Page 280 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

244 part II The Water, Weather, and Climate Systems
All water 100%
Ocean
97.22%
1.321 billion km3 (317 million mi3)
Freshwater 2.78% of all
Surface 77.78%
Groundwater 11.02%
Subsurface
Surface water percentage
Ice and glaciers 99.357%
Freshwater lakes 0.33%
Saline lakes 0.28%
Atmosphere 0.03%
Rivers and streams 0.003%
Percentage of surface water only
(a) The location and percentages of all water on Earth, with detail of the freshwater portion (surface and subsurface) and a breakdown of the surface water component.
(b) The relative percentages and amounts of surface area covered by Earth’s four major oceans.
Animation
Earth’s Water and the Hydrologic Cycle
▲Figure 9.3 Ocean and freshwater distribution on Earth.
Figure 9.3. The oceans contain 97.22% of all water, with about 48% of that water in the Pacific Ocean (as mea- sured by ocean surface area; Figure 9.3b). The remaining 2.78% is freshwater (nonoceanic) and is either surface or subsurface water, as detailed in the middle pie chart in the figure. Ice sheets and glaciers contain the great- est amount of Earth’s freshwater. Groundwater, either shallow or deep, is the second largest amount. The re- maining freshwater, which resides in lakes, rivers, and streams, actually represents less than 1% of all water.
The Hydrologic Cycle
Vast currents of water, water vapour, ice, and associated energy are flowing continuously in an elaborate, open, global system. Together, they form the hydrologic cycle,
which has operated for billions of years, circulating and transforming water throughout Earth’s lower atmosphere, hydrosphere, biosphere, and lithosphere to several kilo- metres beneath the surface.
The water cycle can be divided into three main components: atmosphere, surface, and subsurface. The residence time for a water molecule in any component of the cycle, and its effect on climate, is variable. Water has a short residence time in the atmosphere—an average of 10 days—where it plays a role in temporary fluctuations in regional weather patterns. Water has longer residence times in deep-ocean circulation groundwater, and glacial ice (as long as 3000–10 000 years), where it acts to moder- ate temperature and climatic changes. These slower parts of the hydrologic cycle, the parts where water is stored and released over long periods, can have a “buffering” effect during periods of water shortage.
Fresh 2.78%
Soil moisture 0.18%
Deep groundwater 11.02%
Arctic Ocean
4% of Earth’s ocean area 14 090 000 km2
Atlantic Ocean
28% of Earth’s ocean area 106 450 000 km2
Pacific Ocean
48% of Earth’s ocean area 179 670 000 km2
Indian Ocean
20% of Earth’s ocean area 74 930 000 km2