NASA selects GSFC-led mission to study the role of salinity in ocean circulation and climate

July 11, 2002

As part of the Earth System Science Pathfinder small-satellite program, NASA has selected a new space mission proposal led by NASA's Goddard Space Flight Center in Greenbelt, Md., that will yield fresh insight into how oceans affect and respond to climate change -- knowledge that will help better life here on Earth.

The mission, named Aquarius, promises to explore the saltiness of the seas in order to understand how the massive natural exchanges of water between the ocean, atmosphere and sea ice influence the ocean circulation, our climate, and our weather.

"Aquarius will provide the first-ever global maps of salt concentration on the ocean surface, a key area of scientific uncertainty in the oceans' capacity to store and transport heat, which in turn affects Earth's climate and the water cycle," said Dr. Ghassem Asrar, Associate Administrator for Earth Science at NASA Headquarters, Washington.

The Aquarius mission will be led by principal investigator Dr. Chester J. Koblinsky of Goddard. Goddard will build and calibrate the highly accurate radiometers that are crucial for the detection of ocean salinity and will manage the mission after launch and provide the science data center. The project is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

NASA will partner with the Argentine space program on the Aquarius mission, building on a successful long- standing relationship between NASA and Argentina. In all, over 17 universities and corporate and international partners will be involved in the Aquarius mission.

Aquarius is named after the Water Bearer constellation, because of its objective to explore the role of the water cycle in ocean circulation and climate. Aquarius will launch in 2007 and will orbit the Earth for at least three years, repeating its global pattern every 8 days. Within two months, Aquarius will collect as many sea surface salinity measurements as the entire 125-year historical record from ships and buoys, and provide the first measurements over the 25 percent of the ocean where no previous observations have been made.

"About 80 percent of atmosphere-water exchange occurs over the oceans," says Koblinsky. "These exchanges are important to weather and climate prediction, but are poorly understood."

According to Koblinsky, patterns of ocean surface salt concentration result from many factors: fresh water exchange between the ocean and the atmosphere (evaporation or precipitation), input from rivers and ground water, melting and freezing of polar ice, ocean currents and mixing.

"Global salinity measurements will allow us to closely monitor these processes for the first time, he says. "Global observations of sea surface salinity will also advance our understanding of ocean circulation and, perhaps, allow us to minimize the impacts of large-scale natural events in the future."

Because fresh water is light and floats on the surface, while salty water is heavy and sinks, Koblinsky says changes in salt concentration at the ocean surface affect the weight of surface waters. At high latitudes, melting sea ice, increased precipitation, and/or river inputs will make surface waters less salty.

"This density change could diminish the overturning ocean circulation, which brings warm water poleward on the surface to replace the sinking water," he says. "This would restrict the ocean-atmosphere heat pump that normally warms the atmosphere, leading to possible dramatic changes in climate."

In the tropics, increased precipitation can lead to fresh surface layers on the ocean, which heat up, and modify the energy exchange with the atmosphere, affecting El Nino and Monsoon processes.

NASA will fund up to $175 million for each of the two selected missions. The selected missions will have approximately nine months to refine their proposals to mitigate risk before mission development is fully underway.

NASA issued an Announcement of Opportunity and initially received 18 proposals, six of which were selected for detailed assessment, with two now moving on toward final implementation.

NASA conducts Earth science research to better understand and protect our home planet. Through the examination of Earth, we are developing the technologies and scientific knowledge needed to explore the universe while bettering life on our home planet.
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NASA/Goddard Space Flight Center

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