February 11-16, 2018
Portland, OR USAhttps://agu.confex.com/agu/os18/meetingapp.cgi
The 2018 Ocean Sciences Meeting (OSM), co-sponsored by the American Geophysical Union, the Association for the Sciences of Limnology and Oceanography, and The Oceanography Society, was held February 11-16 in Portland, Oregon. The OSM is an important venue for scientific exchange across broad marine science disciplines. Sessions addressed all aspects of oceanography, especially multidisciplinary topics, as well as presentations that reflect new and emerging research on the global ocean and society, including science education, outreach, and public policy. View the scientific program
Documents: 31Drushka, K., Asher, B., Thompson, E.J., Iyer, S., Jessup, A.T., and Clark, D.
[12-Feb-18]. A major objective of the SPURS-2 project is to understand the processes by which the patchy, shallow layers of fresher water created by rainfall on the ocean surface are transformed into the observed large-scale ocean salinity structures. Here, we focus on the specific question of the role played by turbulence in the upper meter of the ocean in mixing rain-induced fresh lenses. Jacob, M.M., Jones, W.L., Drushka, K., and Scavuzzo, M.
[12-Feb-18]. When rain falls over the ocean, it produces a vertical salinity profile that is fresher at the surface. This fresh water will be mixed downward by turbulent diffusion through gravity waves and the wind stress, which dissipates over a few hours until the upper layer (1-5 m depth) becomes well mixed. Therefore, there will be a transient bias between the bulk salinity, measured by in-situ instruments, and the satellite-measured SSS (representative of the first cm of the ocean depth). Anderson, J.E. and Riser, S.
[12-Feb-18]. During the first Salinity Processes in the Upper Ocean Regional Study (SPURS-1) a unique fleet of instrumentation was deployed in the approximate center of the evaporation dominated North Atlantic salinity maximum (~ 25°N, 38°W) to investigate the physical mechanisms controlling upper ocean salinity on a variety of space and time scales. Previous studies have shown that subsurface processes are as important as surface fluxes in maintaining the salinity maximum. In the present study, we examine the variability of mixed layer properties and subduction of high salinity water in the region during the one-year deployment period (October 2012-October 2013). Park, J-J., Park, K-A., Kang, C-K., and Liu, W.T.
[12-Feb-18]. The accuracy of satellite-observed sea surface salinity (SSS) in the northwest Pacific was evaluated by comparing with in situ salinity measurements from Argo floats and buoys. Differences between satellite SSS and in situ measurements indicated their dependence on geolocation, sea surface temperature (SST), and other oceanic and atmospheric conditions. Meissner, T., Wentz, F.J., Manaster, A., and Lindsley, R.
[12-Feb-18]. The Aquarius Version 5.0 release in late 2017 has achieved an excellent level of accuracy and significantly mitigated most of the regional and seasonal biases that had been observed in prior releases. The SMAP NASA/RSS Version 2.0 release does not quite yet reach that level of accuracy. Our presentation discusses the necessary steps that need to be undertaken in the upcoming V 3.0 of the SMAP salinity retrieval algorithm to achieve a seamless transition between the salinity products from the two instruments. We also discuss where fundamental differences in the sensors make it difficult to reach complete consistency. Farrar, J.T., Rainville, L., Shcherbina, A., Plueddemann, A.J., Hodges, B., Schmitt, R.W., Kessler, W.S., Riser, S., and Edson, J.B.
[12-Feb-18]. The Salinity Processes in the Upper-ocean Regional Study (SPURS) was a two-part field campaign focused on understanding the physical processes affecting the evolution of upper-ocean salinity: SPURS1 focused on the region of climatological maximum sea surface salinity in the subtropical North Atlantic, and SPURS2 focused on the high-precipitation region of the northeastern tropical Pacific Inter-tropical Convergence Zone. Tranchant, B.
