Human life has a close relationship with the Oceans. Oceans cover 70% of the earth, they are responsible for 97% the water supply and an almost endless resource for food. An understanding of how ocean life affects people, even if they spend a lifetime never seeing an ocean, is essential to fighting climate change.
How Oceans Work
There are five oceans; the Atlantic, Pacific, Indian, Southern and Arctic. The movement of ocean water from one of these regions to another is called a current. There are two main categories of currents, surface currents and ocean currents that make up the global conveyor belt. Ocean currents are dictated by temperature changes, winds and gravitational pull from other planets.
Surface currents are anything that take place between the surface and 100 meters down. These are the currents that effect people swimming and fishing from shore. The waves that crash on a beach are created by wind and travel long distances before breaking on the shore. Waves do not break until something disrupts them and a wave can travel hundreds of miles before reaching its final destination.
Currents below 100 meters are called Deep Water Currents. They are part of what is known as the global conveyor belt. The Global conveyor belt is the system of currents that moves water from one ocean to another. The water that starts out in the Arctic travels all around the globe before reaching the arctic again. Scientists believe that it takes 1000 years for a complete circuit. This circuit is essential for the health and well being of the planet. When cold, dense water trades places with warmer surface waters, an important exchange of nutrients, carbon dioxide and oxegyen takes place. The surface waters bring oxegen rich water down to the depths of the ocean while the deeper water from the bottom adds carbon dioxide and nutrients to the surface waters.
The global conveyor belt is powered by a force known as thermohaline circulation. Thermohaline circulation incorporates the temperature of the water and the salinity of the water. Water that is warm and has a low salinity will move differently than water that is cold with a high salinity. Water changing places based on temperature may not appear to be a very powerful force, but in actuality the global conveyor belt will move around the earth’s oceans with a force of 16 times all of the planet’s rivers combined.
Ocean Life
Life in the oceans began approximately three billion years ago. Modern human life didn’t appear until about 50,000 years ago, making the oceans 60 million older than people. Like on land, life in the oceans falls into two distinct categories: plant life and animal life. Scientists have documented one million different plants and animals in the oceans, but suspect that there may be up to eight million undiscovered life forms.
The oceans have three distinct layers. The first is the Euphotic zone, which starts at the surface and descends 200 meters down. This layer has the most sunshine and oxygen. In this layer is where most fish, whales and ocean dwelling mammals live. Coral reefs are here – one of the ocean’s most valuable resources. Changes in salinity, acidity and chemical levels will negatively impact coral reefs. These changes are often indicative of a larger problem and scientists often look at the health of coral reefs when determining water quality and the affects of climate change. The Euphotic zone is also home to the largest animal on the planet, the blue whale and some of the smallest, phytoplankton. And, although they are tiny, phytoplankton are some of the most important organisms on earth, producing half of all the oxygen on the planet.
The next layer is the Bathyal zone, ranging from 200 meters to 1500 meters. This area is dark and only a small amount of animal life lives here. The life that is found here lives off of dead material that floats down from the Euphotic layer. Small fish and zooplankton live here.
The final layer is the Abyssal zone, ranging from 1500 meters to the ocean floor. Scientists are largely unsure of what lives here as it is impossible for humans to descend this far underwater.
Oceans and Climate Change
While it might seem as though oceans are completely separate from life on land, in actuality the two are closely linked. The delicate ecosystems in the ocean are easily disrupted by pollution and other by-products of human activity. The oceans have taken in 118 million tons of carbon from 1800 to 1994, leading to an increase in acidity. This increase has dramatically affected delicate coral reefs, killing them on large scale. Phytoplanktons that take CO2 out of the air and replace it with oxygen have been dying off, leaving more carbon dioxide (a greenhouse gas) in the atmosphere. The global conveyor belt of ocean currents that distributes warm and cool water is at risk. As the polar icecaps melt, there is less cool, dense water shifting to the bottom of the ocean. The less of this water that shifts to the bottom, the less warmer, oxygen rich water is pushed to the surface. The movement of warmer waters around the globe affects the regional and planetary climates in everything from temperature to cloud formation. If this system were to slow down significantly the effects on localized agriculture and fishing could be devastating.
Oceans are an essential part of the maintenance of terrestrial life on earth. Oceans provide food, determine climates and provide a home to almost nine million creatures. The currents that drive their waters around the globe are crucial for the existence of life both in and out of the water. Without monitoring and protection the planet's climate could be devastatingly disrupted.
1. Rouse, Wesley; "Plankton", suite101.com, February 26, 2007
2. Dybas, Cheryl; "Impact of Earth's Rising Atmospheric Carbon Dioxide Found in World's Oceans", earthobservatory.nasa.gov, July 15, 2004
3. Jacquot, Jeremy; "Our Dying Oceans", scienceprogress.org, June 12, 2008
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