Transient climate change scenario simulation of the Mediterranean Sea for the 21st century using a high-resolution ocean circulation model

International audienceA scenario of the Mediterranean Sea is performed for the 21st century based on an ocean modelling approach. A climate change IPCC-A2 scenario run with an atmosphere regional climate model is used to force a Mediterranean Sea high resolution ocean model over the 1960-2099 period. For comparison, a control simulation as long as the scenario has also been carried out under present climate fluxes. This control run shows air-sea fluxes in agreement with observations, stable temperature and salinity characteristics and a realistic thermohaline circulation simulating the different intermediate and deep water masses described in the literature. During the scenario, warming and saltening are simulated for the surface (+3.1°C and +0.48 psu for the Mediterranean Sea at the end of the 21st century) and for the deeper layers (+1.5°C and +0.23 psu on average). These simulated trends are in agreement with observed trends for the Mediterranean Sea over the last decades. In addition, the Mediterranean thermohaline circulation (MTHC) is strongly weakened at the end of the 21st century. This behaviour is mainly due to the decrease in surface density and so the decrease in winter deep water formation. At the end of the 21st century, the MTHC weakening can be evaluated as -40% for the intermediate waters and -80% for the deep circulation with respect to present-climate conditions. The characteristics of the Mediterranean Outflow Waters flowing into the Atlantic Ocean are also strongly influenced during the scenario

Climate change impact on waves in the Bay of Biscay, France

International audienceThe knowledge of offshore and coastal wave climate evolution towards the end of the twenty-first century is particularly important for human activities in a region such as the Bay of Biscay and the French Atlantic coast. Using dynamical downscaling, a high spatial resolution dataset of wave conditions in the Bay of Biscay is built for three future greenhouse gases emission scenarios. Projected wave heights, periods and directions are analysed at regional scale and more thoroughly at two buoys positions, offshore and along the coast. A general decrease of wave heights is identified (up to -20 cm during summer within the Bay of Biscay), as well as a clockwise shift of summer waves and winter swell coming from direction. The relation between those changes and wind changes is investigated and highlights a complex association of processes at several spatial scales. For instance, the intensification and the north-eastward shift of strong wind core in the North Atlantic Ocean explain the clockwise shift of winter swell directions. During summer, the decrease of the westerly winds in the Bay of Biscay explains the clockwise shift and the wave height decrease of wind sea and intermediate waves. Finally, the analysis reveals that the offshore changes in the wave height and the wave period as well as the clockwise shift in the wave direction continue toward the coast. This wave height decrease result is consistent with other regional projections and would impact the coastal dynamics by reducing the longshore sediment flux

The Climate-system Historical Forecast Project: providing open access to seasonal forecast ensembles from centers around the globe

Fil: Tompkins, Adrian M.. The Abdus Salam; ItaliaFil: Ortiz de Zarate, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Centre National de la Recherche Scientifique; FranciaFil: Saurral, Ramiro Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Centre National de la Recherche Scientifique; FranciaFil: Vera, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina. Centre National de la Recherche Scientifique; FranciaFil: Saulo, Andrea Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; ArgentinaFil: Merryfield, William J.. Canadian Centre for Climate Modelling and Analysis; CanadáFil: Sigmond, Michael. Canadian Centre for Climate Modelling and Analysis; CanadáFil: Lee, Woo Sung. Canadian Centre for Climate Modelling and Analysis; CanadáFil: Baehr, Johanna. Universitat Hamburg; AlemaniaFil: Braun, Alain. Météo-France; FranciaFil: Amy Butler. National Ocean And Atmospheric Administration; Estados UnidosFil: Déqué, Michel. Météo-France; FranciaFil: Doblas Reyes, Francisco J.. Institució Catalana de Recerca i Estudis Avancats; España. Barcelona Supercomputing Center - Centro Nacional de Supercomputacion; EspañaFil: Gordon, Margaret. Met Office; Reino UnidoFil: Scaife, Adam A.. University of Exeter; Reino UnidoFil: Yukiko Imada. Japan Meteorological Agency. Meteorological Research Institute. Climate Research Department; JapónFil: Masayoshi Ishii. Japan Meteorological Agency. Meteorological Research Institute. Climate Research Department; JapónFil: Tomoaki Ose. Japan Meteorological Agency. Meteorological Research Institute. Climate Research Department; JapónFil: Kirtman, Ben. University of Miami; Estados UnidosFil: Kumar, Arun. National Ocean And Atmospheric Administration; Estados UnidosFil: Müller, Wolfgang A.. Max-Planck-Institut für Meteorologie; AlemaniaFil: Pirani, Anna. Université Paris-Saclay; FranciaFil: Stockdale, Tim. European Centre for Medium-Range Weather; Reino UnidoFil: Rixen, Michel. World Meteorological Organization. World Climate Research Programme; SuizaFil: Yasuda, Tamaki. Japan Meteorological Agency. Climate Prediction Division; Japó