[12-Feb-18]. An ESA project was set up in October 2016 aimed at assessing the impact of satellite sea surface salinity (SSS) data assimilation on analyses/forecasts of the 2015/16 El Niño event. To improve the uptake and use of SSS data for ocean forecasting this project is designing and performing Observing System Experiments (OSEs) of SSS using ocean modelling and assimilation systems. Melnichenko, O., Amores, A., Hacker, P.W., Maximenko, N.A., and Potemra, J.T.
[12-Feb-18]. Satellite altimetry, sea surface salinity (SSS) and Argo profile data are used to assess the importance of meridional eddy freshwater transport in the interiors of the subtropical gyres. In each of the five subtropical gyres, the role of mesoscale eddies is to pump freshwater into the gyre. The eddy freshwater transport is poleward on the equatorward side of the gyre and equatorward on the poleward side. There are marked differences between the oceans, however. For example, in the North Pacific, North Atlantic, and the South Indian Ocean, the eddy freshwater transport is equally important on both sides of the gyre, while in the South Pacific and the South Atlantic the poleward side dominates. There, the role of eddies is not only to pump freshwater into the gyre, but also to push the gyre center (determined as the SSS-maximum) equatorward. Reul, N.
[12-Feb-18]. A number of weather systems can produce extreme rainfall over the ocean, including squall lines, mesoscale convective complexes, and tropical cyclones (TCs). Intense TCs generate extreme rainfall events with rain rates that can reach local values significantly greater than 45 mm/h, generally found in the vicinity of the storm inner core, but also at the storm's periphery within the spiraling rain bands (Houze, 2010). These events can last sometimes more than 72 hours with such high rain fall rates (Shepherd et al., 2007). Due to those typically very heavy rains associated with TC, the upper ocean salinity can be substantially freshened by those very large and intermittent fresh water flux into the ocean. Thompson, E.J., Drushka, K., Asher, W., Jessup, A.T., Schanze, J.J., and Clark, D.
[12-Feb-18]. This study seeks to understand the impact of spatially and temporally varying rainfall on local salinity stratification. Previous observational studies have demonstrated a positive correlation between maximum salinity stratification and maximum rain rate when wind speed is constant. However, local rain rate and wind speed do not provide sufficient information to completely explain local salinity stratification measurements. Hackert, E.C., Kovach, R.M., Busalacchi, A.J., Ballabrera-Poy, J., and Vernières, G.
[12-Feb-18]. In this presentation we assess the impact of satellite sea surface salinity (SSS) observations on seasonal to interannual variability of tropical Indo-Pacific Ocean dynamics as well as on dynamical ENSO forecasts. Our coupled model is composed of a primitive equation ocean model for the tropical Indo-Pacific region that is coupled with the global SPEEDY atmospheric model (Molteni, 2003; Kucharski et al., 2006). Kovach, R.M., Hackert, E.C., Ballabrera-Poy, J., Busalacchi, A.J., Vernières, G., Molod, A., and Marshak, J.
[12-Feb-18]. In this presentation we assess the impact of satellite sea surface salinity (SSS) observations on dynamical ENSO forecasts for the big 2015 El Niño event. From March to June 2015, the unprecedented availability of two overlapping satellite SSS instruments, Aquarius and SMAP, allows a unique opportunity to compare and contrast forecasts generated with the benefit of these two satellite SSS observation types. We will present four distinct experiments for the overlap period that include 1) freely evolving SSS (i.e. no satellite SSS), 2) climatological SSS (i.e. WOA13 SSS), 3) Aquarius, and 4) SMAP initialization. Boyle, J.P.
[12-Feb-18]. In-situ 'near-surface' salinity data are presented as measured by an extremely small drifter buoy which was deployed in association with the Salinity Processes Upper-ocean Regional Study in the tropical Pacific (SPURS-2). This autonomous, wave-following buoy platform measures conductivity and temperature (~10 cm depth), sea state characteristics and near-surface water temperature (~2 cm depth). Köhler, J., Serra, N., Bryan, F., Johnson, B.K., and Stammer, D.
