Composite Aquarius data from Aug. 25 to Sept. 11, 2011. Warmer colors are higher salinity, image with data scale available at NASA
The world's oceans are some of the most dynamic and important systems on Earth, and in a major way they're powered by salt. Along with temperature, regional changes in salinity help drive the many currents that keep the oceans thriving. Thanks to new research from NASA, we're starting to get a picture of how exactly that works, and thus how climate change might affect our seas.
We know that climate change is causing the world's glaciers to melt, but why is it something to worry about? Glacial melt is releasing tons of freshwater into the world's oceans, which over time will begin to alter how salty oceans are. That spells trouble for the seas: For one, our rapidly-disappearing reefs are highly sensitive to salinity changes, while climate change as a whole is expected to have large deleterious effects to sub-polar biodiversity, which could have a wide-ranging number of cascade effects, from the collapse of fisheries to the loss of the ocean as a carbon sink.
There's another reason to be concerned about the salinity of rising seas: As ocean levels creep up, they have the potential to contaminate freshwater supplies near coastlines. That's a huge deal considering around a third of the world's population lives within 60 miles of shoreline.
Understanding how salt moves through the world's oceans is thus quite important. To study how the complex currents powering the oceans affect their salinity, NASA launched its Aquarius satellite instrument in June 2011. Aquarius measures surface salinity content by measuring the microwave emissivity of the top inch or so of ocean water, which fluctuates on a known scale with temperature and salt content. After collecting a little over a year's worth of data, the Aquarius team has put together a more complete picture of how our oceans work.
The above video is a nice watch, with a good assessment of Aquarius's findings. Warm colors are higher salinity, cooler are lower. Of note is the huge effect the Amazon river has on the Atlantic, with a massive freshwater flow heading north towards the equator to penetrate a giant patch of high-salinity water in the middle of the Atlantic–a feature caused by high levels of evaporation.
It's the opposite situation in the Pacific, where surface waters are relatively low in salinity because the Pacific receives far more rain per annum. That's a fascinating thought on its own: the tropical waters of the Atlantic and Pacific are far different because of atmospheric conditions, which thus affects the biodiversity of creatures under the surface. What a marvelously complex planet this is, right?
So complex, in fact, that the Aquarius crew is still learning what it can do with the incredible treasure trove of data its instrument has collected.
Look at the massive plume of low-salinity water pumped into the Atlantic by the Amazon. Incredible stuff.
“The first year of the Aquarius mission has mostly been about understanding how the instruments and algorithms are performing,” Aquarius project manager Gene Carl Feldman said. “Now that we have overcome the major hurdles, we can really begin to focus on understanding what the data are telling us about how the ocean works, how it affects weather and climate, and what new insights we can gain by having these remarkable salinity measurements.”
To that end, the Aquarius team is trying to figure out how to link up its data with those of a similar instrument being run by the European Space Agency. An additional challenge is figuring out how to make Aquarius work near land and the poles, where the high emissivity of land and ice overwhelms its sensor with noise.
Beyond that, figuring out how melting glaciers will affect the world's oceans–whether that freshwater will spread through the entirety of aquatic systems, stay localized, or something else altogether–first requires understanding how salinity processes work in the first place.
This first year of data is a big start, as it brings together a good picture of saline-driven ocean systems as a whole. We'll see what happens as Aquarius moves forward and that mountain of data are refined. Aquarius is about halfway through its planned three year mission, although the instrument itself is expected to last a lot longer than that. Budgets, of course, are another question, but the importance of the work won't diminish any time soon.