How do we quantify the Jericoacoara coastal currents?

1. Where is Jericoacoara?

Jericoacoara, or simply Jeri, is a small village on the northeast coast of Brazil, in the state of Ceará. The quaint seaside town occupies part of the coast that is renowned for its stunning natural beauty. Huge sand dunes, some towering high into the sky, surround Jericoacoara to form a breathtaking landscape that attracts tourists from all over the world.

Geologically, the area around Jericoacoara consists of a blend of low-coastal plains and the mentioned sand dunes. The coastal area itself comprises sandy, lengthy beaches, rock outcrops, and small estuaries. The estuaries, which are nourished by little streams and rivers, form an interface between land and sea. They possess high diversity in terms of plant and animal species, like mangroves, that serve to nourish the environment. Mangroves naturally protect the coast from erosion, purify pollutants, and serve as a habitat for several species of fish, crustaceans, and birds.

The past of Jericoacoara is eventful. Natives inhabited the region, and their presence is still evident in local traditions, paintings, and legends. Over time, the village developed into a small fishing village. Today, while fishing remains a core activity of the village economy, tourism is the main driver. The natural remoteness of the village and its sunny climate, coupled with the strong winds, have made it a favorite spot for kite-surfing, wind-surfing, and other sea sports.

2. What are the coastal currents off Jericoacoara?

The coastal currents of Jericoacoara are defined by a multi-determination complex. One of the Atlantic Ocean's largest ocean currents, the South Equatorial Current, is one of the larger stakeholders. On its way onto the Brazilian coastline, it merges with local topography and bathymetry to form local coastal currents. In the Jericoacoara strip, the South Equatorial Current may split into smaller ones and create a dynamic pattern of movement of water.

Tides in the Atlantic Ocean play an important role. The semi-diurnal tidal cycle generates frequent variations in water level. During the spring tides, the greater gravitational pull of the sun and the moon creates more powerful tidal currents. The tidal currents merge with the South Equatorial Current and coastal geometry to affect the overall transport of coastal waters.

Regional winds acting over the coastal region affect the coastal currents. The vigorous northeast trade winds have the ability to push surface waters in a particular direction. The tidal current, the South Equatorial Current, and the wind-driven current merge to form a complicated pattern of water flow. The shape of the seafloor, with varying depths and underwater landforms such as sandbars, channels, and reefs, contributes to the complication of coastal currents. These underwater formations can divert or cut off the movement of the currents. Reefs, for example, can act as a water barrier, which has the tendency to push the water in specified directions, while channels would accelerate the current.

3. How to monitor Jericoacoara's coastal water flow?

Surface Drifting Buoy Method

The surface drifting buoy method is a traditional method of observing coastal water flow. Scientists send buoys with tracking instruments floating in the water. By monitoring how the buoys drift through time, they can determine the speed and direction of surface currents. Although this method has its limitations. It provides information only about the surface layer of the water column and is most susceptible to disturbance from wind. The wind can deflect the buoys in a direction that does not represent the actual movement of the underlying current.

Moored Ship Method

The moored ship method involves using a moored ship as a platform to measure the currents. Sensors are dropped from the ship to measure the flow of water at various depths. While this method can provide accurate vertical profiles of the currents, it is not without drawbacks. The geographical extent is limited to the environment of the moored ship, and the existence of the ship can disrupt the natural flow of the water and thus detract from the accuracy of the measurement. Moreover, long-duration mooring of a ship can be logistically cumbersome and costly.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP meter has emerged as a more advanced and efficient technique of coastal current measurement. ADCPs are capable of sampling the water currents along a wide vertical range and accurately reporting in detail the water velocity structure. ADCPs can be mounted on a variety of platforms, from ships, buoys, to seafloor platforms. Ship-mounted ADCPs are capable of continuously sampling the data as the ship travels, sweeping across an extensive area in a reasonable period of time. Bottom - mounted ADCPs can make long - term, fixed - site measurements such that scientists can perform research on long - term trends in coastal currents.

4. How do Doppler principle - based ADCPs work?

ADCPs are based on the Doppler principle. They emit acoustic pulses into the water. The pulses bounce off suspended matter such as sediment, plankton, or air bubbles in the water. If the water is in motion, the frequency of the reflected pulses changes. From this change in frequency, the ADCP can calculate the speed of the water relative to the instrument.

A large number of ADCPs possess various numbers of transducer beams, commonly four or more, but angled in all directions. By means of such multi - beam operation, three - dimensional velocity in the water is determined. Upon combining signals of the beams, the complete velocity of current in different parts of the water column can be established by an ADCP. The data collected by the ADCP may either be treated in real time or stored and analyzed later for useful information about the dynamics of the coastal currents.

5. What's required to measure Jericoacoara coastal currents with high quality

To provide high-quality measurement of Jericoacoara's coast currents, the measuring instruments should possess certain parameters. They should be made of strong materials, compact in size, light, low power consumption, and low cost. All these parameters allow the application of a vast variety of instruments, thus ensuring complete spatial coverage.

ADCPs with titanium alloy casing are highly recommended. Titanium alloy offers good corrosion resistance, as required for long - term operation in the corrosive marine environment. It withstands the corrosive action of seawater and, therefore, protects the internal components of the ADCP profiler from corrosion. Titanium alloy is also light and strong, and it makes the instrument portable and robust. The combination of these features makes it possible to obtain reliable and long - term measurement of the coastal currents off Jericoacoara.

6. How to choose the right equipment for current measurement?

Use-Based Selection

The choice of ADCP will depend on its use. Ship-mounted ADCPs are ideal for measurements taken aboard a ship. They are capable of transmitting real-time data as the ship moves through water, covering a wide area over a relatively short time. For long - term monitoring at a fixed location, bottom - mounted ADCPs are better. They are able to provide continuous data for an extended period of time, allowing scientists to study long - term coastal current trends. Floating ADCPs can be used for tracking the trajectory of water masses for large areas, providing valuable information on the circulation patterns of large scales.

Selection Based on Depth

The ADCP frequency should also be established in relation to the depth of water. For depths below 70m, 600kHz ADCPs are appropriate. They can generate high-resolution measurements in shallow water. For depths of up to 110m, 300kHz ADCPs are appropriate. For deeper waters, ranging up to 1000m, 75kHz ADCPs are more appropriate.

There are several well - known ADCP brands in the market, such as Teledyne RDI, Nortek, and Sontek. However, for those seeking cost - effective options, the ADCP manufacturer China Sonar's PandaADCP is highly recommended. Made entirely of titanium alloy, it offers excellent performance at an affordable price. It is an ideal choice for budget - conscious users who still require reliable ADCPs for coastal current measurements. More about them on their official website: https://china-sonar.com/.

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