[12-Feb-18]. The physical processes that control the seasonal mixed layer salinity (MLS) budget are examined through a combined analysis of an ensemble-mean sea surface salinity (SSS) product based on SMOS and Aquarius data and a high-resolution ocean model simulation using the National Center for Atmospheric Research Community Earth System Model driven by COREv2 forcing. The analyses reveal that SSS variations can be used as a proxy for MLS variations, taking therefore advantage of the high spatial and temporal resolution of the satellite SSS data. Fournier, S., Vialard, J., Lengaigne, M., Lee, T., Gierach, M.M., and Chaitanya, A.V.S.
[12-Feb-18]. The Bay of Bengal receives large amounts of freshwater from the Ganga-Brahmaputra river during the summer monsoon. The resulting upper-ocean freshening influences seasonal rainfall, cyclones, and biological productivity. Sparse in situ observations suggest that the East India Coastal Current (EICC) transports these freshwaters southward after the monsoon as an approximately 200-km wide, 2000-km long 'river in the sea' along the East Indian coast. Sea surface salinity (SSS) from the Soil Moisture Active Passive (SMAP) satellite provides unprecedented views of this peculiar feature from intraseasonal to interannual timescales Parambil, A.V., Vialard, J., Lengaigne, M., Keerthi, M.G., Boutin, J., Vergely, J-L., and Marchand, S.
[12-Feb-18]. The Bay of Bengal (BoB) exhibits a contrasted sea surface salinity (SSS), with very fresh water induced by heavy monsoonal precipitation and river discharge to the north, and saltier water to the south. The strong northern BoB haline stratification is believed to limit vertical mixing of heat and nutrients, with strong impacts on tropical cyclones intensity and primary production. While in situ data is denser since the advent of the Argo program, it is still far from sufficient to provide complete maps of seasonal SSS. The advent of satellite salinity remote sensing (SMOS, AQUARIUS, SMAP) offers a unique opportunity to provide synoptic maps of the BoB SSS every ~8 days. While recent studies have shown a good performance of the so far ~2 years SMAP record in the BoB, the Aquarius mission is now over, and previous retrievals from the longer (2010 to now) SMOS mission did not perform well in this region. In this work, we provide an in-depth assessment of the new CATDS level-3 2010-2017 SSS from the SMOS instrument Hodges, B., Schmitt, R.W., and Fratantoni, D.M.
[12-Feb-18]. At night, the ocean surface cools, forming a superadiabtic temperature gradient that drives convection. The subsurface structure of these convective motions is investigated with measurements of temperature and salinity from autonomous surface vehicles (Wave Gliders). The observations were made as part of NASA's Salinity Processes in the Upper Ocean Regional Study (SPURS) and include measurements with high vertical and horizontal resolution in the upper meter made by a novel 'Salinity Rake' fitted to a Wave Glider. The vertical gradients, the horizontal convective scales, and the diel cycle of convection are characterized. Edson, J.B., Clayson, C.A., Farrar, J.T., Paget, A., and Graham, R.
[12-Feb-18]. A comprehensive set of atmospheric and oceanic data was collected on the R/V Revelle and 3-m discus buoy during the SPURS-2 experiment in the tropical Eastern Pacific Ocean. These measurements are being used to quantify the amount of precipitation versus evaporation (P-E) that drives a freshwater flux into or out of the upper ocean, respectively. Asher, W., Drushka, K., Thompson, E.J., Jessup, A.T., Clark, D.
[12-Feb-18]. Rain on the sea surface can produce a stable near-surface layer of fresher water with a lifetime of O(1-10) hours and a depth of O(1) meter. The surface salinity decrease is a function of wind speed and rain rate, with surface turbulence likely being an important factor in determining the formation and evolution of a fresh lens. Although it is known that both rain and wind generate surface turbulence, the relative importance of rain- and wind-generated turbulence in governing fresh lenses is an open question due to lack of field measurements of surface turbulence during rain. Direct measurement of surface turbulence and vertical profiles of salinity during rain are needed to understand whether the turbulence generated by rain in the upper few centimeters has an impact on fresh lenses generated by rain. Supply, A., Boutin, J., Vergely, J-L., Hasson, A.E.A., Reverdin, G.P., Mallet, C., and Viltard, N.
