How do we measure Whitby's coastal currents

1. Where is Whitby?

Whitby is a charming sea town on the north-east coast of England, located in North Yorkshire county. It stands on the North Sea coast, at the mouth of the River Esk. Its position has made it an important settlement over the centuries, and its past is inextricably linked with the sea.

The history of the town goes back to the Anglo-Saxon era. It was an important religious center, being the location of the famous Whitby Abbey, founded in the 7th century. Whitby developed into a busy fishing and trading seaport over the centuries. Whitby's architecture is a blend of many different periods. There are medieval - style buildings in the old town, with narrow, cobbled streets and ancient houses. Victorian buildings, like the graceful Royal Crescent, sit alongside more modern developments, such as contemporary shops and restaurants. The town has had a long romance with the sea. Fishing has been a traditional way of life for generations. The local fishing fleet, although smaller in number than in the past, continues to work from the harbour, bringing in a range of fish such as cod, haddock, and mackerel. The harbour is also a hub for pleasure boats, with residents and tourists making excursions along the coast.

The beaches of Whitby are not only a bustling tourist destination, but also form an important part of the ecosystem of the area. The surrounding waters of the North Sea are home to a diverse array of marine life. Seals can be spotted on the offshore sandbanks, and the seabed is teeming with a variety of fish, crustaceans, and mollusks. Some of the features of the seafloor are sandy patches, outcrops, and submerged channels, which not only account for the abundance of fauna but also alter the currents.

2. What is the state of the coastal currents off the coast near Whitby?

The coastal currents along Whitby are a result of several complex factors acting together. Some of the major factors include tidal forces. There are semi - diurnal tides, i.e., two high tides and two low tides each day, for the North Sea. There's a variation of the tidal range, and resulting tidal currents tend to be rather strong, between 2 - 3 knots in certain points, particularly by the mouth of the River Esk. During high tide, water moves towards the land and into the river estuary, carrying sediment and nutrients from the open ocean. During low tide, the water moves back, revealing the intertidal shores that provide habitat for shore - dwelling life.

Wind is also a significant factor. Dominant south - westerly winds are likely to push surface waters on to the shore, increasing the coastal currents. These winds also generate waves that interact with the currents, producing a more intricate pattern of flow. Northerly winds are capable of pushing the water offshore. The coastline shape, including the headlands and bays, and the particular shape of the Whitby headland, makes the currents converge and diverge. Submerged rock outcrops and sandbars add to the intricacy of the current patterns. These features can act as barriers or channels, deflecting the path of water flow and creating areas of turbulence and calm. Additionally, the input of freshwater input from the River Esk can affect the local current patterns. The freshwater is of a different density to the seawater, which leads to the formation of density - driven currents that interact with the tidal and wind - induced currents.

3. How to monitor the coastal water current of Whitby?

Surface Drifting Buoy Method

Surface drifting buoys provide a low - cost but effective method of measuring surface - level currents. The buoys are equipped with GPS or satellite - based tracking equipment on them. They are deployed in the water and are transported by the surface currents. Scientists are able to monitor their drift over time, and by following the trajectory of the buoy, they can estimate the direction and speed of the surface waters. This method is restricted to the top few meters of the water column and might not be typical of the deeper water currents.

Moored Ship Method

A ship is moored at a stationary position off the Whitby coast in the moored ship method. Present - measuring instruments, i.e., electromagnetic current meters, are used afterwards. These devices have the capability of measuring the flow of water at varying depths, giving a vertical profile of the direction and velocity of the current in detail. This technique is limited to a single point alone, and the ship's presence can possibly interfere with the natural water flow, thereby influencing the quality of measurements.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have transformed Whitby's coastal current measurement. They are capable of measuring the velocity profile of the whole water column, from the bottom to the surface. ADCPs make use of sound for non-intrusive measurement of the water flow. By emitting acoustic pulses and observing the Doppler shift of the backscattered signals from suspended particles or sediment in the water, they calculate the current velocity at various depths. This provides a comprehensive overview of the current structure, making it highly suitable to study the complex coastal current patterns in waters around Whitby.

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

ADCPs operate on the basis of the Doppler effect. They emit high-frequency acoustic pulses into the water. When these pulses strike tiny particles such as sediment, plankton, or bubbles in the water, the particles scatter the acoustic signals back to the ADCP flow meter. If the particles are moving with the water current, there is a change in the frequency of the returned signal as compared to the transmitted signal. This Doppler shift is directly proportional to the relative velocity of the particles with respect to the ADCP. By recording the Doppler shift at various depths within the water column, the ADCP determines the water velocity at those depths. Different transducers on the ADCP profiler record velocity in various directions, from which the three - dimensional velocity vector of the water flow may be determined.

5. What is required for good quality measurement of Whitby coastal currents?

Equipment Material Reliability

To measure the coastal currents off Whitby with good quality, the material of the equipment has to be durable. The casing of the ADCP current profiler should be one that resists the harsh marine environment of the North Sea. Titanium alloy would be a very good material. Its high strength allows it to resist the force of strong water currents, potential collisions with floating debris, and seawater corrosiveness. Its low elastic modulus allows it to be flexible, reducing the likelihood of mechanical stress damage. Moreover, its very good corrosion resistance allows the ADCP to be operated in seawater for long - term measurement without significant degradation.

Compact Size, Light Weight, Low Power Consumption, and Low Cost

A smaller and lighter ADCP current meter is simpler to deploy and use, whether on a small research vessel, mounted on a buoy, or bottom-mounted on the seafloor. It also interferes less with the natural flow of water, thereby taking more precise measurements. Low power usage is especially important in the instance of long-term stand-alone monitoring, particularly if battery-powered equipment is being used. An inexpensive ADCP meter enables large-scale deployment, which is vital in fully understanding the Whitby coastal current patterns that are complicated in nature.

6. How to Choose Suitable Equipment for Current Measurement?

Based on Usage

• Shipborne ADCP: Best suited for the acquisition of real-time current data along a ship track in the vicinity of Whitby. It may be utilized for oceanographic surveys, investigating the overall circulation in the region, and optimizing shipping routes.
• Bottom - mounted ADCP: Ideal for the long - term, fixed - point measurement of seafloor currents. It can be used for monitoring the long - term trend in the coastal currents, e.g., the effect of climate change on the local sea environment.
• Buoy - mounted ADCP: Ideally situated to measure surface - level currents over a broad area as the buoy moves with the water. It helps in comprehending the spatial variability of the surface currents and the coastal waters interaction with the open North Sea.

Based on Water Depth

• 600kHz ADCP: For water depths up to around 70m, giving high-resolution readings in the comparatively shallow waters close to Whitby.
• 300kHz ADCP: For water depths of around 110m, which can be utilized for the slightly deeper areas in the North Sea close to the town.
• 75kHz ADCP: Suitable for deep-water applications. While the waters off Whitby are not typically very deep, it could be used for research associated with the deeper-layer current or for deeper channel areas, with the capability to measure currents in water depths up to 1000m.

Some of the popular brands of ADCPs available in the international market are Teledyne RDI, Nortek, and Sontek. In case you are looking for an economical option, China Sonar PandaADCP, which is constructed of all-titanium alloy, is a reasonable compromise between price and quality. You can find additional information about it at [https://china-sonar.com/].

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