Science: SPURS

Since August 2011, NASA’s satellite instruments have revealed how sea surface salinity changes over time with unprecedented detail. This new perspective of our ocean provided the scientific motivation for the Salinity Processes in the upper-Ocean Regional Study (SPURS), a coordinated field campaign to understand causes behind the patterns and variations of salinity at the ocean’s surface.

Salty areas are getting saltier, fresh areas are getting fresher, indicating a strong intensification of the water cycle.
Durack and Wijffels (2010), Journal of Climate; Durack, Wijffels and Mercer (2012), Science

Studies indicate that, over the past 50 years, high-salinity regions (subtropics) have been getting saltier and the low-salinity regions (tropical rain belts) have been getting fresher. This is consistent with a warmer world where the atmosphere holds more water vapor. To learn more about the processes behind such salinity trends, SPURS-1 and -2 activities have been conducted in representative “salty” and “fresh” areas of our ocean, respectively (see table below).

SPURS has been designed to examine the salinity balance in the upper ocean through observation of salinity and ocean circulation at various time scales (annual, daily, minutes) and spatial scales (ocean basin, mesoscale, microstructure). The combined analysis of satellite and SPURS in situ data is intended to improve salinity-related computer models. Such information is critical in modeling the dynamics of many ocean phenomena. It also sheds light on the future of our water cycle, one of the most critical issues of climate change facing society.

Focus High evaporation Heavy rain
Region Subtropical N. Atlantic E. Tropical Pacific
Mooring location 25°N / 38°W 10°N / 125°W
Cruise dates Sep-Oct 2012
Mar-Apr 2013
Sep-Oct 2013
Aug-Sep 2016
Oct-Nov 2017
Research vessels Endeavor-1 and -2
Sarmiento de Gamboa
Lady Amber

Learn More

The Why of SPURS »
Ocean salinity plays key roles in the global hydrological cycle, ocean circulation and the regulation of Earth's climate. Having a better understanding of how evaporation and precipitation influence the global hydrological cycle and ocean circulation will improve our abilities to monitor, understand and model the water cycle over the oceans.
The How of SPURS »
Scientific instruments are the tools scientists use to collect data. Here we take a closer look at 13 instruments used to measure ocean salinity, temperature, depth, and turbulence during SPURS.
SPURS Webinars »
The SPURS project represents the collaborative efforts of a diverse group of scientists spanning national and international borders. Six are highlighted here, for their webinar presentations on their involvement with the SPURS expeditions.


Li, Z., Thompson, E., and A., Chen (2023).
The Uncertainty of IMERG Over the Western Edge of the Eastern Pacific Fresh Pool: An Error Model Based on SPURS-2 Field Campaign Observations
, IEEE Trans. Geosci. Remote Sens., 61, 4104914, doi: 10.1109/TGRS.2023.3306795.
Chkrebtii, O., and Bingham, F. (2023).
Automatic Detection of Rainfall at Hourly Time Scales from Mooring Near-Surface Salinity in the Eastern Tropical Pacific
, Artif. Intell. Earth Syst., 2(3), doi: 10.1175/AIES-D-22-0009.1.
Gassen, L., Badewien, T., Ewald, J., Ribas-Ribas, M., and Wurl, O. (2023).
Temperature and Salinity Anomalies in the Sea Surface Microlayer of the South Pacific During Precipitation Events
, J. Geophys. Res. Oceans, 128(6), e2023JC019638, doi: 10.1029/2023JC019638.
Li, Z., Thompson, E., Behrangi, A., Chen, H., and Yang, J. (2023).
Performance of GPCP Daily Products Over Oceans: Evaluation Using Passive Aquatic Listeners
, Geophys. Res. Lett., 50, e2023GL104310, doi: 10.1029/2023GL104310.
Bytheway, J., Thompson, E., Yang, J., and Chen, H. (2023).
Evaluating Satellite Precipitation Estimates Over Oceans Using Passive Aquatic Listeners
, Geophys. Res. Lett., 50(6), e2022GL102087, doi: 10.1029/2022GL102087.
SPURS study areas
SPURS-1 and SPURS-2 study areas.
SPURS-2 data tool
The SPURS-2 Data Tool (shown above) allows you to browse datasets collected during the SPURS-2 Field Campaign.
Click on the large images to learn more.