By Sandra Hines
With the launch earlier this month of NASA’s satellite Aquarius, more than half a dozen University of Washington researchers are involved in projects to calibrate data from space with actual measurements of ocean salinity.
Two of the UW researchers, oceanography’s Stephen Riser and the Applied Physics Laboratory’s William Asher, are members of NASA’s Aquarius Science Team.
By monitoring changes in salinity in the oceans, scientists will learn about the effects of precipitation, melting ice, river runoff and evaporation. Melting ice and rain, for example, adds freshwater, decreasing salinity, while evaporation draws fresh water out, increasing it.
Among other things, the salinity of seawater is one driver of ocean circulation and better data would improve our understanding of circulation, the global water cycle and climate change, Riser says.
The oceans dominate the global water cycle, yet past research has typically focused on the water cycle over land, he says. But we now know, for example, that flood and drought cycles occur in concert with changes in the global ocean water cycle.
“Changes in the water cycle pose the greatest challenge to society,” said the introductory article to a special issue on salinity in the journal Oceanography. “We may be able to deal with an increase in temperature with a bit more air conditioning, but significant intensification in droughts and floods will be a more severe test. Civilization thrives at a range of temperatures at different latitudes, but it cannot cope without water.”
The Aquarius satellite, circling pole-to-pole about 400 miles above Earth, measures salinity by detecting microwaves emitted by blackbody radiation from the ocean’s surface. It can measure salinity within the top 2 centimeters (3/4 of an inch) of the surface. Scientists like Riser and Asher are leading efforts to understand how the measurements made by Aquarius near the ocean surface relate to salinity deeper in the ocean.
Riser will do so using 45 Argo floats, which will be deployed at low latitudes and operate autonomously. Asher and co-PI Andrew Jessup of the Applied Physics Laboratory will use ship mounted sensors during expeditions on the UW’s vessel Thomas G. Thompson and the research vessel Kilo Moana.
“Aquarius, and successor missions based on it, will give us critical data that will be used by models that study how Earth’s ocean and atmosphere interact, to see trends in climate,” said Gary Lagerloef, Aquarius principal investigator. Lagerloef, who is with the Seattle-based independent laboratory Earth & Space Research, earned his doctorate from the UW.
A companion NASA program, called the Salinity Process in the Upper Ocean Regional Study or SPURS, involves the Applied Physics Laboratory’s Craig Lee, Luc Rainville, Eric D’Asaro and Andrey Shcherbina as well as oceanography’s Charlie Eriksen. Lee and Riser are both on the science steering group for that project. The program will attempt to examine salinity in detail in a region of the subtropical Atlantic Ocean.
