The Ocean is the world’s largest reservoir of water, covering 70% of Earth’s surface. It is the primary component of our planet’s hydrosphere and influences climate and weather patterns as a huge heat sink. Its biological processes create at least half of the oxygen people breathe.
It also regulates rainfall and droughts, holds 97% of our planet’s water, absorbs carbon dioxide from the atmosphere, and provides homes and food to countless fish, plants and animals. Scientists estimate that more than 90% of all life on Earth is connected to the Ocean.
The health of the Ocean is critical for us to thrive. Every animal, plant and insect depends on it for protein – and that is only one part of its role. The Ocean also regulates temperature and the flow of moisture through the Earth’s water cycle. And, as a global store of carbon, it has the potential to slow climate change and protect the Earth’s biodiversity.
The ocean is a dynamic system that constantly changes. Its waters are warmed by the sun and move through ocean currents that transport energy around the globe. The evaporation of this warm water forms clouds and increases the air’s humidity, which then causes rain. This water is used by plants, animals and people and makes its way back to the Ocean through a complex cycle of chemical exchanges.
Oceanographers divide the ocean into zones based on their physical characteristics. The photic zone is the area of the open ocean where photosynthesis can occur, where microscopic algae (free floating phytoplankton) use light, water and carbon dioxide to produce organic matter. This is the foundation of all food chains.
Below the surface, differences in ocean temperature and salinity create distinct layers. The layer closest to the equator is called the thermocline and is warmer than deeper waters. The layer at polar latitudes is colder and denser, so it sinks to lower levels.
These layers are influenced by wind, the Coriolis effect and temperature and salinity differences, as well as by the global thermohaline circulation – a huge system of water and heat movement that drives the Atlantic meridional overturning circulation.
The Ocean provides jobs for millions of fishermen, lifeguards, harbours and marine-based tour operators, water sports businesses and holiday accommodations. And, with studies showing a link between time spent in nature and reduced stress levels, it is a source of recreation for billions of people around the world. But the Ocean faces many challenges — from climate change and pollution to overfishing, habitat destruction and unsustainable seafood practices. We must all work together to ensure a healthy future for our Ocean.