Mediterranean Sea response to climate change in an ensemble of twenty first century scenarios

The Mediterranean climate is expected to become warmer and drier during the twenty-first century. Mediterranean Sea response to climate change could be modulated by the choice of the socio-economic scenario as well as the choice of the boundary conditions mainly the Atlantic hydrography, the river runoff and the atmospheric fluxes. To assess and quantify the sensitivity of the Mediterranean Sea to the twenty-first century climate change, a set of numerical experiments was carried out with the regional ocean model NEMOMED8 set up for the Mediterranean Sea. The model is forced by air–sea fluxes derived from the regional climate model ARPEGE-Climate at a 50-km horizontal resolution. Historical simulations representing the climate of the period 1961–2000 were run to obtain a reference state. From this baseline, various sensitivity experiments were performed for the period 2001–2099, following different socio-economic scenarios based on the Special Report on Emissions Scenarios. For the A2 scenario, the main three boundary forcings (river runoff, near-Atlantic water hydrography and air–sea fluxes) were changed one by one to better identify the role of each forcing in the way the ocean responds to climate change. In two additional simulations (A1B, B1), the scenario is changed, allowing to quantify the socio-economic uncertainty. Our 6-member scenario simulations display a warming and saltening of the Mediterranean. For the 2070–2099 period compared to 1961–1990, the sea surface temperature anomalies range from +1.73 to +2.97 °C and the SSS anomalies spread from +0.48 to +0.89. In most of the cases, we found that the future Mediterranean thermohaline circulation (MTHC) tends to reach a situation similar to the eastern Mediterranean Transient. However, this response is varying depending on the chosen boundary conditions and socio-economic scenarios. Our numerical experiments suggest that the choice of the near-Atlantic surface water evolution, which is very uncertain in General Circulation Models, has the largest impact on the evolution of the Mediterranean water masses, followed by the choice of the socio-economic scenario. The choice of river runoff and atmospheric forcing both have a smaller impact. The state of the MTHC during the historical period is found to have a large influence on the transfer of surface anomalies toward depth. Besides, subsurface currents are substantially modified in the Ionian Sea and the Balearic region. Finally, the response of thermosteric sea level ranges from +34 to +49 cm (2070–2099 vs. 1961–1990), mainly depending on the Atlantic forcing

Understanding and predicting seasonal-to-interannual climate variability - the producer perspective

Seasonal prediction is based on changes in the probability of weather statistics due to changes in slowly varying forcings such as sea surface temperature anomalies, most notably those associated with El Niňo–Southern Oscillation (ENSO). However, seasonal weather can be perturbed by many factors, and is very much influenced by internal variability of the atmosphere, so comprehensive models are needed to identify what can be predicted. The predictability and probabilistic nature of seasonal forecasts is explained with suitable examples. Current capabilities for seasonal prediction that have grown out of work done in the research community at both national and international levels are described. Dynamical seasonal prediction systems are operational or quasi-operational at a number of forecasting centres around the world. Requirements for seasonal prediction include initial conditions, particularly for the upper ocean but also other parts of the climate system; high quality models of the ocean-atmosphere-land system; and data for verification and calibration. The wider context of seasonal prediction and seamless forecasting is explained. Recommendations for the future of seasonal prediction and climate services are given

Le changement climatique en France et en Europe atlantique : les domaines méditerranéens et tempérés

A dynamical downscaling of three RCP scenarios over Europe has been produced in 3 steps : (1) global climate model CNRM-CM5 at 150 km resolution, (2) global atmospheric model Arpege at 50 km resolution with sea surface temperature bias removed, (3) regional model Aladin at 12 km resolution. We compare the 1971-2000 model spring and summer climatology with the 2071-2100 one for temperature and precipitation. According to RCP8.5 scenario, the climate is 5°C warmer with a significant decrease in precipitation in western France. The RCP4.5 response is less catastrophic, but if we examine the deficit precipitation minus reference evapotranspiration for the May to September period in the 10% driest years, many regions in France could experience in the end of the 21st century the same deficit as the Mediterranean climate part of the country experienced in the end of the 20th century.Une méthode dynamique de désagrégation de 3 scenarios RCP a été appliquée en trois étapes. (1) modèle climatique global CNRM-CM5 a 150 km de résolution, (2) modèle atmosphérique global Arpege à 50 km de résolution avec élimination des biais de température de surface océanique, (3) modèle régional Aladin de 12 km de résolution. Nous comparons les simulations de la climatologie de la période 1970-2000 pour le printemps et l’été à celles de la période 2071-2100 pour la température et les précipitations. Selon le scénario RCP 8.5, le climat est plus chaud de 5°C avec baisse des précipitations pour l’ouest de la France. La réponse au scénario RCP4.5 est moins catastrophique, mais si l’on examine la différence précipitation – ET° de mai à septembre durant les 10 % d’années les plus sèches, de nombreuses régions de France pourraient connaître le même déficit que connaissait la région méditerranéenne à la fin du 20ème siècle