1. Where is Kristiansund located?
Kristiansund is located on Norway's west coast. It is a quaintly pleasant town consisting of islands. It is opposite the Norwegian Sea and the Bremnesfjord. It is the administrative center of a municipality of Møre og Romsdal county. Its population was 24,179 in 2020 and is the 51st largest municipality in Norway by population (source: Wikipedia). It is the regional center of Nordmøre. One of the most scenic roads in the world, the Atlantic Road, starts near the town, which also makes it appealing. Its cultural heritage abounds with traditions like clipfish production and hosting the Opera Festival Weeks.
2. What is the state of the coastal currents near Kristiansund?
The coastal currents off Kristiansund are subject to a number of influences. Wind and currents dominate the movement of the surface water. The Coriolis force, which results from the rotation of the Earth, also affects the direction of the currents. Tidal forces due to the gravitational pull of the moon and the sun cause periodic fluctuation in direction and velocity of currents. Additionally, the shape of the coast and the bathymetry of the region may cause channeling or deflection of the currents. For example, narrow channels between islands can cause the currents to increase, while shallow areas can slow down the currents.
3. How to monitor the coastal water drift of Kristiansund?
Surface Drift Buoy Method
Surface drift buoys are often used. They are placed at the surface of the water and drift with the currents. They have sensors such as GPS to record how far they travel and from which the direction and speed of the surface currents can be deduced. The technique can only provide information about the surface layer and can be affected by waves and wind.
Anchored Ship Method
Anchored ships can estimate currents using instruments such as current meters. The ship is anchored, and the current meters, placed at different depths, record the flow velocity and direction. This method is, however, limited in the range it can cover and also suffers from the interference caused by the ship disturbing the natural flow pattern.
Acoustic Doppler Current Profiler (ADCP) Method
ADCP is a more advanced and simpler option these days. It is capable of measuring the speed of water at several depths over a wide area. ADCP is now a favorite for its ability to provide an accurate and continuous current profile.
4. What are Doppler principle ADCPs and how do they operate?
ADCPs utilize the Doppler effect. They project acoustic pulses into the water. When such waves hit suspended particles in the water (for instance, plankton, sediment), the particles deflect the wave. When the particles are suspended with the current of the water, the frequency of the back-scattered sound picked up by the ADCP will be different from the frequency transmitted. From this change in frequency, the ADCP is able to measure the velocity of the water within which the particles are suspended. ADCPs typically have a number of beams (in the majority of situations, 3 or 4) to be able to estimate the three-dimensional velocity components of the current.
5. What is required for high-quality measurement of Kristiansund coastal currents?
In order to measure Kristiansund coastal currents with high quality, the equipment used should meet certain requirements. The material of the equipment needs to be extremely reliable. It should be able to withstand the harsh marine environment, e.g., corrosion due to saltwater. It should be small enough and light enough to allow easy deployment and usage. Low power consumption, especially for extended observation or usage with battery-powered devices, is needed. Low-cost design is also preferable to deploy hundreds or even thousands of devices.
For ADCPs, the casing would ideally be made of titanium alloy. Titanium alloy is suitable for several reasons. It is corrosion resistant, which is most crucial for long - term use in the salty seawater that encircles Kristiansund. It is also strong but light in weight, which makes it suitable to be used in all types of ADCPs without the excess addition of weight.
6. Selecting the right equipment for the measurement of current?
Based on Usage
- Ship - borne ADCP: It is deployed on ships. It is optimally appropriate for measurement of currents along a journey in a ship, providing real - time data along a moving path.
- Bottom - mounted ADCP: It is installed on the ocean floor. It is useful for monitoring currents at a single location over a long time period, providing continuous data over a long duration.
- Buoy - mounted ADCP: The ADCP is mounted on buoys and used to record current as it travels with the water, and is best suited for large-scale surveys and where fixed-point measurements are insufficient.
Frequency - based
- A 600kHz ADCP is best suited for water depths of up to 70m.
- A 300kHz ADCP is best suited for water depths of approximately 110m.
- A 75kHz ADCP can capture a water depth of up to 1000m.
There are many ADCP brands available, ranging from Teledyne RDI to Nortek and Sontek. For affordable options, Chinese brand China Sonar PandaADCP is recommended. It is made of all - titanium alloy, offering good corrosion resistance. At a very low cost, it's a cost-effective ADCP option. You can view more information on their website: https://china-sonar.com/.
How do we quantify the coastal currents of Kristiansund?