ALBERT

Description: Comparison of the simulated upper-ocean vertical structure using 1-dimensional mixed-layer models Sonaljit Mukherjee and Amit Tandon Ocean Sci. Discuss., doi:10.5194/os-2016-45,2016 Manuscript under review for OS (discussion: open, 0 comments) Atmospheric fluxes influence the momentum and scalar properties in the upper-cean. Buoyancy fluxes result in a diurnal variability in the sea-surface temperature (SST), whereas the wind stress forms near-inertial currents in the mixed layer (ML). In this study, we investigate the contrasts between the simulated SST and the vertical structure of the temperature and shear by three different mixing models: the PWP bulk mixed-layer model, the KPP non-local boundary layer model and the κ−ϵ local mixing model. We choose two upper-ocean datasets for our studies, namely the SWAPP (1990) and the MLML (1991). The SWAPP dataset shows the presence of strong near-inertial shear below the ML and negligible near-inertial shear within the ML. The MLML dataset shows a negligible rise in the SST during the first 22 day mixing phase, which is followed by a steep rise by 6 °C during the subsequent 75 day restratification phase. Comparison with the SWAPP dataset shows that the KPP and κ−ϵ models form strong shear near the surface due to weak eddy viscosities, thus producing a thin shear layer over the entire range of frequencies in the wind stress. At the ML base, the models form an inertial and a diurnal maximum. The inertial maximum extends over a substantial range of depths, and is continuous for the κ−ϵ model but discontinuous for the KPP and PWP models. Comparison with the MLML dataset reveals that the KPP yields the largest SST amplitude over a 24-hour diurnal cycle, and is followed by the κ−ϵ and PWP. However, the net warming of SST at the end of the diurnal cycle is stronger for the PWP compared to κ−ϵ and KPP. The PWP also forms stronger temperature gradients at the ML base compared to κ−ϵ and KPP. Over multiple diurnal cycles, the shallowing and deepening of the mixed layer results in multiple sharp temperature gradients in PWP, thus forming a serrated vertical profile that remains unaffected during the restratification phase of the MLML dataset.

Description: Developing European operational oceanography for Blue Growth, climate change adaptation and mitigation, and ecosystem-based management Jun She, Icarus Allen, Erik Buch, Alessandro Crise, Johnny A. Johannessen, Pierre-Yves Le Traon, Urmas Lips, Glenn Nolan, Nadia Pinardi, Jan H. Reißmann, John Siddorn, Emil Stanev, and Henning Wehde Ocean Sci., 12, 953-976, doi:10.5194/os-12-953-2016, 2016 This white paper addresses key scientific challenges and research priorities for the development of operational oceanography in Europe for the next 5–10 years. Knowledge gaps and deficiencies are identified in relation to common scientific challenges in four EuroGOOS knowledge areas: European ocean observations, modelling and forecasting technology, coastal operational oceanography, and operational ecology.

Description: Freshening of Antarctic Intermediate Water in the South Atlantic Ocean in 2005–2014 Wenjun Yao and Jiuxin Shi Ocean Sci. Discuss., doi:10.5194/os-2016-54,2016 Manuscript under review for OS (discussion: open, 0 comments) Antarctic Intermediate Water (AAIW) in the South Atlantic Ocean has experienced basin-scaled freshening from 2005 to 2014, reflected by the Argo gridded products. Two zonal sections of WOCE observation also revealed a similar quasi-decadal signal. Our analysis revealed that such freshening was induced by the contemporaneous freshwater input in the AAIW ventilation region and the reduced more saline water carried by Agulhas Leakage.

Description: Changes in extreme regional sea level under global warming S.-E. Brunnabend, H. A. Dijkstra, M. A. Kliphuis, H. E. Bal, F. Seinstra, B. van Werkhoven, J. Maassen, and M. van Meersbergen Ocean Sci. Discuss., doi:10.5194/os-2016-57,2016 Manuscript under review for OS (discussion: open, 0 comments) An important contribution to future changes in regional sea level extremes is due to the changes in intrinsic ocean variability, in particular ocean eddies. Here, we study a scenario of future dynamic sea level (DSL) extremes using a strongly eddying version of the Parallel Ocean Program. Changes in 10-year return time DSL extremes are very inhomogeneous over the globe and are related to changes in ocean currents and corresponding regional shifts in ocean eddy pathways.

Description: A stable Faroe Bank Channel overflow 1995–2015 Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, and Svein Østerhus Ocean Sci. Discuss., doi:10.5194/os-2016-56,2016 Manuscript under review for OS (discussion: open, 0 comments) The Faroe Bank Channel is one of the main passages for the flow of cold dense water from the Arctic into the depths of the World Ocean where it feeds the deep branch of the AMOC transporting heat and carbon dioxide from the atmosphere into the deep ocean. Based on in situ measurements we show that the volume transport of this flow has been stable from 1995 to 2015. The water has warmed, but has not become less dense. Thus, this branch of the AMOC did not weaken during the last two decades.

Description: Accessing diverse data comprehensively – CODM, the COSYNA data portal Gisbert Breitbach, Hajo Krasemann, Daniel Behr, Steffen Beringer, Uwe Lange, Nhan Vo, and Friedhelm Schroeder Ocean Sci., 12, 909-923, doi:10.5194/os-12-909-2016, 2016 The coastal observation system COSYNA aims to describe the physical and biogeochemical state of a regional coastal system. The COSYNA data management (CODM) is the link between observations, model results and data usage. The challenge for CODM is the integration of diverse data sources in terms of parameters, dimensionality and observation methods to gain a comprehensive view of the observations. How this is achieved is described in the paper.

Description: Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009 Abdirahman M. Omar, Ingunn Skjelvan, Svein Rune Erga, and Are Olsen Ocean Sci., 12, 937-951, doi:10.5194/os-12-937-2016, 2016 We have determined, for the first time, the seasonal changes and controlling processes of ocean acidification parameters across western Norwegian fjords, based on data obtained mainly with sensors on board a commercial ship, MS Trans Carrier , in 2005–2009. The study fills an important gap in our knowledge on ocean acidification in western Norwegian fjords, which are important ecosystems: important recreation areas, marine pathways, spawning grounds for different fish species, etc.

Description: Technical note: GODESS – a profiling mooring in the Gotland Basin Ralf D. Prien and Detlef E. Schulz-Bull Ocean Sci., 12, 899-907, doi:10.5194/os-12-899-2016, 2016 A profiling mooring with an interdisciplinary suite of sensors for water depths up to 300 m is described in this note. It can be programmed to take profiles through the water column at set times or intervals and with the standard set of batteries is able to profile about 34 km in total (e.g. 200 profiles of 170 m profiling each). The mooring was designed to observe the dynamics of the redoxcline in the Gotland Basin over periods of up to 3 months.

Description: Sub-basin scale sea level budgets from satellite altimetry, Argo floats and satellite gravimetry in the North Atlantic Marcel Kleinherenbrink, Riccardo Riva, and Yu Sun Ocean Sci. Discuss., doi:10.5194/os-2016-50,2016 Manuscript under review for OS (discussion: open, 0 comments) Satellite altimetry measures changes in sea level, while satellite gravimetry measures mass changes and from Argo temperature and salinity profiles one can infer steric sea level. For the first time it is shown that the mass and steric components match in most cases the total sea level measured by altimetry on a sub-basin scale in terms of trend, annual amplitude and interannual variability. We also find that the choice of gravity field filter is essential to close the budget.

Description: Seiche excitation in a highly stratified fjord of southern Chile: the Reloncaví fjord Manuel I. Castillo, Oscar Pizarro, Nadin Ramirez, and Mario Caceres Ocean Sci. Discuss., doi:10.5194/os-2016-42,2016 Manuscript under review for OS (discussion: open, 0 comments) Here we present the results of an intensive physical oceanography study on the Reloncavi fjord (41.5º S, 72.5º W) focused on the subinertial time-scale. The along-fjord currents presented 3 days oscillations which were consistent with the natural internal period of oscillation of the fjord basin (internal seiche). This oscillation could exexplain more than 44 % of the 3 days variability and contributed levels of kinetic energy as large as the tidal currents.

Description: Evaluation of Peaks-Over-Threshold Method Soheil Saeed Far and Ahmad Khairi Abd. Wahab Ocean Sci. Discuss., doi:10.5194/os-2016-47,2016 Manuscript under review for OS (discussion: open, 0 comments) In this paper, two commonly used extreme value analysis models have been developed (POT and GPD models). Both models use threshold values to censor a range of data. The results of this study show the two models are very sensitive to any changes in threshold value. Moreover, the POT model has shown some imperfections in determining true threshold value and a best fitting distribution function. Two methods were proposed by this paper to deal with the limitations in order to improve the model.

Description: The importance of external climate forcing for the variability and trends of coastal upwelling in past and future climate Nele Tim, Eduardo Zorita, Birgit Hünicke, Xing Yi, and Kay-Christian Emeis Ocean Sci., 12, 807-823, doi:10.5194/os-12-807-2016, 2016 The impact of external climate forcing on the four eastern boundary upwelling systems is investigated for the recent past and future. Under increased radiative forcing, upwelling-favourable winds should strengthen due to unequal heating of land and oceans. However, coastal upwelling simulated in ensembles of climate simulations do not show any imprint of external forcing neither for the past millennium nor for the future, with the exception of the strongest future scenario.

Description: Marine mammal tracks from two-hydrophone acoustic recordings made with a glider Elizabeth T. Küsel, Tessa Munoz, Martin Siderius, David K. Mellinger, and Sara Heimlich Ocean Sci. Discuss., doi:10.5194/os-2016-48,2016 Manuscript under review for OS (discussion: open, 0 comments) An ocean glider was tested during the REP14-MED experiment off the western coast of the Island of Sardinia as a platform for recording sounds produced by whales and dolphins using two sensors. Sperm whale clicks as well as dolphin clicks and whistles were identified in the recordings. Automatically detected sperm whale clicks were used to estimate animal tracks. Such information is useful for marine mammal density estimation studies that use passive acoustics.

