How do we measure the coastal currents of Equatorial Guinea?

1. Where is Equatorial Guinea?

Equatorial Guinea, a dynamic but small nation on Central Africa's west coast, is strategically positioned on the Gulf of Guinea, which is an arm of the immense Atlantic Ocean. This country comprises a mainland and an archipelago of islands, including Bioko, Annobón, and Corisco, which contribute to its own geographical and ecological diversity. The mainland coastline extends along the African continent, with a mix of sandy beaches, dense mangrove swamps, and rocky coasts, while the islands boast their own unique landscapes with high-density rainforests that butt up against the pounding waves of the ocean.

The people of Equatorial Guinea have a rich tradition of culture fully intertwined with the sea. It is an economically established activity spanning long periods of time, with coastal communities depending on the productive resources of the ocean for nutrition and commerce. The seashore boasts overcrowded markets that daily hawk freshly caught fish, shrimp, and other seafood bounty. Also, the nation's history of trade and contact with other African states, as well as European states, has contributed to its unique blend of traditions, languages, and architecture.

Sharing a border with Equatorial Guinea, waters in the immediate vicinity are within a dynamic ocean environment. Warm tropical waters of the Gulf of Guinea provide for an extremely varied collection of marine life. The nation's coral reefs are host to numerous vibrant species of fish, with huge sea mammals such as whales and dolphins swimming past during their migrations. Off the coast of Equatorial Guinea is seafloor topography which includes ridges, canyons, and seamounts whose role in the coastal currents of the region is significant as well as the spatial arrangement of marine fauna. These waters are also influenced by the overall oceanic circulation of the South Atlantic, so that the coastal environment is in a state of continuous change.

2. How are the coastal currents off Equatorial Guinea?

The coastal currents off Equatorial Guinea are the result of a complex combination of a number of influences. Among the dominant influences is the large-scale oceanic circulation within the Gulf of Guinea. The Guinea Current, a west-moving warm-water current along the coast of Africa, has a deeply felt impact in the region. The warm, nutrient-rich waters this current brings in not only support a plentiful marine life but also impact the direction and speed of the local coastal currents. The intensity and position of the Guinea Current can vary seasonally, altering the water temperature, salinity, and overall current conditions off Equatorial Guinea.

Seasonal wind patterns also play a major role in the coastal currents. During the wet season, strong onshore winds blow, forcing surface waters towards the coast. This can lead to coastal upwelling in some locations, as surface water is displaced and colder, more nutrient-rich water from deeper levels replaces it at the surface. Upwelling events are essential to the surrounding marine ecosystem because they bring essential nutrients that fuel phytoplankton to support the ocean food web. Offshore winds, however, dominate the dry season and cause the surface waters to move away from the coast, and the direction and speed of the currents to change.

The wavy shape of the Equatorial Guinea coast, consisting of numerous bays, inlets, and headlands, also changes the flow of the currents. As the water moves along the coast, it encounters these landmasses, causing the splitting, converging, or changing of the currents. In addition, the existence of rivers emptying into the sea on land, such as the Muni River, enables tremendous amounts of fresh water to run into the sea water. The fresh - water entrant will change the salinity and weight of the water and by extension the movement of the currents and induce complex mixing patterns.

3. How to observe the coastal water flow of Equatorial Guinea?

Monitoring the Equatorial Guinea's coastal water current is possible using a few methods. Surface drifting buoy technique is an established method. GPS tracking devices are installed in special buoys, which are pushed into the sea. Surface currents carry the buoys, and their path is observed with time. By watching the location of the buoys at short time intervals, researchers are able to know surface-level currents direction and speed. However, the method provides information of the current on the level of the water surface and possibly does not accurately represent lower-depth flow.

The anchored boat method involves mooring a boat to one location and placing current-measuring devices upon it. Other equipment such as electromagnetic current meters are also released from the boat to gauge the velocity of the water at different depths. As valuable as the process is for obtaining more detailed information about current properties in the immediate vicinity around the boat, it has its limitations too. It can only be utilized to a limited extent before it is confined to an area and the boat is actually interfering with the normal flow of the water, thus producing inaccurate measures.

