From: Andy Soos, ENN
Published September 6, 2012 10:14 AM
Salinity and Climate
The degree of salinity in oceans is a driver of the world's ocean
circulation, where density changes due to both salinity changes and
temperature changes at the surface of the ocean produce changes in
buoyancy, which cause the sinking and rising of water masses. Changes in
the salinity of the oceans are thought to contribute to global changes
in carbon dioxide as more saline waters are less soluble to carbon
dioxide. A NASA-sponsored expedition is set to sail to the North
Atlantic's saltiest spot to get a detailed, 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 part of a multi-year mission, dubbed the Salinity
Processes in the Upper Ocean Regional Study (SPURS), which will deploy
multiple instruments in different regions of the ocean. The new data
also will help calibrate the salinity measurements NASA's Aquarius
instrument has been collecting from space since August 2011. Aquarius
was built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., and
NASA's Goddard Space Flight Center, Greenbelt, Md.
SPURS scientists aboard the research vessel Knorr leave Sept. 6 from
the Woods Hole Oceanographic Institution in Woods Hole, Mass., and head
toward a spot known as the Atlantic surface salinity maximum, located
halfway between the Bahamas and the western coast of North Africa.
The researchers will spend about three weeks on site deploying
instruments and taking salinity, temperature and other measurements,
before sailing to the Azores to complete the voyage on Oct. 9.
They will return with new data to aid 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, altering 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.
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.
Some of the devices used during SPURS to explore the Atlantic's saltiest
spot will focus on the outer edges of the study area, traveling for
hundreds of miles and studying the broadest salinity features. Other
instruments will explore smaller areas nested inside the research site,
focusing on smaller fluxes of salt in the waters. The suite of ocean
instruments will complement data from NASA's salinity-sensing instrument
aboard the Aquarius/SAC-D (Satelite de Aplicaciones Cientificas-D)
observatory, and be integrated into real-time computer models that will
help guide researchers to the most interesting phenomena in the cruise
area.
The 2012 SPURS measurements in the North Atlantic will help scientists
understand the behavior of other high-salinity regions around the world.
A second SPURS expedition in 2015 will investigate low-salinity regions
where there is a high input of freshwater, such as the mouth of a large
river or the rainy belts near the equator.
Sudden decreases in temperature over Greenland and tropical rainfall
patterns during the last Ice Age have been linked to rapid changes in
the salinity of the north Atlantic Ocean, according to research
published Oct. 5, 2006, in the journal Nature.
For further information see
Salinity.
Boat image Bill Ingalls via NASA.
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