Report on the Kick-off workshop of the Network of Experts for ReDeveloping Models of the European Marine Environment

The ‘Kick-off workshop of the Network of Experts for ReDeveloping Models of the European Marine Environment. Eutrophication modelling and Descriptor 5 of the Marine Strategy Framework Directive’ was held on 20-21 January 2016 in Brussels, Belgium, jointly organized by DG Environment and DG JRC (IES –Water Resources Unit) within the framework of the Administrative Arrangement NoENV.C.2/2015/070201/705766 (Deliverable 2.2) and the Marine Strategy Framework Directive (MFSD). The aim of this workshop was to learn about existing modelling work and to draw lessons for the build-up of the European modelling effort. In this context, the workshop consisted of 18 presentations on the use of marine ecosystem models to address indicators within the Eutrophication descriptor (D5) of the MFSD in coastal zones and European regional seas, including assessment, indicator development and scenario building. Some other descriptors were also covered by the presentations and discussions. The presentations dealt with (1) South European regional seas (Black and Mediterranean Seas), (2) Atlantic shelf areas, (3) North Sea and Baltic Sea and (4) General lectures. The workshop also served as the inception meeting of the newly created informal network of experts on the Modelling of the European Marine Environment (MEME). The participants were invited to join the network DG Environment and DG JRC emphasizing the added value of a joint effort to further develop modelling capabilities with the objective of providing useful advice for policy makers. This was well received by the attendants. This report summarizes the workshop and provides further detail on the presentations, discussion and conclusions.JRC.H.1-Water Resource

The seasonal cycle of the Atlantic Jet dynamics in the Alboran Sea: direct atmospheric forcing versus Mediterranean thermohaline circulation

TThe Atlantic Jet (AJ) is the inflow of Atlantic sur- face waters into the Mediterranean Sea. This geostrophically adjusted jet fluctuates in a wide range of temporal scales from tidal to subinertial, seasonal, and interannual modifying its velocity and direction within the Alboran Sea. At seasonal scale, a clearly defined cycle has been previously described, with the jet being stronger and flowing towards the northeast during the first half of the year and weakening and flowing more southwardly towards the end of the year. Different hy- pothesis have been proposed to explain this fluctuation pattern but, up to now, no quantitative assessment of the importance of the different forcings for this seasonality has been provided. Here, we use a 3D hydrodynamic model of the entire Medi- terranean Sea forced at the surface with realistic atmospheric conditions to study and quantify the importance of the differ- ent meteorological forcings on the velocity and direction of the AJ at seasonal time scale. We find that the direct effects of local zonal wind variations are much more important to ex- plain extreme collapse events when the jet dramatically veers southward than to the seasonal cycle itself while sea level pressure variations over the Mediterranean seem to have very little direct effect on the AJ behavior at monthly and longer time scales. Further model results indicate that the annual cycle of the thermohaline circulation is the main driver of the seasonality of the AJ dynamics in the model simulations.JRC.H.1-Water Resource

Application of the Singular Spectrum Analysis Technique to Study the Recent Hiatus on the Global Surface Temperature Record

Global mean surface temperature has been increasing since the beginning of the 20th century but with a highly variable warming rate, and the alternation of rapid warming periods with ‘hiatus’ decades is a constant throughout the series. The superimposition of a secular warming trend with natural multidecadal variability is the most accepted explanation for such a pattern. Since the start of the 21st century, the surface global mean temperature has not risen at the same rate as the top-of-atmosphere radiative energy input or greenhouse gas emissions, provoking scientific and social interest in determining the causes of this apparent discrepancy. Again, multidecadal natural variability is the most commonly proposed cause for the present hiatus period. Here, we analyze the longest and most up-to-date surface temperature database (HadCRUT4) with spectral techniques to separate a multidecadal oscillation (MDV) from a secular trend (ST). Both signals combined account for nearly 88% of the total variability of the temperature series showing the main acceleration/deceleration periods already described elsewhere. Three stalling periods with very little warming could be found within the series, from 1878 to 1907, from 1945 to 1969 and from 2001 to the end of the series. All of them coincided with a cooling phase of the MDV while the ST has shown a quasi-permanent warming trend from the beginning of the 20th century. Henceforth, MDV seems to be the main cause of the different hiatus periods shown by the global surface temperature records. However, and contrary to the two previous events, during the current hiatus period (2001–2013), the ST shows a strong fluctuation on the warming rate, with a large acceleration (from 0.0085°C year-1 to 0.017°C year-1) during 1992 – 2001 a and sharp deceleration (from 0.017°C year-1 to 0.003°C year-1) from 2002 onwards. This is the first time in the observational record that the ST shows such a drastic variability, so determining the causes and consequences of this change of behavior needs to be addressed by the scientific community.JRC.H.1-Water Resource

