Sentinel-6: “ Dog Kennel ” satellite to measure sea level rise

A satellite that will be essential to understanding climate change will be launched Saturday from California.

Sentinel-6 Michael Freilich will become the primary means of measuring the shape of the world’s oceans.

Its data will not only track sea level rise, but reveal how the great mass of water moves around the world.

Looking a bit like a dog kennel, the sophisticated 1.3-ton satellite is scheduled to take off from Vandenberg Base at 9:17 a.m. local time (5:17 p.m. GMT).

The Sentinel is a joint venture between Europe and the United States, and will continue measurements that have been performed by a succession of spacecraft, called the Jason-Topex / Poseidon series, dating back to 1992.

These previous missions have shown unequivocally that the sea level in the world is rising, at a rate of more than 3 mm per year over the period of 28 years. And their most recent data even suggests there is acceleration going on, with levels recorded as increasing to over 4mm per year.

About half of the measured global rise in sea level on Earth is due to warming waters and thermal expansion, one of the main drivers of which is global warming. The other half comes from melting ice.

About a third of the measured global rise in sea level on Earth is due to expanding water warming, one of the main drivers of which is climate change. The rest comes from melting ice.

Sentinel-6, like all satellites before it, will use a radar altimeter to assess the height of the oceans.

This instrument sends a microwave pulse to the surface, then counts the time it takes to receive the return signal, converting it to elevation.

However, Sentinel-6 will fly with significantly improved capability, allowing it to see more clearly what the seas are doing against the coast; and also how the characteristics of inland waters – rivers and lakes – behave.

Elevation is a key parameter for oceanographers. Just as the air pressure at the surface reveals what the atmosphere above is doing, the height of the ocean will betray details of the behavior of the water below.

The data give clues to temperature and salinity. When combined with gravity information, it will also indicate the direction and speed of the current.

The oceans store large amounts of heat from the sun; and how they move that energy around the world and interact with the atmosphere is what drives our climate system.

But it is essential to have the longest possible history of change.

“The longer this time series, the better able we are to separate the natural climate signals from the forced signals, from the human signal,” explained European Space Agency mission scientist Craig Donlon.

“This means we can run climate models backwards and then, through a validation process, be sure that when we run them forward, we have predictive skills.”

The oceans are not increasing at the same rate everywhere. There are parts of the world where the elevation exceeds 1 cm per year.

This is due to a multitude of factors, including changes in ocean circulation, changes in heat content, and the uneven dispersion of meltwater from the ice caps.

It is a little-known fact that the discharge of powerful glaciers, such as the Thwaites Glacier in Antarctica, has the greatest effect on ocean height at long distances.

“Sea level rise is not uniform; it’s really important to recognize that,” Christine Gommenginger, from the UK’s National Oceanographic Center in Southampton, told BBC News.

“These are the regional sea level budgets that we are targeting now. The rise in sea levels around the world – very well, we know that. But it’s the local image we want, and the altimetry can give it to us.

Oceanographers and climatologists, of course. But data is also of utmost importance to forecasters.

The return signal contains information about the state of the ocean – about its degree of roughness, which is also a testament to the strength of the winds.

The ocean and its connection to the atmosphere are perhaps best illustrated in hurricanes. These storms get their energy from warm tropical waters that an altimeter can detect by the way the sea surface swells.

And it’s satellites like Sentinel-6 that announce an El Niño event, which sees the warm waters of the western Pacific move east. This triggers a global disruption of weather systems, redistributing precipitation and raising temperatures.

“Other users understand ship routers – they don’t want their ships to go through storms; they want to avoid the big waves, ”said Remko Scharroo of the intergovernmental weather agency Eumetsat. “With the Sentinel-6 altimeter, we will also see eddies in the ocean, and if you are a ship router, this information will tell you how to go with the current, not against it.”

It goes without saying that coastal and flood defense planning depends on altitude data. No new nuclear power plant can be built without understanding where high tides and storm surges could reach decades into the future.

The nickname “Sentinel” is the name given to all the satellites of the Copernicus Earth observation program of the European Union, of which this mission is a part.

Its number shows that it is the sixth in the series of different types of sensors planned for the network.

The name Michael Freilich commemorates the former director of the earth sciences division of the US space agency Nasa, who died earlier this year. He was a trained oceanographer and was instrumental in establishing the international partnership behind the mission.

Mike Freilich exemplified the commitment to excellence, generosity of spirit and unmatched ability to inspire confidence that has driven so many around the world to want to work with NASA, to advance great goals. on behalf of the planet and its inhabitants, “commented Thomas Zurbuchen, who heads the scientific directorate of NASA.

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