Surface Water

The Geography of Surface Water

The majority of surface water is found in the oceans (97.2%) and is saline. Oceans are the largest input to the global hydrologic cycle, where 320,000 cubic kilometers evaporates from their surfaces each year. The world's oceans are highly influential on climate patterns, as these massive water bodies act as a sink for solar energy. Oceanic water circulation moves warm water away from the equator, while cold water is forced toward lower latitudes. These massive transfers of energy drive global temperature and precipitation patterns and explain a great deal about climate and biogeography. For example, the cold current flowing adjacent to the western edge of South America produces dry air and is a factor in the formation of the Atacama Desert climate, while the warm current of the western Atlantic Ocean flows toward Western Europe and keeps annual temperatures mild.

The remaining 2.8% of the Earth's hydrosphere is the nonocean component, and only a tiny 2.5% of this water is fresh. Termed the cryospbere, ice sheets and glaciers constitute the frozen fraction of the hydrosphere and are the largest nonocean component of surface water (2.15% of the total hydrosphere). These huge volumes of ice are concentrated in alpine regions on every continent and at the polar latitudes, specifically the Arctic, the Greenland Ice Sheet, and the continent of Antarctica. Only a fraction of the total global hydrosphere is fresh, liquid surface water: Lakes and reservoirs make up 0.009%, while only 0.0001% is found in rivers and stream channels. The remaining surface water is found in inland seas and saline lakes (0.008%) and in soil moisture (0.005%).

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