2014 Ocean Salinity Science And Salinity Remote Sensing Workshop

November 26-28, 2014
Exeter, United Kingdom

The Ocean Salinity Science and Salinity Remote Sensing Workshop was held at the Met Office in Exeter, United Kingdom from 26-28 November, 2014.

The objectives of the meeting were to:
  • Review the progress in our understanding of ocean salinity and associated processes
  • Present the status of satellite remote sensing of sea surface salinity and its contribution to ocean science
  • Explore techniques and challenges associated with the use of salinity data in ocean models
  • Identify the most promising future applications for satellite-derived estimates of sea surface salinity
  • Review user requirements for future satellite-derived estimates of sea surface salinity
  • Prioritize future activities for ocean salinity science
Documents (13)
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Assessment of Rain Freshening Effects and Salinity Stratification in the Tropics Based on the Aquarius Version 3 Salinity Product
Meissner, T., Wentz, F., Scott, J., and Hilburn, K. (26-Nov-14). The Aquarius Version 3.0 salinity product has been released to the public in June 2014. The retrieval algorithm and the quality of the data constitute a major improvement from earlier versions. Our presentation starts with a brief overview of the major components of the Aquarius V3.0 salinity retrievals and upgrades that were implemented since prior releases.

Changes in the Seasonal Cycle of Sea Surface Salinity During the Argo-era (2004-2013)
Reagan, J., Boyer, T., Antonov, J., and Zweng, M. (26-Nov-14). The Argo program has provided the scientific community with near-global, seasonally uniform coverage of hydrographic profiles over the past decade. Recent launches of the SAC-D/Aquarius and SMOS satellites have provided near real-time snapshots of global ocean sea surface salinity (SSS). The importance of understanding changes in SSS in both time and space cannot be overstated as it is a direct reflection of changes in our global hydrological cycle and is a major component of ocean circulation. This study attempts to advance our understanding of interannual changes in SSS by looking at year to year changes in the seasonal cycle over the past decade.

Correlative Analysis of Aquarius, Grace and River Discharge Data Indicating the Change of Water Cycle In the India Subcontinent
Yueh, S., Tang, W., Fore, A., Hayashi, A., Lee, T., Bindlish, R., and Jackson, T. (28-Nov-14). Aquarius is a combined passive/active L-band microwave instrument developed to map the sea surface salinity (SSS) field from space. The accuracy of Aquarius monthly averaged SSS product derived from the Combined Active and Passive (CAP) algorithm has been estimated to be about 0.1 to 0.2 psu Root-Mean-Square (RMS) between 40 degrees N and 40 degrees S through comparison with the Argo gridded dataset produced by the Asia-Pacific Data- Research Center (APDRC) and tropical moorings. We find that the regions with larger discrepancy include the ITCZ and near the outflow of major rivers, such as the Ganges, where the surface stratification due to precipitation or river discharge appears to be playing a significant role.

Differences Between the Subtropical Surface Salinity Patterns
Busecke, J., and Gordon, A. (27-Nov-14). The subtropical oceans all display relatively salty surface water, forming a regional sea surface salinity maximum (SSS-max), a response to the global hydrological cycle. Regional differences in basin SSS-max intensity and patterns complicate a direct comparison. We apply a methodology to compare the SSS-max regimes between oceans using a reference salinity based on the MIMOC climatology, eliminating the uncertainty due to an arbitrarily chosen isohaline for each ocean.

Meridional variability of SSS in the North Atlantic Ocean From Satellite and In-Situ Data
Ballabrea, J., Hoareau, N., Garcia, E., Turiel, A., and Portabella, M. (26-Nov-14). Satellite imagery has revealed a series of ocean structures as meandering fronts, eddies and filaments. A high percentage of ocean energy has been found to accumulate at a range of scales (ranging from tens to a few hundred kilometers) known as the ocean mesoscale. Thanks to the SMOS and Aquarius missions, more than four years of satellite-derived sea surface salinity (SSS) data are available. For the first time, satellite data have been providing quasi global, synoptic information of the spatial variability of the ocean surface salinity.

Monitoring Sea Surface Salinity from Space with Aquarius and SMOS Satellites
Reul, N., and Lee, T. (26-Nov-14). An invited talk by Nicholas Reul and Tony Lee, providing an overall context for ocean salinity, from the satellite perspective. The talk reviews the importance of studying ocean salinity and the benefits of looking at data from the unique vantage point of space. The basics of the SMOS and Aquarius SAC-D missions are provided, as well as a high-level review of some of the research outcomes thus far.