Description: Seasonal, Spring-Neap and Tidal Variation of Hydrodynamics and Water Constituents in the Mouth of the Elbe Estuary, Germany Jens Kappenberg, Michael Berendt, Nino Ohle, Rolf Riethmüller, Dagmar Schuster, and Thomas Strotmann Ocean Sci. Discuss., doi:10.5194/os-2016-7,2016 Manuscript under review for OS (discussion: open, 0 comments) Results of long-term measurements of CTD, current velocity, turbidity, and dissolved oxygen from three stations in the mouth of the Elbe Estuary in northern Germany are presented for the period of 2012 and 2013. The focus is on a station named HPA-Elbe 1, which is part of the COSYNA coastal observing system for northern and arctic seas, but data from two neighbouring stations are also presented for comparison and to bridge gaps in the time-series of HPA-Elbe 1. The variations of the variables exhibit distinct tidal patterns related to the longitudinal estuarine gradients of the water constituents and local sediment dynamics. On longer time-scales, spring-neap variability is observed, most prominently in the hydrodynamics. On the seasonal scale, the water temperature influences the degradation processes, which deplete the dissolved oxygen on the one hand and increase the oxygen contents by biological respiration on the other hand. Freshwater events from the catchment play an important role for sediment dynamics and mixing of riverine and coastal waters in the brackish water reach of the estuary. The periods of the deployment of the stations comprise the severest river flood observed so far in the Elbe in June 2013. The effects of the flood at the stations and along the estuary consist of a rapid flushing of the mixing zone and the turbidity maximum to the outer estuary and the transition to freshwater conditions from Hamburg to the mouth at Cuxhaven. The impact of the river flood at the stations is more pronounced in changes in salinity than in turbidity. The restoration of estuarine salinity and turbidity values comparable to those before the river flood took several months.

Description: Ocean Forecasting: From Regional to Coastal Scales Emil V. Stanev, Johannes Schulz-Stellenfleth, Joanna Staneva, Sebastian Grayek, Sebastian Grashorn, Arno Behrens, Wolfgang Koch, and Johannes Pein Ocean Sci. Discuss., doi:10.5194/os-2016-25,2016 Manuscript under review for OS (discussion: open, 0 comments) This paper describes coastal ocean forecasting practices exemplified for the North and Baltic Sea. It identifies new challenges, most of which are associated with the non-linear behavior of coastal ocean. It describes assimilation of remote sensing, in situ and HF radar data, prediction of wind waves and storm surges, as well as possible applications to search and rescue operations, and modelling support for assessing the environmental impact of wind parks. Concepts for seamless approaches to li

Description: A possibility of large scale intrusions generation in the Arctic Ocean under stable-stable stratification: an analytical consideration Natalia Kuzmina Ocean Sci. Discuss., doi:10.5194/os-2016-15,2016 Manuscript under review for OS (discussion: open, 0 comments) Some analytical solutions are found for the problem of three-dimensional instability of a weak geostrophic flow with linear velocity shear taking into account vertical diffusion of buoyancy. The analysis is based on the potential vorticity equation in a long-wave approximation when the horizontal scale of disturbances is taken to be much larger than the local baroclinic Rossby radius. It is hypothesized that the solutions found can be applied to describe stable and unstable disturbances on a planetary scale with respect, especially, to the Arctic Basin, where weak baroclinic fronts with typical temporal variability periods of the order of several years or more are observed and the beta-effect is negligible. Stable (decaying with time) solutions describe disturbances that, in contrast to the Rossby waves, can propagate to both the west and east, depending on the sign of the linear shear of geostrophic velocity. The unstable (growing with time) solutions are applied to describe large-scale intrusions at baroclinic fronts under the stable–stable thermohaline stratification observed in the upper layer of the Polar Deep Water in the Eurasian Basin. The proposed description of intrusive layering can be considered as a possible alternative to the mechanism of interleaving due to the differential mixing.

Description: Multi-sensor in situ observations to resolve the sub-mesoscale features in the stratified Gulf of Finland, Baltic Sea Urmas Lips, Villu Kikas, Taavi Liblik, and Inga Lips Ocean Sci., 12, 715-732, doi:10.5194/os-12-715-2016, 2016 Multi-platform high-resolution observations in the Gulf of Finland in the summers of 2009–2012 revealed pronounced variability at the sub-mesoscale in the presence of mesoscale features, such as upwelling/downwelling events, fronts, and eddies. The analysis suggests that the sub-mesoscale processes could contribute considerably to the downscale energy cascade and play a major role in phytoplankton growth enhancement via vertical transport and re-stratification of the surface layer.

Description: First year of the new Arctic AWIPEV-COSYNA cabled Underwater Observatory in Kongsfjorden, Spitsbergen Philipp Fischer, Max Schwanitz, Reiner Loth, Uwe Posner, Markus Brand, and Friedhelm Schröder Ocean Sci. Discuss., doi:10.5194/os-2016-52,2016 Manuscript under review for OS (discussion: open, 0 comments) We observed oceanographic and community data from October 2013 to November 2014 in the shallow waters of Kongsfjorden on the west coast of Svalbard (Norway) using remote controlled hydrographic and optic sensors. Daily vertical profiles of temperature, salinity and turbidity were sampled together with stereo images of the macrobiotic community, including fish. A distinct seasonal cycle in total species abundances was found with surprisingly high animal counts during the polar winter.

Description: GEM: A Dynamic Tracking Model for Mesoscale Eddies in the Ocean Qiu-Yang Li, Liang Sun, and Sheng-Fu Lin Ocean Sci. Discuss., doi:10.5194/os-2016-49,2016 Manuscript under review for OS (discussion: open, 0 comments) Genealogical Evolution Model (GEM) is an efficient logical model used to track dynamic evolution of mesoscale eddies in the ocean. It can distinguish different dynamic processes (e.g., merging and splitting) within a dynamic evolution pattern with a two-dimensional vector. All of the computational steps are linear and do not include iteration. It is very fast and is potentially useful for studying dynamic processes in other related fields, e.g., the dynamics of cyclones in meteorology.

Description: Observed and simulated full-depth ocean heat-content changes for 1970–2005 Lijing Cheng, Kevin E. Trenberth, Matthew D. Palmer, Jiang Zhu, and John P. Abraham Ocean Sci., 12, 925-935, doi:10.5194/os-12-925-2016, 2016 A new method of observing ocean heat content throughout the entire ocean depth is provided. The new method is compared with simulated ocean heat content changes from climate models. The comparisons are carried out in various depth layers of the ocean waters. It is found that there is excellent agreement between the models and the observations. Furthermore, we propose that changes to ocean heat content be used as a fundamental metric to evaluate climate models.

Description: Transition to El Niño conditions in the eastern tropical Pacific in October 2015 Lothar Stramma, Tim Fischer, Damian S. Grundle, Gerd Krahmann, Hermann W. Bange, and Christa A. Marandino Ocean Sci. Discuss., doi:10.5194/os-2016-14,2016 Manuscript under review for OS (discussion: open, 0 comments) Results from a research cruise on RV Sonne to the eastern tropical Pacific in October 2015 during the 2015–2016 El Niño show the transition of current, hydrographic and nutrient conditions to El Niño conditions in the eastern tropical Pacific in October 2015. Although in early 2015 the El Niño was strong and in October 2015 showed a clear El Niño influence on the EUC, in the eastern tropical Pacific the measurements only showed developing El Niño water mass distributions.

Description: Wind changes above warm Agulhas Current eddies M. Rouault, P. Verley, and B. Backeberg Ocean Sci., 12, 495-506, doi:10.5194/os-12-495-2016, 2016 Our study shows that wind increases of 4 to 8 m s −1 above warm Agulhas Current eddies are not uncommon. This should be taken seriously when sailing in the “Roaring Forties”. Using microwave remote sensing from satellite is a very useful tool for monitoring such eddies. This could be displayed operationally to provide vessels with early warning and to indicate where there are likely to sustain stronger wind. The result is also relevant for the Gulf Stream and the Kuroshio Current.

Description: Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers Miles G. McPhee, Craig L. Stevens, Inga J. Smith, and Natalie J. Robinson Ocean Sci., 12, 507-515, doi:10.5194/os-12-507-2016, 2016 Measurements of turbulent heat fluxes in tidally modulated flow of supercool seawater under Antarctic land-fast sea ice show that turbulent heat exchange at the ocean–ice boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing. Also, the conditions cause platelet ice growth to form on the underside of the sea ice which increases the hydraulic roughness (drag) of fast ice compared to ice without platelets.

Description: Continuous seiche in bays and harbors Joseph Park, Jamie MacMahan, William V. Sweet, and Kevin Kotun Ocean Sci., 12, 355-368, doi:10.5194/os-12-355-2016, 2016 Bays and harbors naturally resonate with standing waves, known as seiches. Seiches are usually considered temporary, however, we identify small-amplitude, continuously present seiches in six bays around the Pacific and suggest that tidally forced, continental shelf resonances are a primary driver of continuous seiches.

Description: Indian Ocean Dipole modulated wave climate of eastern Arabian Sea T. R. Anoop, V. Sanil Kumar, P. R. Shanas, J. Glejin, and M. M. Amrutha Ocean Sci., 12, 369-378, doi:10.5194/os-12-369-2016, 2016 Using measured, modeled and reanalysis wave data and reanalysis wind data, we show that the Indian Ocean Dipole (IOD) plays a role in the variability of wave climate of the eastern Arabian Sea (AS). The change in wind field over the AS due to IOD influences the generation or dissipation of wave field and hence causes the decrease in northwest short period waves during positive IOD and increase during negative IOD.

