NASA voyage seeks ocean salinity/climate answers

An expedition to the most saline part of the North Atlantic ocean set sail on 6 September 2012 as part of a multi-year mission to get a detailed 3D picture of how salt content fluctuates in the ocean’s upper layers and how this relates to shifts in rainfall patterns around the planet.

Sponsored by the US National Aeronautic & Space Administration (NASA), data from the Salinity Processes in the Upper Ocean Regional Study (SPURS) will also help to calibrate salinity measurements which have been collected by NASA’s satellite-based Aquarius instrument since August 2011.

The researchers will spend about three weeks at the Atlantic surface salinity maximum, located halfway between the Bahamas and the western coast of North Africa. They will deploy instruments and taking salinity, temperature and other measurements, before sailing to the Azores to complete the voyage on 9 October 2012.

Their new data will aid understanding of one of the most worrisome effects of climate change – the acceleration of Earth’s water cycle. As global temperatures go up, evaporation increases, altering the frequency, strength and distribution of rainfall around the planet, with far- reaching implications for life on Earth.

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.”