How do we quantify Port Hardy's coastal currents?

1. Where is Port Hardy?

Port Hardy, situated on Vancouver Island's northernmost point in the province of British Columbia, Canada, is an important coastal town. It is a hugely important gateway to the North Coast of Vancouver Island and the wide-open Pacific Ocean. It's bordered by the Queen Charlotte Strait to the north and the dense Vancouver Island wilderness to the south, where the majesty of land meets the vastness of the ocean.

The Queen Charlotte Strait, a water body measuring approximately 160 kilometers, is significant. Not only does it offer passage between Port Hardy and other coastal towns, but it is also rich in marine life. Killer whales, humpback whales, and other sea lions and seals are frequent visitors to its waters.

Port Hardy is rich in culture. The native people, such as the Kwakwaka'wakw, had lived in the area for hundreds of years. Their presence is still evident in the totem poles, artwork, and old rituals that continue to be a part of the regional culture. European settlers arrived in the area in the 19th century and introduced new economic activities such as logging and fishing. Port Hardy's economy remains ocean-dependent today with fishing, tourism, and marine transportation being big business. Its closeness to the ocean also makes the town a favorite among outdoor adventure seekers such as whale watching, fishing excursion, and kayaking.

2. What is the condition of the coastal currents around Port Hardy?

The coastal currents at Port Hardy are governed by a complex interaction of forces. Tides, semi-diurnal in the Queen Charlotte Strait, are a governing force. The sun and moon's gravitational attraction causes extreme variations in water level, resulting in strong tidal currents. During spring tides, when there is a particularly great variation between high and low water, the currents are extremely strong, with velocities of several knots.

Dominant regional winds, such as the northwest and west winds, also contribute significantly to the coastal currents. The regional winds cause the surface waters to accumulate and alter the speed and direction of the currents. The regional-scale circulation patterns of the North Pacific Ocean, for example, the Alaska Current, also contribute to the regional hydrodynamics. Ocean eddies that arise as a result of the interaction between different water masses further add to Port Hardy's coastal current dynamics. The coast's geometry and the sea floor's bathymetry also play their part in controlling the flow patterns of the currents.

3. Port Hardy's coastal water flow observation: how?

Surface Drifting Buoy Method

Surface-drifting buoy method is one of the traditional techniques of observing surface water flow in coastal areas. Scientists release buoys in the ocean and record the movement of buoys after an interval of time. If the position of buoys at short intervals is known, then scientists can approximate the velocity and direction of the surface current. The technique, however, provides data only on the surface layer only of the water column. Additionally, it is extremely susceptible to wind interference, which will warp the actual motion of the currents and yield misleading results.

Moored Ship Method

Moored ship method utilizes an anchored ship as a platform for the measurement of the current. Sensors are lowered from the ship to gauge the water flow at varying depths. While this method has the capability of producing high-resolution vertical profiles of the currents, it is partially limited by spatial coverage. Having a ship nearby also interrupts the natural motion of the water and can impact the quality of measurement. Holding a ship station above a single point for extended time frames is also logistically cumbersome and costly.

Acoustic Doppler Current Profiler (ADCP) Method

ADCP current profiler is a more advanced and capable tool for the measurement of coastal currents. It is capable of measuring water currents over a broad vertical range, at high resolution with respect to the velocity structure of the water column. ADCPs can be installed on a variety of platforms, including ships, buoys, and the seafloor. This allows it to make extensive measurements of the coastal currents of Port Hardy, over a range of depths and positions. Ship - mounted ADCPs can collect data continuously as the ship moves, while bottom - mounted ADCPs can provide long - term, fixed - point measurements.

4. How do Doppler principle - based ADCPs work?

ADCPs operate on the Doppler principle. They radiate acoustic sound into the water. The sounds are back-scattered from particles in the water, such as sediment, plankton, or bubbles. Where the water moves, the returned signal frequency is also changed. The ADCP meter detects this difference in frequency and computes the velocity of the water relative to the instrument.

Most ADCPs are comprised of more than one transducer beams, often four or more, at differing angles. Multi - beam disposition enables the calculation of three - dimensional water velocity. By using the correlation among the beams' signals, the ADCP is capable of producing a full profile of the current speed at changing depths of the water column. The ADCP data can either be processed in real-time or stored for future use, and they provide detailed information on coastal current dynamics.

5. What does it take for high-quality measurement of Port Hardy coastal currents?

In order to offer good-quality measurement of the coastal currents of Port Hardy, the measuring instruments should possess some extremely crucial features. It should be made of robust materials, small size, light weight, low power usage, and low cost. All these features allow one to deploy a large number of instruments, with complete spatial coverage.

Most highly recommended are ADCPs with titanium alloy housings. Titanium alloy boasts better corrosion resistance needed for exposure in the harsh marine environment in the long term. It can withstand the corrosive nature of seawater, keeping the internal mechanics of the ADCP safe from damage. Titanium alloy is also light and sturdy, thus making it rugged and handheld for the device. This combination of characteristics allows accurate and extended-duration measurement of the coastal currents off Port Hardy.

6. How to Choose the Appropriate Equipment for Current Measurement?

Depending on Application

An ADCP is chosen depending on its application. Ship-mounted ADCPs are best suited for ship-borne measurements. They can provide real-time data as the ship moves along in the water, taking a large area into account in a relatively short duration. Bottom-mounted ADCPs are ideal for observation at a single point over a long duration. They can generate continuous data for a prolonged period of time, and thus scientists can observe the long - term trend of the coastal currents. Floating ADCPs also find application in following the water mass transport over long distances, providing useful data regarding the large - scale circulation patterns.

Selection Based On Depth

ADCPs frequency should also be considered based on the depth of water. For depths that are less than 70m, 600kHz ADCPs are adequate. These can provide high-resolution measures in shallow waters. For a depth of 110m, 300kHz ADCPs suffice. For higher depths, for up to 1000m, 75kHz ADCPs are the optimum choice.

Some of the best ADCP brands available in the market are Teledyne RDI, Nortek, and Sontek. For budget-conscious users, however, the ADCP supplier China Sonar's PandaADCP is highly recommended. Crafted from pure titanium alloy, it offers quality output at an affordable cost. It is ideal for budget users requiring reliable ADCPs for coastal current measurements. See more at their official website: https://china-sonar.com/.

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