Description: IEOOS: the Spanish Institute of Oceanography Observing System Elena Tel, Rosa Balbin, Jose-Manuel Cabanas, Maria-Jesus Garcia, M. Carmen Garcia-Martinez, Cesar Gonzalez-Pola, Alicia Lavin, Jose-Luis Lopez-Jurado, Carmen Rodriguez, Manuel Ruiz-Villarreal, Ricardo F. Sánchez-Leal, Manuel Vargas-Yáñez, and Pedro Vélez-Belchí Ocean Sci., 12, 345-353, doi:10.5194/os-12-345-2016, 2016 The Spanish Institute of Oceanography supports different operational programmes in order to observe and measure ocean characteristics. Their combination allows responses to ocean research activities and marine ecosystem management, as well as official agency requirements and industrial and main society demands. All these networks are linked to international initiatives, framed largely in supranational Earth observation sponsored by the United Nations and the European Union.

Description: Remote sensing of chlorophyll in the Baltic Sea at basin scale from 1997 to 2012 using merged multi-sensor data Jaime Pitarch, Gianluca Volpe, Simone Colella, Hajo Krasemann, and Rosalia Santoleri Ocean Sci., 12, 379-389, doi:10.5194/os-12-379-2016, 2016 Several operational satellite chlorophyll a (CHL) in the Baltic Sea were tested at a regional scale. Comparison to an extensive in situ CHL dataset showed low linearity. Bias-corrected CHL annual cycles were computed. The Gulf of Bothnia displays a single CHL peak during spring. In Skagerrak and Kattegat, there is a small bloom in spring and a minimum in summer. In the central Baltic, CHL follows a dynamic of a mild spring bloom followed by a much stronger bloom in summer.

Description: Effects of surface current/wind interaction in an eddy-rich general ocean circulation simulation of the Baltic Sea H. Dietze and U. Löptien Ocean Sci. Discuss., doi:10.5194/os-2016-12,2016 Manuscript under review for OS (discussion: open, 0 comments) Winds blowing over the ocean drive ocean currents. The oceanic response to winds is, in turn, influenced by ocean currents. Theoretical considerations suggest that the latter effect is especially pronounced in the Baltic Sea where the spatial scale of current variability is much smaller than in the open ocean. The study presented here puts theses theoretical considerations in a high-resolution ocean circulation model of the Baltic Sea to the test.

Description: 〈b〉A simple predictive model for the eddy propagation trajectory in the South China Sea〈/b〉〈br〉 Jiaxun Li, Guihua Wang, Huijie Xue, and Huizan Wang〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-116,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 A novel predictive model is built for eddy propagation trajectory using the multiple linear regression method. This simple model has related various oceanic parameters to eddy propagation position changes in the South China Sea (SCS). The performance of the proposed model is examined in the SCS based on twenty years of satellite altimeter data, and demonstrates its significant forecast skills over a 4-week forecast window comparing to the traditional persistence method.

Description: 〈b〉Heat, salt, and volume transports in the eastern Eurasian Basin of the Arctic Ocean from 2 years of mooring observations〈/b〉〈br〉 Andrey V. Pnyushkov, Igor V. Polyakov, Robert Rember, Vladimir V. Ivanov, Matthew B. Alkire, Igor M. Ashik, Till M. Baumann, Genrikh V. Alekseev, and Arild Sundfjord〈br〉 Ocean Sci., 14, 1349-1371, https://doi.org/10.5194/os-14-1349-2018, 2018〈br〉 This study describes along-slope volume, heat, and salt transports derived from observations collected between 2013 and 2015 in the eastern Eurasian Basin of the Arctic Ocean using a cross-slope array of six moorings. Inferred transport estimates may have wide implications and should be considered when assessing high-latitude ocean dynamics.

Description: 〈b〉Arctic Mediterranean Exchanges: A consistent volume budget and trends in transports from two decades of observations〈/b〉〈br〉 Svein Østerhus, Rebecca Woodgate, Héðinn Valdimarsson, Bill Turrell, Laura de Steur, Detlef Quadfasel, Steffen M. Olsen, Martin Moritz, Craig M. Lee, Karin Margretha H. Larsen, Steingrímur Jónsson, Clare Johnson, Kerstin Jochumsen, Bogi Hansen, Beth Curry, Stuart Cunningham, and Barbara Berx〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-114,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 1 comment)〈br〉 Two decades of observations of the Arctic Mediterranean (AM) exchanges shows that the exchanges have been stable in terms of volume transport during a period when many other components of the global climate system have changed. The total AM-import is found to be 9.1 Sv and has a seasonal variation of amplitude close to 17 Sv and maximum import in October. Roughly one third of the imported water leaves the AM as surface outflow with the remain two thirds leaving.

Description: 〈b〉Do sun spots influence the onset of ENSO and PDO events in the Pacific Ocean?〈/b〉〈br〉 Franklin Isaac Ormaza-González and María Esther Espinoza-Celi〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-125,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 Sea surface temperature is affected by sun energy which in turn varies in time due to astronomical factors and sun activity. The activity can be estimated by sun spots (SS). Some oceanographic events like inter-annual El/La Niño/Niña as well as decadal processes should be affected by SS. It was found correlation between SS and various oceanographic indexes in time series from 1954 to 2017. This fact should be considered when dealing and modelling forecasts of such indexes.

Description: 〈b〉Contribution of future wide-swath altimetry missions to ocean analysis and forecasting〈/b〉〈br〉 Antonio Bonaduce, Mounir Benkiran, Elisabeth Remy, Pierre Yves Le Traon, and Gilles Garric〈br〉 Ocean Sci., 14, 1405-1421, https://doi.org/10.5194/os-14-1405-2018, 2018〈br〉 〈p〉The impact of forthcoming wide-swath altimetry missions on the ocean analysis and forecasting system was investigated by means of OSSEs (observing system simulation experiments). These experiments were performed with a regional data assimilation system, implemented in the Iberian–Biscay–Ireland (IBI) region, at 〈span〉1∕12〈/span〉〈span〉〈sup〉∘〈/sup〉〈/span〉 resolution using simulated observations derived from a fully eddy-resolving free simulation at 〈span〉1∕36〈/span〉〈span〉〈sup〉∘〈/sup〉〈/span〉 resolution over the same region. The objective of the experiments was to assess the ability of different satellite constellations to constrain the ocean analyses and forecasts, considering both along-track altimeters and future wide-swath missions; consequently, the capability of the data assimilation techniques used in the Mercator Ocean operational system to effectively combine the different kinds of measurements was also investigated. These assessments were carried out as part of a European Space Agency (ESA) study on the potential role of wide-swath altimetry in future versions of the European Union Copernicus programme. The impact of future wide-swath altimetry data is evident for investigating the reliability of sea level values in OSSEs. The most significant results were obtained when looking at the sensitivity of the system to wide-swath instrumental error: considering a constellation of three nadir and two “accurate” (small instrumental error) wide-swath altimeters, the error in ocean analysis was reduced by up to 50 % compared to conventional altimeters. Investigating the impact of the repetitivity of the future measurements, the results showed that two wide-swath missions had a major impact on sea-level forecasting – increasing the accuracy over the entire time window of the 5-day forecasts – compared with a single wide-swath instrument. A spectral analysis underlined that the contributions of wide-swath altimetry data observed in ocean analyses and forecast statistics were mainly due to the more accurate resolution, compared with along-track data, of ocean variability at spatial scales smaller than 100 km. Considering the ocean currents, the results confirmed that the information provided by wide-swath measurements at the surface is propagated down the water column and has a considerable impact (30 %) on ocean currents (up to a depth of 300 m), compared with the present constellation of altimeters. The ocean analysis and forecasting systems used here are those currently used by the Copernicus Marine Environment and Monitoring Service (CMEMS) to provide operational services and ocean reanalysis. The results obtained in the OSSEs considering along-track altimeters were consistent with those derived from real data (observing system experiments, OSEs). OSSEs can also be used to assess the potential of new observing systems, and in this study the results showed that future constellations of altimeters will have a major impact on constraining the CMEMS ocean analysis and forecasting systems and their applications.〈/p〉

Description: 〈b〉Synergy of wind wave model simulations and satellite observations during extreme events〈/b〉〈br〉 Anne Wiese, Joanna Staneva, Johannes Schulz-Stellenfleth, Arno Behrens, Luciana Fenoglio-Marc, and Jean-Raymond Bidlot〈br〉 Ocean Sci., 14, 1503-1521, https://doi.org/10.5194/os-14-1503-2018, 2018〈br〉 The increase of data quality of wind and wave measurements provided by the new Sentinel-3A satellite in coastal areas is demonstrated compared to measurements of older satellites with in situ data and spectral wave model simulations. Furthermore, the sensitivity of the wave model to wind forcing is evaluated using data with different temporal and spatial resolution, where an hourly temporal resolution is necessary to represent the peak of extreme events better.

Description: 〈b〉What can seabirds tell us about the tide?〈/b〉〈br〉 Matthew Cooper, Charles Bishop, Matthew Lewis, David Bowers, Mark Bolton, Ellie Owen, and Stephen Dodd〈br〉 Ocean Sci., 14, 1483-1490, https://doi.org/10.5194/os-14-1483-2018, 2018〈br〉 This paper describes a feasibility study carried out to determine if information gathered for one discipline could be 〈q〉repurposed〈/q〉 to provide insight in another. Data gathered during a study of bird distribution were used to investigate whether these same data could be used to measure tidal current velocities and direction. The paper concludes that there is potential to use GPS-tagged birds as 〈q〉drifters of opportunity〈/q〉 and that interdisciplinary sharing of data can provide additional insight.

Description: 〈b〉A multiscale ocean data assimilation approach combining spatial and spectral localisation〈/b〉〈br〉 Ann-Sophie Tissier, Jean-Michel Brankart, Charles-Emmanuel Testut, Giovanni Ruggiero, Emmanuel Cosme, and Pierre Brasseur〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-132,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 2 comments)〈br〉 To better exploit the observational information available for all scales in data assimilation systems, we investigate a new method to introduce scale separation in the algorithm. It consists in carrying out the analysis with spectral localisation for the large scales and spatial localisation for the residual scales. The performance is then checked explicitly and separately for all scales. Results show that accuracy can be improved for the large scales while preserving reliability at all scales.

