PROVOR line background and evolutions.

Patrice BRAULT1*, Jerome SAGOT1, David NOGRET1, Christophe SCHAEFFER1

* Presenting author

1) nke-instrumentation, France

IFREMER and NKE have built the French ARGO profiling float offer on the PROVOR model since 1998. Today in the NKE offer, ARVOR replaces PROVOR for the CORE ARGO mission. ARVOR is the object of constant improvements in the goal of reliability, ease of use and functionalities. The PROVOR float remains a mature base for various and new applications. Several evolutions have been carried on tube, the electrical supply, the electronic hardware and firmware: Provbio II (BGC Bio Geo Chemical) and Arctic model will be presented within projects remOcean, IAOSS, BIOMED and EAIMS. The last evolutions with the goal of intelligent floats are in progress with capability of self modification of mission after analysis of according acquired measurements are developed inside the frame of NAOS project for BIOICE and PROVAL.


Global assessment of Level 3 SMOS and Aquarius salinity measurements using Argo and an operational ocean model

Chris Banks1*, Christine Gommenginger1, Meric Srokosz1, Helen Snaith2

* Presenting author

1) National Oceanography Centre, Marine Physics & Ocean Climate, UK
2) National Oceanography Centre, British Oceanographic Data Centre, UK

The launch of the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite in November 2009 marked a new era in satellite oceanography. SMOS was joined in orbit, in June 2011, by the NASA/Argentine Aquarius/SAC-D mission, specifically designed to measure sea surface salinity (SSS). These two satellites have significantly improved our ability to measure SSS synoptically. Despite significant differences in how the two satellites estimate SSS, both utilise passive systems to measure the response of the brightness temperature (Tb) at L-band (1.4 GHz) to SSS and initial results are encouraging.

The UK National Oceanography Centre has produced ‘Level 3’ SSS data products for SMOS and Aquarius using monthly data on a 1º by 1º global grid, between 60ºS and 60ºN, from 1 September 2011 to 31 August 2012. Previous and on-going work shows for both satellites significant temporally varying differences between SSS from ascending passes (satellite moving south to north) and SSS from descending passes (satellite moving north to south). Therefore, for both SMOS and Aquarius, separate Level 3 products are produced from data for ascending and descending passes.

For this study, two separate monthly validation datasets are used based on the same grid as the satellite data. The first is averaged near-surface salinity (depth less than 10 m) as derived from the drifting Argo float programme. The second validation data source is output from the UK Met Office Forecasting Ocean Assimilation Model (FOAM), which is based on NEMO (Nucleus for European Modelling of the Ocean).

We calculate maps of the difference between all possible pairs of SSS data for each month, and consider their relationships using regression on the 1˚ values. The analysis is carried out for the global ocean, as well as for smaller, more homogeneous, study regions (e.g. SPURS in the subtropical North Atlantic).


Effects of very harsh 2012 winter conditions on the deep layer of the Southern Adriatic Sea

Manuel Bensi1, Vanessa Cardin1, Angelo Rubino2, Giulio Notarstefano 1, Pierre M. Poulain 1*

* Presenting author

1) Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Department of oceanography, Trieste
2) Universita’ Ca’ Foscari di Venezia, Dipartimento di Scienze Ambientali, Informatica e Statistica

