The `West Wind Drift` belongs to the category of ocean currents. Ocean currents refer to the continuous and directed movement of seawater in the oceans. They are driven by various factors such as winds, temperature differences, and the rotation of the Earth.

Option 1: Tidal occurrence - This option refers to the rise and fall of sea levels due to the gravitational pull of the Moon and the Sun. Tides are not directly related to the `West Wind Drift`, so this option is incorrect.

Option 2: Wind system - While winds can influence ocean currents, the `West Wind Drift` is not specifically related to wind systems. It is an ocean current itself, so this option is also incorrect.

Option 3: Wave phenomenon - Waves are formed by the transfer of energy from the wind to the surface of the ocean. Wave phenomenon is different from ocean currents, so this option is incorrect.

Option 4: Ocean current - This is the correct answer. The `West Wind Drift` is an ocean current that is driven by the prevailing westerly winds in the Southern Hemisphere. It flows in an eastward direction around Antarctica, contributing to the circulation of global ocean currents.