What is a thermocline?

A thermocline is defined as the transition layer in a body of water where there is a rapid decrease in temperature with increasing depth. This is a critical concept in marine science as it significantly impacts marine ecosystems. The thermocline acts as a barrier between the warmer surface water, which is usually affected by sunlight and atmospheric conditions, and the colder, deeper water that remains at a more stable temperature.

When exploring the ocean's vertical structure, it's essential to understand how the thermocline affects marine life, as temperature can influence the distribution and behavior of various organisms. In many bodies of water, the thermocline can vary in depth and may be influenced by factors such as seasonal changes or geographical location.

The other options do not accurately describe the characteristics of a thermocline. For instance, a layer where temperature remains constant does not account for the specific nature of temperature change that defines a thermocline. Additionally, associating the term with a type of ocean current or the surface layer of warm water misrepresents the physical properties that characterize the thermocline.