Meetings: 2018 AGU Fall Meeting

December 10-14, 2018
Washington, D.C. USA
The American Geophysical Union's 2018 Fall Meeting, held in Washington, D.C., focused on ethics, diversity and inclusion and explored the many dimensions of science's impact on society. Presentations and posters relating to ocean salinity are compiled here.
Documents: 25
Hu, R., Lin, X., and Yu, L. [13-Dec-18]. Measurements from the Soil Moisture Active Passive (SMAP) and Optimum Interpolation Sea Surface Temperature (OISST) acquired during 2016 to 2017 in the Kuroshio-Oyashio Extension Region (KOER) and Gulf Stream (GS) are used to reveal the sea surface salinity (SSS) and temperature (SST) structure of the mesoscale eddies with an unprecedented space and time resolution.
Misra, S., Ramos, I., Felten, C., Bosch-Lluis, J., Brown, S.T., Yueh, S.H., Latham, B., and Lee, T. [14-Dec-18]. NASA's Aquarius and SMAP (Soil Moisture Active Passive) missions operating at 1.4 GHz (L-band) successfully demonstrated the ability to measure sea-surface salinity (SSS) at a high precision. Though successful, a narrow band-width of 24 MHz on both of the passive sensors limited retrievals of sea-surface salinity to global regions with warmer sea-surface temperatures, due to reduced SSS sensitivity at L-band at lower sea surface temperatures (SST). A narrow bandwidth also requires external ancillary wind speed (WS) and sea surface temperature (SST) data to inform the retrieval algorithms.
Gozdz, O., Buckley, M.W., and Shiffer, N.V. [14-Dec-18]. Recently there has been intense debate about the relative roles of external forcing, stochastic atmospheric variability, and ocean dynamics (e.g., the AMOC) in the Atlantic Multidecadal Variability (AMV). While sea surface temperature (SST) variability has been well-studied, analysis of sea surface salinity (SSS) has received less attention. It is compelling to address SSS variability and its relation to the AMV because covariability between temperature and salinity (e.g. warm and salty or cool and fresh) is thought to be a signature of ocean dynamics. We investigate the covariability between temperature and salinity in the North Atlantic in several ocean reanalysis products.
Sahasrabhojanee, A., Ummenhofer, C., Li, L., and Schmitt, R.W. [12-Dec-18]. When water evaporates from the oceans, it causes an increase in the Sea Surface Salinity (SSS). A significant portion of this evaporated water precipitates onto land. This provides a solid connection between change in Sea Surface Salinity and precipitation on land. Currently, it is more typical to use Sea Surface Temperature (SST) as a predictor for land precipitation. SSS is rarely included as a predictor because anomalies in SSS and in SST are often highly correlated and caused partially by the same phenomena, resulting in multicollinearity in the model.
Zhang, Y., Zhao, X., and Zhang, H-M. [10-Dec-18]. As an effort to monitor the NOAA satellite oceanographic products (e.g., NOAA OSTM/Jason-2 and Jason-3 sea level anomaly, SAR ocean surface wind, SST, etc.) served at the NOAA National Centers for Environmental Information (NCEI), we have developed a real-time data quality monitoring system (DQMS) and services for these datasets. The principle concept of the DQMS is to calculate the data quality descriptive statistics for selected parameters as the data files are received at NCEI, along with near-real-time generation of the level-3 quick-look gridded data directly from the level-2 orbit data.
Nichols, R.E. and Bulusu, S. [14-Dec-18]. In recent decades we have seen major changes in Arctic Ocean circulation, salinity, and temperature and associated declines in sea ice coverage and mass balance. There is evidence of connections of these changes with climate indices, and the changes arguably affect climate by changing the radiative heat balance at high latitude, impacting the strength of the global overturning circulation.
Dean, C. and Soloviev, A. [14-Dec-18]. Convective rains and/or river runoff produce localized freshwater lenses in the near-surface layer of the ocean that have significant density anomalies and thus horizontal pressure gradients. As a result, these lenses can spread and propagate as gravity currents, interacting with wind stress. We have modeled freshwater lens dynamics in the near-surface layer of the ocean using computational fluid dynamics (CFD) tools.
