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Although the air-sea gas transfer velocity k is usually parameterized with wind speed, the so-called small-eddy model suggests a relationship between k and the ocean surface turbulence in the form of the dissipation rate of turbulent kinetic energy ε. However, available observations of ε from oceanographic cruises are spatially and temporally sparse. In this study, we use a Gaussian Process (GP) model to investigate the relationship between the observed profiles of ε and co-located atmospheric and oceanic fields from the ERA5 reanalysis. The model is then used to construct monthly maps of ε and to estimate the climatological air-sea gas transfer velocity from existing parametrizations. As an independent validation, the same model is also trained on EC-Earth3 outputs with the objective of reproducing the temporal and spatial patterns of turbulence kinetic energy as simulated by EC-Earth3. The ability to predict ε is instrumental to achieve better estimates of air-sea gas exchange that take into account multiple sources of upper ocean turbulence beyond wind stress.

Organic particle populations in the mesopelagic layer span a wide range of sizes and sinking speeds. A long-standing paradigm in ocean biogeochemistry posits that large, fast-sinking detrital particles contribute to most of the vertical export flux of particulate organic carbon (POC), whereas small, slow-sinking or suspended particles comprise most (>90%) of the stock. Over the last decades, most studies have placed emphasis on understanding and predicting the vertical fluxes driven by large particles owing to their influence on ocean carbon storage. Yet, there are compelling reasons to study the dynamics of suspended and slow-sinking small POC (sPOC) in greater detail. First, sPOC likely supports most of the mesopelagic respiration. Second, recent studies have shown that a number of mechanisms can inject large amounts of sPOC into the mesopelagic layer, to the point that the sPOC fraction may seasonally dominate total vertical POC fluxes. Thus, better accounting for sPOC fluxes might allow us overcome historical difficulties in balancing mesopelagic carbon budgets.In the last decade, hundreds of bio-optical sensors deployed on autonomous profiling robots (bgc-Argo floats) have enabled observation of small particle stocks between the sea surface and 1000 m depth with a profiling frequency of 1-10 days. These observations are showing that mesopelagic sPOC follows distinct seasonal cycles in different oceanic areas, and allow identification of sPOC supply events (e.g., caused by vertical mixing or by disaggregation or fragmentation of larger particles) and of net sPOC removal. Regarding ocean biogeochemistry models, they have traditionally been tuned to estimate sinking POC fluxes but failed to capture POC stocks. Recently, the formulation of POC degradation rates in the model PISCESv2 was changed and a POC reactivity continuum approach was adopted, which greatly improved the representation of small and big POC stocks. These parallel developments now enable the quantitative assessment of mesopelagic POC dynamics.Here we analyze the annual cycles of mesopelagic sPOC in the subpolar North Atlantic, as seen by biogeochemical Argo floats, and compare them to their PISCESv2-simulated counterparts. We then discuss the processes that drive mesopelagic sPOC seasonality in the observations and in 1D model simulations. Finally, we present a genetic algorithm approach that uses biogeochemical Argo float observations to optimize the PISCESv2 parameters that influence sPOC, focusing on the interplay between particle degradation rate and sinking speed.

With the world population rapidly increasing and the related spectre of a global food crisis, the necessity to improve our ability to manage world's fisheries has never been more pressing. One important step in this direction is the improvement of near-term (i.e. seasonal to decadal) predictions of Net Primary Production (NPP). NPP is the rate of production of phytoplankton biomass, the primary source of food for marine animal life and thus a fundamental environmental variable to be taken into account in fishery management strategies. Here, we present results from a suite of simulations carried out with the Earth System Model EC-Earth3. These simulations include reconstructions of the biogeochemical state of the ocean for the period 1958 to present and a set of near-term predictions covering the period from 1979 to present. The simulations are designed to test the ability of two different initialization techniques to provide predictive skill to the simulation. One initialization technique is based on data-assimilation of physical fields only while, the second technique proposed is based on an attempt to partially reconstruct 3D nutrient fields. This combines information from climatological nutrient fields and reconstructed water masses variability. This combination is meant to exploit the ability of mode and intermediate water masses to propagate a signal on nutrient distribution on interannual timescales providing a source of predictability for nutrients and thus for NPP. Skill scores are used to validate these retrospective predictions derived from both techniques in order to obtain a complete evaluation of the predictive capability of the modelling system.

