1. Where is Kandalaksha?
Kandalaksha is a town within the Murmansk Oblast of northwestern Russia[^1^]. It is located on the eastern shore of the Kandalaksha Gulf, which is an arm of the White Sea. Its location within the Arctic - subarctic zone renders it a strange and hostile climate. The Kandalaksha shoreline is dotted by a mix of cliffs and narrow inlets, with the seashore repeatedly recontoured by erosion. The inland area is comprised of rolling hills of open tundra bushes, which withstand the extreme climate. The area is blanketed with thick snow during winter, and the sea freezes to produce a giant sheet of ice. In summer, the region experiences the midnight sun, whereby there is constant daylight that spans both land and sea.
Kandalaksha has a rich industrial and cultural history. It developed as a prominent port and industrial settlement, with the likes of fishing, shipbuilding, and metal manufacturing industries contributing immensely to the economy of the region. The buildings in the town have a blend of Soviet-era constructions and recent buildings. The indigenous people are Russian, with some cultural influences from the indigenous Sami. The Kandalaksha Gulf's natural location and abundant marine resources have been the pillars of the town, shaping its development and people's lives.
2. How are the coastal currents surrounding Kandalaksha conditioned?
The coastal currents surrounding Kandalaksha are conditioned by a number of factors. The interaction with the cold waters of White Sea and Barents Sea inflow, in combination with the influence of the North Atlantic Current, are significant. The White Sea is typically characterized by cold and relatively low - salinity waters. But the influence of the Barents Sea and the North Atlantic Current is able to introduce warmer and saltier water masses, which can induce a mixing process [^2^]. This affects the salinity, temperature, and density of the water column, which leads to upwelling and downwelling areas. These variations control the motion of the coastal currents and greatly influence the local marine environment, the distribution of fish, plankton, and other sea organisms.
The tidal forces likewise heavily influence the current regime in the vicinity of Kandalaksha. The White Sea has a semi - diurnal tidal regime with two high and two low tides daily. The complex geometry of the Kandalaksha Gulf, such as its shallow entrances and non-uniform depths, limits water exchange during tidal fluctuations and gives rise to high tidal currents. The tidal currents are required for sediment, nutrient, and marine organism transport within the gulf. They also have impacts on fishing locally, as it has to be considered by fishermen when planning their travel, and sea transport, as it has to be navigated across the areas of strong currents.
Wind - driven circulation is also of major importance. The region around Kandalaksha is affected by strong and variable winds, especially during winter. These winds are able to drive surface waters, generating surface - level currents. The velocity and direction of the wind can be quite different, leading to fluctuation in the surface - current patterns. Such surface currents mix with the oceanic and tidal force-controlled deeper - layer currents, and this creates a dynamic and complex system of currents in the coastal waters off Kandalaksha.
3. How to observe the coastal water flow of Kandalaksha?
There are several means of observing Kandalaksha coastal water movement. Surface drifting buoy technique is an old method. Researchers deploy buoys carrying monitoring devices, i.e., GPS receivers or radio transmitters, into the ocean. These buoys ride the currents, and by monitoring their path with respect to time, researchers can determine the direction and speed of surface-level currents. But this method only provides information for the surface layer of the water column and may not be a reflection of the currents at deeper levels.
The anchored ship method is also commonly used. There are a number of tools that an anchored ship can use to sample the current's speed and direction at different depths surrounding the ship. While this method involves more direct sampling of the water column than does the buoy method, it is limited to the surrounding environment of the point at which it is anchored and perhaps will not be able to gather the full spatial variability of the Kandalaksha coastal currents.
Over the last few years, the Acoustic Doppler Current Profiler (ADCP) method has been viewed as a more advanced and efficient means to quantify coastal currents. ADCPs can record currents at multiple depths simultaneously and provide an entire description of water flow structure. This makes them a valuable resource for gaining further information about the complex and three-dimensional nature of the coastal currents around Kandalaksha, enabling scientists to gain more accurate and detailed information regarding the current regime within the area.