[12-Feb-18]. Two L-Band (1.4GHz) microwave radiometer missions, Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active and Passive (SMAP), currently provide sea-surface salinity (SSS) measurements. At this frequency, salinity is measured in the first centimetre below the sea surface, which makes it very sensitive to the presence of fresh water lenses linked to rain events. A relationship between salinity anomaly (?S) and rain rate (RR) is derived in the Pacific intertropical convergence zone from SMOS and SMAP SSS measurements, and the RR from the Special Sensor Microwave Imager/Sounder (SSMIS). We look at the robustness of the relationship in various areas. Tesdal, J-E., Abernathey, R., Goes, J., Gordon, A.L., and Haine, T.W.N.
[12-Feb-18]. Examination of a range of salinity products collectively suggest widespread freshening of the North Atlantic from the mid-2000 to the present. Monthly salinity fields reveal negative trends that differ in magnitude and significance between western and eastern regions of the North Atlantic. These differences can be attributed to the large negative interannual excursions in salinity in the western subpolar gyre and the Labrador Sea, which are not apparent in the central or eastern subpolar gyre. This study demonstrates that temporal trends in salinity in the northwest (including the Labrador Sea) are subject to mechanisms that are distinct from those responsible for the salinity trends in central and eastern North Atlantic. Lagerloef, G.S.E., Kao, H-Y., and Carey, D.
[12-Feb-18]. An important scientific goal for satellite salinity observations is to document oceanic climate trends and their link to changes in the water cycle. This study is a re-examination of seasonal to interannual sea surface salinity (SSS) variations from more recent analyses of V5.0 reprocessing of the Aquarius satellite data, Sep 2011 to May 2015. Sensor calibration over these time scales has been a concern, and the V5.0 includes improved calibration reference data compared to previous versions, which will be explained. Gomez-Valdes, J. and Vazquez, J.
[12-Feb-18]. Data from NASA's Soil Moisture Active Passive Mission (SMAP) and from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) were used to examine the freshening that occurred during the Northeast Pacific Warming of 2014-2016. Overall the freshening was found to be related to the warming and the weakening of coastal upwelling. Boutin, J., Vergely, J-L., Marchand, S., D'Amico, F., Hasson, A.E.A., Kolodziejczyk, N., Reul, N., and Reverdin, G.P.
[12-Feb-18]. A main contribution of satellite Sea Surface Salinity (SSS) is the spatio-temporal monitoring of fresh water plumes at mesoscale. In case of the Soil Moisture and Ocean Salinity (SMOS) satellite mission, this monitoring was often hampered due to the land-sea contamination of the SMOS interferometric measurement. Kolodziejczyk et al. (2016) developed a methodology to mitigate the SMOS systematic errors in the vicinity of continents, using self-consistency properties of SMOS SSS, that greatly improved the quality of SMOS SSS but the very fresh SSS anomalies remained often overestimated. Iyer, S. and Drushka, K.
[12-Feb-18]. Freshwater transport, fluxes, and dissipation in the upper ocean are major components of the global hydrologic cycle, which is critically important to study considering the earth's warming climate. It is known that rainfall can form lenses of relatively fresh water at the ocean surface which persist until they are mixed away by turbulent processes. 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 atmospheric parameters (e.g., wind, rain, heat flux) and turbulent dissipation rates at the sea surface have not been widely studied. The objective of this work is to quantify these relationships, determine how the transfer of turbulent energy controls the evolution of fresh lenses, and assess how these processes may impact the large-scale water cycle. Fore, A., Yueh, S.H., Tang, W., and Hayashi, A.
