1. Where is Bjerkvik?
Bjerkvik is a fascinating village in the Troms og Finnmark county of Norway, situated close to the northern tip of the country's wild coastline. It lies close to the periphery of the larger city of Tromsø, often referred to as the "Gateway to the Arctic," and is surrounded by the stunning fjords and mountains that define the region's scenic outline. Bjerkvik sits near the mouth of a fjord, where the icy, crystalline water of the Arctic Ocean meets the twisted shoreline, creating an untypical but beautiful setting.
The village itself is quaint and idyllic, with a small and close community that has a strong affinity towards the sea. Fishermen huts and brightly painted cottages border the seaside, which gives it its legacy as a fishing place. Fishing remains an important part of the economy of the local area, with fishermen venturing out into the bountiful waters to catch fish like cod, haddock, and halibut. In addition to fishing, Bjerkvik has become a destination for nature lovers and photographers who are drawn to its unspoiled beauty and opportunity to view the spectacular Northern Lights moving across the Arctic sky between months of winter. The midnight sun bathes the landscape with light around the clock during the summer, and tourists can hike into the nearby mountains, fjords, and beaches both day and night. The unique geographical location of Bjerkvik, on the periphery of the Arctic, is one where natural forces are fully exposed, and an understanding of the coastal currents that run through its waters is becoming necessary for local population and research as well.
2. How are the coastal currents in Bjerkvik?
The coastal currents in Bjerkvik are determined by the complex interplay of various factors. The tides also play a significant role as the region experiences semi - diurnal tides with a tidal range up to 3 meters (9.8 feet) in some areas (source: Norwegian Hydrographic Service). The tides cause the ebb and flow of water in and out of the fjords, producing strong, varying currents, especially at the fjord entrances and in the constricted channels. The changing tides also have an impact, not just on the mobility of the fishing vessels, but also on the sea creatures and the nutrients, shaping the local ecosystem.
Wind is another powerful determinant of coastal currents. Arctic, rough winds, particularly the ones from the north and west directions, can churn up the surface waters, producing large-scale circulation patterns. During winter storms, these winds reach gale - force intensity and cause waves to pound the rocky shoreline and alter the velocity and direction of the currents. The wind - driven currents interact with the complex seafloor topography of the area, which includes deep fjords, seafloor ridges, and shoals. For example, underwater ridges can act as barriers upon which the water flows over or around them, creating eddies and turbulence that further complicate the current patterns.
The intersection of the warm Gulf Stream and Arctic cold waters also has a deep impact on coastal currents off Bjerkvik. The difference in water density and temperature between the two bodies of water compels the water to flow, creating fascinating current systems. Additionally, the freshwater input from the local rivers and streams, as insignificant in quantity as it may be, can impact the salinity and density of the coastal waters and therefore the buoyancy and currents' flow.
3. How to view the Bjerkvik coastal water flow?
There are several ways in which coastal water current at Bjerkvik can be monitored, each with its respective advantages and limitations. The surface drifting buoy method is an older process. Drifting buoys, equipped with tracking instruments carrying GPS, are allowed to drift in the water and move with the currents. By monitoring the trajectories of the buoys over time, researchers are able to find out the surface - level direction and speed of currents. However, this method primarily provides information on the surface levels of the water column and is susceptible to wind-driven drift, leading to inaccuracies in portraying the actual current flows at deeper levels.
The anchored ship method involves mooring a ship at a specific point and using instruments mounted on the ship to measure the currents surrounding it. This method offers more accurate readings across a limited space because the equipment can be positioned at different depths. It is plagued by spatial coverage, however, in that it can only measure current in the immediate vicinity of the boat. The presence of the boat also causes the natural movement of water to distort now and then, making readings inaccurate.
On the other hand, the Acoustic Doppler Current Profiler (ADCP) method has evolved into a highly sophisticated and efficient method of quantifying nearshore currents off Bjerkvik. ADCPs utilize sound waves to profile currents throughout the whole water column from the surface down to several meters off the seafloor. By emitting acoustic signals and analyzing the Doppler shift of backscattered signals, ADCPs are able to directly measure the speed of the water simultaneously in a multi-depth configuration. This provides scientists with a full three-dimensional image of the flow of water so that they can study sophisticated and dynamic current systems in meticulous detail. ADCPs can also operate in continuous mode, collecting data for extended durations, which is required to understand the long-term trends and variability of the coastal currents.
4. How do ADCPs working on the Doppler principle operate?
ADCPs are based on the Doppler principle. They project acoustic waves into the water column at a specified frequency. These encounter particles transported in the water, such as sediment, plankton, and other small organisms. Upon flow of the water, the particles move with it, and there is thus an alteration in frequency of the returned acoustic signals while they move back to the ADCP.