Description: 〈b〉Modelling study of transformations of the exchange flows along the Strait of Gibraltar〈/b〉〈br〉 Antonio Sanchez-Roman, Gabriel Jorda, Gianmaria Sannino, and Damia Gomis〈br〉 Ocean Sci., 14, 1547-1566, https://doi.org/10.5194/os-14-1547-2018, 2018〈br〉 We explore the vertical transfers of heat, salt and mass between the inflowing and outflowing layers at the Strait of Gibraltar by using a 3-D model with very high spatial resolution that allows for a realistic representation of the exchange. Results show a significant transformation of the water mass properties along their path through the strait, mainly induced by the recirculation of water between layers, while mixing seems to have little influence on the heat and salt exchanged.

Description: 〈b〉Hydrography, transport and mixing of the West Spitsbergen Current: the Svalbard Branch in summer 2015〈/b〉〈br〉 Eivind Kolås and Ilker Fer〈br〉 Ocean Sci., 14, 1603-1618, https://doi.org/10.5194/os-14-1603-2018, 2018〈br〉 Measurements of ocean currents, stratification and microstructure collected northwest of Svalbard are used to characterize the evolution of the warm Atlantic current. The measured turbulent heat flux is too small to account for the observed cooling rate of the current. The estimated contribution of diffusion by eddies could be limited to one half of the observed heat loss. Mixing in the bottom boundary layer, driven by cross-slope flow of buoyant water, can be important.

Description: 〈b〉The effect of vertical mixing on the horizontal drift of oil spills〈/b〉〈br〉 Johannes Röhrs, Knut-Frode Dagestad, Helene Asbjørnsen, Tor Nordam, Jørgen Skancke, Cathleen E. Jones, and Camilla Brekke〈br〉 Ocean Sci., 14, 1581-1601, https://doi.org/10.5194/os-14-1581-2018, 2018〈br〉 Simulations of hypothetical oil spills are presented to investigate how the vertical mixing of oil affects transport towards various directions. It is shown that the horizontal transport of oil greatly varies for different oil types and weather conditions. These differences are a consequence of the entrainment of oil from the surface into the ocean. While oil spills often get entrained into the water by waves, we show that submerged oil typically resurfaces after a few hours or days.

Description: 〈b〉Can wave coupling improve operational regional ocean forecasts for the North-West European Shelf?〈/b〉〈br〉 Huw W. Lewis, Juan Manuel Castillo Sanchez, John Siddorn, Robert R. King, Marina Tonani, Andrew Saulter, Peter Sykes, Anne-Christine Pequignet, Graham P. Weedon, Tamzin Palmer, Joanna Staneva, and Lucy Bricheno〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-148,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 0 comments)〈br〉 Forecasts of ocean temperature, salinity, currents and sea height can be improved by linking state-of-the-art ocean and wave models, so that they can interact to better represent the real world. We test this approach in an ocean model of north-west Europe which can simulate small-scale details of the ocean state. The intention is to implement the system described in this study for operational use so that improved information can be provided to users of ocean forecast data.

Description: 〈b〉The Pelagic In situ Observation System (PELAGIOS) to reveal biodiversity, behavior and ecology of elusive oceanic fauna〈/b〉〈br〉 Henk-Jan Hoving, Svenja Christiansen, Eduard Fabrizius, Helena Hauss, Rainer Kiko, Peter Linke, Philipp Neitzel, Uwe Piatkowski, and Arne Körtzinger〈br〉 Ocean Sci. Discuss., https//doi.org/10.5194/os-2018-131,2018〈br〉 〈b〉Manuscript under review for OS〈/b〉 (discussion: open, 1 comment)〈br〉 The pelagic in situ observation system (PELAGIOS) is a new towed observation system with HD video camera and environmental sensors. It is used for pelagic video transects down to 3000 m. The system enables the visualization and exploration of pelagic organisms (〉 1 cm), in particular delicate gelatinous fauna, that cannot be captured by nets. The video and hydrographic data gives insight in the biodiversity, abundance and distribution of oceanic pelagic organisms, from the surface to the deep sea.

Description: Major improvement of altimetry sea level estimations using pressure-derived corrections based on ERA-Interim atmospheric reanalysis Loren Carrere, Yannice Faugère, and Michaël Ablain Ocean Sci., 12, 825-842, doi:10.5194/os-12-825-2016, 2016 New dynamic atmospheric (DAC_ERA) and dry tropospheric (DT_ERA) correction have been computed for the altimeter period using the ERA-Interim meteorological reanalysis. The corrections improve sea level estimations in Southern Ocean and in shallow waters; the impact is the most important for the first decade of altimetry, when operational meteorological models had a weaker quality. DT_ERA remains better in the recent period. New corrections significantly impact long-term regional trends.

Description: Quality assessment of the TOPAZ4 reanalysis in the Arctic over the period 1991–2013 Jiping Xie, Laurent Bertino, Francois Counillon, Knut A. Lisæter, and Pavel Sakov Ocean Sci. Discuss., doi:10.5194/os-2016-38,2016 Manuscript under review for OS (discussion: open, 0 comments) The Arctic Ocean plays an important role in the global climate system, but the concerned interpretation about its changes is severely hampered by the sparseness of the observations of sea ice and ocean. The focus of this study is to provide a quantitative assessment of the performance of the TOPAZ4 reanalysis for ocean and sea ice variables in the pan-Arctic region (north of 63 °N) in order to guide the user about its skills and limitations.

Description: Seabirds as samplers of the marine environment – a case study in Northern Gannets Stefan Garthe, Verena Peschko, Ulrike Kubetzki, and Anna-Marie Corman Ocean Sci. Discuss., doi:10.5194/os-2016-22,2016 Manuscript under review for OS (discussion: open, 0 comments) Understanding distribution patterns, activities, and foraging behaviours of seabirds requires interdisciplinary approaches. In this paper, we provide examples of the data and analytical procedures from a new study in the German Bight, North Sea, tracking Northern Gannets (Morus bassanus) at their breeding colony on the island of Helgoland. Individual adult Northern Gannets were equipped with different types of data loggers for several weeks, measuring geographic positions and other parameters mostly at 3–5 min intervals. Birds flew in all directions from the island to search for food, but most flights targeted areas to the (N)NW of Helgoland. Foraging trips were remarkably variable in duration and distance; most trips lasted 1–15 h and extended from 3–80 km from the breeding colony on Helgoland. Dives of gannets were generally shallow, with more than half of the dives only reaching depths of 1–3 m. The maximum dive depth was 11.4 m. Gannets showed a clear diurnal rhythm in their diving activity, with dives being almost completely restricted to the daylight period. Most flight activity at sea occurred at an altitude between the sea surface and 40 m. Gannets mostly stayed away from the wind farms and passed around them much more frequently than flying through them. Detailed information on individual animals may provide important insights into various processes, based on multi-layer information.

Description: Operational Assimilation of glider temperature and salinity in a mesoscale flow field: Eastern Mediterranean test case Daniel R. Hayes, Srdjan Dobricic, and Hezi Gildor Ocean Sci. Discuss., doi:10.5194/os-2016-43,2016 Manuscript under review for OS (discussion: open, 0 comments) This research has shown that it is possible to estimate ocean currents more accurately when using autonomous underwater glider observations of ocean temperature and salinity in conjunction with numerical ocean current models. This allows offshore activities to be more safely carried out, since currents can transport pollutants or disrupt operations in unpredictable ways. Using only models is not as reliable as using a merged result of observations and models, which can be done in near real time.

Description: An atmosphere-wave regional coupled model: improving predictions of wave heights and surface winds in the Southern North Sea Kathrin Wahle, Joanna Staneva, Wolfgang Koch, Luciana Fenoglio-Marc, Ha T. M. Ho-Hagemann, and Emil V. Stanev Ocean Sci. Discuss., doi:10.5194/os-2016-51,2016 Manuscript under review for OS (discussion: open, 0 comments) Reduction of wave forecasting errors is a challenge especially in dynamically complicated coastal ocean areas as the southern part of the North Sea area. We study the effects of coupling between an atmospheric and a wind wave model. This leads to a reduction of both the surface wind speeds and wave heights and improves the agreement between observations and simulations. The improved skills resulting from the proposed method justifies its implementations for operational and climate studies.

Description: Glider Technology for Ocean Observations: A Review David Meyer Ocean Sci. Discuss., doi:10.5194/os-2016-40,2016 Manuscript under review for OS (discussion: open, 0 comments) This review covers a wide range of topics – from the history and the development of glider technology to its application in a variety of field studies regarding ocean sciences. It offers a comprehensive overview of both, the technical and the scientific dimension, facilitating a fast access to the world of glider. It was shown that glider can be used for very specific research tasks, as well as for common environmental monitoring purposes.

Description: Effects of surface current–wind interaction in an eddy-rich general ocean circulation simulation of the Baltic Sea Heiner Dietze and Ulrike Löptien Ocean Sci., 12, 977-986, doi:10.5194/os-12-977-2016, 2016 Winds blowing over the ocean drive ocean currents. The oceanic response to winds is, in turn, influenced by ocean currents. Theoretical considerations suggest that the latter effect is especially pronounced in the Baltic Sea. The study presented here puts theses theoretical considerations in a high-resolution ocean circulation model of the Baltic Sea to the test.

Description: Impact of vertical and horizontal advection on nutrient distribution in the southeast Pacific Bàrbara Barceló-Llull, Evan Mason, Arthur Capet, and Ananda Pascual Ocean Sci., 12, 1003-1011, doi:10.5194/os-12-1003-2016, 2016 Vertical velocity in the ocean makes an important contribution to the modulation of marine ecosystems through its impact on fluxes of nutrients and phytoplankton. Here, we estimate full 3-D current velocity fields from an observation-based data product. The 3-D currents are used to force a set of particle-tracking (Lagrangian) experiments. The Lagrangian results show that vertical motions induce local increases in nitrate uptake reaching up to 30 %.