An unusual harsh and extended (20 days) episode of Bora wind during the first half of February 2012 was responsible for a large production of very dense water (σθ > 30 kg m-3) in the northern basin of the Adriatic Sea (Eastern Mediterranean). Here, we use an integrated approach merging Temperature (T), Salinity (S) and current time-series collected at the deep-ocean observatory of the Southern Adriatic (E2M3A, at 41°32' N, 18° 05’ E) and CTD (Conductivity-Temperature-Depth) profiles obtained from freely drifting profiling floats to analyse the drastic thermohaline changes which occurred in the deep layer (>1000m depth) of the Southern Adriatic Pit (SAP) after the arrival of the dense water formed on the northern shelf. This episode interrupted the positive T and S bottom trends observed in the SAP during the last years, which were quantified by ~0.05°C y-1 and ~0.004 y-1, respectively. Presumably, those trends were associated to the combined effect of local mesoscale activity, large scale circulation changes and dense water formation processes. The descent of dense waters of Northern Adriatic origin caused an abrupt bottom T and S decrease (~0.15 °C and ~0.015, respectively). As a consequence, a density increase of ~ 0.02 kg m-3 was observed. Our data confirm that the deepest part of the SAP undergoes intense modifications only after very strong winter convection phases, which implies large volume contributions from the northern and middle Adriatic sub-basins. Moreover, they show that the exceptionally dense waters produced locally on the northern shelf arrived in the deep layer of the SAP, under the form of pulses, after the 10th of March 2012. However, a stronger signal definitively modified the thermohaline properties in that layer only after the 10th of April 2012. CTD float profiles collected in the Strait of Otranto, which connects the Adriatic Sea with the Ionian Sea, reveals that the Adriatic outflow in July 2012 was characterized by θ (potential temperature)~13.08°C, S~38.71, and σθ (potential density)~29.25 kg m-3. This fact reveals that the very harsh winter conditions, responsible for an exceptional production of very dense water in the Northern Adriatic, caused also modifications in the thermohaline properties of the Adriatic outflow with respect to those observed in the previous years (Δθ~ -0.2°C, ΔS~ 0.01, Δσθ~ +0.02-0.03 kg m-3). Hence, based on these results, possible implications on the deep Ionian circulation and variability need to be investigated.


The Euro-Argo education web site: using Argo data to teach data analysis and marine science

Valborg Byfield1*, Carolyn Scheurle2, John Gould1

* Presenting author

1) National Oceanography Centre, Marine Physics and Ocean Climate, U.K.
2) Observatoire Océanologique de Villefranche sur Mer, France

The Euro-Argo education website aims to make Argo and its data accessible to a non-specialist audience. The site is centred on a selection of floats, which have been chosen because of the insight they provide into key oceanographic processes, the physical and biogeochemical characteristics of different ocean regions around the world, and the role of the ocean in the global climate system.
The float selection is a vehicle for teaching data analysis skills, linking these to current topics in the ocean and climate sciences. Each float in the selection has its own page, which provides access to the float data, data plots, background information on the ocean region in which the float can be found, and questions to guide data interpretation. Hidden 'model answers' allow users to check their understanding by comparing their own answers to those provided.
The interactive component of the site also includes a series of quizzes, designed to teach data interpretation skills. These start at a basic level and take the students step by step through the most common ways to plot oceanographic data in space and time.
More general background information covers the main aspects of the Argo programme, its history and applications, and basic technical information about the floats and sensors. 'World Tour' pages linked to the float selection provide information about the main ocean regions and link information from the Argo programme to oceanographic information from other sources such as satellite observations.
The site is primarily aimed at young people between 11 and 18 years of age. However experience from using selected material from the site during science open days shows that children as young as 8-9 and adults of all ages also enjoy the challenge of using and interpreting the Argo data in different contexts.
Links to education outreach in the Euro-Argo member countries will give young people access to resources in their own laguage. The collaboration allows partners to share resources and build on successful ideas in existing projects. An example of how this can be done is the collaboration between the 'Adopt a Float' programme in Mon Ocean et Moi ( By sharing data, background information and ideas, we may get 'more for less' and reach a wider audience.


Consistency checks of delayed mode float analysis in the North Atlantic

Cécile CABANES1*, Virginie THIERRY2, Catherine LAGADEC2

* Presenting author


We are investigating the performance of the calibration method (OW method, Owens Wong, 2009) used to detect and correct salinity sensor bias or drift in the North-Atlantic. Our objective is to propose a kind of cookbook on how to use OW in this region. We have first selected all floats in the Subpolar gyre region that have been processed in delayed mode and for which no correction for salinity bias or drift was necessary according to the PI’s decision. We have then used this subset of “unbiased” floats to test the OW method in the Subpolar gyre region.
One would expect that the corrections proposed by OW for this subset of floats would be distributed around zero. However this is not the case when using historical CTDs as the reference. Indeed, negative corrections are systematically proposed (-0.02 to -0.03PSU) particularly along the Reykjanes Ridge and the topography in the Labrador sea. We have checked that these results were not strongly related to the choice of the parameters of the OW method. Instead, the systematically negative corrections proposed along the topography in the Labarador and Irminger seas are mainly explained by a large decadal variability that is not well captured in the CTD reference database. In consequence, salinity corrections estimated with OW and using the more recent Argo reference database seem to be more reliable. It is even necessary to select reference data within +/-2yr of the date of the profile in the Labrador Sea region because of large interannual variability. Finally, we have checked the corrections made on Argo profiles on the GDAC. We counted 8 floats in the subpolar gyre that have been corrected for positive salinity biases (negative corrections) comparable to those systematically proposed by the OW method in our test study. Therefore these floats may have been over-corrected and should be checked again.


