Automated in situ observations of upper ocean biogeochemistry, bio-optics, and physics and their potential use for global studies

The processes controlling the flux of carbon in the upper ocean have dynamic ranges in space and time of at least nine orders of magnitude. These processes depend on a broad suite of inter-related biogeochemical, bio-optical, and physical variables. These variables should be sampled on scales matching the relevant phenomena. Traditional ship-based sampling, while critical for detailed and more comprehensive observations, can span only limited portions of these ranges because of logistical and financial constraints. Further, remote observations from satellite platforms enable broad horizontal coverage which is restricted to the upper few meters of the ocean. For these main reasons, automated subsurface measurement systems are important for the fulfillment of research goals related to the regional and global estimation and modeling of time varying biogeochemical fluxes. Within the past few years, new sensors and systems capable of autonomously measuring several of the critical variables have been developed. The platforms for deploying these systems now include moorings and drifters and it is likely that autonomous underwater vehicles (AUV's) will become available for use in the future. Each of these platforms satisfies particular sampling needs and can be used to complement both shipboard and satellite observations. In the present review, (1) sampling considerations will be summarized, (2) examples of data obtained from some of the existing automated in situ sampling systems will be highlighted, (3) future sensors and systems will be discussed, (4) data management issues for present and future automated systems will be considered, and (5) the status of near real-time data telemetry will be outlined. Finally, we wish to make it clear at the outset that the perspectives presented here are those of the authors and are not intended to represent those of the United States JGOFS program, the International JGOFS program, NOAA's C&GC program, or other global ocean programs

Les îles d'Hyères dans le système de circulation marine et atmosphérique de la Méditerranée

International audienceThe scope of this paper is the general features of the marine and atmospheric circulations in the Mediterranean. It aims at providing keys to managers and other scientists to better understand the physical phenomena that impact the Hyères archipelago, in order to improve the environmental management if needed, and face potential risks.Cet article a pour but de présenter les grandes lignes du fonctionnement de la circulation marine et atmosphérique de la Méditerranée, afin de mieux comprendre les phénomènes physiques qui affectent les îles d'Hyères, d'optimiser la gestion de leur environnement et le cas échéant des risques potentiels. Mots-clés : Méditerranée, îles d'Hyères, Port-Cros, circulation des masses d'eau, courant, vent, état de mer, circulation atmosphérique, moyenne échelle. Abstract. The Hyères Archipelago in the marine and atmospheric circulation systems. The scope of this paper is the general features of the marine and atmospheric circulations in the Mediterranean. It aims at providing keys to managers and other scientists to better understand the physical phenomena that impact the Hyères archipelago, in order to improve the environmental management if needed, and face potential risks

La circulación superficial en la cuenca oriental del mar Mediterráneo

The schema of the Atlantic Water (AW, 100-200 m thick) circulation in the eastern basin of the Mediterranean Sea elaborated in the 1990s (and widely referred to nowadays) mainly shows jets meandering offshore across the whole basin. However, all previous schemata (since the 1910s) and an analysis of infrared (IR) satellite images in the 1990s show counterclockwise circulation at basin scale. A former controversy about the circulation was elucidated in the western basin where IR images helped describe the mesoscale features and demonstrate their role in the circulation. This motivated the detailed analysis of IR daily and weekly composites (~1000) from 1996 to 2000, and of monthly composites since 1985. We show that AW circulates along the upper part of the continental slope in a counterclockwise direction around the whole basin. In the south and all year long, this circulation is unstable and generates mesoscale anticyclonic eddies that spread AW offshore; in the north dense water formation induces larger seasonal variability. These mesoscale eddies, as well as the Etesian-induced eddies Ierapetra and Pelops, can be followed for years, sometimes several hundreds of km away from where they are formed, and they can merge and/or interact with the alongslope circulation.Los esquemas de circulación del Agua Atlántica (AW, 100-200 m de grosor) en el Mediterráneo oriental elaborados en los años 1990 (y abundantemente citados en la actualidad) presentan principalmente una corriente en chorro ondulante atravesando el centro de la cuenca. Por el contrario, todos los esquemas anteriores (desde los años 1910) y un análisis de imágenes infrarojas (IR) de satélite en los noventa presentan una circulación antihoraria a escala de la cuenca. Una controversia anterior sobre la circulación en la cuenca occidental fue resuelta gracias a que las imágenes IR ayudaron a describir los fenómenos de mesoescala y demostrar su papel en la circulación. Esto motivó un análisis detallado de imágenes IR compuestas diarias y semanales (~1000) durante 1996-2000 y mensuales desde 1985. Aquí demostramos que el AW en general circula sobre la parte superior del talud continental, de forma antihoraria por toda la cuenca. En el sur, y a lo largo de todo el año, esta circulación es inestable y genera remolinos anticiclónicos de mesoescala que esparcen el AW hacia alta mar; en el norte la formación de agua densa induce una gran variabilidad estacional. Estos remolinos de mesoescala, así como los inducidos por los vientos Etesios (Ierapetra y Pelops), pueden ser seguidos durante años, a veces por varios centenares de quilómetros a partir de su lugar de formación, y pueden unirse y/o interaccionar con la circulación a lo largo del talud.

