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Oceans

Satellites keep a watchful eye on the world’s oceans

Whether it is following rising sea levels, mapping ocean surface winds and currents, monitoring water quality, or helping track sea turtles or sharks, satellites have made a huge difference to our ability to monitor the world’s oceans.

And because the ocean, land and atmosphere are inextricably linked, what happens in the oceans makes a big difference for life on Earth.

Absorbing and moving heat

More than 70% of the Earth’s surface is covered by oceans and they play a crucial role in determining our weather and climate because of their ability to absorb, store and transport heat from the sun.

The oceans store vast amounts of energy in the form of heat and help to keep the Earth’s temperature in relative balance by dampening the much higher temperature changes that would otherwise occur each day, season and year. Over 90% of the excess heat energy stored by the Earth over the last 50 years is estimated to be stored in the oceans.

An ocean scene
The ocean receives most of its heat along the equator where incoming solar radiation is about double that received at the poles.

Exchanges of heat, water and momentum (wind) at the sea surface are important factors for driving the circulation of the oceans. Ocean currents can be driven by tides, wind, bottom topography, the Earth’s rotation, and differences in seawater temperature and salinity, the so-called thermohaline circulation.

Greenhouse gases

Warming oceans

The IPCC stated that the upper ocean (0−700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971. The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.

The ocean and the atmosphere are also linked by the fact that the ocean is a source and sink for greenhouse gases.

Most of the heat that escapes from the ocean is in the form of evaporated water – the most significant greenhouse gas of all. But water vapour also contributes to the formation of clouds, which shade the surface and have a net cooling effect.

The oceans also absorb carbon dioxide and can hold 50 times more carbon than the atmosphere. They are thought to be currently slowing the rate of climate change by absorbing 30% of human emissions of carbon dioxide from fossil fuel burning, cement production, deforestation and other land use change.


Carbon dioxide at the ocean surface (red curves) and the decrease in pH (purple) as the ocean becomes more acidic. Source: IPCC

Water cycle

The oceans play a key role in the Earth’s water cycle, as most of the water that evaporates into the atmosphere originally comes from the ocean. This water in turn condenses to form clouds which can then fall to earth as precipitation (rain or snow). Water then returns to oceans via rivers or to the atmosphere via evaporation from the land/lakes etc or from plants. Click here to learn more.

Monitoring the oceans from space

Scientists monitor the world’s oceans using a combination of satellites and in-water recording devices such as buoys, tide gauges and more than 3000 Argo profiling floats. Find out more

Data from in-water samplers provide the detail on conditions in specific locations, but for the big picture of what is happening in the world’s oceans, scientists need satellites.

As examples, the Jason-2 satellite monitors sea level rise, wave height and winds, while EUMETSAT’s Meteosat satellites constantly monitor the exchange of heat at the sea’s surface and the surface temperature. Find out more

The polar orbiting Metop satellites monitor global sea surface temperature and ocean surface winds. They also carry ARGOS receivers, provided by the French Space Agency (CNES), that collect data from in-water recording devices such as buoys, Argo profiling floats, and even animals that have been tagged with satellite transmitters.

 

Satellite image of the Gulf Stream

One of the best studied currents in the Atlantic is the Gulf Stream, a warm ocean current which flows at an average speed of 6.4 km/h (four miles an hour) from the Gulf of Mexico parallel with the American coast towards Newfoundland, and then continues across the Atlantic Ocean towards northwest Europe as the North Atlantic Drift.
Click for more about ocean currents.

Ocean monitoring and forecasting data

To get the latest info about the oceans visit MyOcean which provides open access to real-time information about the state of the oceans – temperature, currents, salinity, sea level, sea ice, sea winds, etc. via a web portal.

Key Facts

  • More than 70% of the Earth’s surface is covered by oceans.
  • The oceans store vast amounts of the sun's energy as heat and help to keep the Earth’s temperature in balance.
  • Exchanges of heat, water and wind at the sea surface drive the circulation of the oceans.
  • The oceans can absorb and hold up to 50 times more carbon dioxide than the atmosphere.
  • The oceans also play a key role in the Earth’s water cycle.
  • Scientists can monitor sea-level rise, surface temperature, wave height and ocean winds via satellite

Further Reading

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