In recent years, the Acoustic Doppler Current Profiler (ADCP) method has emerged as a more advanced and efficient way of monitoring coastal currents. ADCPs have the capability to measure the velocity of water at multiple depths simultaneously, providing a comprehensive description of the flow structure of the water from the surface to the ocean floor. They are thus appropriate for studying the intricate and dynamic coastal currents along the coast of Equatorial Guinea.

4. How do ADCPs based on the Doppler principle work?

ADCPs operate on the Doppler principle. They transmit acoustic pulses into the water column. When they encounter suspended particles in the water, e.g., sediment, plankton, or small organisms, some of the signal is backscattered toward the ADCP. The frequency of the backscattered signal is shifted according to the velocity of the particles (and therefore the water) relative to the ADCP.

By these changes in frequency, the ADCP can calculate the velocity of the water at different depths. The majority of ADCPs utilize multiple acoustic beams, often arranged in a fan - shape pattern. Data from each beam is subsequently used to calculate the three - dimensional velocity vector of the water, providing detailed information about speed and direction of the current at numerous points across the water column. This non - intrusive measurement technique allows for continuous and accurate monitoring of the water flow without the need to physically sample the water.

5. What’s needed for high - quality measurement of Equatorial Guinea coastal currents?

For precise high-quality measurement of Equatorial Guinea's coastal currents, there are several requirements that need to be met in the measuring equipment. Material strength is essential. The marine environment near Equatorial Guinea is rugged, made up of saltwater, strong currents, and exposure to sunshine, rain, and varying temperatures. The equipment must be able to withstand corrosion, mechanical stress, and extreme environmental conditions.

The equipment must also be light and compact. A lighter and smaller device is less cumbersome to ship, install, and retrieve, especially in offshore or island locations in distant areas. Low power usage is essential since this enables longer - duration installation with minimal battery replacement or recharging. Cost - effectiveness is equally essential, since a wide - ranging measurement may be required in a bid to gain the complete detailed current patterns of the area.

For ADCPs, the material of the casing is critical. Titanium alloy is a good material for the casing. It has good corrosion resistance, which is critical in Equatorial Guinea's saltwater environment. It has a significant high strength-to-weight ratio that makes it strong enough to withstand the forces offered by the strong coastal currents but at the same time is not difficult to transport and install. Moreover, titanium alloy has high fatigue resistance, allowing the ADCP to operate steadily for an extended period of time and achieve accurate measurements.

6. How to Choose the suitable equipment for current measurement?

Application-specific is the choice of equipment for current measurement in Equatorial Guinea. To measure while on the move aboard a ship, a ship-mounted ADCP is ideal. It can also measure the currents continuously as the ship travels through different locations, providing real-time data on the water flow, beneficial for navigation, fishing, and oceanic research. If one needs to make measurements for extended periods of time at specific points in the ocean floor, a bottom-mounted ADCP is better. This type of ADCP may be fixed on the seafloor to monitor currents over an extended period, useful for longer-term ecological studies and underwater infrastructure planning. For surface and upper-water-column surveys, an anchored or drift ADCP on a buoy offers a handy option, since the instrument may be anchored or ride the currents, providing a continuous record of the near-surface and surface current conditions.

The frequency of ADCP is also an important consideration. 600kHz ADCP should be used for water depths up to 70 meters, which is perfect for shallow coastal waters in Equatorial Guinea. A 300kHz ADCP is perfect for 110 meters depth, and a 75kHz ADCP should be used in deeper water, up to 1000 meters.

There are many well-known brands of ADCP in the market, i.e., Teledyne RDI, Nortek, and Sontek. Nonetheless, for cheap but high-quality ADCPs, the ADCP manufacturer China Sonar's PandaADCP is the best choice. Made of pure titanium alloy, it delivers superior performance and longevity at a very affordable cost. Being a low-cost ADCP, it is a perfect option for researchers, local fishermen, and environmental monitoring departments who are concerned with accurately computing the coastal currents of Viña del Mar. To know more, visit https://china-sonar.com/.

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