WHAT IS BATHYMETRY? - SCIENCE - 2024

The bathymetry is the study and mapping of the ocean floor. It involves obtaining measurements of the depth of the ocean and is equivalent to topographic mapping of the land.

Originally, this term referred to the relative depth of the ocean above sea level. However, today it means underwater topography or the depths and shapes of the underwater terrain.

In the same way that topographic maps represent the terrain features of the ground in three dimensions, bathymetric maps illustrate the surface that is under water.

Variations in ocean relief can be represented in color or by contour lines called depth contours or isobatics.

Bathymetry is the foundation of the science of hydrography, which measures the physical characteristics of bodies of water.

But hydrography includes not only the bathymetry, but also the shape and characteristics of the coast; the characteristics of tides, currents, and waves, and the physical and chemical properties of water.

Bathymetry characteristics

Bathymetry consists of measuring the depth of water in oceans, rivers, or lakes. Bathymetric maps are very similar to topographic maps, which use lines to indicate the shape and elevation of soil features.

However, on topographic maps, lines connect points with the same elevation. In contrast, in bathymetric maps, points of equal depth are connected.

For example, a circular shape with smaller and smaller circles within it indicates an ocean trench; they can also indicate a seamount.

In ancient times, scientists conducted bathymetric measurements by casting a rope next to a boat and recording the length it took for the rope to reach the ocean floor.

However, these measurements were not precise and incomplete; additionally, the string could only measure the depth of one point at a time.

How is bathymetric information collected today?

Information from satellites can be used to produce low-resolution maps showing general features over a large area.

Satellite altimetry measures the height of the ocean surface. If there are mountains or hills on the ocean floor, the gravitational pull of that region will be greater and the surface of the ocean will have a bulge.

This measurement can also be used to show where the ocean floor is highest; this can be used to produce maps showing general features over a large region at low resolution.

There is also a team that captures fringes of the data by acquiring multiple depth points in each region, such as echo sounders or aerial laser measurements. In this way high resolution data can be collected.

Today, sonar echoes are the primary method by which bathymetric information is collected.

Echo probes

An echo sounder sends a pulse of sound from the bottom of a boat to the ocean floor. Then the sound wave bounces back towards the ship.

The time it takes for a pulse to leave and return to the boat determines the topography of the underwater ground: the longer it takes, the deeper the water.

Sonar echoes are capable of measuring small areas of the ocean floor. However, the precision of these measurements is still limited.

The vessel from which the measurements are taken is in motion, changing the depth of the ground by centimeters or even feet.

Additionally, some aquatic organisms, such as whales, can interrupt the transit of sound waves.

The speed of sound in water also varies depending on the temperature, salinity, and pressure of the water. Generally, sound travels faster as temperature, salinity, and pressure increase.

The ocean has different currents, with different temperatures and salinity. The constant movement of the ocean makes bathymetry difficult.

To improve these problems, multibeam echo sounders have been developed. These are characterized by having hundreds of narrow beams that send out pulses of sound.

This set of pulses gives a great angular resolution. Angular resolution is the ability to measure different angles on a single object.

Having a higher angular resolution means that a single feature of the ocean floor - such as the top of a mountain - can be measured from a variety of angles, from the sides to the top.

Multibeam echo sounders also have better accuracy. They allow scientists to map more ocean floor in less time.

Additionally, they can provide information on the physical characteristics of the soil; for example, they can indicate whether it is composed of soft or hard sediment.

Importance of bathymetry

Bathymetric records are used for a range of purposes, including:

• Trace the oceanic routes and for the navigation of the ships.
• Manage fishing.
• Evaluation of alternative energies (such as supporting the wind from the coasts and evaluating the energy of the waves).
• Environmental management, including the establishment of base records to maintain environmental monitoring.
• Evaluation of environmental considerations for resource management of marine geology; This includes the identification of geological hazards such as subaqueous landslides.
• The determination of maritime boundaries.
• Investigation of coastal processes and ocean currents, such as tsunami models.

The International Hydrographic Organization measures and records bathymetric information. These measures help maintain safe navigation and protect marine environments around the planet.

With this information you can also create models that simulate tsunamis. This is useful as the presence of underwater trenches can affect the strength and path of a tsunami or hurricane.

Hydrography is the study of the depth of water features; bathymetry is part of hydrography. It is an integral part in this science that involves the study and mapping of aquatic bodies.

References

1. Bathymetry. Recovered from nationalgeographic.org
2. Bathymetry. Recovered from ga.gov.au
3. What is Bathymetry? Recovered from oceanservice.noaa.gov
4. Bathymetry. Recovered from visibleearth.nasa.gov
5. Bathymetry systems. Recovered from woodshole.er.usgs.gov