The hydrosphere includes all water on Earth in all its forms: liquid, frozen or vapour, meaning all water found in oceans, lakes, rivers, groundwater, ice, snow and glaciers. The biosphere also includes water bound up in life, such as the water in plants, fungi and animals. Of all the water on Earth, about 97.5 % is salt water, and only 2.5 % is fresh water.
The word hydrosphere comes from the Greek hydros = water and sphaira = sphere or ball.
The frozen water on the Earth’s surface, such as snow, glaciers, ice sheets and permafrost, is called the cryosphere and is part of the hydrosphere. This frozen water plays an essential role in regulating the Earth’s temperature, influencing sea levels and reflecting solar radiation, and is therefore also important for the climate. The temperature and composition of the atmosphere affect the cryosphere by regulating melting and freezing. Meltwater from the cryosphere can affect the hydrosphere’s volume, temperature, salt value and sea levels.
Sources
MeteorologienRed – Hydrosphere 
Scied.ucar.edu – earth-system – cryosphere
October 2023, TÄNKOM | Revised November 2023 RETHINK