Description: Characteristics of Global Oceanic Rossby Wave and Mesoscale Eddies Propagation from Multiple Datasets Analysis Yunfan Zhang, Fenglin Tian, and Ge Chen Ocean Sci. Discuss., doi:10.5194/os-2016-64,2016 Manuscript under review for OS (discussion: open, 0 comments) The oceanic rossby wave and mesoscale eddies are widely existed in oceans worldwide. They are closely related to our life as they would more or less affect local or global climate. We present this study to investigate the relationship between the waves and the eddies by using multiple datasets and low-pass filtering method. We have found that the Rossby wave may play an accelerative or moderative role in the eddy propagation, and the results will help us to further understand them.

Description: Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013 Villu Kikas and Urmas Lips Ocean Sci., 12, 843-859, doi:10.5194/os-12-843-2016, 2016 Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll  a fluorescence and turbidity and takes water samples for further analyses at a predefined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criteria, 33 coastal upwelling events were identified in May–September 2007–2013. The number of events, as well as the frequency of their occurrence and intensity expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coasts. Nevertheless, the wind impulse, which was needed to generate upwelling events of similar intensity, differed between the northern and southern coastal areas. It is suggested that the general thermohaline structure adapted to the prevailing forcing and the estuarine character of the basin weaken the upwelling created by the westerly to southwesterly (up-estuary) winds and strengthen the upwelling created by the easterly to northeasterly (down-estuary) winds. Two types of upwelling events were identified – one characterized by a strong temperature front and the other revealing gradual decrease in temperature from the open sea to the coastal area, with maximum temperature deviation close to the shore.

Description: Observed El Niño conditions in the eastern tropical Pacific in October 2015 Lothar Stramma, Tim Fischer, Damian S. Grundle, Gerd Krahmann, Hermann W. Bange, and Christa A. Marandino Ocean Sci., 12, 861-873, doi:10.5194/os-12-861-2016, 2016 Results from a research cruise on R/V Sonne to the eastern tropical Pacific in October 2015 during the 2015–2016 El Niño show the transition of current, hydrographic, and nutrient conditions to El Niño conditions in the eastern tropical Pacific in October 2015. Although in early 2015 the El Niño was strong and in October 2015 showed a clear El Niño influence on the EUC, in the eastern tropical Pacific the measurements only showed developing El Niño water mass distributions.

Description: Modelling wave–current interactions off the east coast of Scotland Alessandro D. Sabatino, Chris McCaig, Rory B. O'Hara Murray, and Michael R. Heath Ocean Sci., 12, 875-897, doi:10.5194/os-12-875-2016, 2016 The present research describes the effect of wave–current interactions and wave–wave interactions during severe storms on the east coast of Scotland. In this area, results show that the currents contribute substantially to the modification of wave properties in the shallow coastal areas, while the wave–wave interactions are more important offshore.

Description: Technical Note: Algal Pigment Index 2 in the Atlantic off the Southwest Iberian Peninsula: standard and regional algorithms Priscila Costa Goela, Sónia Cristina, Tamito Kajiyama, John Icely, Gerald Moore, Bruno Fragoso, and Alice Newton Ocean Sci. Discuss., doi:10.5194/os-2016-41,2016 Manuscript under review for OS (discussion: open, 0 comments) In this study, the MERIS (ocean colour sensor from European Space Agency) algorithm for the quantification of Chlorophylla in coastal waters – API2 – is investigated in an area located in the Atlantic off the southwestern Iberian Peninsula. The study demonstrates the importance of regional algorithms for the study area that could complement upcoming standard results of the present Sentinel-3/OLCI space mission.

Description: Large-scale forcing of the European Slope Current and associated inflows to the North Sea Robert Marsh, Ivan D. Haigh, Stuart A. Cunningham, Mark E. Inall, Marie Porter, and Ben I. Moat Ocean Sci. Discuss., doi:10.5194/os-2016-61,2016 Manuscript under review for OS (discussion: open, 0 comments) To the west of Britain and Ireland, a strong ocean current follows the steep slope that separates the deep Atlantic and the continental shelf. This ''Slope Current'' exerts an Atlantic influence on the North Sea and its ecosystems. Using a combination of computer modelling and archived data, we find that the Slope Current weakened over 1988–2007, reducing Atlantic influence on the North Sea, due to a combination of warming of the subpolar North Atlantic and weakening winds to the west of Scotland.

Description: Effects of lateral processes on the seasonal water stratification of the Gulf of Finland: 3-D NEMO-based model study Roman E. Vankevich, Ekaterina V. Sofina, Tatiana E. Eremina, Vladimir A. Ryabchenko, Mikhail S. Molchanov, and Alexey V. Isaev Ocean Sci., 12, 987-1001, doi:10.5194/os-12-987-2016, 2016 This paper aims to fill the gaps in knowledge of processes affecting the seasonal water stratification in the Gulf of Finland (GOF). We used a state-of-the-art modelling framework NEMO (Nucleus for European Modelling of the Ocean) designed for oceanographic research, operational oceanography, seasonal forecasting, and climate studies to build an eddy-resolving model of the GOF. To evaluate the model skill and performance, two different solutions were obtained on 0.5 km eddy-resolving and commonly used 2 km grids for a 1-year simulation. We also explore the efficacy of non-hydrostatic effect (convection) parameterizations available in NEMO for coastal application. It is found that the solutions resolving submesoscales have a more complex mixed layer structure in the regions of the GOF directly affected by the upwelling/downwelling and intrusions from the open Baltic Sea. Presented model estimations of the upper mixed layer depth are in good agreement with in situ CTD (BED) data. A number of model sensitivity tests to the vertical mixing parameterization confirm the model's robustness. Further progress in the submesoscale process simulation and understanding is apparently not connected mainly with the finer resolution of the grids, but with the use of non-hydrostatic models because of the failure of the hydrostatic approach at submesoscale.

Description: Technical note: Common characteristics of directional spreading–steepness joint distribution in freak wave events Shouhua Liu, Yizhen Li, and Xinyang Yue Ocean Sci., 12, 781-786, doi:10.5194/os-12-781-2016, 2016 Common visual features were found in the joint distribution of directional spreading--steepness when freak waves occurred among seven “freakish” sea states. It's interesting that the visual features look similar. The common visual features supply an important cue for the theoretical and experimental research of freak waves.

Description: Seasonal resonance of diurnal coastal trapped waves in the southern Weddell Sea, Antarctica Stefanie Semper and Elin Darelius Ocean Sci. Discuss., doi:10.5194/os-2016-36,2016 Manuscript under review for OS (discussion: open, 0 comments) Velocity measurements from moorings at the shelf break in the southern Weddell Sea reveal strong diurnal tidal currents, which are enhanced by ca. 50 % in austral summer compared to winter. A numerical code describing coastal trapped waves (CTWs) is used to explore the effect of changing stratification and circulation on wave properties. It is found that near-resonance between CTWs and diurnal tides during summer can explain the observed enhancement of diurnal tidal currents.

Description: Core operational Sentinel-3 marine data product services as part of the Copernicus Space Component Hans Bonekamp, Francois Montagner, Vincenzo Santacesaria, Carolina Nogueira Loddo, Sally Wannop, Igor Tomazic, Anne O'Carroll, Ewa Kwiatkowska, Remko Scharroo, and Hilary Wilson Ocean Sci., 12, 787-795, doi:10.5194/os-12-787-2016, 2016 This paper describes the marine data available from the Marine Centre, part of the Sentinel-3 Payload Data Ground Segment, located at the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). Descriptions include the scientific and operational feedback mechanisms on the performance of the services as well as practical information and user support mechanisms.

Description: Coupling of wave and circulation models in coastal–ocean predicting systems: a case study for the German Bight Joanna Staneva, Kathrin Wahle, Heinz Günther, and Emil Stanev Ocean Sci., 12, 797-806, doi:10.5194/os-12-797-2016, 2016 This study addresses the impact of coupling between wind wave and circulation models on the quality of coastal ocean predicting systems. This topic reflects the increased interest in operational oceanography to reduce prediction errors of state estimates at coastal scales. The improved skill of the coupled forecasts compared to the non-coupled ones, in particular during extreme events, justifies the further enhancements of coastal operational systems by including wind wave models.

Description: Acoustic and optical methods to infer water transparency at the Time Series Station Spiekeroog, Wadden Sea (southern North Sea) Anne-Christin Schulz, Thomas H. Badewien, Shungudzemwoyo P. Garaba, and Oliver Zielinski Ocean Sci. Discuss., doi:10.5194/os-2016-24,2016 Manuscript under review for OS (discussion: open, 0 comments) Water transparency is a key indicator of optical water quality that is driven by suspended particulate and dissolved material. In this study we carried out an intercomparison of observations related to water transparency, determine correlations among the measured parameters and demonstrate the utility of both acoustic and optical tools in monitoring water transparency. The data set used here is from the operational Time Series Station Spiekeroog located at a tidal inlet of the Wadden Sea. An Acoustic Doppler Current Profiler was used to obtain acoustic measurements in the water column. Optical observations were determined using a set of three radiometers above water to collect radiometric quantities and a turbidity sensor within the water column. Bio-fouling was identified as a source of anomaly in turbidity measurements. We observed significant correlations between in-situ optically measured turbidity and derived turbidity from above water color sensing and acoustic backscattering strength. These findings underline that both optical and acoustic measurements can be reasonable proxies of water transparency with the potential to mitigate gaps and increase data quality in long-time observation of marine environments.

Description: Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean Julien Jouanno, Xavier Capet, Gurvan Madec, Guillaume Roullet, and Patrice Klein Ocean Sci., 12, 743-769, doi:10.5194/os-12-743-2016, 2016 The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized configuration of the NEMO model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean. Challenging issues concerning how numerical models are able to represent interior mixing forced by high-frequency winds are exposed and discussed, particularly in the context of the overturning circulation.

