The international Surface Water and Ocean Topography (SWOT) mission—led by NASA and the Centre National d’Études Spatiales (CNES)—has sent back some of its first glimpses of water on the planet’s surface, showing ocean currents like the Gulf Stream in unprecedented detail.
This image (right), produced with data acquired by SWOT on January 21, 2023, shows sea level in a part of the Gulf Stream off the coast of North Carolina and Virginia. The two antennas of SWOT’s Ka-band Radar Interferometer (KaRIn) instrument acquired data that was mapped as a pair of wide, colored strips spanning a total of 75 miles (120 kilometers) across. Red and orange areas in the images represent sea levels that are higher than the global average, while the shades of blue represent sea levels that are lower than average.
For comparison, the new data is shown alongside sea surface height data (left) taken by space-based instruments called altimeters. The instruments—widely used to measure sea level—also bounce radar signals off of Earth’s surface to collect their measurements. But traditional altimeters are able to look only at a narrow beam of Earth directly beneath them, unlike KaRIn’s two wide-swath strips that observe sea level as a two-dimensional map.
The spatial resolution of SWOT ocean measurements is 10 times greater than the composite of sea surface height data gathered over the same area by seven other satellites: Sentinel-6 Michael Freilich, Jason-3, Sentinel-3A and 3B, Cryosat-2, Altika, and Hai Yang 2B. The composite image was created using information from the Copernicus Marine Service of ESA (European Space Agency) and shows the same day as the SWOT data.
SWOT is also capturing views of freshwater features such as lakes, rivers, and other water bodies down to about 300 feet (100 meters) wide (not pictured). Such data will be used to produce an extraordinary accounting of the freshwater on Earth’s surface in ways useful to researchers, policymakers, and water resource managers.
Launched on December 16, 2022, from Vandenberg Space Force Base in central California, SWOT is now in a period of commissioning, calibration, and validation. Engineers are checking out the performance of the satellite’s systems and science instruments before the planned start of science operations in summer 2023.
The satellite will measure the elevation of nearly all the water on Earth’s surface and provide one of the most comprehensive surveys yet of our planet’s surface water. SWOT’s measurements of freshwater bodies and the ocean will provide insights into how the ocean influences climate change and the water cycle; how a warming world affects water storage in lakes, rivers, and reservoirs; and how communities can better manage their water resources and prepare for floods and other disasters.
“SWOT’s advanced imagery will empower researchers and advance the way we manage fresh water and the effects of sea level rise across the globe,” said NASA Administrator Bill Nelson. “Water is one of our planet’s most important resources—and it’s proven to be vulnerable to the impacts of climate change. SWOT will provide critical information that communities can use to prepare for the impacts of a warming climate.”
NASA Earth Observatory images by Lauren Dauphin, using SWOT data provided by Shailen Desai/JPL and sea surface height data courtesy of the Copernicus Marine Service. Bathymetry data is from the General Bathymetric Chart of the Oceans (GEBCO). Story by Jane Lee/JPL, originally published by NASA’s Jet Propulsion Laboratory on March 24, 2023, and adapted for Earth Observatory by Kathryn Hansen.
