Obviously salinity levels and
their variability is neither understood nor perhaps much studied for simple
lack of data. This satellite mission
ends that pretty completely and we will soon have several seasons of mapped
variability to work with. Soon enough we
will have decades of data as we are now gaining with a number of other
variables.
Like any nascent science there
are surprises in store.
Some assertions are made here
that may not hold up, so it is best to ignore them and see what a lot of new
data does for us. It looks like fun.
Aquarius to Study the Power of Sea Salt
June 7, 2011: A new observatory is about to leave Earth to map a
powerful compound of global importance: Common everyday sea salt.
An artist's concept of Aquarius/ SAC-D in orbit.
Researchers suspect that the salinity of Earth's oceans has
far-reaching effects on climate, much as the salt levels within our bodies
influence our own delicate internal balance. An international team of
scientists from NASA and the Space Agency of Argentina
"Based on decades of historical data gathered from ocean areas by ships and buoys, we know the salinity has changed over the last 40 years," says Aquarius principal investigator Gary Lagerloef. "This tells us there's something fundamental going on in the water cycle."
Salinity is increasing in some ocean regions, like the subtropical
Within a few months, Aquarius will collect as many sea surface salinity measurements as the entire 125-year historical record from ships and buoys.
"Salinity, along with temperature, governs the density of
seawater," says Lagerloef. "The saltier the water, the denser it is,
and density drives the currents that determine how the ocean moves heat around
the planet. For example, the Gulf Stream
carries heat to higher latitudes and moderates the climate. When these currents
are diverted by density variations, weather patterns such as rainfall and
temperature change."
Scientists have gathered an ensemble of measurements over the ocean--e.g., wind speed and direction, sea surface heights and temperatures, and rainfall. But these data do not provide a complete picture.
"We've been missing a key element – salinity," says Lagerloef. "A better understanding of ocean salinity will give us a clearer picture of how the sea is tied to the water cycle and help us improve the accuracy of models predicting future climate."
A pre-launch view of the Aquarius radiometer.
Aquarius is one of the most sensitive microwave radiometers ever
built, and the first NASA sensor to track ocean salinity from space.
"It can detect as little as 0.2 parts salt to 1,000 parts water -- about the same as a dash of salt in a gallon of water. A human couldn't taste such a low concentration of salt, yet Aquarius manages to detect it while orbiting 408 miles above the Earth."
The Aquarius radiometer gets some help from other instruments onboard the satellite. One of them helps sort out the distortions of the choppy sea. CONAE's Sandra Torrusio, principal investigator for the Argentine and other international instruments onboard, explains:
"One of our Argentine instruments is another microwave radiometer in a different frequency band that will measure sea surface winds, rainfall, sea ice, and any other 'noise' that could distort the Aquarius salinity measurement. We'll subtract all of that out and retrieve the target signal."
Torrusio is excited about the mission.
"I've met so many new people, not only from
Working together, these international "people of science" will tell us more about the ocean's role in our planet's balance – and in our own – no matter where we live.
For whatever we lose (like a you or a me),
It's always our self we find in the sea.
(e.e. cummings)"
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