Report on scenarios for the Mediterranean Sea

The SEACOAST project of the Water Resources Unit (H01) of the Institute of Environment and Sustainability (IES) has aimed during 2015 to monitor, model and assess the environmental status of the marine and coastal waters of European seas. The SEACOAST project assists in implementing the objectives of the Marine Strategy Framework Directive (MSFD) by the assessment of the marine environment through targeted modelling and monitoring activities. Specifically, the main objective of the modelling activities within SEACOAST 2015 has been to assess the anthropogenic and climate driven changes on the marine environment by using adequate numerical modelling tools that include the main components of the Earth System; atmosphere, ocean, land and anthroposphere. In the scientific jargon, an integrated modelling system of this nature is typically referred as a Regional Earth System Model (RESM). In this context, the marine modelling group has been working to develop such modelling system for the Mediterranean Sea as a ‘benchmark’ case of EU regional seas. Within Deliverable 6 of SEACOAST 2015 on scenarios of the Mediterranean Sea, we have used a regional climate model (RCM) developed within the EuroCORDEX initiative to obtain atmospheric conditions for the Mediterranean region for the 21st century. However, before using the RCM variables to force the ocean model an intense work was necessary to reduce the bias in surface properties induced by model deficiencies. Once the present-day conditions in the basin could be satisfactorily simulated by using the RCM variables, this coupled atmosphere/ocean/hydrology system has been used to create a set of scenario simulations into the future under various emission scenarios (business as usual and worst case) and considering different options for freshwater management (associated with socio-economic scenarios). The objective of this work during 2015 has been to create the model system and to test its capability to perform in scenario mode for the Mediterranean Sea. Now that the tool is created and tested, it could be used to explore consequences of different policy options for Europe in near future in combination with expected climatic changes in the context of the MSFD.JRC.H.1-Water Resource

Adaptive nitrogen to phosphate ratio in biogeochemical models, consequences for the stoichiometry of the Mediterranean Sea

Biogeochemical marine models aim to replicate the chemical and low-trophic levels conditions of marine ecosystems. There are many types of such models, depending on complexity, specific aims and formulations. All of them are but rough approximation of the real ecosystems with many shortcomings and drawbacks so improvements and new formulations are always needed in order to increase their capability to reproduce real-life conditions. Here we present a modification of the biogeochemical model developed at JRC for representing marine conditions in the Mediterranean Sea, the MedERGOM model. This model has been demonstrated to properly represent biological production patterns in the basin but had some difficulties in simulating correctly concentrations of free nutrients in the seawater. In the present report we modify the internal ratio of the two main nutrients in the sea (nitrate and phosphate) by taking into account the physiological flexibility plankton communities show in the real environment. By making this simple modification we show how nutrients levels in seawater simulated by MedERGOM become much closer to observations, enhancing the capability of the marine modelling framework to simulate chemical conditions in nutrient-starved basins such as the Mediterranean Sea.JRC.D.2-Water and Marine Resource

Understanding The Causes of Recent Warming of Mediterranean Waters. How Much Could be Attributed to Climate Change?

During the past two decades Mediterranean waters have been warming at a quite high rate (De Madron et al., 2011) with the consequent scientific and social concern. This warming trend is observed in satellite data, in field sampling and in modeling simulations affecting surface and deep waters in the whole Mediterranean basin (Bethoux and Gentil, 1996; Nykjaer, 2009). The warming rate is, however, regionally different and also seems to change with time (Lelieveld et al., 2002) which has led to questioning what are the underlying causes of observed trends (Vargas-Yanez, 2008). Here we analyze available satellite information on sea surface temperature (SST) during the last 25 years with spectral techniques and find that more than half of the warming tendency during this period is due to a non-linear, wave-like tendency. Using a state of the art hydrodynamic model we perform a hindcast simulation and we obtain the SST evolution on the Mediterranean basin for the last 52 years. These SST results show clear sinusoidal tendency that follows the Atlantic Multidecadal Oscillation (AMO) during the simulation period. The acceleration of water warming during the 90’s seems, thus, to be caused by a superimposition of global warming with the positive phase of the AMO, while recent slow-down of the tendency is likely due to a shift in the AMO phase (Keenlyside et al., 2008). This change in AMO phase has been proposed to mask the effect of global warming in the forthcoming decades (Faurshou-Knudsen et al., 2011) and our results indicate that the same could be applicable to the Mediterranean Sea. Henceforth, natural multidecadal temperature oscillations should be taken into account to avoid an underestimation of anthropogenic-induced warming of the Mediterranean basin in the next future.JRC.H.1-Water Resource

Report on the second workshop of the Network of Experts for ReDeveloping Models of the European Marine Environment