Liu, W.T. and Xie, X. [14-Dec-18]. Ocean surface wind speed, sea surface temperature (SST), and integrated water vapor (W) have been derived, under clear and cloudy conditions, starting with Scanning Multichannel Microwave Radiometer (SMMR) on Seasat and Nimbus-7. The 1982-83 El Niño and Southern Oscillation episode initially escaped notice because it was obscured from spacebased visible and infrared sensors by volcanic aerosols. Nimbus-7 SMMR demonstrated for the first time the all-weather capability by monitoring the eastward migration of atmosphere convection and ocean warming along the equator during the episode. By deriving a statistical relation between W and near surface humidity, based on the coherence of vertical humidity profile, we pioneered the method of spacebased estimation of surface evaporation/latent heat flux, using bulk parameterization, in the 1980s.
Hackert, E.C., Kovach, R.M., Marshak, J., Borovikov, A., Molod, A., and Vernieres, G. [14-Dec-18]. El Niño/Southern Oscillation (ENSO) has far reaching global climatic impacts and so extending useful ENSO forecasts would be of great benefit for society. However, one key variable that has yet to be fully exploited within coupled forecast systems is accurate estimation of near-surface ocean density. Satellite Sea surface salinity (SSS), combined with temperature, help to identify ocean density changes and associated mixing near the ocean surface. We assess the impact of satellite SSS observations for improving near-surface dynamics within ocean analyses and how these impact dynamical ENSO forecasts using the NASA GMAO Sub-seasonal to Seasonal (S2S Version 2) coupled forecast system (Molod et al. 2018 - i.e. NASA's contribution to the NMME project). For all initialization experiments, all available along-track absolute dynamic topography and in situ observations are assimilated using the LETKF scheme similar to Penny et al., 2013. A separate reanalysis additionally assimilates Aquarius V5 (September 2011 to June 2015) and SMAP V4 (March 2015 to present) along-track SSS data.
Kerr, Y.H., Bindlish, R., Yueh, S.H., Entekhabi, D., Rodriguez Fernandez, N., Lee, T., Wigneron, J-P., Lagerloef, G.S.E., Boutin, J., Escorihuela, M.J., and Anterrieu, E. [13-Dec-18]. The Soil Moisture and Ocean Salinity (SMOS) mission was launched in November 2009 and is still fully operational. The Aquarius Radiometer on board SAC-D was launched in June 2011 and operated until July 2015. Finally the Soil Moisture Active and Passive (SMAP) mission was launched in January 2015 and its radiometer has been fully operational. These three missions have a unique feature in common, that is an L band radiometer. For the first time - with SMOS - the globe was operationally covered with such measurement.
Xie, X. and Liu, W.T. [14-Dec-18]. The critical dependence of the food production and agrarian economy on rainfall makes the linkage of the oceanic and terrestrial water balances through monsoon of paramount importance to many countries in South Asia. We found that the onset of summer monsoon is always preceded by sea surface temperature (SST) rises above deep convection threshold (approximately 27°C) in both the Bay of Bengal and the Arabian Sea.
Lee, T., Fournier, S., Gordon, A.L., and Sprintall, J. [14-Dec-18]. The Maritime Continent (MC) offers the only low-latitude connection of the world oceans. The oceanography within the MC regulate the characteristics of the Indonesian throughflow (ITF), linking the tropical Pacific and Indian Oceans, with strong implications to climate variability and biogeochemistry. Previous studies suggested that the relatively fresh South China Sea (SCS) waters advected by the monsoonal wind-driven ocean currents create an upper-layer "freshwater plug" in the Java Sea and Makassar Strait during boreal winter, which modulates the vertical structure and variability of the ITF. Using a suite of satellite observations to characterize the freshwater plug and examine its sources, we find that the main source of the freshwater is derived directly from the Java Sea precipitation and the Kalimantan(Borneo) rivers.