Description: The implications of initial model drift for decadal climate predictability using EC-Earth Andreas Sterl Ocean Sci. Discuss., doi:10.5194/os-2016-27,2016 Manuscript under review for OS (discussion: open, 0 comments) Attempts at decadal climate predictions have largely failed so far. We here investigate two reasons. The first is the large drift occurring after initialization, and which masks the signal to be predicted, and the second is the fact that a sub-surface heat signal has to be connected to the surface to influence the atmosphere. However, vertical mixing in the ocean to expose a sub-surface anomaly to the surface depends on unpredictable atmospheric variability.

Description: The Coastal Observing System for Northern and Arctic Seas (COSYNA) B. Baschek, F. Schroeder, H. Brix, R. Riethmüller, T. H. Badewien, G. Breitbach, B. Brügge, F. Colijn, R. Doerffer, C. Eschenbach, J. Friedrich, P. Fischer, S. Garthe, J. Horstmann, H. Krasemann, K. Metfies, N. Ohle, W. Petersen, D. Pröfrock, R. Röttgers, M. Schlüter, J. Schulz, J. Schulz-Stellenfleth, E. Stanev, C. Winter, K. Wirtz, J. Wollschläger, O. Zielinski, and F. Ziemer Ocean Sci. Discuss., doi:10.5194/os-2016-31,2016 Manuscript under review for OS (discussion: open, 0 comments) The Coastal Observing System for Northern and Arctic Seas (COSYNA) was established in order to better understand the complex interdisciplinary processes of northern seas and the arctic coasts in a changing environment. Particular focus is given to the heavily used German Bight in the North Sea. The automated observing and modelling system is designed to monitor real time conditions, provide short-term forecasts and data products, and to assess the impact of anthropogenically induced change.

Description: The connection of the Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current Erwin Lambert, Dewi Le Bars, and Wilhelmus P. M. de Ruijter Ocean Sci., 12, 771-780, doi:10.5194/os-12-771-2016, 2016 In the upper layers of the South Indian Ocean, three anomalous currents are observed: The South Indian Ocean Countercurrent, the Leeuwin Current and the Indonesian Throughflow. Using two models of different complexity, we show how these three currents can be dynamically connected, unravelling the large-scale connectivity. Further, we produce a conceptual theory of how this current system follows an idealized pattern of wind stress and buoyancy forcing.

Description: Bridging the Gap between Observational Oceanography and Users Christiane A. Eschenbach Ocean Sci. Discuss., doi:10.5194/os-2016-21,2016 Manuscript under review for OS (discussion: open, 0 comments) COSYNA (Coastal Observing System for Northern and Arctic Seas) pursued various activities for stakeholder interaction. The steps, e.g. initial survey, external evaluation, interviews and workshops with stakeholders from the offshore wind sector, are integrated into the COSYNA product life cycle outlined here and exemplified for the product “Surface Current Fields“. By sharing first hand experiences this study contributes to the emerging knowledge on integration of coastal research and end-users.

Description: DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years Marie-Isabelle Pujol, Yannice Faugère, Guillaume Taburet, Stéphanie Dupuy, Camille Pelloquin, Michael Ablain, and Nicolas Picot Ocean Sci., 12, 1067-1090, doi:10.5194/os-12-1067-2016, 2016 The new DUACS DT2014 reprocessed products have been available since April 2014. Numerous innovative changes have been introduced at each step of an extensively revised data processing protocol. The use of a new 20-year altimeter reference period in place of the previous 7-year reference significantly changes the sea level anomaly (SLA) patterns and thus has a strong user impact. The use of up-to-date altimeter standards and geophysical corrections, reduced smoothing of the along-track data, and refined mapping parameters, including spatial and temporal correlation-scale refinement and measurement errors, all contribute to an improved high-quality DT2014 SLA data set. Although all of the DUACS products have been upgraded, this paper focuses on the enhancements to the gridded SLA products over the global ocean. As part of this exercise, 21 years of data have been homogenized, allowing us to retrieve accurate large-scale climate signals such as global and regional MSL trends, interannual signals, and better refined mesoscale features. An extensive assessment exercise has been carried out on this data set, which allows us to establish a consolidated error budget. The errors at mesoscale are about 1.4 cm 2 in low-variability areas, increase to an average of 8.9 cm 2 in coastal regions, and reach nearly 32.5 cm 2 in high mesoscale activity areas. The DT2014 products, compared to the previous DT2010 version, retain signals for wavelengths lower than  ∼  250 km, inducing SLA variance and mean EKE increases of, respectively, +5.1 and +15 %. Comparisons with independent measurements highlight the improved mesoscale representation within this new data set. The error reduction at the mesoscale reaches nearly 10 % of the error observed with DT2010. DT2014 also presents an improved coastal signal with a nearly 2 to 4 % mean error reduction. High-latitude areas are also more accurately represented in DT2014, with an improved consistency between spatial coverage and sea ice edge position. An error budget is used to highlight the limitations of the new gridded products, with notable errors in areas with strong internal tides.

Description: Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air–sea flux Carolyn F. Walker, Mike J. Harvey, Murray J. Smith, Thomas G. Bell, Eric S. Saltzman, Andrew S. Marriner, John A. McGregor, and Cliff S. Law Ocean Sci., 12, 1033-1048, doi:10.5194/os-12-1033-2016, 2016 The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air–sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the sea-surface microlayer and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF 〉 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air–sea DMS flux, measured by eddy covariance, exceeded the flux calculated using National Oceanic and Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response Experiment (COARE) parameterized gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air–sea emissions may be influenced by near-surface DMS production under certain conditions, and highlight the need for further study to constrain the magnitude and mechanisms of DMS production in the sea-surface microlayer.

Description: Parameterization of the light absorption properties of chromophoric dissolved organic matter in the Baltic Sea and Pomeranian lakes Justyna Meler, Piotr Kowalczuk, Mirosława Ostrowska, Dariusz Ficek, Monika Zabłocka, and Agnieszka Zdun Ocean Sci., 12, 1013-1032, doi:10.5194/os-12-1013-2016, 2016 Three alternative models for estimation of absorption of chromophoric dissolved organic matter (CDOM) have been formulated. The models were based on empirical database containing measurements from different regions of the Baltic Sea and three Pomeranian lakes in Poland. An assumption regarding continuum of inherent optical properties in marine and estuarine waters and freshwater has been proved and enabled the accurate estimation of CDOM absorption in various environments.

Description: El Niño, La Niña, and the global sea level budge Christopher G. Piecuch and Katherine J. Quinn Ocean Sci. Discuss., doi:10.5194/os-2016-66,2016 Manuscript under review for OS (discussion: open, 0 comments) We use satellite and in situ data to elucidate global-mean sea level (GMSL) changes related to El Niño-Southern Oscillation (ENSO) over 2005–2015. Steric and mass effects make comparable contributions to the GMSL budget during ENSO, in contrast to previous interpretations based largely on hydrological models, which emphasize mass contributions. Results exemplify the usefulness of the Global Ocean Observing System for understanding the Earth's radiation imbalance and hydrological cycle.

Description: Statistical Analysis of Wave Energy Resources Available for Conversion at Natural Caves of Cape-Verde Islands W. M. L. Monteiro, A. J. Sarmento, A. J. Fernandes, and J. M. Fernandes Ocean Sci. Discuss., doi:10.5194/os-2015-108,2016 Manuscript under review for OS (discussion: open, 0 comments) The results and conclusion about the wave climate achivied in this paper, constitute a very important information that provide a consistent basis for decision-making, relative to any project on the area of wave energy to be submitted for grant support in Cape Verde. These results will support to assess the participation of wave energy in the context of reducing dependence of Cape Verde on fossil fuels.

Description: Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean J. Jouanno, X. Capet, G. Madec, G. Roullet, P. Klein, and S. Masson Ocean Sci. Discuss., doi:10.5194/os-2016-3,2016 Manuscript under review for OS (discussion: open, 0 comments) The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized configuration of the NEMO model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean. Challenging issues concerning how numerical models are able to represent interior mixing forced by high-frequency winds are exposed and discussed, particularly in the context of the overturning circulation.

Description: Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm M. Grifoll, A. L. Aretxabaleta, J. L. Pelegrí, and M. Espino Ocean Sci., 12, 137-151, doi:10.5194/os-12-137-2016, 2016 We investigate the rapidly changing equilibrium between the momentum sources and sinks during the passage of a single two-peak storm over the Catalan inner shelf (NW Mediterranean Sea). At 24m water depth, a primary momentum balance between acceleration, pressure gradient and frictional forces (surface and bottom) is established. The frictional adjustment timescale was around 10h, consistent with the e-folding time obtained from bottom drag parameterizations.

Description: Developing European operational oceanography for Blue Growth, climate change adaptation and mitigation and ecosystem-based management J. She, I. Allen, E. Buch, A. Crise, J. A. Johannessen, P. Y. Le Traon, U. Lips, G. Nolan, N. Pinardi, J. H. Reißmann, J. Siddorn, E. Stanev, and H. Wehde Ocean Sci. Discuss., doi:10.5194/os-2015-103,2016 Manuscript under review for OS (discussion: open, 0 comments) This white paper addresses key scientific challenges and research priorities for the development of operational oceanography in Europe for the next 5-10 years. Knowledge gaps and deficiencies are identified in relation to common scientific challenges in four EuroGOOS knowledge areas: European Ocean Observations, Modelling and Forecasting Technology, Coastal Operational Oceanography and Operational Ecology.

Description: Factors favouring phytoplankton blooms in the northern Adriatic: towards the northern Adriatic empirical ecological model R. Kraus, N. Supić, and R. Precali Ocean Sci., 12, 19-37, doi:10.5194/os-12-19-2016, 2016 Seasonal and interannual production changes in the northern Adriatic (NA) reflect on the total Adriatic bioproduction of certain species (i.e. anchovy). Long-term (1990-2004) phyto-abundance and geostrophic current analysis relieve the basic mechanism of NA biomass production changes. The results present a first step in building an empirical ecological model of the region, aiming to predict the amount of organic production in NA, which is to be used in the environmental management of the region.

