Question

What causes the sinking of water during the autumn (fall) overturn?

1. The surface water gets warmer and sinks.
2. The surface water cools down to 4°C, becoming denser and sinking.
3. The density of water decreases as it cools.
4. Increased solar radiation causes the water to become heavier.

• A. All
• B. 2 only
• C. 4 only
• D. 1 only

Answer 1

Answer:

B. 2 only

Spring overturn

• In spring and early summer season the increased solar radiation melts the ice cover, which, as it attains a temperature of 4 degree Celcius, becomes dense and heavy and sinks to the bottom, displacing the lower water which moves up.

• This circulation of water is further helped by the prevailing summer winds and is called spring overturn