Intensive measurements of oxygen concentrations during an open sea convection process in the Northwestern Mediterranean Sea using Argo floats

Laurent Coppola1*, Louis Prieur1, Fabrizio D\'Ortenzio1, Dominique Lefèvre2, Serge Le Reste3, Virginie Thierry4, Sophie Belamari5, Isabelle Taupier-Letage2, Claude Estournel6

* Presenting author

1) Laboratoire Océanographique de Villefranche/Mer, UMR 7093 CNRS/UPMC, France
2) Institut Méditerranéen d'Océanographie, UMR 7294 CNRS/IRD/Université d'Aix Marseille, France
3) Ifremer, RDT/EIM, France
4) Laboratoire de Physique des Océans, UMR 6523 CNRS/IFREMER/IRD/UBO, France
5) Meteo France, CNRM/GMGEC/MEMO, France
6) Laboratoire d'Aérologie et d'Océanographie Côtière, UMR 5560 CNRS/UPS, France

During the winter 2012/2013, an increased observation monitoring has been performed in the Northwestern Mediterranean Sea to study the deep water formation process that drive the thermohaline circulation and the biogeochemical processes (HYMEX and MERMEX projects). To understand the impact of the convection process, it was important to emphasize the hierarchy of the processes and the complexity of the interaction between these processes acting in the successive phases of preconditioning, convection, re-stratification including the very badly known dispersion of dense water formed during each storm event, as well as the complexity of their interaction. The corresponding observation strategy relies on the enhancement of the Argo floats network to monitor the offshore dense water formation area (DWF) in the Gulf of Lions - where the convection area is known to occur - prior to and at the end of the convective period (September 2012-April 2013).

To perform an effective observation of the deep convection process, we deployed four PROVOR-DOI floats: two during the preconditioning phase (late November 2012) in the northwest side of the DWF area and two in the middle of the DWF area (42°N5°E, late January 2013) during the active convection phase started in mid-January 2013 (as observed by satellite and gliders data). Within the framework of the NAOS French project, three more biogeochemical floats were deployed in the region to increase our observation capabilities. This deployment area is identified as a high priority for a future Mediterranean BioArgo network

The floats are based on a PROVOR CTS3, with a standard CTD sensor, and have been equipped with a new oxygen optode with faster time response (Aanderra 4330) to measure accurately the dissolved oxygen concentration which is considered as a good proxy for quantifying and tracking the newly formed water masses during the convection process. Following the Argo oxygen meeting (Brest in May 2011), the Aanderaa optodes 4330 have been sent to the CSIRO facilities for a more robust calibration (Uchida et al, 2008). These optodes have been cross-validated in laboratory before deployment and also during the floats deployment by co-located CTD profiles and water samples. The four PROVOR floats were also equipped with an iridium antenna to ensure a two-way communication. It allowed us to shift the Argo floats cycle during their deployment from one cycle (0-2000m depth) every five days before and after the convection process to one cycle every day during the convection period.

In the present study, we will show how extensive oxygen measurements from PROVOR-DOI floats can improve our understating on the convection extent, on the water masses properties changes, on the thermohaline circulation and on the spreading of the newly formed water at the NW Mediterranean Sea basin scale.


The North Icelandic Jet and its contribution to the Denmark Strait overflow water in a high-resolution ocean model

Carlo Corsaro1,2, Andreas Sterl2*

* Presenting author

1) Università di Catania, Dipartimento di Fisica e Astronomia, Italy
2) Royal Netherlands Meteorological Institute, Global Climate, Netherlands

Denmark Strait overflow water (DSOW) is a main contributor to the formation of the deep branch of the Atlantic Meridional Overturning Circulation. The origin of this overflow is generally attributed to the East Greenland Current (EGC). However, recent observations reveal that the North Icelandic Jet (NIJ) has a main role in the formation of the dense overflow water. Here we investigate the NIJ and its role among the current system north of the Denmark Strait by using an ocean general circulation model coupled to a prescribed atmosphere. The model gives a realistic depiction of the circulation and shows good agreement with the latest estimates of the mean transport of the NIJ, the North Icelandic Irminger Current and the DSOW. A good correlation between the time series of the NIJ and the DSOW suggests that the jet significantly contributes to the formation of the overflow water. The analysis of the dense water paths suggests that different sources feed the NIJ and, in particular, a southeastward branch of the EGC might be the main contributor to its transport.


