- Fisheries: Marine fisheries have traditionally been located near the coast, both because this requires simpler technology and because coastal waters are much more productive than the open ocean. However, many of the most commonly caught species - such as tuna, swordfish, herring, sardine, and anchovy - are also caught in the open ocean, often on the high seas. In addition, as overfishing has depleted epipelagic and coastal fisheries, fishers are targeting new species in deeper waters: as many as 40% of the world’s fishing grounds are now in waters deeper than 200m.
- Shipping routes: The oceans provide convenient transport routes - which we take full advantage of. Around 90% of all trade between countries is carried by ships. These transport everything from food and fuel to construction materials, chemicals, and household items.
- Oxygen: It’s not just ocean life that depends on phytoplankton. These tiny marine plants are estimated to produce over half the oxygen that we, and all other land animals, breathe.
- CO2 sink: Ocean waters have the capacity to absorb vast amounts of the greenhouse-warming gas carbon dioxide (CO2), and thus have helped to buffer human-caused global warming and climate change. Indeed, nearly half the CO2 produced by human activities in the last 200 years has dissolved into the ocean. Phytoplankton also lock CO2 away. Like land plants, these microscopic algae use CO2 to grow. When they die, this CO2 sinks as organic matter to the bottom of the ocean, keeping it out of the atmosphere.
- Temperature and weather control: The surface layer of the ocean absorbs over half the heat reaching the Earth from the sun. By distributing this heat around the world, ocean currents - which flow for thousands of kilometres, both at the surface and far below - are extremely important in determining the climate of the world’s continents.
For example, the Gulf Stream carries warm water from the Gulf of Mexico all the way to western Europe. This water warms the air above, which is then blown across to the land. As a result, northwest Europe is much warmer than other lands at the same latitude.
Hurricanes and cyclones can be destructive when they hit land, but these tropical storms also help distribute heat from the tropics to higher latitudes through the atmosphere.
- Water cycle: The oceans are also an integral part of the water cycle. Vast amounts of water evaporate from the ocean surface, rising into the atmosphere as water vapour. When this vapor collides with colder air, it condenses to form clouds and rain.