Special issue Selected Papers from the 2019 IMEKO TC-19 International Workshop on Metrology for the Sea.-- 17 pages, 11 figures, 1 table, 1 appendix, supplementary material https://doi.org/10.3390/s20092658, Since 2014, the global land and sea surface temperature has scaled 0.23 °C above the decadal average (2009–2018). Reports indicate that Mediterranean Sea temperatures have been rising at faster rates than in the global ocean. Oceanographic time series of physical and biogeochemical data collected from an onboard and a multisensor mooring array in the northwestern Mediterranean Sea (Blanes submarine canyon, Balearic Sea) during 2009–2018 revealed an abrupt temperature rising since 2014, in line with regional and global warming. Since 2014, the oligotrophic conditions of the water column have intensified, with temperature increasing 0.61 °C on the surface and 0.47 °C in the whole water column in continental shelf waters. Water transparency has increased due to a decrease in turbidity anomaly of −0.1 FTU. Since 2013, inshore chlorophyll a concentration remained below the average (−0.15 mg·l−1) and silicates showed a declining trend. The mixed layer depth showed deepening in winter and remained steady in summer. The net surface heat fluxes did not show any trend linked to the local warming, probably due to the influence of incoming offshore waters produced by the interaction between the Northern Current and the submarine canyon. Present regional and global water heating pattern is increasing the stress of highly diverse coastal ecosystems at unprecedented levels, as reported by the literature. The strengthening of the oligotrophic conditions in the study area may also apply as a cautionary warning to similar coastal ecosystems around the world following the global warming trend, The OOCS was initially funded by the Spanish National Research Project OAMMS Ref. CTM2008-03983 (PI. A.C). The research projects ADEPT Ref. CTM2011-23458 Ref. CTM2008-03983 (PI. F.P) and CONECTA Ref. CTM2014-54648-C2−1-R (PI J.B.C) partially contributed to the OOCS operations, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Shrimp farm aquaculture causes environmental impacts, notably decreased water quality due to the release of nutrient-rich effluents. Pond wastewater is usually discharged without treatment, and tidal conditions are not taken into account in the management plans. However, natural variability of nutrients makes difficult field evaluation and attribution of impacts. Here we implemented a three-dimensional coupled hydrodynamic-biogeochemical model (spatial resolution = 50 m × 50 m, time resolution = 4 s) in order to evaluate the dispersion conditions under specific tidal conditions of nutrient discharges from a semi-intensive shrimp farm during spring and neap tide. Ammonia was quickly assimilated by plankton and its concentration recovered initial levels 10 days after the beginning of the harvest. Due to the higher salinity of the pond effluents, shrimp farm discharges accumulate in waters and sediments of the upper lagoon creeks, mostly affecting the benthos, thus implying a potential risk of shrimp farm self-contamination. Maximum concentrations of most biogeochemical tracers occurred when the harvest ends and the ponds are fully emptied. We show that maximum nutrient concentrations can be reduced by ~ 10% when the harvest ends during spring tides compared to harvests ending during neap tides. This work may be useful to improve the management of shrimp farm effluents by reducing, easily and at little cost, nutrient impacts on tropical and sub-tropical receiving ecosystems.