A Bio-Argo pilot network in the Mediterranean Sea.

Fabrizio D\'Ortenzio1*, Susana Augusti5, Giuseppe Civitarese3, Hervé Claustre1, Carlos Duarte5, Clement Fontana1, Miroslav Gacic3, Pierre-Yves LeTraon6, Tommy S. Moore5, Laurent Mortier4, Pierre-Marie Poulain3, Louis Prieur1, Maurizio Ribera d\'Alcalà2, Vincent Taillandier1

* Presenting author

1) Laboratoire d’Océanographie de Villefranche, Centre National de la Recherche Scientifique and Universite ́ Pierre et Marie Curie, Paris O6
2) Stazione Zoologica Napoli , Italy
3) Istituto Nazionale Oceanografia e Geofisica Sperimentale, Italy
4) Ecole Nationale Supérieure de Techniques Avancées, France
5) Instituto Mediterráneo de Estudios Avanzados, Spain
6) IFREMER, France

Profiling floats measuring biogeochemical and bio-optical parameters (O2, Chl, CDOM, NO3, Irradiance) have been successfully developed and deployed during the last 5 years (among the others, Boss et al 2008, Johnson, et al. 2010, Xing et al. 2011). However, several issues still require to be addressed to transform the presently scattered use of biogeochemical profiling floats in a consolidated Bio-Argo network: real-time and delayed modes data quality control, data distribution, management costs, communication, deployment and sampling strategies. Implementing pilot networks over regional/sub-basin areas appears a suitable approach to address most of these issues, and to prepare a more global Bio-Argo network. In the framework of the French NAOS (Novel Argo Ocean observing System, PIs P.Y. LeTraon, F. D’Ortenzio) project, more than 30 biogeochemical profiling floats will be deployed in the period 2013-2016 in the Mediterranean Sea. Over the same period, additional biogeochemical floats (about 10-15) will be also deployed in the framework of other national and international programs. For the NAOS floats, a first deployment roadmap has been established, by evaluating the benefits and the disadvantage of different deployment strategies and the expected results in terms of scientific questionings. Here, we present an overview of the NAOS deployment roadmap and of the main scientific considerations related to the Mediterranean Bio-Argo network. A first analysis, based on the biogeochemical floats already deployed, will be discussed. Links with ocean colour observations is also presented, demonstrating the applications of paired satellite and Argo systems in observing biogeochemical variability.


Seasonal particle dynamics in the euphotic and mesopelagic regions of the Nordic Seas

Giorgio Dall\'Olmo1*, Kjell Arne Mork2

* Presenting author

1) PML, Plymouth, UK
2) IMR, Bergen, Norway

The Earth's climate and marine ecosystems in general depend on the transfer of carbon from the atmosphere to the interior of the ocean. Since this transfer is also mediated by oceanic particles such as phytoplankton and detritus, much efforts have been spent in perfecting satellite remote-sensing techniques to monitor the surface dynamics of these particles. However, relatively large uncertainties remain on the fate of these particles once they leave the surface ocean. These uncertainties could be reduced by exploiting Argo floats equipped with bio-optical sensors. We will report on the seasonal dynamics of bio-optical proxies for marine particles in the Nordic Seas as measured by bio-Argo floats over the course of two years. Preliminary results show that the inferred mesopelagic particle dynamics differ considerably between spring and summer. During the spring, fresh phytoplankton material appears to be rapidly exported below the euphotic zone. On the other hand, summer periods are characterized by slowly sinking particles, with sporadic pulses of highly refractive material. We hypothesize that the observed differences are related to the seasonal succession of phytoplankton at the surface. A comparison between satellite estimates of phytoplankton functional types and in-situ observations will be employed to test this hypothesis.