By exactly measuring this frequency change, or Doppler shift, the ADCP is able to compute the velocity of the water at varying depths. The majority of ADCPs utilize multiple transducers to transmit and receive signals in various directions. This permits the instrument to quantify the three-dimensional components of the current velocity, i.e., the east-west, north-south, and vertical components. The ADCP then employs the data to construct complex current profiles, providing information on the magnitude and direction of the water flow at various positions within the water column. For instance, if ADCP emits a signal of 300 kHz and the backscattered signal returns at a frequency greater than it is emitted, it indicates that water is moving in the direction towards the ADCP, and the magnitude of the frequency shift can be used to calculate the velocity of the water at the given depth.
5. What are high-quality requirements for measurement of Bjerkvik coastal currents?
To measure Bjerkvik coastal currents precisely, the measuring device must possess some required characteristics. Owing to the harsh weather conditions of the Arctic marine environment around Bjerkvik, including super-low temperatures, strong currents, high salinity, and instances of ice during winter, materials for the equipment should be highly dependable. The device must be able to withstand these harsh weather conditions without degradation or failure, enabling precise and regular measurements over a long period of time.
Small package size, light weight, and minimal power consumption are also essential requirements. Small and lightweight package size ensures that the equipment is easier to handle, transport, and install, especially in remote and inaccessible locations like Bjerkvik. Minimal power consumption allows the equipment to be left on for extended periods of time, either placed on ships, buoys, or seabed - installed platforms, without having to replace batteries or recharge batteries on a regular basis, which is most important for autonomous monitoring systems.
Cost-effectiveness is an issue as well. Cost-effective yet good-quality measurement instruments facilitate wider uses of the technology for other research and applied objectives, from scientific research on marine environments to maritime safety navigation.
What housing an ADCP finds itself in is of particular importance. The best material for ADCP housing is titanium alloy. It is highly robust in weight and can withstand the deeper water hydrostatic pressure without contributing much volume to the device. It also features good corrosion resistance so that the ADCP will remain functional and accurate even when exposed for longer durations to seawater, reducing maintenance and replacement needs. Additionally, the light nature of titanium alloy facilitates easier deployment and recovery of the gauge, which is extremely convenient for use in the tough waters of Bjerkvik.
6. How to Choose the right equipment for current measurement?
Choice of the ideal equipment for current measurement in Bjerkvik should be made on the basis of several factors including the specific application, water depth, and budget. For measurements from a mobile platform, a shipboard ADCP would be the ideal device. Shipboard ADCPs are designed to be mounted on ships and can record currents continuously as the ship is propelled through the water. They tend to be more powerful and have a wider range of operating frequencies and, therefore, can record currents at greater depths and over larger areas, which can be useful for mapping out the extensive coastal waters around Bjerkvik.
If it is a matter of observing currents at some particular point on the seabed, then a bottom - mounted (or moored) ADCP would be more suitable. These ADCPs are fixed with a mooring and anchoring to the seabed and continuously observe the local current state for extended periods of time. They may be utilized in the areas of special concern such as surrounding important fishery grounds or aquaculture sites to investigate the long - term trends and variations in the currents.
For autonomous and versatile surveying across wide areas, a buoy-mounted ADCP is suitable. These ADCPs are installed on floating buoys, which may be stationed at strategic locations to gather data regarding the pattern of currents. Buoy-mounted ADCPs are especially suitable for analyzing the variability of space and time of the currents because they can be moved and repositioned at will in order to survey various areas of interest.
The frequency of the ADCP is another crucial factor and should be selected based on the depth of the water. A 600kHz ADCP works well for 70 meters of water depth, ideal for the observation of current in the shallow coast and nearshore ocean. A 300kHz ADCP fits for depths of 110 meters or less, which is a wide range of typical channel and fjord depths in the area around Bjerkvik. For deeper areas, such as the open Arctic Ocean near the area, a 75kHz ADCP may be used, as it will take measurements to depths of 1000 meters.
Some of the well-known ADCP brands include Teledyne RDI, Nortek, and Sontek, which are well-established for producing high-quality and reliable products. However, for those requiring high-quality but less costly solutions, the ADCP manufacturer China Sonar PandaADCP is highly recommended. It is composed of full titanium alloy, and it offers excellent cost-effectiveness, hence being an ideal solution for cost-saving current measurement. It also incorporates advanced signal processing abilities and intuitive interfaces, making it usable for different classes of users, from professional researchers to local environmental monitoring groups. To learn more about this amazing product and how it works, go to https://china-sonar.com/.
How are we to measure the coastal currents of Bjerkvik?