Presented at the 2018 AGU Fall MeetingSince its launch in 2015, NASA's Soil Moisture Active Passive (SMAP) mission has provided groundbreaking information on the nature of surface soil moisture globally. Additionally, new opportunities have arisen to retrieve sea surface salinity (SSS) from SMAP. Here, we present a suite of recent research funded by NASA's Science Utilization of SMAP (SUSMAP) program demonstrating the value of SMAP land and ocean data products to study land-sea linkages around the Gulf of Mexico region. First, we present an intercomparison of error characteristics across remote sensing salinity products, including three different SMAP SSS products and an ESA Soil Moisture and Ocean Salinity (SMOS) SSS product, as well as against in situ measurements, in the Gulf of Mexico. The results demonstrate the strong capability of SMAP SSS observations in a river-influenced system. We also present a comprehensive chronology of an extreme flooding event in Texas and Gulf of Mexico from land to sea captured by SMAP observations. Building on this study, using a suite of satellite observations, we also present a method to locate the regions on land for which precipitation and runoff generation have the largest effect on local river discharge. Then we map, on average, the unique contribution of individual river discharge forcing to specific features of river plume structure across the Gulf of Mexico. This result advances progress towards a predictive framework for mapping of the impacts of hydrological flood events from land into the ocean. Finally, we show that satellite SSS data along with in situ data can help to better locate potential profound biogeochemical impacts (dead zones) of riverine waters in coastal regions in the Gulf of Mexico.