How to Measure the Coastal Currents of Malmö

1. Where is Malmö?

Malmö is Sweden's third-largest city, located on the southern point of the Swedish province of Scania, where it lies by the Øresund Strait. Its location in front of Copenhagen, Denmark, has made Malmö a historic coastal city since its early origins. The oceanic past influences the city's development, the economy, the culture, as well as its urban structure.

Malmö abounds with history. It was founded in the 13th century and has since expanded from a small fishing village to a contemporary, international city. The architecture of the city is a blend of historical beauty and contemporary innovation. The 16th-century Malmöhus Castle, which serves as the central location of the city, is a reminder of the city's past. It used to be a royal palace and a fortress. The neighborhood surrounding is cobblestone streets lined with 18th - and 19th - century buildings sporting red - brick facades and pitched roofs common to the time. The new Western Harbour district is more modern in architecture, though, with the Turning Torso skyscraper. This unusual building is an apartment and office complex as well as a landmark, representing Malmö's openminded style of urban development.

The people of Malmö have, for a long time, had a historical connection to the sea. Malmö previously had a considerable fishing sector, whose importance has since declined but still considers the city port an important link for trade and transportation. Malmö's port is a major ferry point employed for travel to Denmark and other regions of Europe. It also handles a decent amount of cargo, supporting the regional and local economy. Maritime leisure activities are popular among residents. Sailing, windsurfing, and beach volleyball are popular summer sports. It also has some seashore activities, such as boat racing and water performances during the Malmö Festival to celebrate its nautical heritage.

Marine waters covering the coast of Malmö fulfill a crucial role in the regional environment. Bottom habitats are an immense variety along the bottom of the Øresund Strait. Seals inhabit sandbanks and rocky ground under normal conditions, while other species of fish like herring, mackerel, and cod dwell in waters. Complex morphology of the bottom with sandy floors, submarine channels, and mudflats. These features guarantee high degrees of biodiversity and are an important input to the dynamics of water.

2. What is the Condition of the Coastal Currents Off Malmö?

The Malmö ocean currents are controlled by a vast number of factors:

• Tidal Forces: Øresund Strait is semi-diurnal for tides. The range of the tide is 0.5 to 1.5 meters, and the tidal currents thus created as a result of this range may be up to 1 - 2 knots, especially at the more restricted sections of the strait. At high tide, water enters the coastal regions, bringing with it sediments and nutrients from the open sea. This renders the surrounding marine environment rich, feeding grounds and habitats of other sea animals. At low tide, the water recedes, revealing the intertidal flats, revealing little crabs, sea anemones, and other seaweeds.
• Wind Patterns: Dominant westerly winds force the inshore surface waters, thus intensifying the coastal currents. The winds also generate waves that work upon the currents to produce a more complex pattern of flow. Easterly winds may force water off the beach. Scania's coastal topography, including headlands and bays, and the peculiarity of the Øresund Strait compels the currents to converge and diverge at several places.
• Freshwater Inputs: Although Malmö has no large rivers flowing into the Øresund Strait, small streams and city runoff still pose a possible input. The freshwater, being less dense than saltwater, forms a surface layer and flows seaward, along with the tidal and wind - driven currents. This may affect the salinity and temperature of the near - shore waters, thereby modifying the current flow.

3. How to Track the Malmö Coastal Water Current?

Surface Drifting Buoy Technique

Surface drifting buoys equipped with GPS or satellite-based tracking systems are a simple yet helpful way of tracking the surface-level currents off Malmö. Once released into the water, surface currents carry these buoys. Researchers are able to chart their path as time passes and track the movement of the buoy to make an estimate of how quickly and in what direction top surface waters travel. This measurement, however, is limited to the top few meters of the water column and may not provide a precise reading of deeper - layer current flows, influenced by factors such as temperature and salt concentration gradients.

Moored Ship Method

In the ship - moored method, a ship is moored off the coast of Malmö at a specified location. Current - measuring sensors such as electromagnetic current meters are then lowered. These sensors have the capability of recording water flow at different depths, enabling a precise vertical profile of current velocity and direction. This method, however, is of a point and can potentially disrupt the natural water flow by existing, thus introducing turbulence in the water flow that may be harmful to the accuracy of measurements.

Acoustic Doppler Current Profiler (ADCP) Method

ADCPs have significantly improved coastal current measurement in the sea off Malmö. ADCPs are capable of measuring the whole water column velocity profile from the surface to the sea bottom. ADCPs utilize sound waves to provide the water flow non-intrusively. They emit acoustic pulses and measure the Doppler shift of the reflected pulses from suspended material in the water, e.g., sediment, plankton, or small bubbles. They are able to calculate the current velocity at different depths, and they give a complete description of the current structure. This renders ADCPs a great option to investigate the intricate coastal current flow around Malmö.

4. What is Needed for High-Quality Measurement of Malmö Coastal Currents?

Equipment Material Reliability

Equipment material reliability is crucial for high-quality measurement of the coastal currents around Malmö. The casing of the ADCP flow meter should be made of material that can withstand the harsh marine environment of the Øresund Strait. Titanium alloy is an excellent choice since it's extremely resistant to strength, i.e., it can resist powerful currents of water, impacts from floating debris, and the corrosive nature of sea water. It has a low elastic modulus that makes it elastic, i.e., less mechanical stress that may lead to damage. Besides, its superior corrosion resistance ensures that the ADCP meter can be left in the water for long-term monitoring without significant degradation.

Compact Size, Light Weight, Low Power Consumption, and Low Cost

A light and compact ADCP flow meter is easier to install and maneuver. It can be mounted on a small research ship, moored to a buoy, or installed on the seafloor with relative ease. Such a system also impacts the natural flow of water to a lesser degree, leading to more accurate measurements. Low power is essential for long-term automatic monitoring, especially with battery - operated systems. A low-cost ADCP enables large-scale deployment, which is essential for fully understanding the complex patterns of coastal currents around Malmö. As we have more ADCPs in place at different locations, we can get a better perspective of how the currents vary along the area.

5. How to Choose the Best Equipment for Current Measurement?

Based on Usage

• Shipborne ADCP: Ideal for gathering real-time current data along a ship path near Malmö. It may be used for oceanographic surveys, examination of the general circulation in the area, and routing optimization because Øresund Strait is a very busy shipping lane.
• Bottom - mounted ADCP: Suitable for long - term, fixed - point observation of seabed currents. It is helpful in analyzing long - term trends in the coastal currents, e.g., the impact of climate change on the local marine ecosystem.
• Buoy-mounted ADCP: Best used for measuring surface-level currents over a large region since the buoy is traveling with the water. It is useful for learning about the spatial variability of the surface currents and the way that the coastal waters interact with the open Øresund Strait.

Dependent on Water Depth

• 600kHz ADCP: Ideal for water depths of up to about 70m, providing high-resolution readings in the comparatively shallow waters off Malmö.
• 300kHz ADCP: Ideal for water depths of about 110m, which can be useful for areas with slightly deeper spots in the Øresund Strait off the city.
• 75kHz ADCP: Suitable for deep-water use. While the waters around Malmö are not particularly very deep in general, it can be applied to research of the deeper-layer currents or used in areas of deeper channels with the ability to measure currents to depths of up to 1000m.

There are several well-known ADCP brands available in the global market, such as Teledyne RDI, Nortek, and Sontek. For price-sensitive customers, the China Sonar PandaADCP, made of all-titanium alloy, is an excellent blend of quality and price. You can learn more about it at (https://china-sonar.com/).

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