SWOT’s solar panels were opened as part of a test in January at the Thales Alenia Space facility in Cannes, France, where the satellite is being assembled. The SWOT will measure the elevation of the oceans and water above the Earth’s surface, providing researchers with an unprecedented level of detail. Credits: CNES / Thales Alenia Space
The Ocean Topography and Surface Water mission will explore how the oceans absorb atmospheric heat and carbon, regulate global temperature and climate change.
Although climate change is causing sea levels to rise over time, the researchers also believe that differences in surface elevation between places in the ocean may affect Earth’s climate. These highs and lows are associated with currents and eddies, the swirling rivers in the ocean, which affect how it absorbs heat and carbon in the atmosphere.
Enter the topography of surface water and ocean (SWOT) mission, a joint effort of NASA and the French space agency, Center National d’Études Spatiales (CNES), with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. Launching in November 2022, SWOT will collect ocean elevation data to study currents and eddies up to five times smaller than previously detectable. It will also collect detailed information about freshwater lakes and rivers.
The SWOT mission will collect information on sea level elevation, helping scientists study the role of currents in regulating climate change, as well as the elevation of freshwater bodies. The mission is jointly led by NASA and CNES, with contributions from UKSA and CSA. Vendor: NASA / JPL-Caltech / CNES / Thales Alenia Space
Observing the ocean on a relatively small scale will help scientists assess its role in regulating climate change. As the planet’s largest store of atmospheric heat and carbon, the ocean has absorbed more than 90% of the heat generated by anthropogenic greenhouse gas emissions.
Much of the continued absorption of that heat — and the excess carbon dioxide and methane that produces it — is thought to occur around currents and vortices less than 60 miles (100 km) in length. These flows are small compared with flows like the Gulf Stream and the California Current, but the researchers estimate that overall they transfer up to half the heat and carbon from surface waters to the ocean depths.
A better understanding of this phenomenon could be key to determining if there is a ceiling on the ocean’s ability to absorb heat and carbon from human activities.
“Where is the turning point at which the oceans begin to release massive amounts of heat back into the atmosphere and accelerate global warming, rather than limit it?” Nadya Vinogradova Shiffer, SWOT program scientist at NASA Headquarters in Washington. “SWOT can help answer one of the most important climate questions of our time.”
Small thoughts
Existing satellites cannot detect flows and eddies on smaller scales, limiting the study of how those features interact with each other and with larger-scale flows.
“That’s where we’re going to learn a lot from better observing small scales,” said J. Thomas Farrar, head of the SWOT oceanographic science group at the Woods Hole Oceanographic Institution in Falmouth, Massachusetts. .
In addition to helping researchers study the climate impacts of small streams, SWOT’s ability to “see” smaller areas of the Earth’s surface will allow it to collect more precise data along the coastlines, where sea level rise and the flow of currents can have immediate impacts on inland ecosystems and human activity.
For example, higher seas can cause storm surges to penetrate further inland. In addition, enhanced flows due to sea level rise could increase saline intrusion into deltas, estuaries and wetlands, as well as groundwater supplies.
“In the open ocean, all the heat and carbon reductions will affect humanity in the long run,” said Lee-Lueng Fu, a SWOT project scientist at NASA’s Jet Propulsion Laboratory in Southern California. many years to come. “But in coastal waters, the effects of currents and sea elevation are felt over days and weeks. They directly affect human life”.
So how will measuring ocean heights help you have a better knowledge of currents and eddies?
The researchers use elevation differences between points – called slopes – to calculate the motion of currents. The math shows Earth’s gravity, which pulls water from high to low, and the planet’s rotation, in the Northern Hemisphere, which bends the flow clockwise around the high points and counterclockwise. clockwise around the low points. In the south, the effect is opposite.
A system of currents hundreds of miles wide that flows around large areas of the ocean. Along the way, currents and smaller eddies cycle and interact with each other. When they come together, they channel water from the surface to colder depths, carrying heat and carbon from the atmosphere. When those smaller currents and eddies separate, water from those colder depths rises to the surface, ready to reabsorb heat and carbon.
This vertical movement of heat and carbon also occurs at the eddies themselves. In the Northern Hemisphere, clockwise vortex produces downflow, while counterclockwise vortex produces upward current. The opposite happens in the Southern Hemisphere.
Fill in the Gaps
By measuring ocean heights down to 0.16 inches (0.4 cm) increments, as well as their slopes, the two antennas of the SWOT Ka-Band Radar Interferometer (KaRIn) will help Researchers distinguish currents and eddies as small as 12 miles (20 km).
The SWOT will also use the nadir altimeter, an older technology that can identify currents and eddies about 60 miles (100 km) wide. Where the nadir altimeter will point straight down and take data in one direction, the KaRIn antennas will tilt. This will allow the KaRIn antennas to scan the surface in two dimensions and work in tandem, collecting data with greater accuracy than nadir altimeter alone.
“Currently, to get a two-way view from a one-way street, we take all of our one-way lines and estimate what’s going on between them,” said Rosemary Morrow, head of the SWOT oceanographic science team. at the Laboratoire d’Études en Géophysique et Océanographie Spatiales in Toulouse, France. “SWOT will observe directly what is in the void.”
More information about the mission
SWOT is being jointly developed by NASA and CNES, with contributions from the CSA and the UK Space Agency. JPL, managed by Caltech for NASA in Pasadena, California, leads the composition of the project in the United States. For the payload of the flight system, NASA is providing the KaRIn instrument, a GPS science receiver, a laser reflector, a dual-beam microwave radiometer, and operations on the NASA instrument. CNES is providing the satellite-integrated orbital Doppler and radiation navigation system (DORIS), the nadir altimeter, the KaRIn RF subsystem (with support from the UK Space Agency), platform and ground control segment. CSA is providing a KaRIn high power transmitter assembly. NASA is providing launch vehicle and related launch services.
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