Hydrochanges Gibraltar Campaign - characterization of Mediterranean Outflow through the Strait of Gibraltar

The precise characterization of the Mediterranean outflow through the Strait of Gibraltar is a very well know issue although a question rather far to be resolved completely. Many scientific efforts have been invested to try to define the exact composition and evolution of the Mediterranean waters (MWs) raising at the entrance of the strait and crossing one of the most dynamically active site of the worldwide oceans. In the framework of the Hydrochanges European programme, the “Gibraltar International Campaign” was carried out onboard the R/V Tethys II by the French Mediterranean Institute of Oceanography (MIO) in June 2012, with the chance to perform a series of highresolution CTD meridional transects. The instrument used is a Moving Vessel Profiler (MVP), a towed free-falling CTD, which enables a very high spatial resolution semi-autonomous monitoring of the column water. This work presents the hydrological data set retrieved in the campaign and proposes their usage as tool for the characterization of the composition and the evolution of the Mediterranean outflow along the strait. Two main assumptions are discussed: the generally accepted hypothesis of only two main Mediterranean waters crossing the strait, the Levantine IntermediateWater (LIW) and theWestern Mediterranean DeepWater (WMDW), and the novel theory, principally supported by the MIO group since last years, of the presence of up to four Mediterranean waters raising at the strait entrance: two intermediate waters, the LIW and the Winter Intermediate Water (WIW) and a further dense water, the Tyrrhenian Deep Water (TDW) flanking the WMDW. In both cases the mixing within these MWs and between them and the Atlantic inflowing waters, namely the Surface Atlantic Water (SAW) and the North Atlantic Central Water (NACW), are analyzed and discussed. A classical mixing triangle approach is proposed for the first assumption, with the definition of a third vertex as a general Atlantic water, and a novel approach based on a simplified cluster analysis of the Temperature/Salinity/Density diagrams of the transects, is applied to the six water masses considered in the second assumption. The latter is also applied to the GIBEX2 (Gibraltar Experiment) dataset in order to confirm, by a completely subjective approach, the rather arbitrary definition of the MWs accepted so far. A clear differentiation of the MWs along the cross-strait direction is observed, with intermediate waters laying on the northern Spanish slope and the denser ones flowing along the southern slope. However, this structure is deeply modified by the very strong mixing occurring in the strait and it ends to nearly disappear at west of the Camarinal Sill. The temporal variability, strictly related to the tidal dynamics, is very high, inducing strong changes in this structure throughout the strait, up to substantially modify it. In order to investigate this temporal variability, the recent series of current and thermohaline characteristics of the MWs, sampled simultaneously at Espartel and in two (north and south) extremes of the Camarinal Sill by the Physical Oceanography Group of the University of Málaga, have also been examined with interesting results on the characterization of the outflow evolution along the strait.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

