How do we measure Lynn's coastal currents?

1. Where is Lynn?

Lynn is a town in Essex County, Massachusetts, USA. It is located in the northeastern part of the country, and its geography is different from that of most locations. It is rich in history and culture, and it is home to a close community that has lived there for centuries. Lynn is situated alongside the Atlantic Ocean, and nearby, it is near Nahant Bay. The sea surrounding this area belongs to the wider system of the coast, which is controlled by a number of natural factors. The coast supports various environments from sandy beaches to rocky shores, which, apart from being entertaining to tourists, provide various sea creatures as well. The climate at Lynn is temperate, and it has developed seasons. It is very hot in summer and cold in winter, which influences the coastal atmosphere and the coastal currents in the oceans surrounding it.

2. What is the coastal current off Lynn?

The coastal current off Lynn is influenced by numerous factors. The tidal forces are the principal contributors. Periodic rise and fall of tides, caused by moon and sun gravitations, create rhythmic flow of water along the seashore. Water flows in during high tide and flows out during low tide, affecting the direction and speed of the coastal currents. Wind also plays an important role. The dominant winds can drive the surface waters forward, making them flow in the wind direction. Stronger winds can produce stronger currents. The shape of the coast and the sea floor topography (bathymetry) of the area also affect the currents. Shallow areas or the areas of narrow channels can potentially block the flow of water, and the blocked water can accelerate the water, while deep and broad areas can permit wider spread and slower currents.

3. How will the coastal water flow of Lynn be tracked?

Surface Drift Buoy Method

Surface drift buoy method is one of the traditional methods by which coastal water flow is tracked. They are dropped on the surface of the water and are swept along by the currents. They have tracking devices like GPS attached to them, by which their movement over a period of time can be tracked. By following the path of the buoys, scientists can have an idea of the surface current flow. But this method provides information only for the water surface and is susceptible to being affected by wind-driven currents, and hence is not that effective in determining the actual current flow.

Anchor - Moored Ship Method

The ship - moored anchor method is a fixed-location anchored ship. Shipborne equipment, e.g., current meters, are lowered to the water at different depths to monitor the speed and direction of the currents. The method can record multiple depths but is relatively immobile and will not be able to detect the large - scale variation of the coastal currents in a large area.

Acoustic Doppler Current Profiler (ADCP) Technique

Over the past few years, the ADCP has become increasingly popular as a better and simpler measurement system. As ADPCs have widespread use in coastal survey and oceanography, they can measure water velocity at a range of different depths over a wide vertical area, which generates a more realistic representation of current structure in the water column. This makes it highly suitable to investigate the dynamic Lynn coast currents.

4. How do ADCPs work based on the Doppler principle?

ADCPs are based on the Doppler principle. They emit acoustic pulses into the water. When those acoustic pulses pass through moving particles in the water, e.g., suspended sediments or plankton, the backscattered signal frequency changes. If the particles are moving toward the ADCP, the frequency of the backscattered signal will be greater, and if they are moving away from the ADCP, the frequency will be less. Measuring this frequency change, the ADCP can calculate the water velocity at different depths. The device is typically equipped with a number of transducers that can transmit and receive at different angles. This allows for the calculation of the east-west, north-south, and vertical components of three-dimensional water flow velocity. By combining the velocity measurements with time and depth, scientists can precisely map the coastal currents surrounding Lynn.

5. What does Lynn coastal current high-quality measurement need?

High-quality measurement of Lynn coastal currents depends on a number of features that are welcomed in the measuring equipment. The equipment needs to be constructed from highly reliable materials. Since the equipment will be exposed to the corrosive marine environment, it must be corrosion-resistant, water pressure withstanding, and long-term durable. The equipment size must be small. With small size, it is more convenient to maneuver and deploy in different coastal locations, especially in locations with complex topography or accessibility issues. Light weight is also preferable since it reduces the effort in terms of handling and transport. Secondly, low power consumption is extremely critical. This is due to the fact that the device can function for extended periods without battery replacement from time to time or consume much power that cannot be economically sourced in remote areas far from main ports. Cost - effectiveness is also crucial. Low-cost equipment facilitates bulk deployment and enables bulk measurement of the coastal currents.

For the ADCPs, the casing plays an important part. A casing for an ADCP can ideally be constructed with titanium alloy. Titanium alloy is of a multitude of advantages. It has very high corrosion resistance, which is most significant for ensuring long-term usage in seawater. It is also extremely lightweight, but strong enough to protect the internal ADCP parts from mechanical stress. Titanium alloy toughness ensures that the ADCP will withstand the aggressiveness of the marine environment and make long-term measurements.

6. Selection Tips for the Right Equipment for Current Measurement?

ADCPs by Purpose

The choice of ADCP depends on its purpose. For instance, when measurement is to be conducted aboard a moving ship, a ship - mounted ADCP is ideal. It measures the currents aboard a moving ship, giving real - time information along the track of the ship. A bottom - moored (or sit - on - the - bottom) ADCP is well suited for long - term monitoring at fixed points. It can be installed on the seafloor and permitted to record current data for numerous days. Buoy-based ADCPs or floating ADCPs are most appropriate to monitor large - scale ocean or coastal processes because they can be carried by the currents, providing data from multiple points as they move.

Frequency Selection

The frequency of the ADCP also needs to be taken into consideration. Different frequencies are optimum for different water depths. For water depths of up to about 70m, a 600kHz ADCP would be an appropriate choice. This frequency provides relatively high-resolution measurements in shallow water. For depths of about 110m, a 300kHz ADCP would be more appropriate. It can penetrate deeper into the water column but still provide good accuracy. For very deep waters, up to 1000m, a 75kHz ADCP would be most appropriate. Lower frequency is capable of traveling greater distances in the water, making measurements possible at greater depths.

Recommended Brands

There are a number of popular ADCP brands, including Teledyne RDI, Nortek, and Sontek. But for those who want an economical option without sacrificing quality, the ADCP supplier China Sonar's PandaADCP is a good choice. Further details are available on its official website: https://china-sonar.com/.

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