Perspectives and Integration in SOLAS Science

Why a chapter on Perspectives and Integration in SOLAS Science in this book? SOLAS science by its nature deals with interactions that occur: across a wide spectrum of time and space scales, involve gases and particles, between the ocean and the atmosphere, across many disciplines including chemistry, biology, optics, physics, mathematics, computing, socio-economics and consequently interactions between many different scientists and across scientific generations. This chapter provides a guide through the remarkable diversity of cross-cutting approaches and tools in the gigantic puzzle of the SOLAS realm. Here we overview the existing prime components of atmospheric and oceanic observing systems, with the acquisition of ocean–atmosphere observables either from in situ or from satellites, the rich hierarchy of models to test our knowledge of Earth System functioning, and the tremendous efforts accomplished over the last decade within the COST Action 735 and SOLAS Integration project frameworks to understand, as best we can, the current physical and biogeochemical state of the atmosphere and ocean commons. A few SOLAS integrative studies illustrate the full meaning of interactions, paving the way for even tighter connections between thematic fields. Ultimately, SOLAS research will also develop with an enhanced consideration of societal demand while preserving fundamental research coherency. The exchange of energy, gases and particles across the air-sea interface is controlled by a variety of biological, chemical and physical processes that operate across broad spatial and temporal scales. These processes influence the composition, biogeochemical and chemical properties of both the oceanic and atmospheric boundary layers and ultimately shape the Earth system response to climate and environmental change, as detailed in the previous four chapters. In this cross-cutting chapter we present some of the SOLAS achievements over the last decade in terms of integration, upscaling observational information from process-oriented studies and expeditionary research with key tools such as remote sensing and modelling. Here we do not pretend to encompass the entire legacy of SOLAS efforts but rather offer a selective view of some of the major integrative SOLAS studies that combined available pieces of the immense jigsaw puzzle. These include, for instance, COST efforts to build up global climatologies of SOLAS relevant parameters such as dimethyl sulphide, interconnection between volcanic ash and ecosystem response in the eastern subarctic North Pacific, optimal strategy to derive basin-scale CO2 uptake with good precision, or significant reduction of the uncertainties in sea-salt aerosol source functions. Predicting the future trajectory of Earth’s climate and habitability is the main task ahead. Some possible routes for the SOLAS scientific community to reach this overarching goal conclude the chapter

Experimental study of the Rhone plume. Part I: Physics and dynamics

The complicated dynamic processes occurring when fluvial waters mix with marine waters control the nature and the fluxes of materials exported tay rivers to the sea. Understanding these processes is of primary importance in evaluating budgets. In wide-open estuarine situations these processes take place under the influence of an intense turbulence induced by tides. Conversely, the Rhone waters spread into the Mediterranean Sea in the form of an easily distinguishable buoyant plume often extending far offshore from the mouth of the river. The aim of this study is to describe the dynamic and hydrological fields on the basis of eulerian VHF radar mapping of surface currents coupled with lagrangian in situ physical or geochemical measurements. This paper focuses mainly on physical processes. Data analysis provides an insight into the typical scales of variability of the phenomena, either vertically or horizontally. It is shown that morphological fluctuations can occur (mainly in orientation and offshore extent) according to wind and outflow forcing conditions, and that the vertical structure variations can range from an almost unaltered two-layer distribution to an evolving and deepening mixed layer situation, or even to a more complex superimposed multi-layered structure. The simultaneous examination of radar maps and lagrangian drifter tracking allows the main dynamic tendencies of the Rhone plume to be sketched out.La zone de mélange entre les eaux d'un fleuve et les eaux marines est le siège de processus dynamiques complexes qui conditionnent la nature et les flux de matières apportées au milieu marin. La compréhension de ces mécanismes est primordiale pour effectuer des bilans. Contrairement aux estuaires où la dilution est induite par une turbulence intense entretenue par les flux entrant et sortant de marée, les eaux du Rhône s'épanchent en Méditerranée sous forme d'un panache flottant sur de grandes distances au large de l'embouchure. L'objet du présent travail est d'appréhender les champs dynamiques et hydrologiques de cette structure au moyen de cartographies de vitesses eulériennes de courant superficiel par radar VHF et au moyen de mesures lagrangiennes in situ physiques et géochimiques. Cet article est consacré aux processus physiques. L'analyse des données permet de cerner la variabilité du phénomène, tant horizontale que verticale. Les fluctuations de morphologie (orientation et extension vers le large) du panache en fonction des conditions météorologiques et de débit fluvial sont mises en évidence, ainsi que les variations de sa structure verticale, allant d'une structure bicouche pratiquement non altérée à une couche bien mélangée, de caractéristiques en évolution et d'épaisseur croissante, ou à une superposition multicouche plus complexe. L'examen simultané des cartes de courant et des données physiques lagrangiennes permet de dégager les grandes tendances du fonctionnement dynamique du panache du Rhône

