A poster of past, present and future sea-level altimetry missions.
This poster shows past, present and future sea-level altimetry missions. Credit: NASA (Learn more about sea level change missions here.)

NASA studies changes in sea-level primarily by using orbiting spacecraft. These satellites capture the changes with altimeters – instruments that rely on radar or laser pulses. These altimetry measurements can be combined with data from coastal tide gauges and from Argo floats, a global network of mobile ocean sensors that move up and down the water column, to provide a fuller picture of sea-level rise. To ensure the accuracy of such measurements, NASA helps maintain another global network of ground-based and orbital instruments that track the position and drift of geographic points – creating the International Terrestrial Reference Frame.

A photo of an Argo float in the foreground and a ship in the background
An Argo float, foreground. Credit: Argo program, Germany/Ifremer.

NASA also computes components of sea level using measurements by ship and plane, through campaigns like “Oceans Melting Greenland (OMG)” and Operation IceBridge. The idea is to measure a variety of contributors to sea-level rise, including melting land ice and other factors, to see how they all “add up” to observed sea-level rise.

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