The ocean and Earth’s systems and cycles

The ocean plays an important part in several Earth systems and cycles. This is hardly surprising, as it covers two-thirds of the planet’s surface. It is difficult to study any of these systems and cycles separately, as they often overlap, but the ocean links them all. Here are some ways the ocean is involved in major Earth systems and cycles.

Hydrosphere

This system is made up of all the water on Earth, including water that is liquid, solid (ice and snow) or vapour (in the atmosphere¹). The ocean contains most of the water on the planet² – far more than the freshwater in ice, lakes, rivers, groundwater³ and clouds.

Atmosphere

The atmosphere is the layer of gas around the planet that supports life and climate⁴. There is a lot of movement between the ocean and atmosphere. Water is exchanged as part of the water cycle⁵, and carbon dioxide⁶ is exchanged as part of the carbon cycle⁷. In some places, the ocean gives up its heat⁸ to the atmosphere – in others, it takes up heat. This exchange helps form ocean currents that move energy around the planet and so control Earth’s climate.

Biosphere

The biosphere⁹ includes all living things and their environments. The sunlit upper part of the ocean supports vast food webs, from microscopic plants and animals in plankton¹⁰ to huge marine predators. Life also thrives in the dark ocean depths. The ocean supports this life because of the nutrients¹¹ and warmth that it contains and circulates.

Geosphere

There is a lot of exchange of material between the ocean and the geosphere¹² – the land and rock of the Earth. The ocean takes material from the edge of the land through erosion¹³, and rivers add material from inland. Vast amounts of sediments¹⁴ settle to the bottom of the ocean, and these eventually get turned into sedimentary¹⁵ rocks (see the rock cycle below).

Water cycle

Liquid water enters the ocean through rain, rivers and melting ice. Water vapour¹⁶ evaporates from the ocean into the atmosphere to form clouds. Every year, 300,000 cubic kilometres of water evaporates into the atmosphere. Much falls back into the ocean, but a third of it condenses and falls onto land as rain and snow.

Dynamic and complex: the global water cycle

Water in the Earth system is influencing all aspects of life on Earth. Pathways, storage, transfers and transformations have an effect on the global climate and human welfare. Within this interactive 4 scientists talk about some of the complex aspects of the water cycle.

To use this interactive, move your mouse or finger over any of the labelled boxes and click to obtain more information.

Read The water cycle article to find out more.

Carbon cycle

The ocean is one of the main stores of carbon¹⁷ on Earth. Most of the carbon is obtained from the atmosphere as carbon dioxide¹⁸. Chemical and biological processes in the upper ocean combine the carbon with other chemicals¹⁹, and much of the resulting material (mostly calcium carbonate) ends up sinking into the ocean deeps. Here, the carbon cycle²⁰ overlaps the rock cycle, as the carbonate sediments eventually get turned into sedimentary rocks.

Rights: The University of Waikato Te Whare Wānanga o Waikato

Ocean and Earth cycles

Water and carbon dioxide are exchanged between the ocean and the atmosphere. Material eroded from land sinks to the bottom of the ocean where it eventually forms new rocks.

Read The ocean and the carbon cycle article and then explore our Carbon cycle interactive diagram to learn more.

Rock cycle

The ocean continually batters the edge of the land, eroding it, breaking down the rock and transporting it out to sea. Chemical and biological processes in the ocean also ensure that there is a build-up of sediment²¹ at the bottom of the ocean. Over millions of years, these sediments are physically and chemically changed into sedimentary rock. Movements of the Earth’s crust²² eventually raise these rocks to form land, which is gradually eroded back into the ocean, and the cycle continues.