Description: Bio-optical characterization and light availability parameterization in Uummannaq Fjord and Vaigat–Disko Bay (West Greenland) L. Holinde and O. Zielinski Ocean Sci., 12, 117-128, doi:10.5194/os-12-117-2016, 2016 In 2012 measurements were conducted in two adjacent estuary systems on Greenland’s western coast that are strongly influenced by glacial meltwater. Results described in this study show the relevance of inorganic SPM and Chl a alike, while colored dissolved organic matter is less prominent. Light availability was recorded throughout the cruise and an effective two-component (Chl a and inorganic SPM) model for PAR is developed to fill observational gaps from insufficient light conditions.

Description: Ocean modelling for aquaculture and fisheries in Irish waters T. Dabrowski, K. Lyons, C. Cusack, G. Casal, A. Berry, and G. D. Nolan Ocean Sci., 12, 101-116, doi:10.5194/os-12-101-2016, 2016 The Marine Institute, Ireland, runs a suite of operational regional and coastal ocean models. Recent developments include several tailored products that focus on the key needs of the Irish aquaculture sector. In this article, an overview of the products and services derived from the models are presented. The authors give an overview of a shellfish model developed in-house and that was designed to predict the growth, the physiological interactions with the ecosystem, and the level of coliform contamination of the blue mussel. As such, this model is applicable in studies on the carrying capacity of embayments, assessment of the impacts of pollution on aquaculture grounds, and the determination of shellfish water classes. Further services include the assimilation of the model-predicted shelf water movement into a new harmful algal bloom alert system used to inform end users of potential toxic shellfish events and high biomass blooms that include fish-killing species. Models are also used to identify potential sites for offshore aquaculture, to inform studies of potential cross-contamination in farms from the dispersal of planktonic sea lice larvae and other pathogens that can infect finfish, and to provide modelled products that underpin the assessment and advisory services on the sustainable exploitation of the resources of marine fisheries. This paper demonstrates that ocean models can provide an invaluable contribution to the sustainable blue growth of aquaculture and fisheries.

Description: The Civitavecchia Coastal Environment Monitoring System (C-CEMS): a new tool to analyze the conflicts between coastal pressures and sensitivity areas S. Bonamano, V. Piermattei, A. Madonia, F. Paladini de Mendoza, A. Pierattini, R. Martellucci, C. Stefanì, G. Zappalà, G. Caruso, and M. Marcelli Ocean Sci., 12, 87-100, doi:10.5194/os-12-87-2016, 2016 The Civitavecchia Coastal Environment Monitoring System (C-CEMS) has been developed by the Laboratory of Experimental Oceanology and Marine Ecology in order to analyze the conflicts between human pressures and ecosystem conservation. As examples, the analysis of faecal bacteria dispersion for bathing water quality assessment and the evaluation of the effects of the dredged activities on Posidonia meadows are reported. Finally, C-CEMS can be considered a useful tool for coastal zone management.

Description: Spatial scales of temperature and salinity variability estimated from Argo observations F. Ninove, P.-Y. Le Traon, E. Remy, and S. Guinehut Ocean Sci., 12, 1-7, doi:10.5194/os-12-1-2016, 2016 Argo floats are one of the main components of the in situ observation network in the ocean. Nowadays, more than 3500 profiling floats are sampling the world ocean. In this study, they are used to characterize spatial scales of temperature and salinity variations from the surface down to 1500m. The scales appear to be anisotropic and vary from about 100km at high latitudes to 700km in the Indian and Pacific equatorial and tropical regions.

Description: Modeling the ocean and atmosphere during an extreme bora event in northern Adriatic using one-way and two-way atmosphere–ocean coupling M. Ličer, P. Smerkol, A. Fettich, M. Ravdas, A. Papapostolou, A. Mantziafou, B. Strajnar, J. Cedilnik, M. Jeromel, J. Jerman, S. Petan, V. Malačič, and S. Sofianos Ocean Sci., 12, 71-86, doi:10.5194/os-12-71-2016, 2016 We compare the northern Adriatic response to an extreme bora event, as simulated by one-way and two-way (i.e. with ocean feedback to the atmosphere) atmosphere-ocean coupling. We show that two-way coupling yields significantly better estimates of heat fluxes, most notably sensible heat flux, across the air-sea interface. When compared to observations in the northern Adriatic, two-way coupled system consequently leads to a better representation of ocean temperatures throughout the event.

Description: The flow field of the upper hypoxic eastern tropical North Atlantic oxygen minimum zone L. Stramma, R. Czeschel, T. Tanhua, P. Brandt, M. Visbeck, and B. S. Giese Ocean Sci., 12, 153-167, doi:10.5194/os-12-153-2016, 2016 The subsurface circulation in the eastern tropical North Atlantic OMZ is derived from velocity, float and tracer data and data assimilation results, and shows a cyclonic flow around the Guinea Dome reaching into the oxygen minimum zone. The stronger cyclonic flow around the Guinea Dome in 2009 seem to be connected to a strong Atlantic Meridional Mode (AMM) event. A continuous deoxygenation trend of the low oxygen layer was confirmed. Eddy influence is weak south of the Cape Verde Islands.

Description: Accuracy of the mean sea level continuous record with future altimetric missions: Jason-3 vs. Sentinel-3a L. Zawadzki and M. Ablain Ocean Sci., 12, 9-18, doi:10.5194/os-12-9-2016, 2016 The reference mean sea level (MSL) record, essential for understanding climate evolution, is derived from the altimetric measurements of the TOPEX/Poseidon mission, followed by Jason-1 and later Jason-2 on the same orbit. Soon, Jason-3 will be launched on the same historical orbit, followed by Sentinel-3a on a new one. This paper shows linking missions with the same orbit enables meeting climate user requirements regarding the MSL trend while using Sentinel-3a would increase the uncertainty.

Description: On the feasibility of the use of wind SAR to downscale waves on shallow water O. Q. Gutiérrez, F. Filipponi, A. Taramelli, E. Valentini, P. Camus, and F. J. Méndez Ocean Sci., 12, 39-49, doi:10.5194/os-12-39-2016, 2016 High-resolution wave hindcast has been performed for the N Adriatic Sea using a hybrid methodology, combining a regional wave hindcast database, wind reanalysis, satellite SAR wind fields and data mining techniques. Comparison with in situ instrumental data indicates the good quality of the downscaled waves; moreover, a good correlation was found on the downscaled waves forced with different wind fields. Results demonstrate how SAR wind fields can be successfully up-taken in wave downscaling.

Description: Investigation of model capability in capturing vertical hydrodynamic coastal processes: a case study in the north Adriatic Sea W. J. McKiver, G. Sannino, F. Braga, and D. Bellafiore Ocean Sci., 12, 51-69, doi:10.5194/os-12-51-2016, 2016 First modeling work comparing SHYFEM and MITgcm performance in the north Adriatic Sea; the treatment of heat/mass fluxes at the surface affects the models skill to reproduce coastal processes; high resolution is needed close to the coast, while lower resolution in the offshore is adequate to capture the dense water event; correct river discharges and temperature are vital for the reproduction of estuarine dynamics; non-hydrostatic processes do not influence the dense water formation.

Description: Impact of variable seawater conductivity on motional induction simulated with an ocean general circulation model C. Irrgang, J. Saynisch, and M. Thomas Ocean Sci., 12, 129-136, doi:10.5194/os-12-129-2016, 2016 In this study, the influence of a spatio-temporally variable seawater conductivity on ocean-circulation-induced magnetic signals is investigated. To simulate the ocean-circulation-induced magnetic field, a combination of an ocean general circulation model (OMCT) and an electromagnetic induction model is used. It is found that a spatially varying seawater conductivity has a significant impact on the temporal variability of the induced magnetic field.

Description: Total suspended matter derived from MERIS data as indicator for coastal processes in the Baltic Sea D. Kyryliuk and S. Kratzer Ocean Sci. Discuss., doi:10.5194/os-2016-2,2016 Manuscript under review for OS (discussion: open, 0 comments) Total suspended matter (TSM) is an indicator of coastal processes and can be retrieved reliably from MERIS (Medium Resolution Imaging Spectrometer) data. In this project we used MERIS TSM data from a Swedish coastal monitoring system www.vattenkvalitet.se to evaluate the physical extend of coastal processes. The data set consisted of all viable MERIS scenes during summer (June–August) 2009–2011, covering the whole Baltic Sea area. Monthly composite images were produced for each year, and the monthly composites were subsequently evaluated with regards to terrestrial influence, and the typical features caused by cyanobacteria blooms (typically during July and August). Next, a composite image from early June 2011 was generated in order to exclude a possible influence from cyanobacteria on the patterns of TSM distribution. This early June composite was then used as a basis to evaluate the extent of terrestrial influence using the NW Baltic Proper (Swedish coastal areas) and the SE Baltic Proper (Latvian, Lithuanian and Polish coastal waters) as examples. In both areas the averaged TSM scenes from early June were used to extract transects of TSM data perpendicular to the coast, spanning from coastal to offshore waters. Based on previous bio-optical research in the NW Baltic Sea and on further statistical analysis of MERIS scenes local coastal water thresholds were defined for different areas in the Baltic Sea. Using these local thresholds, it was found that coastal processes in the NW Baltic Sea extend to approximately 15–27 km off-shore, whereas in the SE Baltic Sea the coastal influence extended to about twice the distance i.e. to about 34–52 km off-shore. Next, the trendlines of TSM distribution along transects was evaluated mathematically. The trend line for the NW Baltic proper was best described by a polynomial equation, whereas the trend line from the transect in SE coastal waters was best described logarithmically in areas of high resuspension. These differing trends indicate different hydrological regimes in the two areas, which are mostly driven by a combination of land run-off distributed by diffusional processes, and coastal dynamics driven by local wind exposure. The results demonstrate that ocean colour remote sensing can provide important information for Baltic Sea research and management, as well as for the monitoring of coastal processes. The method allows for an evaluation of the extent of coastal influence, and of seasonal fluctuations in river run-off and phytoplankton dynamics. Furthermore, the concentrations of total suspended matter in the different sub-basins of the entire Baltic Sea can be compared synoptically.

