Water distribution on Earth
Source of water Volume of water in km³ ( cu mi ) % total water
Oceans 1,338,000,000 ( 321,000,000 ) 96.5
Pacific Ocean 669,880,000 ( 160,710,000 ) 48.3
Atlantic Ocean 310,410,900 ( 74,471,500 ) 22.4
Indian Ocean 264,000,000 ( 63,000,000 ) 19.0
Southern Ocean 71,800,000 ( 17,200,000 ) 5.18
Arctic Ocean 18,750,000 ( 4,500,000 ) 1.35
Ice and snow 24,364,000 ( 5,845,000 ) 1.76
Glaciers 24,064,000 ( 5,773,000 ) 1.74
Antarctic ice sheet 21,600,000 ( 5,200,000 ) 1.56
Greenland ice sheet 2,340,000 ( 560,000 ) 0.17
Arctic islands 83,500 ( 20,000 ) 0.006
Mountain ranges 40,600 ( 9,700 ) 0.003
Ground ice and permafrost 300,000 ( 72,000 ) 0.022
Groundwater 23,400,000 ( 5,600,000 ) 1.69
Saline groundwater 12,870,000 ( 3,090,000 ) 0.93
Fresh groundwater 10,530,000 ( 2,530,000 ) 0.76
Soil moisture 16,500 ( 4,000 ) 0.0012
Lakes 176,400 ( 42,300 ) 0.013
Saline lakes 85,400 ( 20,500 ) 0.0062
Caspian Sea 78,200 ( 18,800 ) 0.0056
Distribution of saline and fresh water
The total volume of water on Earth is estimated at 1.386 billion km³ ( 333 million cubic miles ) , with 97.5% being salt water and 2.5% being fresh water . Of the fresh water , only 0.3% is in liquid form on the surface . [ 7 ] [ 8 ] [ 9 ] In addition , the lower mantle of inner earth may hold as much as 5 times more water than all surface water combined ( all oceans , all lakes , all rivers ) . [ 10 ]
Most water in the Earth's atmosphere and crust comes from the world ocean's saline seawater, while freshwater accounts for only 2.5% of the total. Because the oceans that cover roughly 71% of the area of the Earth reflect blue light, the Earth appears blue from space, and is often referred to as the blue planet and the Pale Blue Dot. An estimated 1.5 to 11 times the amount of water in the oceans may be found hundreds of miles deep within the Earth's interior, although not in liquid form. The oceanic crust is young, thin and dense, with none of the rocks within it dating from any older than the breakup of Pangaea. Because water is much denser than any gas, this means that water will flow into the depressions formed as a result of the high density of oceanic crust. (On a planet like Venus, with no water, the depressions appear to form a vast plain above which rise plateaux). Since the low density rocks of the continental crust contain large quantities of easily eroded salts of the alkali and alkaline earth metals, salt has, over billions of years, accumulated in the oceans as a result of evaporation returning the fresh water to land as rain and snow. As a result, the vast bulk of the water on Earth is regarded as saline or salt water, with an average salinity of 35‰ (or 4.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land. In all, water from oceans and marginal seas, saline groundwater and water from saline closed lakes amount to over 97% of the water on Earth, though no closed lake stores a globally significant amount of water. Saline groundwater is seldom considered except when evaluating water quality in arid regions. The remainder of the Earth's water constitutes the planet's fresh water resource. Typically, fresh water is defined as water with a salinity of less than 1 percent that of the oceans - i.e.