Coastal lagoons provide important ecosystem services worldwide but are subject to high and multiple environmental stresses. Little information exists on the inner creeks of low-flow coastal lagoons, where the low-exchange rates may exacerbate anthropogenic impacts. In this work, we used a model with high spatio-temporal resolution to describe the hydrodynamics and to estimate the accumulation of conservative contaminants in the upper estuary of the Urias sub-tropical coastal lagoon, in northwestern Mexico. The lagoon shows a weak anti-estuarine behavior and its hydrodynamics is governed by astronomical tides and topography. The mean steady-state water age in the three lagoon areas was ∼15, ∼30 and ∼70 days in the Harbor, Intermediate and Upper Areas, respectively. Thus, the Upper Area, which shelters a mangrove forest, is the most vulnerable to pollution due to the high potential for accumulation. As a best case scenario, the simulation of the release of conservative substances in the Upper area indicated that, 50 days after the release started, conservative pollutants mostly remained in the Upper Area and were not significantly exported to the open ocean. This methodology can be used to model the impact of conservative substances in coastal lagoons worldwide, and can be complementary and useful for the optimization of long-term coastal zone management activities.

The ocean’s biological carbon pump plays a central role in regulating atmospheric CO2 levels. In particular, the depth at which sinking organic carbon is broken down and respired in the mesopelagic zone is critical, with deeper remineralisation resulting in greater carbon storage. Until recently, however, a balanced budget of the supply and consumption of organic carbon in the mesopelagic had not been constructed in any region of the ocean, and the processes controlling organic carbon turnover are still poorly understood. Large-scale data syntheses suggest that a wide range of factors can influence remineralisation depth including upper-ocean ecological interactions, and interior dissolved oxygen concentration and temperature. However these analyses do not provide a mechanistic understanding of remineralisation, which increases the challenge of appropriately modelling the mesopelagic carbon dynamics. In light of this, the UK Natural Environment Research Council has funded a programme with this mechanistic understanding as its aim, drawing targeted fieldwork right through to implementation of a new parameterisation for mesopelagic remineralisation within an IPCC class global biogeochemical model. The Controls over Ocean Mesopelagic Interior Carbon Storage (COMICS) programme will deliver new insights into the processes of carbon cycling in the mesopelagic zone and how these influence ocean carbon storage. Here we outline the programme’s rationale, its goals, planned fieldwork and modelling activities, with the aim of stimulating international collaboration.

14 páginas, 5 tablas, 6 figuras., Remote sensing of sea surface temperature (SST) is widely used in climate science because it provides a quasi-synoptic coverage of the ocean. However, the use of these data for near-shore habitats is hindered by the proximity of the coast, therefore further investigation is needed. We compared remote-sensing SST from the MODIS sensor (aboard the Aqua satellite) to near-shore seawater temperature (ST) recorded in situ with data loggers at 5 locations in the western Mediterranean Sea. In situ ST data were collected at 5 m depth over a ~6 yr period and at depths below 5 m at 3 of the locations. We evaluated the suitability of MODIS to represent the temperature at shallow subtidal depths relative to different modes of variability. MODIS reproduced seasonal variability with high correlations (r > 0.98) and biases (0.59 ± 0.03°C) only slightly higher than the accuracy of the loggers (0.50°C). MODIS also captured interannual variability with no systematic biases. When evaluated for intra-seasonal temperature variability, MODIS showed limited biases (up to 0.79°C) with a tendency to overestimate the variability (between 4 and 64%) in both cold and warm seasons. Finally, MODIS over-/underestimated only the most extreme unseasonably cold/warm events (by 1.51 and −0.79°C, respectively). The observed limited differences between the 2 methods can be explained by the particular hydro dynamics of the area and by methodological constraints. Overall, MODIS SST data proved to be a reliable proxy for near-shore ST in the western Mediterranean Sea, and are thus considered suitable for studies requiring temperature reconstruction in shallow near-shore environments., The study was funded in part by the Spanish Government through CSI-Coral Project (CGL2013- 43106-R). This is a contribution from the Marine Biogeochemistry and Global Change research group funded by the Catalan Government (2014SGR1029).

