Characteristics of the Oceans
Often overlooked in the geosciences, Oceanography concerns the oceans that cover two thirds of the surface of the Earth. The oceans have a tremendous impact upon weather and climate.
The oceans contain much more than pure water. Many dissolved minerals are present in the water, chiefly sodium and chloride (UIUC, Stanford), the constituents of ordinary table salt.. Gasses such as oxygen and carbon dioxide are also present. Most carbon dioxide absorption occurs in the oceans, either consumed by phytoplankton or absorbed into organic matter that often becomes limestone.
The depth of the oceans range from negligible at beaches to several kilometers in deep ocean trenches. Ocean temperatures are dependent upon depth, latitude and also currents.
Ocean Currents
An important topic in oceanography is the major oceanic currents that loop around the continents and affect navigation and climate (see figure).
Warm and cool ocean currents. Photo credit: NOAA.
Life and Pollution
The oceans contain tiny organisms near their surface called phytoplankton. These organisms utilize sunlight to convert carbon dioxide into oxygen and other molecules. Without phytoplankton, we would not have vital oxygen to breath. They are also the major source of carbon sequestration.
Phytoplankton (credit: U.S. National Oceanic and Atmospheric Administration)
The oceans contain much other life, such as crustaceans, fish, dolphins and whales, and above the surface, birds. Unfortunately, considerable quantities of pollution and waste also flow into the oceans. Of particular concern is plastic, which gets eaten by the sea creatures who cannot digest it and can die.
Reference
NOAA, http://oceanservice.noaa.gov/facts/phyto.html.