The Oceans There are five main oceans: –Pacific, Atlantic, Indian, Arctic, Antarctic
The Oceans The oceans contain 97 percent of the water found on Earth. The remaining 3 percent is freshwater located in: frozen ice caps rivers and lakes underground sources
Source of Earth’s Water Comets Shortly after the formation of Earth, violent volcanism released huge amounts of water vapor and other gases. As the planet cooled, the water vapor condensed into oceans.
Distribution of Earth’s Water Approximately 71 percent of Earth’s surface is covered by oceans that have an average depth of 3800 m. Northern hemisphere: oceans only cover 61 percent of the surface. Southern hemisphere: water covers 81 percent.
Salinity The Composition of Seawater Salinity is the total amount of solid material dissolved in water. oceanographers typically express salinity in parts per thousands: 35 ppt (or 3.5 percent) Most of the salt in seawater is sodium chloride, common table salt.
Salinity The Composition of Seawater Sources of Sea Salt Chemical weathering of rocks on the continents is one source of elements found in seawater. The second major source of elements found in seawater is from Earth’s interior.
Ocean Temperature Variation The ocean’s surface water temperature varies with the amount of solar radiation received, which is primarily a function of latitude. The Composition of Seawater Thermocline: layer of ocean water between about 300 - 1000 meters where there is a rapid change of temperature with depth. Temperature Variation with Depth The thermocline is a very important structure because it creates a barrier to marine life.
Primary Productivity Productivity in Polar Oceans Oceanic Productivity The low availability of solar energy limits photosynthetic productivity in polar areas. Productivity in Tropical Oceans Productivity in tropical regions is limited by the lack of nutrients.