Measuring the Immeasurable

Professor Fred Bingham of UNCW's physics and physical oceanography department has partnered with NASA to track the movement of water around the globe with the help of the space satellite, Aquarius.

They seek to understand the patterns in water distribution that the planet depends on-patterns that, until recently, have been impossible to measure.

"The purpose behind Aquarius is try to understand what we call the global hydrologic cycle" or the worldwide movement of water through lakes, rivers and oceans, due to alternating rainfall and evaporation, Bingham said.

"That's really straightforward to measure on land, to know how much rain there is, how much water is evaporating," Bingham explained. "All you need to do is put out a rain gauge. But it's extraordinarily difficult to measure the cycle over the ocean. You can't put a rain gauge there."

Until recently, the oceanic portion of the global hydraulic cycle had never been measured. Bingham estimates that about 78 percent of worldwide precipitation and around 86 percent of evaporation occurs over the ocean. The difference-roughly 8 percent-constitutes the amount of water continually being removed by the ocean and redistributed onto land, eventually making its way into rivers and ultimately, winding back to the sea.

"That's where we get all the water that we need for things like agriculture which obviously we couldn't survive without. It's essential," Bingham said.Fred Bingham

But how to measure this crucial portion the global hydraulic cycle?

Enter NASA and Bingham, an expert in sea salinity or how much salt exists in ocean water.

In particular stretches of ocean, Bingham reports that salinity can provide clues as to recent phenomena. During rainfall, for example, the ocean receives an influx of water, which subsequently dilutes the salt content. The reverse is true when a particular stretch of ocean experiences evaporation; it naturally loses water and the salt content becomes more concentrated.
Add a NASA satellite capable of detecting ocean salt from space and North American scientists have a way to measure the previously immeasurable.

"It's totally unique," Bingham said. "The European satellite and Aquarius are the first missions to do this." The result: unprecedented insights into the planet's most precious natural resource.

Within two months after it was launched in 2011, Aquarius collected as many sea surface salinity measurements as the entire 125-year historical record from ships and buoys and provided measurements over the 25 percent of the ocean where no previous observations had been made, according to the mission's website.