HyMeX: A 10-Year Multidisciplinary Program on the Mediterranean Water Cycle

Drobinski, P. ... et. al.-- 20 pages, 10 figures, 1 table, supplement material http://journals.ametsoc.org/doi/suppl/10.1175/BAMS-D-12-00244.1HyMeX strives to improve our understanding of the Mediterranean water cycle, its variability from the weather-scale events to the seasonal and interannual scales, and its characteristics over one decade (2010–20), with a special focus on hydrometeorological extremes and the associated social and economic vulnerability of the Mediterranean territoriesHyMeX was developed by an international group of scientists and is currently funded by a large number of agencies. It has been the beneficiary of financial contributions from CNRS; Météo-France; CNES; IRSTEA; INRA; ANR; Collectivité Territoriale de Corse; KIT; CNR; Université de Toulouse; Grenoble Universités; EUMETSAT; EUMETNET; AEMet; Université Blaise Pascal, Clermont Ferrand; Université de la Méditerranée (Aix-Marseille II); Université Montpellier 2; CETEMPS; Italian Civil Protection Department; Université Paris- Sud 11; IGN; EPFL; NASA; New Mexico Tech; IFSTTAR; Mercator Ocean; NOAA; ENEA; TU Delft; CEA; ONERA; IMEDEA; SOCIB; ETH; MeteoCat; Consorzio LAMMA; IRD; National Observatory of Athens; Ministerio de Ciencia e Innovación; CIMA; BRGM; Wageningen University and Research Center; Department of Geophysics, University of Zagreb; Institute of Oceanography and Fisheries, Split, Croatia; INGV; OGS; Maroc Météo; DHMZ; ARPA Piemonte; ARPA-SIMC Emilia-Romagna; ARPA Calabria; ARPA Friuli Venezia Giulia; ARPA Liguria; ISPRA; University of Connecticut; Università degli Studi dell'Aquila; Università di Bologna; Università degli Studi di Torino; Università degli Studi della Basilicata; Università La Sapienza di Roma; Università degli Studi di Padova; Università del Salento; Universitat de Barcelona; Universitat de les Illes Balears; Universidad de Castilla-La Mancha; Universidad Complutense de Madrid; MeteoSwiss; and DLR. It also received support from the European Community's Seventh Framework Programme (e.g., PERSEUS, CLIM-RUN)Peer reviewe

Characterizing, modelling and understanding the climate variability of the deep water formation in the North-Western Mediterranean Sea

Observing, modelling and understanding the climate-scale variability of the deep water formation (DWF) in the North-Western Mediterranean Sea remains today very challenging. In this study, we first characterize the interannual variability of this phenomenon by a thorough reanalysis of observations in order to establish reference time series. These quantitative indicators include 31 observed years for the yearly maximum mixed layer depth over the period 1980–2013 and a detailed multi-indicator description of the period 2007–2013. Then a 1980–2013 hindcast simulation is performed with a fully-coupled regional climate system model including the high-resolution representation of the regional atmosphere, ocean, land-surface and rivers. The simulation reproduces quantitatively well the mean behaviour and the large interannual variability of the DWF phenomenon. The model shows convection deeper than 1000 m in 2/3 of the modelled winters, a mean DWF rate equal to 0.35 Sv with maximum values of 1.7 (resp. 1.6) Sv in 2013 (resp. 2005). Using the model results, the winter-integrated buoyancy loss over the Gulf of Lions is identified as the primary driving factor of the DWF interannual variability and explains, alone, around 50 % of its variance. It is itself explained by the occurrence of few stormy days during winter. At daily scale, the Atlantic ridge weather regime is identified as favourable to strong buoyancy losses and therefore DWF, whereas the positive phase of the North Atlantic oscillation is unfavourable. The driving role of the vertical stratification in autumn, a measure of the water column inhibition to mixing, has also been analyzed. Combining both driving factors allows to explain more than 70 % of the interannual variance of the phenomenon and in particular the occurrence of the five strongest convective years of the model (1981, 1999, 2005, 2009, 2013). The model simulates qualitatively well the trends in the deep waters (warming, saltening, increase in the dense water volume, increase in the bottom water density) despite an underestimation of the salinity and density trends. These deep trends come from a heat and salt accumulation during the 1980s and the 1990s in the surface and intermediate layers of the Gulf of Lions before being transferred stepwise towards the deep layers when very convective years occur in 1999 and later. The salinity increase in the near Atlantic Ocean surface layers seems to be the external forcing that finally leads to these deep trends. In the future, our results may allow to better understand the behaviour of the DWF phenomenon in Mediterranean Sea simulations in hindcast, forecast, reanalysis or future climate change scenario modes. The robustness of the obtained results must be however confirmed in multi-model studies