Shoup, C.G. and Bulusu, S. [13-Dec-18]. The Madden-Julian Oscillation (MJO) is a mode of intraseasonal variability that affects the tropics through air-sea interaction. Anomalous convective and clear-sky conditions associated with the MJO propagate eastward at 3-5 m s-1over the tropical Indian and Pacific Oceans repetitively with a typical period of 40-50 days. Although the MJO was first detected in the zonal wind over the tropical Pacific, its association with many other atmospheric and oceanic properties has been documented. Using salinity to study the MJO is important because it allows for atmospheric conditions to be inferred from the freshwater flux (precipitation minus evaporation) on which SSS is highly dependent.
Iler, S. and Drushka, K. [14-Dec-18]. Freshwater transport, surface fluxes, and turbulent mixing in the upper ocean are components of the global hydrologic cycle, which is critically important to study in the context of Earth's warming. Rainfall can form lenses of relatively fresh water at the ocean surface which persist until they are mixed away by turbulent processes or advection. Previous studies have suggested that stratification suppresses turbulence below and enhances turbulence within fresh lenses until lenses are mixed away by wind or nighttime convection. However, the specific relationships between wind, rain, and dissipation rates at the sea surface, and the turbulent conditions necessary to mix away fresh lenses, have not been widely studied. The objective of this work is to analyze these relationships and determine the effects of turbulence on the evolution of fresh lenses.
Fournier, S. [14-Dec-18]. Salinity is a key parameter reflecting the global water cycle changes, including impacts of precipitation, evaporation, and runoff. The water cycle is dominated by ocean-atmosphere exchanges, with 86% (76%) of the evaporation (precipitation) occurring over the ocean. The net evaporation-precipitation ends up on land, and returns to the ocean via runoff. Although runoff only accounts for about 10% of the total oceanic freshwater input, it is critical to the coastal oceans through its effects on marine biogeochemistry and physical processes. Terrigenous matters carried by rivers can have a profound impact on marine ecology, and river discharge affects the surface layer buoyancy, ocean currents, and air-sea interactions.
Ren, L., Xie, P., Xue, Y., Kumar, A., Boyer, T., and Bayler, E.J. [14-Dec-18]. A analysis of observation-based global oceanic data, comprising pentad (5-day mean) data sets of global sea-surface salinity (SSS) and associated freshwater fluxes (precipitation (P) and evaporation (E)), is developed at the NOAA Climate Prediction Center (CPC) for real-time monitoring of sub-seasonal variations. SSS analysis, at pentad temporal resolution, is developed through blending in situ measurements from the NOAA National Center for Environmental Information (NCEI), retrievals from the European Space Agency's (ESA) Soil Moisture - Ocean Salinity (SMOS) mission, the joint U.S. and Argentinian Aquarius mission, and the National Aeronautics and Space Administration's (NASA) Soil Moisture Active-Passive (SMAP) mission.
Manaster, A., Meissner, T., and Wentz., F.J. [14-Dec-18]. Our presentation gives a detailed account of the RSS Version 3 SMAP SSS release, which is scheduled for summer 2018. This release represents several significant upgrades over the previous RSS Version 2 SMAP SSS products.
Yu, L. [14-Dec-18]. The subtropical underwater (STUW) salinity maximum is a component of the Central Waters formed by subduction of the subtropical sea-surface salinity maximum (SSS-max). In recent decades, the Atlantic Central Water is found to have become saltier, thicker, and deeper, meanwhile the SSS-max water has become saltier on the edge and fresher in the center. The pattern change at the surface seems to be different from the "dry-gets-drier-and-wet-gets-wetter" (DDWW) scenario that predicts the global water cycle intensifies under the global warming and the subtropical SSS-max should also intensify. In this study, we present observation evidence showing that the subtropical net evaporation zone has widened and weakened since 1979, and the pattern change in satellite-derived evaporation-minus-precipitation (E-P) flux is consistent with the SSS-max pattern change.
