[Susan Lozier] And it seems a little odd in a way because salt is really a molecule
in the ocean water, but collectively, that salinity plays a role in the ocean
circulation. [Narrator] It's these differences in salinity that
play a role in the processes that affect weather, climate, sea life, and the whole
ocean system itself. And not all oceans have the same salinity. In fact, the North
Atlantic Ocean tends to be the saltiest, much more than the Pacific. [Susan Lozier] The salt in
the ocean affects its density, just like the temperature affects its density, and
the density, meaning the amount mass per volume, is going to then impact where the
water goes as it circulates throughout the globe. [Jeff Halverson] Differences in temperature and
salt content of the water cause some areas of water to sink in some areas of
water to rise. And so we tend to see the sinking water at the poles, the water
rising back up at the equator, and if you connect the two together, what you have
is an overturning that is deep in the ocean. It's like a big conveyor belt that
operates in the ocean. [Narrator] This overturning moves warm water from the tropics toward
the poles, and cold water from the poles toward the tropics. In this way the
overturning regulates Earth's climate. [Susan Lozier] And the atmosphere and the ocean, both being
fluids of the Earth, really work together. We consider them sort of equal partners
in the redistribution of this heat on the planet. So when those warm waters are
returning, as they're moving up to the higher and higher latitudes then, they're
releasing that heat to the atmosphere. Then the winds blow over the ocean, they
pick up that heat and those winds over the Atlantic Ocean are moving from the
North American continent to the European continent. [Jeff Halverson] It takes perhaps a thousand
years for the water to cycle through the deep ocean. So we say the oceans have a
memory. They're like a tape recorder. Things that happen now will still be
manifest hundreds of years in the future as that cold water moves through this
giant circulation. [Susan Lozier] So if there's any change to that overturning circulation, that
means that Northern Europe and the British Isles would be robbed of that
heat due to those waters that are returning to the high latitudes.
[Narrator] The oceans are vast, covering 70 percent of our planet, and so it is no surprise that we
still know only a little about this system, and how it will respond to change,
and furthermore, create change. [Jeff Halverson] Climate change on earth is complicated by the
fact that the ocean moves much more slowly than the atmosphere. So you have
warming in the atmosphere, warming in the ocean, but they're occurring at different
speeds. So they're out of sync, and that makes predicting what's going to
happen in the next hundred or two years very, very difficult. [Susan Lozier] Now what we might expect
happens, in a very simplistic sense, is that as the ocean warms, there's going to
be more evaporation. And that more evaporation would would mean that oceans
become saltier. But really it's not just that simple because there's also
evaporation, precipitation, and the ice as well, and that's all wrapped up in the
study of the hydrologic cycle. [Narrator] People have been measuring salinity for
centuries, but ships and buoys alone cannot match the perspective from space.
In fact, a whole quarter of the oceans--larger than the size of Africa-- have no
salinity data at all. [Susan Lozier] Up until now when we've been trying to how
density changes impact ocean circulation, we've really just had half the picture.
[Narrator] When the Aquarius satellite is launched, scientists, for the first time, can look
at salinity of the surface of the ocean from 400 miles above the earth. [Susan Lozier] But now
with the Aquarius mission, we'll be able to complete the other half. We'll be able
to look at the salinity information. And so salinity, combined with temperature,
will give us the information about the density field. [Narrator] In the first two months of
Aquarius' launch, the satellite will gather more salinity data than in the
last 125 years. This mission will help scientists better understand how
salinity and ocean circulation are tied to global climate and how both systems
are changing throughout time.
[natural sound, waves, bubbles]