[Biology Class Notes] on Back to Oceans Pdf

Earth is known as the ” Blue planet ” due to abundant water present in it. Oceans are the storehouse of water. There is approximately 320,000,000 litres of water present in the Ocean. But from where does all this water come from?

It is the result of the continuous water cycle which provides water to earth and to oceans. Over a short period of time the amount of water in the ocean doesn’t change but in a longer span it does have an impact. Let’s have a look at the water cycle which keeps on circulating huge amounts of water from the ocean and then gives back to oceans.

The Water Cycle

Evaporation, cooling, freezing condensation, melting are all important processes that drive the hydrological cycle which is a never-ending process of water circulation from oceans to clouds and rivers and back to oceans. The steps involved in cycling of huge amount of water are – 

• Evaporation – The sun which is the primary source of energy heats up the large surface area of oceans and causes the water from oceans to evaporate. This large amount of water constitutes the atmospheric water vapour. Warm water vapour rises up thereby cooling the surface of water. Huge amount of heat is absorbed by the ocean for the heating up of water from the surface of Ocean continuously. 

• Condensation – the water vapour rises up continuously and is carried away by the atmospheric air currents where it cools and condenses to form the clouds. Condensing water vapour releases latent heat and this latent heat plays an important role in Earth’s heat balance.The clouds are accumulation of fine droplets of water at extremely low temperature and remain suspended at high altitudes.

• Precipitation – the clouds collide and their the electrical discharge which results in the precipitation of water droplets to the ground. The precipitation may be in the form of rain, snow, hail etc. Most precipitation falls on water bodies or on land.

• Surface runoff – The water that falls on land meets a different fate. A portion of water flows over the ground as runoff and due to gravity it eventually is discharged into rivers and other water bodies.

• Stream flow – The water accumulated from surface runoff and drainage flows into streams, lakes and rivers which travel along the surface of earth to reach sea and finally meet the oceans.

• Soil moisture – Some water infiltrates into the soil which is utilised by plants and returns to the atmosphere by evapotranspiration.

• Groundwater – Deep infiltration of water results in replenishing ground water table which then later emerges as springs or is taken by humans for their use.

Over time all this water keeps circulating through various channels, but ultimately it is poured back to the oceans from where it’s journey started.

Significance of Water Cycle

1.The cycling of water is related to energy exchange between ocean, atmosphere and land.

2.It influences Earth’s climatic conditions and climate change to a great extent.

3. Large amounts of heat absorbed by the ocean helps in buffering the green house effect from increasing carbon dioxide and other gases.

4.Condensed water vapour releases latent heat which drives atmospheric circulation in the tropical regions.