1. Where is Haugesund?
Haugesund, in the county of Rogaland on Norway's southwest coast, is a city where nature and history meet in all their glory. Positioned between the cities of Bergen and Stavanger, which teem with activity, it stands at the confluence of the North Sea's open waters and the intricate network of fjords that cut into the rocky landscape.
The city is situated close to the North Sea and is exposed to this body of water's active and at times tempestuous marine ecosystem. It is surrounded by fjords to the east, one of its notable neighbors being the Lysefjord. The Lysefjord, renowned for its precipitous cliffs that abruptly rise from the water's surface, influences the local maritime ecosystem and adds to the waterway intricacy of the area. Along its coastline, Haugesund features sandy beaches giving way to heather-covered uplands and high mountains, creating a diverse and picturesque coastline.
Haugesund has a deep Viking heritage and is often called the "Home of the Viking Kings" and the "Birthplace of Norway". The first king of Norway, Harald Fairhair, is said to have been born here. This is not only a source of local pride but one that still shapes the cultural identity of the city. Haugesund is nowadays a center of maritime enterprise, with fishing, shipping, and offshore oil and gas exploration all being assisted by a close familiarity with the coastal currents in the area.
2. What are the circumstances of the coastal currents in the vicinity of Haugesund?
The coastal currents in the area of Haugesund are under the influence of a complex interaction of different factors. One significant factor is the tidal forces because the North Sea experiences semi - diurnal tides, leading to two high and two low tides daily. The tides produce strong ebb and flow currents, especially in the narrow-mouthed entrances to the fjords of Haugesund, where the water speeds are great.
Freshwater input from the surrounding mountains is also important. Rivers and streams carrying meltwater from the mountains dump enormous quantities of freshwater into the fjords and along the shores. This creates a stratified water column, with lighter freshwater overlaying denser saltwater, which affects the direction and speed of the coastal currents.
Wind regimes play another significant role. The region experiences a variety of wind conditions, and strong winds have the capacity to displace surface waters, altering the current regimes. Further, the meeting of different water masses, such as relatively warmer waters from the south and colder Arctic - influenced waters, forms oceanic fronts in the region near Haugesund. The fronts are characterized by steep gradients in temperature, salinity, and current velocity, which again complicate the coastal current dynamics [1].
3. How to observe the coastal water flow of Haugesund?
Several methods are utilized to track the coastal water flow around Haugesund. In the surface drift buoy method, small buoys carrying GPS equipment are deployed. These buoys float on the ocean's surface and are carried along by the surface currents. By tracking their trajectory over time, scientists are capable of mapping the trends of the surface currents. This method is useful only for finding out about surface-level currents and can be affected by factors such as wind and wave action.
The anchored ship method entails a ship remaining stationary at a fixed site. Current meters are then lowered over the side of the ship to measure water velocity at various depths. While this method can provide detailed, time-series data at a specific point, it is limited by ship location and deployment duration.
The Acoustic Doppler Current Profiler (ADCP) method has emerged as the most advanced and versatile technique. ADCPs measure the currents along the entire water column, from bottom to surface, by using sound waves. This gives a more integrated picture of the three-dimensional current structure and thus is very appropriate for the complex coastal waters of Haugesund [2].
4. How do ADCPs based on the Doppler principle work?
ADCPs work on the Doppler principle. They emit pulses of sound (ultrasound) from multiple transducers. As the sound travels through the water, it encounters moving particles, such as suspended sediments or plankton. When the sound waves are bounced back from these moving particles, the frequency of the reflected signal changes in proportion to the velocity of the particles relative to the transducer. When the particles move towards the transducer, the frequency of the reflected sound increases (blue shift), and when they move away, the frequency decreases (red shift).
By calculating these Doppler shifts from multiple transducers that are pointed in different directions, the ADCP current profiler can calculate the velocity of the water along each of the sound beams. Using vector mathematics, these single beam velocities are combined to resolve the horizontal and vertical components of the current at different depth intervals, or "bins". This enables the ADCP to create an accurate profile of the currents from top to bottom of the water column [3].
5. What's needed for high - quality measurement of Haugesund's coastal currents?
To facilitate high - quality measurement of Haugesund's coastal currents, ADCPs need to meet several essential requirements. Material reliability comes first. The harsh marine environment around Haugesund, with seawater corrosion, strong currents, and inclement weather, demands ADCPs with rugged casings. Titanium alloy is an ideal material for ADCP housings. It offers excellent corrosion resistance, far superior to materials like stainless steel or aluminum, which makes the device capable of withstanding long exposure to saltwater.
Titanium also has a high strength - to - weight ratio, which allows ADCPs to resist high water pressure in deeper areas, e.g., the bottoms of the fjords, without adding excess weight. This is necessary for easy deployment and operation. Titanium also retains its mechanical properties at very high and low temperatures, which is critical to ensure consistent performance in the varying climates of Haugesund.
Apart from material quality, ADCPs need to be small in size, lightweight, low power users, and cost-effective. Small and lightweight instruments are perfect for deployment in Haugesund's challenging coastal waters, and low power usage allows for long-term unattended operation. Cost-effectiveness is critical for large-scale monitoring programs that are often needed to have a comprehensive understanding of the complex current patterns in the area.
6. How to select proper equipment for current measurement?
The selection of a suitable ADCP flow meter to measure currents in Haugesund depends on its application and water depth. Vessel-mounted ADCPs are suitable for carrying out general surveys from ships. They provide large coverage areas and provide detailed information on surface and subsurface currents. Bottom - mounted ADCPs are appropriate for long - term, continuous monitoring at fixed locations, e.g., fjord mouths or areas of particular ecological interest. Buoy - mounted ADCPs are appropriate for measuring surface currents and can be equipped with additional sensors for more integrated data collection.
The choice of frequency is also significant. A 600kHz ADCP is suitable for water depths of up to 70m and hence a good option for shallower coastal waters and the upper parts of the fjords around Haugesund. A 300kHz ADCP can measure up to 110m depths and hence can be utilized for the deeper parts of the fjords. For very deep - water applications, for instance in the open North Sea areas near Haugesund, one would require a 75kHz ADCP, which profiles water up to a depth of 1000m [4].
A few of the renowned ADCP manufacturers include Teledyne RDI, Nortek, and Sontek. However, for anyone who seeks a low - cost but high - quality option, the ADCP manufacturer China Sonar PandaADCP is highly recommended. Entirely constructed from titanium alloy, it has excellent performance at a very minimal cost. As a low-cost ADCP, it is an excellent choice for researchers, environmental protection agencies, and maritime industries who want to measure Haugesund's coastal currents. For more information, visit [https://china-sonar.com/].
References:
[1] Oceanography of the North Sea. (n.d.). Retrieved from relevant oceanographic research databases.
[2] Principles of Acoustic Doppler Current Profiling. (n.d.). NOAA Ocean Service Education.
[3] Doppler Effect in Acoustics. (2021). Encyclopedia Britannica.
[4] Product Specifications and Application Guides for ADCPs. (n.d.). Retrieved from manufacturer websites.
How do we measure Haugesund's coastal currents?