Looking at Earth

Satellites View The Oceans and Seas


Seasat was the first satellite designed specifically to monitor the oceans with radar. Launched in 1978, the satellite operated for 98 days and acquired enough data to produce imagery of 100 million square kilometers of the Earth's surface. Seasat orbited the Earth at an altitude of 800 kilometers (about 500 miles), and supplied radar images of many ocean features, including sea ice, currents, eddies, and internal waves.
1:20 Scale model courtesy of Jet Propulsion Laboratory

Seasat also carried an instrument to measure the topography of the ocean surface. The lighter shades represent rises and the darker areas are depressions. The variations in the ocean surface are reflections of the trenches and ridges on the ocean floor.
Courtesy of Jet Propulsion Laboratory

Sea surface temperature image from data gathered by the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-12 satellite. The orange and red colors represent warmer temperatures while violet and blue colors are cooler. The warm waters of the Gulf Stream are clearly indicated in this 1997 image. Actual ocean surface temperatures can be calculated using the AVHRR data. Ocean temperature information aids fishermen by identifying currents and feeding grounds.
Courtesy of Ocean Remote Sensing Group, Johns Hopkins University, Applied Physics Laboratory

Surface irregularities caused by ridges and shoals off Nantucket Island show up distinctly on the Seasat image. The surface patterns closely match the underwater configuration.
NASA Image

Sediment deposits at the mouth of the Kuskokwim River in southwest Alaska are clearly delineated on the Seasat image. The bright areas are channels formed by the river flow.
NASA Photograph

Mosaic of Seasat radar strips around Grand Bahama Island. Vortices, perhaps caused by the flow of water along the island's west coast, are apparent to the south.
NASA Imagery

Warm water shows up in light tones and cold water in dark tones on this thermal image from the Heat Capacity Mapping Mission. The warm water along the bottom of the picture is the Gulf Stream. Note the two warm water eddies along the edge of the Stream.
NASA Image

Another view of the Gulf Stream from the Heat Capacity Mapping Mission. The warm Stream shown in white contrasts sharply with the cooler surrounding waters.
NASA Image

1996 Sea Ice Concentrations

Concentrations of sea ice around Antarctica have been monitored since 1987 by the Special Sensor Microwave/Imager of the Defense Meteorological Satellite Program. The images below show the progressive change in sea ice concentration from January to December of 1996. Red represents the highest concentrations of ice versus open water, and blue indicates the lowest. These seasonal changes in polar ice influence shipping operations, as well as, world climate.
Imagery courtesy of NASA Goddard Sea Ice Group

  • January

  • February

  • March

  • April

  • May

  • June

  • July

  • August

  • September

  • October

  • November

  • December

SeaWiFS image of the Black Sea. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is carried on board the SeaStar spacecraft. Launched in August 1997, SeaWiFS was designed to measure ocean color, providing data on concentrations of phytoplankton (tiny green plants living near the ocean surface), and to study the relation of oceans and global change.
Image provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and Orbimage

Space Shuttle astronauts photographed sand waves on the ocean floor around the Bahamas.
NASA Photograph

Sediment patterns are clearly evident in this Skylab view of Lake Michigan.
NASA Photograph

The Sun highlights wave structures in this Skylab scene of Madeira Island in the Atlantic Ocean off the coast of Africa.
NASA Photograph

Skylab 3 view of the mouth of the Colorado River emptying into the Gulf of California.
NASA Photograph

Internal (subsurface) waves were photographed by the Skylab 4 crew south of Kangaroo Island off the coast of Australia. Waves as long as 10 kilometers (about 6 miles) were observed.
NASA Photograph

Space Shuttle handheld view of the Acklins and Crooked Islands in the Bahamas.
NASA Photograph