So then why are oceans so important? Oceans are the lifeblood of planet Earth and humankind. They flow over nearly three-quarters of our planet, and hold 97% of the planet's water. They produce more than half of the oxygen in the atmosphere, and absorb the most carbon from it. The air that you breathe, the water you drink, the food you eat, the products that keep you warm, safe, informed, and entertained all can come from or be transported by the ocean. About half of the world’s population lives within the coastal zone, and ocean-based businesses contribute more than $500 billion to the world’s economy. Historically, we thought that we could never take too much out of, or put too much waste into, the oceans. The sheer number of people who use and depend on the ocean, and the sometimes unwise practices we adopt, have created problems such as over harvest of resources, reduction in biodiversity, and degradation of marine habitats and species, among others. We risk the very ecosystems on which our survival depends.
Ocean Currents:The world’s ocean is crucial to heating the planet. While land areas and the atmosphere absorb some sunlight, the majority of the sun’s radiation is absorbed by the ocean. Particularly in the tropical waters around the equator, the ocean acts a as massive, heat-retaining solar panel. Earth’s atmosphere also plays a part in this process, helping to retain heat that would otherwise quickly radiate into space after sunset. The ocean doesn't just store solar radiation; it also helps to distribute heat around the globe. When water molecules are heated, they exchange freely with the air in a process called evaporation. Ocean water is constantly evaporating, increasing the temperature and humidity of the surrounding air to form rain and storms that are then carried by trade winds, often vast distances. In fact, almost all rain that falls on land starts off in the ocean. The tropics are particularly rainy because heat absorption, and thus ocean evaporation, is highest in this area. Outside of Earth’s equatorial areas, weather patterns are driven largely by ocean currents. Currents are movements of ocean water in a continuous flow, created largely by surface winds but also partly by temperature and salinity gradients, Earth’s rotation, and tides (the gravitational effects of the sun and moon). Major current systems typically flow clockwise in the northern hemisphere and counterclockwise in the southern hemisphere, in circular patterns that often trace the coastlines. Ocean currents act much like a conveyor belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics. Thus, currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. Without currents, regional temperatures would be more extreme—super hot at the equator and frigid toward the poles and much less of Earth’s land would be habitable.