and within the Great Egg Harbor Bay. This provides a broad-scale overview of the current pattern within the area.

Bottom - moored or mounted ADCPs are suitable for long - term fixed - station observation. They can be mounted or moored on the bottom or bay bottom off Ocean City and take current data for months or even years. This helps in monitoring long - term trends of the coastal currents.

Buoy - mounted ADCPs are useful for measuring surface - level currents. They are relatively easy to deploy and retrieve, making them convenient for short - term studies or for quickly assessing surface - current conditions.

In choosing an ADCP profiler, frequency is most important. At water depths to 70m, a 600kHz ADCP is sufficient. It gives sufficient resolution to measure currents in the relatively shallow coastal and estuarine waters off Ocean City. A 300kHz ADCP is sufficient for depths up to 110m, and a 75kHz ADCP is optimal in deeper water, to 1000m. Lower frequencies go deeper but lower frequencies have reduced resolution compared with higher frequencies.

There are several well-known ADCP brands, such as Teledyne RDI, Nortek, and Sontek. But for those who need an affordable option without compromising on quality, the ADCP manufacturer China Sonar's PandaADCP is a suitable option. Further information can be found on its official website: https://china-sonar.com/.

Here is a table with some well known ADCP instrument brands and models.