In the proposed project we intend to improve ocean salinity satellite products and to use these improved products to study the interaction between salinity and ocean circulation. The product…

This federal contract award provides a $686,144.64 grant to the University of Hawaii at Manoa to improve ocean salinity satellite products and study the interaction between salinity and ocean circulation. The proposed research aims to enhance the accuracy of mesoscale satellite sea surface salinity (SSS) maps, detect advection of salinity anomalies, explain the seasonal salinity cycle in the Southern Ocean, and synthesize data from multiple NASA satellite missions. This grant aligns with the National Aeronautics and Space Administration (NASA) Ocean Surface Salinity Topography (OSST) research priorities. No set-aside designation was used for this award. The University of Hawaii System, which includes the University of Hawaii at Manoa, is the prime contractor for this grant, which is being funded by NASA.

In the proposed project we intend to improve ocean salinity satellite products and to use these improved products to study the interaction between salinity and ocean circulation. The product improvements we plan to make and the scientific questions we intend to answer are challenging and will require the diverse skills and experience that our team possesses. In the science part, we will investigate how ocean salinity interacts with the ocean circulation with the foci on (i) the salinity anomaly advection by larger-scale ocean currents and (II) the salinity contribution to the dynamics of ocean fronts and striations. We will compare the motion of salinity anomalies detected with spectral and statistical methods with the velocities of mixed-layer drifters that have been extended to the global grid using a diagnostic model (scud) based on satellite observations of ocean topography and wind. We will pay particular attention to the southern ocean region, where we will study the northward ekman transport of salty and fresh anomalies generated during sea ICE formation and melting. We will also compare mesoscale salinity fronts and striations with their analogues in ocean topography and sea surface temperature to understand more clearly the role played by salinity through its control of sea water density. To find answers to the above questions, we will first use multi-scale variational methods to correct errors and biases known or suspected in the current satellite salinity products. Based on these corrected results, we will create a synthetic sea surface salinity (SSS) dataset that is accurate across a broad range of spatial scales and that extends seamlessly across individual satellite missions. The proposed research is significant because IT targets tasks that were not feasible before the introduction of satellite salinity missions and plans analyses that challenge the technical limits of the satellite products. Our objectives are to: 1. Improve the accuracy of mesoscale satellite SSS maps by analyzing and understanding the dynamical structures of such persistent ocean features as fronts and striations. 2. Detect advection of salinity anomalies of different scales by the ocean circulation. 3. Explain the seasonal cycle in salinity anomalies that are observed in the southern ocean in association with the formation and melt of sea ICE. 4. Compile aquarius, smap, and smos data into a seamless salinity product. 5. Improve aquarius data by understanding and correcting the artificial features detected in level 2, version 4.0 dataset. The proposed project is directly relevant to all four topics listed in the NASA osst call for proposals: 1. We will exploit NASA satellite SSS measurements to investigate SSS variability, its interaction with the ocean circulation, and its link to the seasonal water cycle in the southern ocean. 2. We will synthesize NASA SSS measurements (aquarius and smap) with smos and argo. 3. We will evaluate and improve aquarius and smap SSS products to assure the continuity and consistency of the SSS products across the two missions. 4. We will compare the seasonal cycle in the southern ocean seen in satellite-derived SSS with argo-measured subsurface salinity. We will also study the interaction between salinity stratification and the sheared ekman current by comparing movements of fresh and salty anomalies.