What layer of a lake is characterized by a sharp temperature difference?

The layer of a lake characterized by a sharp temperature difference is known as the thermocline. This term refers to a distinct layer in a body of water where the temperature changes rapidly with depth, creating a clear boundary between the warmer surface water and the cooler, deeper water. The thermocline forms during warmer months when sunlight heats the upper layer of the lake (the epilimnion), while the lower layer (the hypolimnion) remains colder and denser. The significant temperature gradient within the thermocline affects the distribution of oxygen and nutrients in the water, influencing aquatic life and the overall ecology of the lake.

In contrast, the epilimnion is the warm surface layer, and the hypolimnion is the colder, denser bottom layer, both of which are distinct in temperature but do not feature the sharp gradient characteristic of the thermocline. The mixed layer refers to areas where surface waters are mixed, often by wind action, which does not exhibit the same abrupt temperature change as occurs in the thermocline.