SPURS Sets Sail to Elucidate Oceanic Salinity Processes with Linkage to the Water Cycle (September, 2012)

The Motivation for SPURS

The motivation for SPURS stems from a variety of sources:
  • The recent ability due to Aquarius to accurately and routinely monitor salinity on a global scale (Figure 5), combined with new advances in data assimilation and physical modeling approaches.
  • The presence of certain gaps in our understanding of processes influencing salinity (interplay of precipitation, evaporation, transport, mixing) that complicate inferences about the oceanic water cycle from space-borne salinity observations.
  • Recent evidence from trends in regions of salinity extremes of an accelerating water cycle consistent with climate mechanisms, but also uncertainties regarding the details and possible future implications to global climate via key processes such as thermohaline circulation (the “great ocean conveyor belt”).
 
The Goal

The goal is to better understand the role changes in salinity have on the Earth’s water cycle and its relationship to climate.
 
Field Campaign Information

The R/V Knorr cruise starts on September 6, 2012 and runs for 33 days.  During this time, 3 SPURS moorings with diverse instrumentation will be deployed, a 6 day period of control volume sampling within a 200x200km2 region for both bulk and micro salinity structure characterization will occur, and a similar period of dynamical feature site sampling is scheduled for the tail end of the cruise before it terminates in the Azores on October 9 (Figure 1).  The Knorr cruise overlaps in part with a cruise by the R/V Thalassa (August 16 -September 13, 2012), which is part of the French contribution to SPURS.  During this time, a large number of drifters, Argo floats and array of other instruments will be deployed within the study region.  A further three cruises for SPURS are scheduled to occur in 2013.   A possible follow-on field campaign in a salinity minimum region of the world’s oceans is envisaged as a potential future activity for the SPURS project.  This will likely complement the important new insights on salinity processes expected from the SPURS campaign field program in the subtropical North Atlantic.
 
What is SPURS?

Final preparations of the research vessel (R/V) Knorr are underway at the Woods Hole Oceanographic Institute for one of a series of 5 cruises during 2012 and 2013 that are part of an innovative research program called SPURS.   Funded by NASA in collaboration with NSF, NOAA and also involving European participation (e.g. France, Spain), the Salinity Processes in the Upper Ocean Regional Study (SPURS) project aims to improve our understanding of salinity processes in the upper ocean. Along with the AQUARIUS/SAC-D mission, a collaboration between NASA and the Argentinian Space Agency CONAE, SPURS will provide new insights into the Earth's global water cycle and the relationship to climate.  AQUARIUS data is available through the PO.DAAC at http://podaac.jpl.nasa.gov/aquarius/ through the acknowledgement of a simple disclaimer. 

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Figure 1:
Location of the SPURS study site in the salinity maximum region of the subtropical N.Atlantic with the planned R/V Knorr cruise track.  Overlaid on the map are remotely sensed salinity data from Aquarius/SAC-D showing salinity high values (deeper orange) of 37 PSU (practical salinity units or grams salt per kg seawater) at the 25N, 38W epicenter of the SPURS sampling area. 

 

 

SPURS will employ an advanced suite of in-situ sampling technologies (Figure 1) combined with remotely sensed salinity fields from the Aquarius/SAC-D satellite to provide a detailed characterization of salinity structure over a range of spatio-temporal scales within a 900 x 800-mile square study area centered at 25N, 38W (Figure 2).  Coupling of data from this “sensor web” (Figure 3) with physical oceanographic models and simulation experiments (Figure 4) is a further distinguishing feature of SPURS aimed at both elucidating the underlying physical processes at play in this salinity maximum region of the subtropical N. Atlantic and providing tools for adaptive survey design to investigate dynamical features of interest.  Situational awareness capabilities are further enhanced by the development of an Internet-based visualization system that is hosted on the project website facilitating the near real-time integration of in-situ, satellite and model observations.  The project is novel in its use of online collaboration tools for researchers and emphasis on public outreach and education.  The project website includes a science lesson plan section that leverages actual components of the SPURS analysis toolkit.  An active cruise blog documenting science activities as they occur is also being maintained by Eric Lindstrom, the NASA Physical Oceanography Program Scientist, and an interactive cruise plan widget on the website allows the public to view the instrument deployment schedule and objectives for each phase of the cruise.
 

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Figure 2:
Examples of some of the sampling platforms and instrumentation employed by SPURS. (left to right) . An Autonomous Underwater Vehicle (AUV) that will be patrolling the study area and taking salinity and temperature measurements as it undulates vertically through the water column.  Argo floats will drift and passively move vertically through the water column, transmitting measurement data via satellite when at the surface.  An array of moorings loaded with instrumentation at a range of depths will provide SPURS with a multiple high frequency measurements, from meteorological observations to current information and salinity/temperature data.
 
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Figure 3:
The SPURS sensor-web illustrating a diverse array of sampling platforms and advanced instrumentation providing coverage of the study area and detailed observations of salinity processes over a range of spatio-temporal scales.
 
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Figure 4:
Outputs from the SPURS ocean modeling and forecast system illustrating dynamical eddy features within a nested set of three spatial domains configured for the SPURS region at horizontal resolutions of 9, 3 and 1 km and for 50 vertical levels.  This model is based on the community Regional Ocean Modeling System (ROMS).
 
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Figure 5:
PO.DAAC provides access the full series of archived Aquarius data together with interactive tools for data visualization, such as the Level 3 image browser shown here.
   

 

PO.DAAC Science Team