Observations of a phytoplankton spring bloom onset triggered by a density front in NW Mediterranean

Phytoplankton blooms in the northwestern Mediterranean Sea are seasonal events that mainly occur in a specific area comprising the Gulf of Lion and the Provençal basin, where they are promoted by a general cyclonic circulation, strong wind-driven mixing and subsequent re-stratification of the water column. At the southern boundary of this area, a persistent density front known as the north Balearic front can be found. The front is presumed to cause an early phytoplankton bloom in its vicinity because (a) it enhances the transport of nutrients into the euphotic layer and (b) it promotes the speedy re-stratification of the water column (through frontal instabilities). In February and March 2013, a glider, equipped with a CTD (conductivity, temperature, and depth device) and a fluorometer, was deployed on a mission that took it from the Balearic Islands to Sardinia and back. The frontal zone was crossed twice, once during the outbound leg and the once on the return leg. The data provided by the glider clearly showed the onset of a bloom soon after a decrease in wind-driven turbulent convection and mixing. The in situ observations were supported and confirmed by satellite imagery. It is shown that frontal dynamics play a key role in the promotion and acceleration of re-stratification, which is a necessary pre-conditioning factor for the onset of blooms much like other relevant processes such as an enhanced biological pump. Swift re-stratification stimulates new production by inhibiting mixing. Finally, viewing the blooming phenomenon from a regional perspective, it seems that Sverdrup's critical depth model applies in the northern well-mixed area whereas, in the south, front-related re-stratification seems to be the principal cause. © Author(s) 2014.The research described in this paper was funded by the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262584, JERICOPeer Reviewe

IAPSO: tales from the ocean frontier

Our 21st century perspective on the oceans is due to the realization that knowledge of them and specifically their role in earth's climate are central to determining the future health of our planet. This present knowledge of the oceans builds on the farsighted work of people who, over the past century, worked to address seemingly intractable problems. The International Association for the Physical Sciences of the Oceans (IAPSO) has, over that long time span, promoted and supported the international approach that is now commonplace and has championed the provision of cross-cutting activities, the value of which we now fully recognize. This paper describes the key events in IAPSO's history and the roles played by the scientists involved

Decadal variability of the Turner Angle in the Mediterranean Sea and its implications for double diffusion

The physical reanalysis component of the Mediterranean Forecasting System is used to construct a high- resolution three-dimensional atlas of the Turner Angle. An assessment of the model quality shows a maximum degree of agreement with observations in the water column between 150 and 1000 m depth. The mean state of the favourable conditions for double diffusion processes is evaluated and the recent decadal variability is studied in terms of changes in the water mass properties. The results show that approximately 50% of the Mediterranean Sea is favourable to double diffusion processes, from which around 47% is associated with salt fingering. The Tyrrhenian, Ionian and southwestern Mediterranean are the most vulnerable basins to salt fingering, and the strongest processes can occur in the Tyrrhenian deep waters. Diffusive convection is most likely to occur in the Ionian, Aegean and eastern Mediterranean at vertical levels deeper than 1000 m. The observed gradual warming and salinification of the Medi- terranean after 1997 decreased and increased the possibilities of the occurrence of salt fingers and double diffusive convections, respectively. The climatological atlas that is presented in this paper pro- vides a three-dimensional picture of the regions that are either doubly stable or favourable to double diffusion instability and allows for the characterization of the diffusive properties of the water masses.Published64-774A. Oceanografia e climaJCR Journa

Thermohaline evolution at 400 m depth in the Sicily Channel, a choke point of the Mediterranean Sea

The Sicily Channel (SC) site has been monitored for thermohaline properties and water mass exchanges since 1993 by two moorings located within parallel trenches in the 150 km-long transect between Tunisia and Sicily. They form two of the longest Mediterranean time series of thermohaline properties. Due to the Coriolis effect, the IW core at the sill that funnel its westward flow is squeezed to the right, in both trenches, with the 400 m deep record in the north-eastern mooring (called C01) showing slightly warmer (by about 0.04 °C) and saltier (by about 0.01) values than the south-western one (called C02). As the temperature (T) and salinity (S) time series at both sites are very similar only the C02 (WMO code: 6101022, position: 37.2843° N, 11.4995° E) time series is presented here. The nominal depth of the instruments is 400 m, which is however subject to slight variations between servicing of the mooring, of the order of few tens of meters. From 1993 to November 2002 temperature and conductivity have been recorded by means of Aanderaa RCM7 current meters, with an accuracy of 0.05 °C and 0.05 for T and S, respectively. Since November 2002, SBE37 probes have been used, which further improved the quality of the measurements, yielding 0.002 °C and 0.001 for T and S, respectively. Both types of instruments (RCM and SBE) have been regularly calibrated (at least on an annual basis)

Thermohaline evolution at 400 m depth in the Sicily Channel, a choke point of the Mediterranean Sea, NetCDF

