By Danny Freedman
Anyone who’s dunked their head underwater at the beach knows the ocean is salty, but just how salty and how does that vary? The questions are critical to better understanding the climate, and a GW researcher is helping NASA find the answer—within a pinch of salt per gallon of seawater.
What’s more, NASA plans to make these observations from 400 miles above the surface, aboard a satellite called Aquarius that is slated to launch next year.
“The whole project requires a great deal of accuracy,” says Roger Lang, a professor of engineering and applied science at GW and a member of NASA’s scientific team for the Aquarius mission. Dr. Lang’s role has been to perfect a mathematical formula that will allow for the amount of salt to be tabulated within 1/8th of a teaspoon per gallon of ocean water.
Over the scheduled three-year mission, NASA hopes to gain insight into the system of ocean currents (like the Gulf Stream), which rely in part on salty waters in order to carry heat from the sun throughout the oceans and regulate climate.
The mission also will study the impact of changes to the water cycle. That process increases salt content in areas where water evaporates and decreases it where water is replenished through precipitation, and has an influence on events like monsoons and El Ninos.
“The ocean really governs what happens in the atmosphere, to a large extent,” says Dr. Lang. For instance, the Gulf Stream carries warm water up the coast of North America then crosses northeast toward England, releasing heat into the atmosphere. The water then sinks—an effect of the colder temperature and high density from the salt—and returns south. “If icebergs are melting and putting fresh water into the sea, the water becomes less salty and it doesn’t sink as fast,” says Dr. Lang. “That’s backing up the Gulf Stream, making colder winters in Europe.”
Ships and buoys at sea have been measuring salinity for 125 years, providing only limited data—a quarter of the oceans are completely unmonitored, according to NASA. Aquarius will circle the earth once per week looking for salt just below the water’s surface, where it interacts most with the atmosphere.
In just three months of operation, the space agency anticipates Aquarius will collect more data than the past 125 years combined.
Dr. Lang and a handful of students have been testing and tweaking the algorithm using a model they built in a Tompkins Hall lab. The satellite’s equipment will be able to measure some properties of the water directly, like temperature, but not salinity—so Dr. Lang is zeroing in on how those factors very precisely relate to salt levels. Data collected by the satellite then can be plugged into the formula to determine salinity.
“The ocean is a very complicated affair,” says Dr. Lang, particularly from space. His job is among a laundry list of difficult adjustments that need to be accounted for on this mission by NASA and its other partners: “The roughness of the sea, the atmosphere, the ionosphere; they have to worry about galaxies producing noise and reflecting off the ocean’s surface,” says Dr. Lang. “It’s quite an operation making all these corrections.”
Dr. Lang has also been working with NASA on a related, future mission that would study moisture in soil, which also impacts the climate. “There’s a whole string of these that NASA wants to put up to make more accurate measurements of the variables of the Earth,” he says, “which are very important if we’re going to try to predict what’s going on and if we’re going to be able to actually document changes that are occurring.”