Science Results from the NASA Soil Moisture Active Passive (SMAP) Satellite Prime-Phase Mission and Extended-Phase Plans
Entekhabi, D., Yueh, S.H., O'Neill, P.E., Entin, J.K., and You, T-H. [13-Dec-18]. NASA's Soil Moisture Active Passive (SMAP) mission now has completed its three-years prime-phase mission and is entering extended phase. In this presentation the science results addressing the prime-phase science requirements related to water-energy-carbon linkages over land are highlighted. Examples of SMAP data in applications (flood prediction, drought-monitoring and weather forecasts) are presented. Uses of SMAP instrument data in ocean, cryosphere and ecological sciences are also included. The presentation ends with a discussion of the new science priorities and their implementation plan for the extended phase.
Garcia-Eidell, C., Comiso, J.C., Dinnat, E., and Brucker, L. [12-Dec-18]. Sea surface salinity (SSS) retrieved from the Aquarius and Soil Moisture and Ocean Salinity (SMOS) satellites were compared with quality-controlled measurements from ship, floats, moored buoys and others to evaluate the accuracy of satellite-derived SSS data in the Southern Ocean. Latest versions of the Aquarius official release, Combined Active-Passive product, weekly polar-gridded product, as well as the SMOS BEC Objectively-Analyzed L3 product were used and results show root-mean-square error values with respect to in-situ measurement ranging from 0.25 to 0.58 psu.
De Morais Chiossi, P. and Sato, O.T. [10-Dec-18]. Observations of the temporal and spatial variability of the South Atlantic Ocean are of great scientific interest due to its influence on the regional weather and global climate through the Meridional Overturning Circulation (MOC). These changes directly affect society through variations in the pattern of rain, humidity, heat flux, and wind patterns. Despite this, there are still many gaps in understanding the full implications and impacts of ocean variability. The salinity is one of the least understood, mainly due to the absence of broad and long-term sustainable in situ data in the South Atlantic. Although, this has been changing lately with the surge of satellite missions designed to measure surface salinity, along with the increase of active Argo profilers.
Feng, Y. and Menemenlis, D. [14-Dec-18]. River plume dynamics generated considerable research interests for the past decade due to the important role in coastal ecology, biogeochemistry, shoreline morphology and climate. Previous investigators have utilized satellite ocean color or configured regional models in studying the dispersal of river plumes, with focusing on a certain continental shelf. In this study, we used high-resolution satellite sea surface salinity (SSS) observations and a globally configured 18-km resolution, eddy permitting model (ECCO2) with the river source improvement to investigate seasonal variability of river plumes at three continental shelves, namely the Northern Brazilian (NB) Shelf, the Northern Angola (NA) Basin, and the Texas-Louisiana (TL) Shelf.
Bulusu, S. [14-Dec-18]. Indian Southwest monsoon (or Summer monsoon) has strong intraseasonal oscillations in the form of active and break spells of monsoon rainfall within the monsoon season. These Intraseasonal oscillations (ISOs) are a critical driver of air-sea fluxes in the Indian Ocean. The impacts of ISOs at three major periodicities (30-90 days, 10-20 days, and synoptic 3-7 day periods) were investigated using satellite-derived estimates of sea surface salinity (SSS) from NASA's Soil Moisture Active Passive (SMAP) mission.
Schmitt, R.W. [12-Dec-18]. Most water on Earth is in the ocean and it is the ultimate source of terrestrial rain. The latent heat flux due to evaporation also dominates the transfer of energy from ocean to the atmosphere and land. While about 50% of surface evaporation from the ocean falls back as local precipitation, the rest is exported from the evaporation-dominated subtropical high pressure systems. This generates high sea surface salinity (SSS) in the subtropical gyres and low SSS in the high and low latitude oceans and coastal regions that receive runoff. About one third of the water exported from the subtropical oceans rains out on land. Anomalously large water export leads to higher SSS, guaranteeing that some part of the climate system will experience more rain; lower SSS indicates less export and less rain elsewhere. We have found that seasonal anomalies in SSS in particular areas of the ocean have remarkable skill for predicting future rainfall in certain regions on land.
Reager, J.T., Fournier, S., Vazquez, J., and Dzwonkowski, B. [13-Dec-18]. Since 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.