13 páginas, 10 figuras, 1 tabla., Mid-latitude spring blooms of phytoplankton show considerable year-to-year variability in timing, spatial extent and intensity. It is still unclear to what degree the bloom variability is connected to the magnitude of the vertical flux of organic matter. A coupled three-dimensional hydrodynamic-biogeochemical model is used to relate interannual variability in phytoplankton spring-bloom dynamics to variability in the vertical export of organic matter in the NW Mediterranean Sea. Simulation results from 2001 to 2010, validated against remote-sensing chlorophyll, show marked interannual variability in both timing and shape of the bloom. Model results show a tendency for the bloom to start later after cold and windy winters. However, the onset of the bloom occurs often when the mixed layer is still several hundred metres deep while the heat flux is already approaching zero and turbulent mixing is low. Frequency and intensity of wind episodes control both the timing and development of the bloom and the consequent export flux of organic matter. The wintertime flux is greater than zero and shows relatively low interannual variability. The magnitude of the interannual variability is mainly determined in March when the frequency of windy days positively correlates with the export flux. Frequent wind-driven mixing episodes act to increase the export flux and, at the same time, to interrupt the bloom. Perhaps counterintuitively, our analysis shows that years with discontinuous, low-chlorophyll blooms are likely to have higher export flux than years with intense uninterrupted blooms. The NW Mediterranean shows strong analogy with the North Atlantic section within the same latitude range. Hence, our results may also be applicable to this quantitatively more important area of the world ocean., This work was partly funded by the Spanish Ministry of Science and Innovation project “Observation, analysis and modelling of the Mediterranean Sea – OAMMS” CTM2008–03983. The first author (R.B.) would like to thank the Catalan regional government for financial support through the program FI.

We analyse simulations of the Pacific Ocean oxygen minimum zones (OMZs) from 11 Earth system model contributions to the Coupled Model Intercomparison Project Phase 5, focusing on the mean state and climate change projections. The simulations tend to overestimate the volume of the OMZs, especially in the tropics and Southern Hemisphere. Compared to observations, five models introduce incorrect meridional asymmetries in the distribution of oxygen including larger southern OMZ and weaker northern OMZ, due to interhemispheric biases in intermediate water mass ventilation. Seven models show too deep an extent of the tropical hypoxia compared to observations, stemming from a deficient equatorial ventilation in the upper ocean, combined with too large a biologically driven downward flux of particulate organic carbon at depth, caused by particle export from the euphotic layer that is too high and remineralization in the upper ocean that is too weak. At interannual timescales, the dynamics of oxygen in the eastern tropical Pacific OMZ is dominated by biological consumption and linked to natural variability in the Walker circulation. However, under the climate change scenario RCP8.5, all simulations yield small and discrepant changes in oxygen concentration at mid depths in the tropical Pacific by the end of the 21st century due to an almost perfect compensation between warming-related decrease in oxygen saturation and decrease in biological oxygen utilization. Climate change projections are at odds with recent observations that show decreasing oxygen levels at mid depths in the tropical Pacific. Out of the OMZs, all the CMIP5 models predict a decrease of oxygen over most of the surface and deep ocean at low latitudes and over all depths at high latitudes due to an overall slow-down of ventilation and increased temperature.

Tropical coastal areas are sensitive ecosystems to climate change, mainly due to sea level rise and increasing water temperatures. Furthermore, they may be subject to numerous stresses, including heat releases from energy production. The Urias coastal lagoon (SE Gulf of California), a subtropical tidal estuary, receives cooling water releases from a thermoelectric power plant, urban and industrial wastes, and shrimp farm discharges. In order to evaluate the plant thermal impact, we measured synchronous temperature time series close to and far from the plant. Furthermore, in order to discriminate the thermal pollution impact from natural variability, we used a high-resolution hydrodynamic model forced by, amongst others, cooling water release as a continuous flow (7.78 m3 s?1) at 6 °C overheating temperature. Model results and field data indicated that the main thermal impact was temporally restricted to the warmest months, spatially restricted to the surface layers (above 0.6 m) and distributed along the shoreline within ?100 m of the release point. The methodology and results of this study can be extrapolated to tropical coastal lagoons that receive heat discharges.

