NASA to investigate how ocean salinity affects climate change

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A brand new expedition will set sail to the North Atlantic’s saltiest spot to test how ocean salinity affects climate change.

The voyage is a NASA-sponsored quest, and will provide a 3-D picture of how salt content fluctuates in the ocean’s upper layers and how these variations are related to shifts in rainfall patterns around the planet.

The research voyage is dubbed the ‘Salinity Processes in the Upper Ocean Regional Study’ (SPURS). It is part of a multi-year mission, which will deploy multiple instruments in different regions of the ocean.

Also, the new data will help calibrate the salinity measurements that NASA’s Aquarius instrument has been collecting from space since August 2011.

SPURS scientists are currently aboard the research vessel Knorr. The ship will leave sometime today from the Woods Hole Oceanographic Institution in Woods Hole, Massachusettes. It will then head toward a spot known as the Atlantic surface salinity maximum, located halfway between the Bahamas and the western coast of North Africa.

The expedition is also supported by the National Oceanic and Atmospheric Administration and the National Science Foundation.

The researchers are expected to spend about three weeks on site deploying instruments and taking salinity, temperature and other measurements. After that, they will sail to the Azores to complete the voyage on Oct. 9.

The team hopes to return with fresh data to help in understanding one of the most worrisome effects of climate change — the acceleration of Earth’s water cycle. As global temperatures go up, evaporation increases. This alters the frequency, strength, and distribution of rainfall around the planet, with far-reaching implications for life on Earth.

“What if the drought in the U.S. Midwest became permanent? To understand whether that could happen we must understand the water cycle and how it will change as the climate continues to warm,” said Raymond Schmitt, a physical oceanographer at Woods Hole and principal investigator for SPURS. “Getting that right is going to involve understanding the ocean, because the ocean is the source of most of the water.”

Oceanographers believe the ocean retains a better record of changes in precipitation than land, and translates these changes into variations in the salt concentration of its surface waters. Scientists studying the salinity records of the past 50 years say they already see the footprint of an increase in the speed of the water cycle. The places in the ocean where evaporation has increased and rain has become scarcer have turned saltier over time, while the spots that now receive more rain have become fresher. This acceleration ultimately may exacerbate droughts and floods around the planet. Some climate models, however, predict less dramatic changes in the global water cycle.

“With SPURS we hope to find out why these climate models do not track our observations of changing salinities,” said Eric Lindstrom, physical oceanography program scientist at NASA Headquarters in Washington. “We will investigate to what extent the observed salinity trends are a signature of a change in evaporation and precipitation over the ocean versus the ocean’s own processes, such as the mixing of salty surface waters with deeper and fresher waters or the sideways transport of salt.”

To learn more about what drives salinity, the SPURS researchers will deploy an array of instruments and platforms, including autonomous gliders, sensor-laden buoys and unmanned underwater vehicles. Some will be collected before the research vessel heads to the Azores, but others will remain in place for a year or more, providing scientists with data on seasonal variations of salinity.

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