Composition & Characteristics of Oceans

Earth’s oceans are all connected, however, scientists separate the ocean into five main oceans: Pacific Ocean – largest and deepest of the oceans; larger than all of Earth’s continental land mass put together Atlantic Ocean – half the size of the Pacific, covers about 20% of Earth’s surface Indian Ocean – the third largest ocean that is located between India, Africa and the Indonesian Islands Southern Ocean – surrounds the Antarctic continent and is covered by ice part of the year Arctic Ocean – smallest and shallowest ocean that is located near the North Pole and is also covered by ice part of the year

How Deep is the Ocean?

seawater – water from a sea or ocean that has an average salinity of 35 ppt (parts per thousand), or one kg of ocean water contains about 35 g of salt   salinity – measure of the mass of dissolved solids in a mass of water

Oceans are divided into zones based on physical characteristics that include sunlight, temperature, salinity and density

Surface zone – area of shallow seawater that receives the most sunlight; organisms that perform photosynthesis are located here Middle zone – receives very little sunlight and of it only the blue-green wavelengths Deep zone – plants that photosynthesize are not found here because there is NO light; many organisms produce light using chemicals in a process called bioluminescence

Bioluminescence

Temperature – temperature changes from surface to about 1000 m depending if located in polar or tropical regions Salinity – top 500 m of water is saltier in warmer water than polar water since it evaporates faster leaving behind salt at surface Density – ocean water is layered since cold water is denser than warm water and salt water is denser than fresh water

Pollution Causes many negative things in the ocean. Although oil spills pollute the ocean, they only account for approximately 12% of the oil polluting the ocean. The rest reaches the oceans from land, through drainage. The ocean's oxygen content is depleted by the runoff of fertilizer that causes an increase of algae growth. It is estimated that every square mile of ocean has more than 45,000 pieces of plastic floating in it.