The Sicily Channel (SC) site has been monitored for thermohaline properties and water mass exchanges since 1993 by two moorings located within parallel trenches in the 150 km-long transect between Tunisia and Sicily. They form two of the longest Mediterranean time series of thermohaline properties. Due to the Coriolis effect, the IW core at the sill that funnel its westward flow is squeezed to the right, in both trenches, with the 400 m deep record in the north-eastern mooring (called C01) showing slightly warmer (by about 0.04 °C) and saltier (by about 0.01) values than the south-western one (called C02). As the temperature (T) and salinity (S) time series at both sites are very similar only the C02 (WMO code: 6101022, position: 37.2843° N, 11.4995° E) time series is presented here. The nominal depth of the instruments is 400 m, which is however subject to slight variations between servicing of the mooring, of the order of few tens of meters. From 1993 to November 2002 temperature and conductivity have been recorded by means of Aanderaa RCM7 current meters, with an accuracy of 0.05 °C and 0.05 for T and S, respectively. Since November 2002, SBE37 probes have been used, which further improved the quality of the measurements, yielding 0.002 °C and 0.001 for T and S, respectively. Both types of instruments (RCM and SBE) have been regularly calibrated (at least on an annual basis)

Observations of a phytoplankton spring bloom onset triggered by a density front in NW Mediterranean

Phytoplankton bloom in NW Mediterranan sea is a seasonal event that mainly occurrs in a limited area (Gulf of Lyon and Provençal basin) where this phenomenon is promoted by a cyclonic circulation, strong wind-driven mixing and subsequent spring restratification. At the southern boundary of this area a density front (North Balearic Front) separating denser waters from the lighter Modified Atlantic Waters reservoir at south is suspected to trigger weaker and earlier (late winter) blooms by (a) enhanced pumping of nutrients into the euphotic layer and (b) promoting an early restratification of the water column (by frontal instabilities). A multisensor glider round trip, equipped with CTD and fluorimeter, crossing the frontal area in February–March 2013, allowed to observe the bloom triggering after the decrease of intense wind-driven turbulent convection and mixing. Satellite imagery supports and confirms in-situ observations. It was shown that frontal activity has a relevant role in the promotion and acceleration of the dynamical restratification, with a consequent biological response in terms of primary production. Restratification is necessary preconditioning factor for bloom triggering in frontal area, net of other involved mechanism promoting the bloom as the enhanced biological pump. So, like for high-latitude fronts (Taylor and Ferrari, 2011a), also for this mid-latitude oligotrophic region front seems to promote new production by dynamically enahnced restratification inhibiting mixing. Finally, we argued that Sverdrup's Critical Depth criterion seems to apply in the northern well-mixed area, where the zeroing of heat fluxes (and related turbulent convection) does not correspond to a prompt onset of the bloom (which appeared 1 month later).The research leading to results discussed in this paper has received funding by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262584, JERICO. In particular, we especially thank the JERICO TNA programPeer Reviewe

JERICO. Report after JERICO Meeting in Brussels 26-27 feb. 2014

The objective of the workshop was to address main issues of JERICO project: - TNA: overview and formal approval of the selected proposals after the 3rd call - The JERICO Label document: content and issues - The JERICO strategy for the future. The document reports hereafter the synthesis of the discussion

Rapporto tecnico-scientifico sullo stato dell'arte dei sistemi oceanografici operativi in Mare Mediterraneo e nei mari italiani con particolare riguardo ai sistemi osservativi

L’attività dell’Unità Operativa 2 (UO02) all’interno della Azione 1 (AZ1) del progetto bandiera RITMARE (La Ricerca ITaliana per il MARE; http://www.ritmare.it/), del Programma Nazionale della Ricerca finanziato dal Ministero dell’Università e della Ricerca, è iniziata effettuando una ricognizione completa dei sistemi osservativi attualmente funzionanti in maniera operativa o pre-operativa nei mari Italiani i cui dati sono utilizzati per la validazione dei sistemi numerici o per essere assimilati al loro interno. La ricognizione sarà propedeutica al fine di mettere in evidenza punti deboli e ridondanze sia in termini generali che in base a specifiche zone geografiche, nonché per evidenziare possibili potenzialità future, attraverso una sintesi delle informazioni raccolte ed incontri con i soggetti attivi nell’oceanografia operativa in Italia. I risultati della UO02 in questa attività saranno accorpati con le informazioni acquisite dalle altre UO partecipanti all’azione e utilizzati dall’Azione 2- “Disegno e architettura delle linee di sviluppo e aggiornamento dei sistemi di previsione”, Work Package 4 (WP4) “Sistemi di previsione”, Sottoprogetto 5 (SP5) – “Sistemi Osservativi”. Durante i primi 24 mesi del progetto, il CNR ha provveduto a raccogliere le informazioni sui prodotti dei sistemi osservativi in real-time o near-real-time dei mari italiani, con l’obiettivo di validare i sistemi di previsione del mare disponibili nel 2012 – metà 2013, nell’ambito del WP4 Azione 1. Questo servirà in generale per poter cominciare a valutare i prodotti sui quali sviluppare le future attività di validazione dei sistemi di previsione del mare. In tale direzione è stato proposto un questionario ai diversi istituti ed enti di ricerca operanti sul territorio nazionale. I risultati del sondaggio hanno evidenziato almeno quattro grossi poli di osservazioni disponibili: l’area del Mar Ligure, il basso Tirreno, l’Adriatico e il canale di Sicilia. Questo rapporto è stato integrato inoltre con l’analisi e le conclusioni di un’attività di censimento dei sistemi di osservazione presenti in Italia, fatta nell’ambito del progetto nazionale “SSD Pesca - Sistema di supporto alle decisioni per la gestione sostenibile della pesca nelle regioni del Mezzogiorno d’Italia” (Sparnocchia et al., 2012), con lo scopo di valutarne la consistenza (distribuzione geografica, parametri misurati) ed evidenziarne i punti di forza e le criticità da risolvere per il migliore impiego a supporto del sistema pesca, con particolare riguardo al Mezzogiorno d’Italia