How Satellites See the Sea: Temperature, Color, Sea Level and More

The ocean covers more than 70 percent of the planet, far too much to measure from ships alone. Satellites fill the gap. By sensing remotely from orbit, they gather far more information than could ever be collected from the surface — about the ocean's temperature, color, height, shape and weather, and about the animals and people moving across it.

The Geostationary Operational Environmental Satellite-16 (GOES-16), the first of NOAA's next generation of geostationary weather satellites, which also collects ocean and climate data. Credit: NOAA.

Temperature

The temperature of the sea surface says a lot: changes influence how fish behave, can bleach corals and affect coastal weather. Satellite images of SST also reveal circulation patterns — upwelling, where cold water rises from the depths near coasts, and warm currents like the Gulf Stream. The instrument most used is the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA/NASA Suomi NPP satellite, which collects new data every day so scientists can map changes over time.

Color

Ocean color shows the impact of coastal floods, reveals river plumes and pinpoints harmful algal blooms that can contaminate shellfish and kill fish and marine mammals. It shows not only where a bloom is forming, but where it may drift — and water treatment plants use NOAA's bloom forecasts to decide when to change how they treat water.

Sea level

A map of total sea level change since 1993. Credit: NOAA.

Sea level rise is one of the most significant potential impacts of climate change: it can flood coasts and islands, erode shorelines and destroy wetlands and mangroves. Radar altimeters on satellites, combined with precisely known orbits, measure sea level around the globe with unprecedented accuracy, and long-term changes in global mean sea level offer a way to test climate models' predictions of warming.

The seafloor, seen through the surface

Ships have charted only a small fraction of the seafloor. But because of gravity, the ocean's surface bulges and dips in broad patterns that mirror the topography of the floor below — bumps too small to see, but measurable by a very accurate radar altimeter on a satellite. Satellite imagery can also map features such as coral reefs.

Weather

Hurricane Ivan on September 15, 2004, before it struck the U.S. Gulf Coast. Credit: NOAA.

Weather is the best-known use of satellites, and the ocean plays a major role in weather and climate. NOAA's system uses two types: geostationary satellites (GOES) for short-range forecasts, warnings and observations, and polar-orbiting satellites for longer-term forecasting. A complete global weather-monitoring system needs both.

Tracking animals — and people

Sea turtles and manatees can be fitted with transmitters that report their positions to orbiting satellites. Satellites also relay data from ground transmitters measuring tides and the migrations of whales, and positions from emergency beacons, helping to save people in distress on boats, on airplanes or in remote areas. The same kind of technology is used in search and rescue.

A simulation of sea-surface temperatures from the Geophysical Fluid Dynamics Laboratory.

Sources

Based on "How are satellites used to observe the ocean?" from NOAA's National Ocean Service, a work of the United States government in the public domain. Pictures an earlier version of this page left out were restored on 2026-09-26.