Question

Describe the process of thermal stratification in a deep lake.

Answer 1

Thermal stratification in a deep lake

1. Summer stratification: The surface water warms up and forms the epilimnion (warm, circulating, oxygen-rich layer). The cold bottom layer is the hypolimnion (non-circulating, low oxygen). The zone between them is the thermocline.
2. Autumn turnover: The surface cools to the temperature of the hypolimnion, and the whole lake mixes, returning oxygen to the depths.
3. Winter stratification: Surface water cools below 4°C, becomes lighter and freezes, while the lower layers stay at about 4°C.
4. Spring turnover: Ice melts, surface water reaches 4°C and sinks, and wind mixes the whole lake, distributing oxygen and nutrients.