Oceans

۱٬۷۶۵ طرفدار

۱۷ انتشار • فعال از ۲۰۱۹

The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as oceans (in descending order by area: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Antarctic/Southern Ocean, and the Arctic Ocean), and are themselves mostly divided into seas, gulfs, and subsequent bodies of water. The ocean contains 97% of Earth's water and is the primary component of Earth's hydrosphere, acting as a huge reservoir of heat for Earth's energy budget, as well as for its carbon cycle and water cycle, forming the basis for climate and weather patterns worldwide. The ocean is essential to life on Earth, harboring most of Earth's animals and protist life. It originated photosynthesis and therefore Earth's atmospheric oxygen, and still supplies half of it. Ocean scientists split the ocean into vertical and horizontal zones based on physical and biological conditions. Horizontally, the ocean covers the oceanic crust, which it shapes. Where the ocean meets dry land, it covers relatively shallow continental shelves, which are part of Earth's continental crust. Human activity is mostly coastal, with high negative impacts on marine life. Vertically, the pelagic zone is the open ocean's water column from the surface to the ocean floor. The water column is further divided into zones based on depth and the amount of daytime sunlight present. The photic zone starts at the surface and is defined as "the depth at which light intensity is only 1% of the surface value" (approximately 200 m in the open ocean). This is the zone where photosynthesis can occur. In this process, plants and microscopic algae (free-floating phytoplankton) use light, water, carbon dioxide, and nutrients to produce organic matter. As a result, the photic zone is the most biodiverse and the source of the food supply that sustains most of the ocean ecosystem.