4. How do ADCPs using the Doppler principle operate?
ADCPs operate on the Doppler principle. ADCPs propagate sound waves into the water column. These signals bounce off suspended tiny particles of water, such as sediment, plankton, or tiny organisms, and are bounced back to the ADCP in the form of echoes. When water is flowing, the frequency of the returning echo signals is altered relative to the frequency of the emitted signals. This frequency shift, or Doppler shift, is proportional to the velocity of the water flow.
By comparing the Doppler shifts of the sound waves detected at different depths, the ADCP can calculate the speed and direction of the current at various points in the water column. In so doing, scientists can achieve a three-dimensional view of the water flow, both horizontally and vertically. According to this in-depth information, scientists would better understand the intricate dynamics of coastal currents around Kandalaksha, which is essential for marine ecosystem management, navigation safety, and environmental research.
5. High-quality measurement of Kandalaksha coastal currents requires
To ensure high-quality measurement of coastal currents near Kandalaksha, ADCP instruments must meet several significant requirements. Material reliability is critical. The marine environment near Kandalaksha is harsh, with freezing waters, strong currents, and corrosive seawater. The ADCP must be constructed using materials that are tough and resilient enough to withstand such harsh conditions for extended deployments.
The size and weight of the ADCP must be minimal. It should be a light and compact design so that it is easy to deploy within the region. Mounted on a small research fishing vessel, attached to a buoy, or mounted on the ocean floor, a lighter and smaller ADCP is easier to work with and more convenient. It should also use low power consumption, especially since Kandalaksha is off-shore, and power sources can be difficult to locate. This allows long deployment without battery replacement or recharging on a regular basis, with continuous data collection. In addition, a relatively low-cost solution is also preferable, as this allows multiple ADCPs to be deployed to read an area and get a better picture of the complex current patterns.
The ADCP should have a titanium alloy casing. Titanium alloy has excellent corrosion resistance, which is crucial for resisting the long-term immersion in the harsh White Sea saltwater. It also has a high strength-to-weight ratio, being strong enough to resist the mechanical stresses of the ocean and light enough to be easily transported and deployed in the challenging conditions of the Kandalaksha area. These are the features that make titanium alloy an appropriate choice in providing long-lasting and stable operation of ADCPs used for monitoring coastal currents in this region.
6. How to Choose the right equipment for current measurement?
The selection of ADCP gear is based on the particular measuring needs. For large - scale current pattern observation over the entire Kandalaksha Gulf and along its connection to the White Sea, a ship - mounted ADCP would be an appropriate solution. It may be mounted on research ships that patrol the waters, taking data as the ship travels and offering a broad - scale image of the current systems in the area.
For fixed-point, long-term monitoring of specific points, such as near significant fishing grounds or areas of ecological significance, a bottom-mounted ADCP is more suitable. Once deployed on the seabed, it is able to continuously record current information for extended periods of time, giving detailed insight into local current conditions.
A buoy-mounted ADCP is the optimal choice where mobility and flexibility are required. The buoy is permitted to drift by the currents, providing real-time data on the movement of masses of water and allowing one to track dynamic fluctuations in currents in the Kandalaksha coastal waters.
Frequency is also a critical parameter. A 600kHz ADCP is suitable for depths up to 70 meters, a 300kHz ADCP for depths up to 110 meters, and a 75kHz ADCP for depths up to 1000 meters[^3^]. A few established ADCP producers are Teledyne RDI, Nortek, and Sontek. But for those who need an affordable yet quality ADCP, the ADCP manufacturer China Sonar PandaADCP is a good recommendation. Entirely made from titanium alloy, it is worth the money and an excellent choice for price-conscious users. For more information, visit https://china-sonar.com/.
[^1^]: Information on Kandalaksha's geography and location can be found through official Russian geographic databases and tourist publications.
[^2^]: Research on the interaction of White Sea water masses and their impact on coastal zones is published in scientific marine science journals.
[^3^]: Standard marine instrumentation handbooks are the source of general rules for ADCP frequency choice in relation to water depth.
How do we measure the coastal currents of Kandalaksha?