The separate impacts of wind stress, buoyancy fluxes, and CO2 solubility on the oceanic storage of natural carbon are assessed in an ensemble of twentieth- to twenty-first-century simulations, using a coupled atmosphere–ocean–carbon cycle model. Time-varying perturbations for surface wind stress, temperature, and salinity are calculated from the difference between climate change and preindustrial control simulations, and are imposed on the ocean in separate simulations. The response of the natural carbon storage to each perturbation is assessed with novel prognostic biogeochemical tracers, which can explicitly decompose dissolved inorganic carbon into biological, preformed, equilibrium, and disequilibrium components. Strong responses of these components to changes in buoyancy and winds are seen at high latitudes, reflecting the critical role of intermediate and deep waters. Overall, circulation-driven changes in carbon storage are mainly due to changes in buoyancy fluxes, with wind-driven changes playing an opposite but smaller role. Results suggest that climate-driven perturbations to the ocean natural carbon cycle will contribute 20 Pg C to the reduction of the ocean accumulated total carbon uptake over the period 1860–2100. This reflects a strong compensation between a buildup of remineralized organic matter associated with reduced deep-water formation (+96 Pg C) and a decrease of preformed carbon (−116 Pg C). The latter is due to a warming-induced decrease in CO2 solubility (−52 Pg C) and a circulation-induced decrease in disequilibrium carbon storage (−64 Pg C). Climate change gives rise to a large spatial redistribution of ocean carbon, with increasing concentrations at high latitudes and stronger vertical gradients at low latitudes.

26 páginas. 11 figuras,1 tabla.

22 páginas, 8 figuras, 1 tabla., The new pelagic Operational Observatory of the Catalan Sea (OOCS) for the coordinated multisensor measurement of atmospheric and oceanographic conditions has been recently installed (2009) in the Catalan Sea (41°39'N, 2°54'E; Western Mediterranean) and continuously operated (with minor maintenance gaps) until today. This multiparametric platform is moored at 192 m depth, 9.3 km off Blanes harbour (Girona, Spain). It is composed of a buoy holding atmospheric sensors and a set of oceanographic sensors measuring the water conditions over the upper 100 m depth. The station is located close to the head of the Blanes submarine canyon where an important multispecies pelagic and demersal fishery gives the station ecological and economic relevance. The OOCS provides important records on atmospheric and oceanographic conditions, the latter through the measurement of hydrological and biogeochemical parameters, at depths with a time resolution never attained before for this area of the Mediterranean. Twenty four moored sensors and probes operating in a coordinated fashion provide important data on Essential Ocean Variables (EOVs; UNESCO) such as temperature, salinity, pressure, dissolved oxygen, chlorophyll fluorescence, and turbidity. In comparison with other pelagic observatories presently operating in other world areas, OOCS also measures photosynthetic available radiation (PAR) from above the sea surface and at different depths in the upper 50 m. Data are recorded each 30 min and transmitted in real-time to a ground station via GPRS. This time series is published and automatically updated at the frequency of data collection on the official OOCS website (http://www.ceab.csic.es/~oceans). Under development are embedded automated routines for the in situ data treatment and assimilation into numerical models, in order to provide a reliable local marine processing forecast. In this work, our goal is to detail the OOCS multisensor architecture in relation to the coordinated capability for the remote, continuous and prolonged monitoring of atmospheric and oceanographic conditions, including data communication and storage. Accordingly, time series of measurements for a number of biological parameters will be presented for the summer months of 2011. Marine hindcast outputs from the numerical models implemented for simulating the conditions over the study area are shown. The strong changes of atmospheric conditions recorded in the last years over the area have altered the marine conditions of living organisms, but the dimension of the impact remains unclear. The OOCS multisensor coordinated monitoring has been specifically designed to address this issue, thus contributing to better understand the present environmental fluctuations and to provide a sound basis for a more accurate marine forecast system., The OOCS is supported by the Spanish Ministry of Science and Innovation project “Observation, analysis and modelling of the Mediterranean Sea—OAMMS” CTM2008-03983.Part of this research was funded within the framework of the National Research Project RITFIM (CTM2010-16274). Jacopo Aguzzi is a Postdoctoral Fellow of the Ramón y Cajal Program (MICINN).