Description: Combining operational models and data into a dynamic vessel risk assessment tool for coastal regions R. Fernandes, F. Braunschweig, F. Lourenço, and R. Neves Ocean Sci., 12, 285-317, doi:10.5194/os-12-285-2016, 2016 A combined methodology to estimate time and space variable shoreline risk levels from ships has been developed, integrating metocean forecasts and oil spill simulations with vessel tracking automatic identification systems (AIS) and coastal vulnerability indices. Results show the ability of the proposed methodology to estimate the risk properly sensitive to dynamic metocean conditions and oil transport behaviour, enhancing the maritime situational awareness and the decision support model.

Description: On the near-inertial variations of meridional overturning circulation in the South China Sea Jingen Xiao, Qiang Xie, Dongxiao Wang, Lei Yang, Yeqiang Shu, Changjian Liu, Ju Chen, Jinglong Yao, and Gengxin Chen Ocean Sci., 12, 335-344, doi:10.5194/os-12-335-2016, 2016 We examine near-inertial variability of the meridional overturning circulation in the South China Sea (SCSMOC) using a global 1 / 12° ocean reanalysis. Based on wavelet analysis and power spectrum, we suggest that deep SCSMOC has a significant near-inertial band. The maximum amplitude of the near-inertial signal in the SCSMOC is nearly 4 Sv. The spatial structure of the signal features regularly alternating counterclockwise and clockwise overturning cells.

Description: The sound speed anomaly of Baltic seawater C. von Rohden, S. Weinreben, and F. Fehres Ocean Sci., 12, 275-283, doi:10.5194/os-12-275-2016, 2016 The variability of the relative salt composition in seawater may have significant influence on physical properties. Based on off-shore and laboratory measurements, this effect is quantified for the first time for speed of sound in Baltic seawater. Time-of-flight sensors with sufficient resolution were applied to resolve the small sound speed anomaly to values in the range of several cm s −1 . The results suggest that the effect can be reasonably predicted by the recent equation of state (TEOS-10).

Description: Transient tracer distributions in the Fram Strait in 2012 and inferred anthropogenic carbon content and transport Tim Stöven, Toste Tanhua, Mario Hoppema, and Wilken-Jon von Appen Ocean Sci., 12, 319-333, doi:10.5194/os-12-319-2016, 2016 The article describes transient tracer distributions of CFC-12 and SF6 in the Fram Strait in 2012. The SF6 excess and the anthropogenic carbon content in this area was estimated assuming a standard parameterization of the inverse-Gaussian–transit-time distribution. Hydrographic data were obtained along a mooring array at 78°50’N and a mean velocity field was used for flux estimates.

Description: Interactions between the Somali Current eddies during the summer monsoon: insights from a numerical study C. Q. C. Akuetevi, B. Barnier, J. Verron, J.-M. Molines, and A. Lecointre Ocean Sci., 12, 185-205, doi:10.5194/os-12-185-2016, 2016 The NW Indian Ocean is the siege of two very intense anticyclonic eddies, the Great Whirl and the Southern Gyre, the rapid development of which makes their observation difficult. Model simulations propose an interaction scenario between the two eddies not described in observations up to now. When the summer monsoon intensifies, the Southern Gyre moves northward, collides with the Great Whirl and takes it place. The Great Whirl is pushed to the east of Socotra Island and forms the Socotra Eddy.

Description: Effects of vertical shear in modelling horizontal oceanic dispersion A. S. Lanotte, R. Corrado, L. Palatella, C. Pizzigalli, I. Schipa, and R. Santoleri Ocean Sci., 12, 207-216, doi:10.5194/os-12-207-2016, 2016 The paper investigates the role of vertical shear on the horizontal ocean dispersion of tracer particles or concentration fields. We compare in situ measurements to GCM numerical data of the magnitude and the typical timescale of the vertical shear. We discuss how an appropriate sub-grid-scale parameterization can account for an anomalous numerical shear dispersion due to the model poor time resolution. The analysis focuses on the mixing layer, and on the region of the south Mediterranean Sea.

Description: Research priorities in support of ocean monitoring and forecasting at the Met Office J. R. Siddorn, S. A. Good, C. M. Harris, H. W. Lewis, J. Maksymczuk, M. J. Martin, and A. Saulter Ocean Sci., 12, 217-231, doi:10.5194/os-12-217-2016, 2016 The Met Office provides a range of services in the marine environment. To support these services, and to ensure they evolve to meet the demands of users and are based on the best available science, a number of scientific challenges need to be addressed. The paper summarises the key challenges, and highlights some priorities for the ocean monitoring and forecasting research group at the Met Office.

Description: The Barents Sea frontal zones and water masses variability (1980–2011) L. Oziel, J. Sirven, and J.-C. Gascard Ocean Sci., 12, 169-184, doi:10.5194/os-12-169-2016, 2016 The Barents Sea (BS) is a subpolar region and a zone transition where the Atlantic and the Arctic water masses meets and creates the "Polar Front". This study, based on one of the largest hydrological data set, showed for the first time that the "Polar Front" splits into two branches in the eastern part of the BS. This study also showed that, in a context of climate change, the BS experiences an "Atlantification", which goes along with a north-eastward shift of the frontal structure.

Description: Monitoring Atlantic overturning circulation and transport variability with GRACE-type ocean bottom pressure observations – a sensitivity study K. Bentel, F. W. Landerer, and C. Boening Ocean Sci., 11, 953-963, doi:10.5194/os-11-953-2015, 2015 The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism for large-scale northward heat transport and plays an important role for global climate. Previously, AMOC changes have been inferred from in situ ocean bottom pressure (OBP) observations at single latitudes. We extend the analysis to space-based observations (and the whole North Atlantic) and show on data from the ECCO2 model that AMOC anomalies can be inferred from OBP at a resolution resembling the GRACE gravity mission.

Description: Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (~ 30° S) based on a high-resolution atmospheric regional model (WRF) L. Bravo, M. Ramos, O. Astudillo, B. Dewitte, and K. Goubanova Ocean Sci. Discuss., 12, 3003-3041, doi:10.5194/osd-12-3003-2015, 2015 Manuscript under review for OS (discussion: open, 1 comment) We evaluated the seasonal variability in Ekman transport, pumping and their relative contribution to total upwelling along the central-northern Chile region (~30ºS) from a high-resolution atmospheric model simulation. The results showed that the relative contribution of Ekman transport and pumping to the vertical transport along the coast, considering the estimated wind drop-off length, indicated meridional alternation between both mechanisms, modulated by orography and the intricate coastline.

Description: Spatial scales of temperature and salinity variability estimated from Argo observations F. Ninove, P.-Y. Le Traon, E. Remy, and S. Guinehut Ocean Sci., 12, 1-7, doi:10.5194/os-12-1-2016, 2016 Argo floats are one of the main components of the in situ observation network in the ocean. Nowadays, more than 3500 profiling floats are sampling the world ocean. In this study, they are used to characterize spatial scales of temperature and salinity variations from the surface down to 1500m. The scales appear to be anisotropic and vary from about 100km at high latitudes to 700km in the Indian and Pacific equatorial and tropical regions.

Description: An improved method for the determination of dissolved nitric oxide (NO) in seawater samples H. E. Lutterbeck and H. W. Bange Ocean Sci., 11, 937-946, doi:10.5194/os-11-937-2015, 2015 Nitric oxide (NO) is a short-lived intermediate of the oceanic nitrogen cycle; however, due to its high reactivity, measurements of dissolved NO in seawater are rare. Here we present an improved method to determine NO concentrations in discrete seawater samples. The set-up of our system consisted of a chemiluminescence NO analyser connected to a stripping unit. The limit of detection for our method is 5 pmol NO in aqueous solution, which translates into 0.25 nmol L −1 when using a 20 mL seawater sample volume. Our method was applied to measure high-resolution depth profiles of dissolved NO during a cruise to the eastern tropical South Pacific Ocean. It is fast and comparably easy to handle; thus it opens the door for investigating the distribution of NO in the ocean, and it facilitates laboratory studies on NO pathways.

Description: Projected sea level rise and changes in extreme storm surge and wave events during the 21st century in the region of Singapore H. Cannaby, M. D. Palmer, T. Howard, L. Bricheno, D. Calvert, J. Krijnen, R. Wood, J. Tinker, C. Bunney, J. Harle, A. Saulter, C. O'Neill, C. Bellingham, and J. Lowe Ocean Sci. Discuss., 12, 2955-3001, doi:10.5194/osd-12-2955-2015, 2015 Manuscript under review for OS (discussion: open, 1 comment) The Singapore government commissioned a modelling study of regional projections of changes in (i) long-term mean sea level and (ii) the frequency of extreme storm surge and wave events. We find that changes to long-term mean sea level constitute the dominant signal of change to the projected inundation risk for Singapore during the 21st century, these being 0.52 m(0.74 m) under the RCP 4.5(8.5) scenarios respectively.

Description: Core operational Sentinel-3 marine data product services as part of the Copernicus Space Component H. Bonekamp, F. Montagner, V. Santacesaria, C. Nogueira Loddo, S. Wannop, I. Tomazic, A. O' Carroll, E. Kwiatkowska, R. Scharroo, and H. Wilson Ocean Sci. Discuss., doi:10.5194/os-2015-89,2016 Manuscript under review for OS (discussion: open, 0 comments) This paper describes the marine data available from the Marine Centre, part of the Sentinel-3 Payload Data Ground Segment, located at the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). Descriptions include the scientific and operational feedback mechanisms on the performance of the services as well as practical information and user support mechanisms.