Answer:
Because the water-specific heat is much higher than land specific -heat.
Explanation:
When water solidifies due to the temperature descent, it forms hydrogen bridges between water molecules, separating them from each other. This is the reason for water expansion during the freezing process. To go back to the liquid state, and break down the hydrogen bridges, too much heat is needed. This means that water has high water-specific heat.
Water-specific heat is the amount of energy in the form of heat needed to raise the temperature of one gram of water one degree Celsius.
Due to its high specific heat capacity, water reduces the temperature changes. For instance, when we are at the river or sea, during sunset, it gets colder because the sun is not heating directly the earth anymore. However, if we touch the water it seems to be warmer. This is because the water calorific capacity is about five times higher than the sand calorific capacity. The land gets colder faster than the water.
In the same way, when a water body such as a lake is frozen, and there is also ice on the land surface surrounding the lake, and the environment rises its temperature, first the ice on the land defrost and then, after a certain lapse of time, the ice of the water surface also defrosts.