Observations and Modeling of Rain-Induced Near Surface Salinity Anomalies
Asher, W. (28-Nov-14). Vertical salinity gradients in the top few meters of the ocean surface can exist due to the freshwater input from rain. If present, they will complicate comparing salinity measured by ARGO drifters at typical depths of a few meters to salinities retrieved using L-band microwave radiometers such as SMOS and Aquarius, whose measurement depths are on order of 0.01 m. Therefore, understanding the spatial scales and the frequency of occurrence of these vertical gradients and the conditions under which they form will be important in understanding sea surface salinity maps provided by SMOS and Aquarius.

Satellite Sea-Surface Salinity Data and Product Biases and Differences
Bayler, E. (26-Nov-14). Satellite sea-surface salinity (SSS) observations provide broad coverage that contributes to addressing spatial and temporal gaps due to irregular observations in the in situ record. While satellite SSS retrievals continue to mature, significant differences continue between the SSS observations from the European Space Agency’s (ESA) Soil Moisture – Ocean Salinity (SMOS) mission and the joint United States and Argentine Aquarius/SAC-D mission.

Sea Surface Salinity from Space: a Future for Operational Oceanography?
Tranchant, B., Gernier, E., Garric, G., Drevillon, M., and Reginer, C. (27-Nov-14). Improving the SSS (Sea Surface Salinity) constrain at various scales is an important issue for ocean forecasting. It concerns the short term meso-scale and the seasonal anomalies. Both strongly depend on the surface freshwater budget (evaporation, precipitation and runoff). Presently, it is not yet possible to fully remove SSS biases with the poorly sampled Argo network data near the surface (depth < 5m). It encourages us to find the best way to deal with SSS data observed from space (SMOS and Aquarius).

Status of Aquarius Salinity Retrievals and Applications
Le Vine, D., Dinnat, E., Lagerloef, G., de Matthaeis, P., Kao, H.Y., Meissner, T., and Wentz, F. (26-Nov-14). This paper will give the status of the Aquarius instrument and salinity retrieval, mention some new applications of the data and summarize the current research issues being addressed to improve the retrieved salinity. Aquarius was launched on June 10, 2011 to monitor the global salinity field in the open ocean. This radiometer/scatterometer (i.e. passive/active) instrument is part of the Aquarius/SAC-D observatory. The instrument has been operating continuously since being turned on in August and the initial map of sea surface salinity was released one month later (September, 2011). The quality of the salinity retrieval has improved continuously since then and is approaching the goal of 0.2 psu accuracy (RMS globally each month).

Surface Freshwater Plumes Contributing to the Formation of the Barrier Layer and Salinity Fronts
Soloviev, A., Matt, S., and Fujimura, A. (28-Nov-14). Surface freshwater plumes contributing to the formation of the barrier layer and salinity fronts Some areas of the World Ocean are characterized by substantial influx of freshwater. Localized rain and river runoff may produce relatively shallow, near-surface freshwater plumes. Due to buoyancy forces, these plumes have a tendency to spread in the horizontal direction. These buoyancy-driven flows are a type of the organized structure resembling a classical gravity current. Buoyancy-driven surface currents are an important component of the oceanic environment, leading to water mass exchange by horizontal advection and enhanced vertical mixing. The freshwater plumes can be linked to larger scale features such as the barrier layer and fronts, contributing to the salinity field in the Aquarius and SMOS footprints.

Synergy Between Remote Sensing Variables: Level 4 Research Products of Sea Surface Salinity
Umbert, M., Portabella, M., Guimbard, S., Ballabrea, J., and Turiel, A. (26-Nov-14). Remote sensing imagery of the ocean surface provides a synoptic view of mesoscale signatures from different ocean scalars advected by the oceanic flow. The most probable origin of the observed structures is the turbulent character of the oceanic flow as they slowly evolve and are very persistent over time scales compatible with ocean mesoscale dynamics. At spatial scales of kilometers, turbulence is mainly 2D, and a complex geometry, full of filaments and eddies of different sizes, emerges in remote sensing images of surface chlorophyll-a concentration (Chl-a) and sea surface salinity (SSS), as well as in the better resolved sea surface temperature (SST) and sea surface height (SSH).

The Relative Influence of Surface Sea Salinity and Temperature on Surface Density Gradient in the Tropical Pacific Ocean
Hasson, A., and Lee, T. (27-Nov-14). Horizontal gradients of surface density in the ocean are important to frontal genesis and instability associated with ocean currents. They also have significant implications to air-sea interaction and biogeochemistry. Sea Surface Temperature (SST) and Salinity (SSS) both contribute to the horizontal density gradient. For the first time surface density can be globally inferred from remote sensing with unprecedented spatial and temporal scales. Since August 2011, NASA’s Aquarius/SAC-D satellite mission and since January 2010, ESA’s SMOS mission have provided global high resolution SSS datasets. In this study, we use various satellite measurements of SSS and SST to characterize the mean spatial structure and temporal variability of surface density gradients in the tropical Pacific Ocean from 2011 to present.