The second workshop of the ‘Network of Experts for ReDeveloping Models of the European Marine Environment’ was held on 22-23 March 2017 in Brussels, Belgium, jointly organized by DG Environment and DG JRC (Water and Marine Resources Unit) within the framework of the Administrative Arrangement (N110661/ENV.C.2/2016/733192) and the Marine Strategy Framework Directive (MFSD). The aim of this workshop was to continue the information exchange between the Commission and marine modelling experts. Another important objective of this initiative is to narrow the gap between modellers and decision makers in order to better exploit the full utility of models. In this context, the workshop consisted of 17 presentations covering the wide use of marine ecosystem models to address several indicators of the MFSD in coastal zones and European regional seas, including assessment, indicator development and scenario building. The presentations dealt with (1) General lectures, (2) Eutrophication, (3) Hydrography, (4) Higher Trophic Levels and (5) Fish. The participants were invited to join the network informal ‘Network of experts on the Modelling of the European Marine Environment (MEME)’. DG Environment and DG JRC emphasized the added value of a joint effort to further develop modelling capabilities with the objective of providing useful advice for policy makers. This report summarizes the workshop and provides further detail on the presentations, discussion and conclusions.JRC.D.2-Water and Marine Resource

Separating Contributions from Anthropogenic Warming and from Natural Oscillations to Global Warming

During the past five decades, global air temperatures have been warming at a rather high rate (IPCC-2013) resulting in scientific and social concern. This warming trend is observed in field data sampling and model simulations and affects both air temperatures over land and over the ocean. However, the warming rate changes with time and this has led to question the causes underlying the observed trends. Here, we analyze recent measured and modeled data on global mean surface air temperature anomalies (GMTA) covering the last 160 years using spectral techniques. The spectral analysis of the measured data does show a strong secular trend (ST) and a clear multidecadal sinusoidal oscillation (MDV) that resembles the Atlantic Multidecadal Oscillation (AMO). The observed acceleration of the warming during the period from 1970 to 2000 therefore appears to be caused by a superimposition of anthropogenic-induced warming (~60%) with the positive phase of a multidecadal oscillation (~40%), while the recent slowdown (hiatus) of this tendency is likely due to a shift in the MDV phase. It has been proposed that this change in the MDV phase could mask the effect of global warming in the forthcoming decades and our analysis indicates that this is quite likely, the current hiatus being already a manifestation of this phenomenon. Most current generation global circulation models (CMIP5) do not reproduce this MDV and are missing the actual temperature hiatus. Therefore, it is less likely that such models could correctly forecast the temperature evolution during the coming decades. We propose here to use the climate dynamics that is inherent in the GMTA data to forecast temperatures until 2100. These forecasts, based on the analyzed secular trend and the multidecadal oscillations are indeed capable of reproducing the actual hiatus and generally result, in comparison to CMIP5 forecasts, in much lower temperature increases for 2100 of only about 1oC. Global mean air temperatures could be even decreasing for the next 2-3 decades. Henceforth, for a correct assessment of the anthropogenic-induced warming of the global air temperatures in the future natural multidecadal temperature oscillations should be taken into account.JRC.H.1-Water Resource

Multi-year simulations of future socio-economic and climate scenarios in the Mediterranean Sea

The Modelling Framework for European regional seas developed at unit D02 of the JRC is applied to explore plausible consequences for the Mediterranean Sea marine ecosystems of a set of climate and socio-economic scenarios for the 2030 horizon. The main objective of this work is to test the capability of the Modelling Framework to perform scenario forecasts. Therefore an ensemble of two different regional climate models under two selected emissions scenarios are combined with two socio-economic pathways to force a single hydrodynamic-biogeochemical ocean model. Socio-economic alternatives are reflected in the modelling system through changes in the river water quality (nutrient levels) that are flowing into the ocean basin. A step-wise approach allows to compare the different scenarios (combination of climate and socio-economic changes) and to quantify the induced changes in the marine ecosystem status. The model performance and the achieved results are strongly influenced by the reliability of the applied hydro-meteorological forcings. The applicability of the Modelling Framework to this type of scenario investigations could be successfully demonstrated.JRC.D.2-Water and Marine Resource

Revised Black Sea ecosystem model

The regional Black Sea Ecosystem Model (BSEM) has been updated to describe better the Black Sea phytoplankton growth specific features, like the strong winter-spring blooms followed by usually less intense blooms in fall. The revised BSEM model includes a phosphorus cycle in order to explore variability of phytoplankton blooms under phosphorus limitation. Two specific features of the upper layer water-column physical and biogeochemical structures have been addressed in the present study. - A detailed view of the large- and mesoscale-circulation characteristics, and thus more detailed interpretation of the spreading and mixing of nutrients is achieved by the use of tracer model simulations. They give us knowledge on the spreading of nutrients and biological matter, coming from the main Black Sea rivers, deep basin pool and intermediate layers, respectively, to the euphotic zone. - BSEM model calibration with constant and variable phosphorous/nitrogen ratio is performed. The relative importance of both fertilizers (nitrate and phosphate) on the phytoplankton growth is shown.JRC.D.2-Water and Marine Resource