The effects of a strong winter storm on physical and biological variables at a shelf site in the Mediterranean

A survey involving both permanent mooring and high frequency sampling was carried in the Bay of Banyuls-sur-Mer during the fall of 1999 to assess the effect of strong and unpredictable meteorological events on the functioning of a coastal Mediterranean ecosystem. A severe winter storm took place on 12 November, which generated waves with a significant height of 7 m and a sea surface rise of about 0.5 m. The near-bottom current speed at 24 m reached 30 cm s(-1). This storm induced a significant increase in total suspended matter through resuspension and then a subsequent increase in gross sedimentation rates. It also resulted in an increase of the proportion of refractory particulate organic matter in the water column. It also tended to increase nutrient availability in the water column through resuspension and desorption processes. The kinetic of this increase differed among nutrients. Bacterial biomass and production were significantly enhanced by the storm. These effects were transitory and probably not due to resuspension alone. The distribution of plant pigments was modified at the immediate vicinity of the water-sediment interface due to differential resuspension and sedimentation but the storm had no effect on integrated phytoplanktonic biomass. Such a lack of response may be linked to low precipitations and/or light limitation. The storm resulted in a transitory increase of the abundance of fine particles at the water-sediment interface. These particles were coated with refractory organic matter. The storm induced a significant decrease of meiofauna abundance. The duration of the relaxation periods varied among parameters. It lasted 2 weeks for total suspended matter, surface sediment granulometry and carbohydrate contents.Une étude faisant intervenir des mouillages permanents et un échantillonnage haute fréquence a été conduite en baie de Banyuls-sur-Mer pendant l'automne 1999 afin de déterminer les effets d’événements météorologiques forts et imprévisibles sur le fonctionnement d’un écosystème côtier méditerranéen. Une forte tempête hivernale a eu lieu le 12 novembre 1999. Cette tempête a engendré des vagues dont la hauteur était proche de 7 mètres ainsi qu’une élévation du niveau de la mer voisine d’un demi-mètre. La vitesse du courant à 24 mètres de profondeur a alors atteint 30 cm s–1. Cette tempête a induit une augmentation significative de la concentration de matières en suspension dans l’eau puis une augmentation des taux de sédimentation brute. Elle a également résulté en une augmentation de la proportion de matière organique particulaire réfractaire dans la colonne d’eau. La tempête a également contribué à augmenter la disponibilité des sels nutritifs dans la colonne d’eau. La cinétique de cette augmentation a cependant différé d’un sel à l’autre. La biomasse et la production bactérienne ont toutes deux été positivement affectées par la tempête. Ces augmentations ont été transitoires et n’étaient probablement pas liées au seul processus de resuspension. La composition pigmentaire du phytoplancton a été modifiée à proximité immédiate de l’interface eau-sédiment mais la tempête n’a pas eu d’effet significatif sur la biomasse phytoplanctonique intégrée. Une telle absence de réponse pourrait être liée à la faiblesse des précipitations et/ou à une limitation par la lumière. La tempête a induit une augmentation transitoire de la proportion de particules fines à la surface du sédiment. Ces particules étaient associées à de la matière organique réfractaire. La tempête a également engendré une diminution significative de l’abondance de la meiofaune. La durée de la période de relaxation a varié d’un paramètre à l’autre. Elle a duré deux semaines pour les matières en suspension ainsi que pour la granulométrie et le contenu en carbohydrates des sédiments de surface