US: NASA’s Aquarius satellite has revealed changes in ocean salinity patterns. Aquarius is NASA’s first satellite instrument specifically built to study the salt content of ocean surface waters. Salinity variations, one of the main drivers of ocean circulation, are closely connected with the cycling of freshwater around the planet and provide scientists with valuable information on how the changing global climate is altering global rainfall patterns.
“With a bit more than a year of data, we are seeing some surprising patterns, especially in the tropics,” said Aquarius Principal Investigator Gary Lagerloef, of Earth & Space Research in Seattle. “We see features evolve rapidly over time.”
The animated version of Aquarius’ first year of data has unveiled a world of varying salinity patterns. The Arabian Sea, nestled up against the dry Middle East, appears much saltier than the neighboring Bay of Bengal, which gets showered by intense monsoon rains and receives freshwater discharges from the Ganges and other large rivers. Another mighty river, the Amazon, releases a large freshwater plume that heads east toward Africa or bends up north to the Caribbean, depending on the prevailing seasonal currents. Pools of freshwater carried by ocean currents from the central Pacific Ocean’s regions of heavy rainfall pile up next to Panama’s coast, while the Mediterranean Sea sticks out in the Aquarius maps as a very salty sea.
One of the features that stand out most clearly is a large patch of highly saline water across the North Atlantic. This area, the saltiest anywhere in the open ocean, is analogous to deserts on land, where little rainfall and a lot of evaporation occur. A NASA-funded expedition, the Salinity Processes in the Upper Ocean Regional Study (SPURS), traveled to the North Atlantic’s saltiest spot last fall to analyze the causes behind this high salt concentration and to validate Aquarius measurements.
“My conclusion after five weeks out at sea and analyzing five weekly maps of salinity from Aquarius while we were there was that indeed, the patterns of salinity variation seen from Aquarius and by the ship were similar,” said Eric Lindstrom, NASA’s physical oceanography program scientist, of NASA Headquarters, Washington, and a participant of the SPURS research cruise.
“The Aquarius prime mission is scheduled to run for three years but there is no reason to think that the instrument could not be able to provide valuable data for much longer than that,” said Gene Carl Feldman, Aquarius project manager at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The instrument has been performing flawlessly and our colleagues in Argentina are doing a fantastic job running the spacecraft, providing us a nice, stable ride.”