Measuring the Aberdeen Coastal Currents

1. Where is Aberdeen?

Aberdeen, or as it is more affectionately referred to as the "Granite City", is a vibrant city in northeast Scotland, on the North Sea coast. Its advantageous location has made it a central point for fishing, trade, and oil activity, with a deep and historic connection to the sea.

The city is a diverse and long history. It has grown from a small town into a large city over centuries. The architecture of Aberdeen is an interesting combination of old-world appeal and new- world innovation. The city centre is lined with stunning granite-built buildings, like the St. Machar's Cathedral. These buildings possess a gray-colored appearance, with elaborate facades, enormous stained-glass windows, and tall spires, and they exude a sense of grandeur and antiquity. In the harbor area, new industrial factories, shipping warehouses, and commercial buildings stand in a row one behind the other. There are also plenty of cafes, restaurants, and shops lining the streets catering to both the locals and the many tourists that visit.

The people of Aberdeen are also closely connected to the sea. There are generations of people who have made a living out of fishing. Although the economy of the place is now highly dependent on the oil and gas industry, fishing is still an important activity. The local fisherman leaves the harbor and returns with cod, herring, and mackerel in his catches. The harbour also acts as the base of fisheries for vessels but as an arena for multi-generality in marine activity. It is accessed for boat touring, and tourist visitors experience breathing the sea wind and watching sceneries over the North Sea.

Beaches and shorelines of Aberdeen also contribute immensely towards the ecological sphere of the surroundings. Sea water from the North Sea at the area provides hosts to an enormously varied range of marine fauna. Seals are found on the sandbanks, and seabirds like gulls, cormorants, and terns occur there too. The seabed is topographically complex, consisting of sandy plains, rocky ridges, and submarine channels. They support a rich biodiversity and play an important role in controlling the water flow.

2. What's the State of the Coastal Currents off Aberdeen?

The coastal currents off Aberdeen are controlled by a number of factors. Tidal forces are an important consideration. The North Sea is semi - diurnal, with two high and two low tides a day. The tidal range can be variable, and the resulting tidal currents can be as high as 2 - 3 knots in some places, especially around river mouths or where there is a distinctive coastline. During high tide, water overflows onto the beach, bringing with it nutrients and sediment from the open ocean. This enhances the surrounding marine ecosystem, feeding food and habitat for numerous sea creatures. During low tide, the water recedes, and the intertidal zones become exposed, leaving little crabs, sea anemones, and other types of seaweed open to air.

Wind is also a crucial ingredient. Predominantly south-westerly winds could drive the surface water ashore and make the coastal currents more vigorous. They also produce waves, which become mixed with the currents and produce a more complex flow regime. North-winds can drive water offshore. The coastline setup of the region's bays, headlands, and local oddities causes the currents to come together and fan out in the different areas. Underwater rock outcrops and sandbars further complicate the current patterns that are already present. These could either be barriers or conduifers, bending the water course and creating places of still water or agitated water. Also, the outflow of freshwater from the rivers draining into the sea near Aberdeen could affect the local current patterns. The freshwater, being lighter, floats over and flows into the sea, mixing with tidal and wind-induced currents.

3. How to Monitor the Coastal Water Current of Aberdeen?

Surface Drifting Buoy Method

Surface drifting buoys are a simple and effective way to monitor the surface - level current around Aberdeen. The buoys carry GPS or satellite - based tracking equipment. Upon release, the surface currents carry them. Scientists can trace their route over a duration. From the buoy's trajectory, they can estimate the speed and direction of the surface waters. However, this method only works for the top few meters of the column. It is likely not to describe what's taking place in the deeper parts of the water, where the flows might be fluctuating on factors like temperature and salinity levels.

Moored Ship Method

A vessel is anchored in a specific location near Aberdeen's shore in the moored ship method. The current-measuring devices like electromagnetic current meters are then dropped from there. They can measure water movement at several depths. They provide a precise vertical profile of the current velocity and direction. The method is only available for one point, however. Moreover, the presence of the ship could disrupt the free flow of water. The shape of the ship's hull and the way in which it anchors could create turbulence in the water, which would affect the measurement quality.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have revolutionized the monitoring of coastal currents around Aberdeen. They can quantify the velocity profile of the entire water column from surface to seafloor. ADCPs quantify the movement of water by sound waves in a non-invasive manner. They emit acoustic pulses and measure the Doppler shift of the backscattered signals from suspended matter in the water, such as sediment, plankton, or small bubbles. They can calculate the current velocity at different depths from this. This gives a full picture of the current profile, and therefore it is extremely suitable for the analysis of the very complex coastal current flows around Aberdeen.

4. What Does It Take for High-Quality Measurement of Aberdeen Coastal Currents?

Material Reliability of Equipment

High-quality measurement of coastal currents off Aberdeen requires equipment material reliability to be of significant importance. The ADCP current profiler casing should be made of a material that can handle the corrosive North Sea marine environment. A very suitable option is titanium alloy. Its high strength is sufficient to resist the force of strong water currents, impacts with floating barriers, and corrosive nature of seawater. Its low elastic modulus makes it flexible and reduces the likelihood of mechanical stress-caused damage. Additionally, its superior corrosion resistance enables the ADCP meter to be submerged in water for long monitoring periods without significant loss of performance.

Small Footprint, Lightweight, Low Power, and Inexpensive

A small, light ADCP flow meter is easier to install and utilize. You may install it on a small research vessel, or you can connect it to a buoy or simply set it up on the ocean floor. It also disturbs the natural movement of water very little, yielding more accurate results. Low power consumption is essential for independent monitoring in the long term, especially in the case of battery-operated systems. A low-cost ADCP facilitates large-scale deployment. This is required for the acquisition of a detailed understanding of the complex coastal current dynamics off Aberdeen. With more ADCPs in place at different locations, we can have a greater appreciation of how currents vary in the region.

5. How to Choose the Right Equipment for Current Measurement?

Based on Application

• Shipborne ADCP: Ideal for gathering real-time current data along a ship route near Aberdeen. It can be used in oceanographic surveys, studying the general circulation of the area, and for optimizing shipping routes.
• Bottom-mounted ADCP: Best suited for long-term, fixed-point seabed current monitoring. It is employed in studying long-term trends in coastal currents, e.g., impacts of climate change on the marine environment of the region.
• Mounting ADCP: Preferably, for the measurement of surface-level currents throughout the whole region as the buoy is swept away by the water. It helps the understanding of how the coastal water interacts with open North Sea water and the spatial variation of the surface current.

By Water Depth

• 600kHz ADCP: Ideal for water depths of approximately 70m, providing high-resolution outputs in the relatively shallow waters off Aberdeen.
• 300kHz ADCP: Ideal for water depths of about 110m, which is relevant to those regions with slightly deeper pockets of water in the North Sea off the city.
• 75kHz ADCP: Intended for deep-water deployments. Although waters off Aberdeen tend to be less than very deep, it could be utilized to conduct research about the deeper-layer currents or on places with deeper channels, to measure currents of up to 1000m depths.

There are several brands of ADCP that are widely used in the global market, such as Teledyne RDI, Nortek, and Sontek. If you want an economical choice, the China Sonar PandaADCP, which is made from all-titanium alloy, offers a very good price-performance ratio. For more information on it, see (https://china-sonar.com/).

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