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

This paper is the outcome of a workshop held in Rome in November 2011 on the occasion of the 25th anniversary of the POEM (Physical Oceanography of the Eastern Mediterranean) program. In the workshop discussions, a number of unresolved issues were identified for the physical and biogeochemical properties of the Mediterranean Sea as a whole, i.e., comprising the Western and Eastern sub-basins. Over the successive two years, the related ideas were discussed among the group of scientists who participated in the workshop and who have contributed to the writing of this paper. Three major topics were identified, each of them being the object of a section divided into a number of different sub-sections, each addressing a specific physical, chemical or biological issue: 1. Assessment of basin-wide physical/biochemical properties, of their variability and interactions. 2. Relative importance of external forcing functions (wind stress, heat/moisture fluxes, forcing through straits) vs. internal variability. 3. Shelf/deep sea interactions and exchanges of physical/biogeochemical properties and how they affect the sub-basin circulation and property distribution. Furthermore, a number of unresolved scientific/methodological issues were also identified and are reported in each sub-section after a short discussion of the present knowledge. They represent the collegial consensus of the scientists contributing to the paper. Naturally, the unresolved issues presented here constitute the choice of the authors and therefore they may not be exhaustive and/or complete. The overall goal is to stimulate a broader interdisciplinary discussion among the scientists of the Mediterranean oceanographic community, leading to enhanced collaborative efforts and exciting future discoveries

Utilisation de l'imagerie satellitaire thermique pour les études de la circulation: application au bassin oriental de la Méditerranée

International audienceThe use of satellite thermal infrared images to infer marine circulation features is presented, here in the case of the eastern basin of the Mediterranean. Indeed, although the first schema of the surface circulation (water of Atlantic origin: AW) in the Mediterranean is one century old, the path of AW in the Eastern Basin is still debated nowadays. Does it flow along the Libyan and Egyptian slopes in a counterclockwise circuit at basin scale, or as an offshore jet that crosses the basin in its central part ("Mid-Mediterranean Jet")? In this paper we describe the use and contribution of the thermal images for the study of the surface circulation in the Eastern Basin, currently underway within the framework of the programs EGYPT (Eddies and GYres Paths Tracking) and EGITTO (2005-2008)

Biodynamique du bassin algerien : estimation de la reponse biologique a certaines structures hydrodynamiques de moyenne echelle par teledetection (AVHRR et CZCS) et mesures in situ

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Courants profonds et conséquences environnementales : l'exemple de la Méditerranée

Actes du colloque interdisciplinaire Droit & Océanographie « Les Fonds Marins : du Littoral aux Abysses » (Toulon, 24-25 novembre 2022)National audienceL'idée qu'il n'y a pas de courant en profondeur est encore relativement répandue. Le colloque interdisciplinaire Droit & Océanographie « Les Fonds Marins : du Littoral aux Abysses » (Toulon, 24-25 novembre 2022) est l'occasion de montrer des exemples, pris en Méditerranée, de courants non seulement horizontaux mais également verticaux, qui concernent (perturbent) la colonne d'eau, parfois jusqu'au fond (~3000m). Il est important de les prendre en compte car ils participent au transport et à la redistribution des particules ( nutrients et polluants), et peuvent perturber les installations et les mesures. La rareté des séries temporelles de longue durée de courant dans l'ensemble de l'océan (et en Méditerranée particulièrement, étant données les multiples échelles de variabilité) est préoccupante pour la bonne compréhension des effets d'installations ou d'activités dans le domaine maritime