[12-Feb-18]. The Soil Moisture Active Passive (SMAP) mission was launched January 31st, 2015. It is designed to measure the soil moisture over land using a combined active / passive L-band system. Due to the Aquarius mission, L-band model functions for ocean winds and salinity are already mature and have been directly applied to the SMAP mission. In contrast to Aquarius, the higher resolution and scanning geometry of SMAP allows for wide-swath ocean winds and salinities to be retrieved. In this talk we present the SMAP Sea Surface Salinity (SSS) dataset and algorithm. Maamaatuaiahutapu, K., Witting, J., and Martinez, E.C.
[12-Feb-18]. Spreading and transport of the Maximum Salinity Core Layer (MSCL), defined as water with salinity higher than 36 psu, is investigated from hydrographic data sets collected along twelve cross-sections by the Sea education Association (SEA) between Tahiti and the equator from 2008 and 2015, the ARGO data objectively mapped from JAMSTEC and satellite remote sensing. Aquarius sea surface salinity data show that the MSCL occupied an area averaged over time of about 6.7 106 km2
with an increase of the occupancy in 2015. Schanze, J.J., Springer, S.R., Lagerloef, G.S.E., and Thompson, E.J.
[12-Feb-18]. An instrument capable of measuring surface salinity and temperature at satellite radiometric depths of 1-2 cm (the 'Salinity Snake') was deployed during two cruises of the Salinity Processes in the Upper Ocean Regional Study 2 (SPURS-2) during August-September 2016 and SPURS-2 and October-November 2017. Additional measurements at 1m, 2m, and 5m from through-hull systems allow the near-surface stratification to be estimated. Approximately 100 freshwater lenses with significant (>0.5 g/kg) salinity differences between the surface and 5m were found, ranging in size from 3 to 50 km. A significant portion (>40%) of these lenses were encountered during calm conditions without any measured precipitation on the ship. This suggests the potential persistence of such freshwater lenses for many hours or even days, and a strong dependence on wind-driven mixing, which acts to destroy very-near surface stratification. Ruiz-Etcheverry, L., Maximenko, N.A., and Melnichenko, O.
[12-Feb-18]. The Equatorial Atlantic Ocean is a region dominated by the seasonal trade winds and Inter Tropical Convergence Zone (ITCZ). It is also marked by the existence of a strong sea surface temperature (SST) front due to the formation of the equatorial cold tongue. These features are believed to have strong effects on the atmospheric circulation in the region and thus climate. Little, however, is known about the salinity front, whose study became possible only with the release of high-resolution salinity products. In this study, we use three years of sea surface salinity (SSS) observations from Aquarius satellite to investigate the spatial structure, temporal variability, and driving dynamics of the frontal SSS feature in the equatorial Atlantic, its evolution between seasons and differences between individual years. Levang, S. and Schmitt, R.W.
[12-Feb-18]. Global patterns of salinity are an imprint of the atmospheric water cycle, which tends to intensify as the climate warms, making fresh regions fresher and salty regions saltier. However, transport and stirring of salt in the ocean complicate the details of this response. Here we use the Simple Ocean Data Assimilation (SODA) v3.4.1 to investigate timescales of exchange between evaporative and precipitative regimes of the world oceans. Bingham, F., Busecke, J.J.M., Gordon, A.L., Giulivi, C.F., and Li, Z.
[12-Feb-18]. The sea surface salinity (SSS) maximum area of the South Pacific subtropical gyre was examined using satellite and in situ data. The mean center of the feature is at 21°S,120°W. It tilts northwest-southeast and has a size of about 30 degrees in longitude and 8 degrees in latitude as measured by the area of a given surface isohaline (36.258). The area enclosed by this isohaline has nearly doubled between 2012 and 2017 from 2 to 4X106 km2. The mean SSS within the feature has been increasing as well as maintaining a robust seasonal cycle with maximum SSS in winter (June-July). We tracked the east-west and north-south movement of the feature's centroid. Most significantly, it has been moving northward steadily since 2011. The different datasets generally agree, but SMAP and binned Aquarius ('SCI') tend to be outliers.