Question

DYNAMIC THEORY OF TIDES. What are partial tides and how are they used to

estimate the observed (actual) tides at a specific location on a coastline? EXPLAIN IN
DETAIL.

Answer 1

The Dynamic Theory of Tides is a complex model that explains the movements of the ocean's tides by taking into account not only the gravitational pull of the Moon and the Sun but also the motion of Earth, the depth and topography of the ocean floor, and the interactions between the water and the continents.

**Partial tides** are individual components of the overall tide. They represent the separate responses of the ocean to different forcing frequencies, such as the diurnal and semidiurnal cycles caused by the Moon's orbit around Earth and the Earth's rotation on its axis, as well as longer cycles like the lunar nodal cycle and the solar cycle.

Each partial tide is associated with a particular period and amplitude. They are identified by their speed, which is determined by the celestial bodies that generate them. For example, the principal lunar semidiurnal tide, known as M2, has a period of about 12.42 hours, which corresponds to the average time between two moonrises.

To estimate the observed tides at a specific location, harmonic analysis is used. This process involves:

1. **Data Collection**: Observing and recording the actual tides at the location over a certain period, typically 19 years, which is known as the National Tidal Datum Epoch in the United States.

2. **Harmonic Analysis**: Breaking down the observed tide into many different sinusoidal components or partial tides. Each partial tide is characterized by its frequency (or speed) and amplitude.

3. **Harmonic Constants**: Determining the amplitude and phase (the "lag" or "lead" of a tide relative to the position of the Moon and Sun) for each partial tide component.

4. **Prediction**: Using the harmonic constants to reconstruct the tide by summing the partial tides. The superposition of all these partial tides approximates the observed tides.

The utility of partial tides in this context is that they can be used to predict tides for future dates or to reconstruct historical tide conditions. Since the positions of the Moon and Sun and the rotation of the Earth are predictable, the partial tides they generate are also predictable. By knowing how each partial tide affects a particular location, one can accurately estimate the actual tides for that location. This information is vital for coastal navigation, fishing, marine construction, and other coastal activities.

Answer 2

Partial tides are smaller tidal components that contribute to the overall tidal pattern. To estimate the observed tides at a specific location on a coastline, mathematical models are used that incorporate factors such as the interactions between the Moon and the Sun, the shape of the coastline, and the bathymetry of the ocean floor.

Step-by-step explanation:

Partial tides are the smaller tidal components that contribute to the overall tidal pattern at a specific location. They are caused by a variety of factors, including the interaction between the Moon and the Sun, the shape of the coastline, and the bathymetry of the ocean floor. To estimate the observed tides at a specific location, scientists use mathematical models that take into account these partial tides and their interactions. These models incorporate data such as the positions of the Moon and the Sun, the topography of the shoreline, and the depth of the ocean. By considering all these factors, the models can accurately predict the timing and magnitude of the tides at a specific location on a coastline.