The surface of the Earth is 70 percent covered by oceans – hence Earth's nickname of "The Blue Planet." The Earth's oceans differ based on a variety of ocean characteristics. Variables such as surface temperature, salinity, presence of sea ice and phytoplankton density can all help characterize different marine climate zones. Temperate oceans and tropical oceans are both marine climate zones with a few similarities and some crucial differences.
Differences in Location
One of the biggest differences between temperate oceans and tropical oceans is their location. Tropical oceans are located between two lines of latitude: the Tropic of Cancer to the north and the Tropic of Capricorn to the south. These lines are located at 23.5 degrees north and 23.5 degrees south, respectively. Tropical oceans incorporate the equator and therefore receive direct sunlight for most of the year. Tropical oceans include the central portion of the Pacific and Atlantic Oceans, as well as the Caribbean Ocean and most of the Indian Ocean.
Temperate oceans are located between the Tropics of Cancer and Capricorn and the north and south polar regions of the globe. Temperate oceans, such as regions of the Atlantic and Pacific oceans, include both subtropical and subpolar locations. Temperate oceans are locations where the water is a mixture of cold polar ocean water and warm tropical water. These oceans are the locations of major ocean currents such as the Polar Jet Stream and the North American Gulf Stream.
Differences in Climate and Temperature
Because tropical oceans are near the equator, they receive direct sunlight more or less constantly throughout the year. This causes the average temperature of tropical oceans to be above 68 degrees Fahrenheit (20 degrees Celsius). Temperatures usually range between 68 degrees and 95 degrees Fahrenheit (35 degrees Celsius) in tropical marine climates. Rainfall in tropical marine climates averages between 39 and 59 inches (1,000 and 1,500 mm) per year.
Climate in temperate oceans – called an oceanic climate, marine climate or maritime climate – tends toward mild summers and cool (but not freezing) winters, with temperatures averaging between 32 degrees Fahrenheit (0 degrees Celsius) and 72 degrees Fahrenheit (22 degrees Celsius). The precipitation in temperate ocean climates is predominantly in the form of rain. Annual rainfall in oceanic climates varies by location.
Differences in Biodiversity
Tropical and temperate seas both boast a wide array of living things. Temperate marine communities such as estuaries and kelp forests are host to a variety of species of fish and invertebrates, and also provide food and homes to coastal birds. From whales and sharks to tuna and bluefish, many marine species that prefer slightly cooler waters make temperate ocean climates their home.
Warm tropical oceans are home to a very specialized type of ecosystem: coral reefs. Coral reefs are created by stony coral, tiny polyp-shaped animals that leave behind a calcium carbonate skeleton. Over time, these skeletons increase in size until they form an entire reef, which then provides habitat and food for marine life. Coral reefs form in shallow tropical seas, typically around islands or on continental shelves, ideally away from river deltas. Large, notable coral reefs can be found in the Caribbean ocean and the southwestern Pacific ocean. The Great Barrier Reef in northeast Australia covers thousands of square kilometers.
Threats to Oceans
Both temperate oceans and tropical oceans face a variety of modern threats. Human development along the coastlines in both temperate and tropical locations encroaches on coastal waters and therefore threatens the wildlife that lives there. Delicate coastal habitats, such coral reefs and estuaries, are home to a wide variety of living organisms. Many ocean creatures return to shallow coastal waters to spawn, and these protected marine habitats provide homes to these vulnerable organisms. Construction of homes and hotels, including the pollution produced from these activities, is very damaging to these habitats.
Global climate change may also be a threat to marine ecosystems, both temperate and tropical. Small changes in temperature or salinity can have devastating effects on coastal marine ecosystems. Coral bleaching, for example, is a detrimental response of coral reefs to rising ocean temperatures. Overfishing or otherwise bad fishing practices also have negative effects on marine ecosystems. Global pollution issues such as plastics and agricultural runoff in the oceans are also causing serious damage to marine ecosystems.
- Water Encyclopedia: Oceans, Tropical
- National Geographic: Tropics
- FOSS Weather: Climate Region Temperate Ocean
- NOAA Ocean Exploration: How Does the Ocean Affect Climate and Weather on Land?
- Climate.gov: Ocean – Oceanic Climate Variables
- NOAA: Coral Reef Ecosystems
- Australian Marine Conservation Society: Coral Bleaching
- National Geographic Kids: Ocean Habitat
About the Author
Emily Neal is a freelance science writer and nature photographer. She has a B.A. in Environmental Science from Mount Holyoke College and has worked for many years teaching science at the middle school level. For fun and inspiration she transcribes and edits novels, writes and plays music, and forages for wild mushrooms and mineral specimens.