The sinking branch of the Atlantic Meridional Overturning Circulation

Sybren Drijfhout1*

* Presenting author

1) National Oceanography Centre, School of Ocean and Earth Sciences, UK

Regions with overturning feature large vertical heat transport, but little vertical mass transport. Intense downwelling in convective plumes is balanced by upwelling in surrounding areas and the area-integrated vertical mass transport in convective regions is small, because downwelling affects the vorticity by vortex stretching. In the interior the vorticity balance cannot be closed if significant downwelling occurs. Only near boundaries dissipation is large enough to balance the generation of vorticity by stretching of planetary vorticity. In a series of papers Spall and co-workers have shown that buoyancy forced downwelling is concentrated near lateral boundaries. Analysis of a NEMO025 hindcast confirms that the majority of the AMOC sinking branch indeed occurs in the boundary current along the northern half of the subpolar gyre. In the papers of Spall and others scaling relations that link the sinking to measurable, large-scale parameters have been proposed. These relations have been tested in the NEMO025 model. In this presentation I will review the recently developed sinking paradigm, how well it describes the sinking branch in an eddy-permitting model, and to what extent the sinking can be monitored from observations.


Optimal deployment of the BioArgo network: a modelling approach.

Clément Fontana1*, Hervé Claustre1, Fabrizio D\'Ortenzio1

* Presenting author

1) Laboratoire d'Océanographie de Villefranche, UPMC-CNRS / UMR 7093 Villefranche-sur-mer, France

In the last years, a new generation of biogeochemical marine sensors appeared (i.e. for chlorophyll, nitrate or oxygen concentration). Miniaturized and characterized by very low energy consumption, they are already successfully mounted on profiling floats, opening the way to imagine a global network of drifting autonomous platforms measuring biogeochemical parameters. Such a network will provide in a near future in situ estimation of ocean primary production at large scale. More than fifty of these floats should be deployed in 2013 in the North Atlantic region and in the Mediterranean sea.
The aim of this study is to draw up guidelines for optimally define such deployments on the basis of past-recorded trajectories of existing floats and modelling/assimilation projections. To define a deployment strategy, a focus on the characterization of a given process through an optimal spatio-temporal sampling will be considered as the main criteria.
The first step is to estimate the accuracy that could be expected in modelling of the sampling of biogeochemical quantities along realistic lagrangian paths. Float available trajectories are compared to trajectories computed with a lagrangian numerical model, based on velocity fields extracted from the NEMO model, in its ¼° configuration of the North Atlantic basin. Biogeochemical quantities (e.g. chlorophyll concentrations) sampled along real versus modelled float trajectories are then compared.
A method, based on a cloud of numerical floats deployed at the same place and same time as a real float, is proposed. The idea is then to compare a biogeochemical parameters (e.g. variable of the biogeochemical model) sampled along the real float trajectory with the equivalent mean-averaged quantity sampled by the cloud of numerical floats. We show that this method helps in modeling more precisely the sampling of biogeochemical quantities (through the description of the spring bloom phenology) along lagrangian trajectories. Results show that the chlorophyll concentration sampled along a lagrangian path can generally be numerically-forecasted with a satisfying accuracy for a complete seasonal cycle. The model performances are nevertheless highly dependent of the deployment positions, with consideration to geographical and hydrodynamical conditions (subpolar jet, subpolar gyre, intermediate area).
The perspectives of this work is the set up of data assimilation experiments aiming to quantify the amount of informations brought by a given network of drifting biogeochemical sensors.


Physical processes in the eastern Greenland Sea – observations from Argo floats accompanied by CTD surveys

Ilona Goszczko1*

* Presenting author

1) Institute of Oceanology Polish Academy of Sciences, Physical Oceanography Department, Poland

The Greenland Sea and its northern gate – the Fram Strait are the only deep connection between the North Atlantic and the Arctic Ocean. The heat and mass budget of this specific ocean region is simply constituted by two large current systems transferring water masses southward and poleward, along the underwater slopes of the East Greenland and the West Spitsbergen, respectively. Furthermore, other important physical phenomena, such as drifting and melting of sea ice, air-sea interactions, convection and deep water formation, dense water cascading from the shallow shelf peripheries, mesoscale features, altogether have a significant impact on the exchange of properties and water masses transformation. More of these physical processes may be recognized and well described from the dataset collected by Argo profiling floats. Nevertheless, the total number of floats deployed and having enough long life-time in this region of harsh conditions is not sufficient yet to cover all the fields of interest and needs, particularly the spatial and temporal resolution.

Long study of the eastern Greenland Sea summer hydrography based on repeated CTD sections conducted by the Institute of Oceanology PAS since 2000 show clearly the complex pattern of the Atlantic water advection, redistribution and recirculation into the colder and fresher environment between the Lofoten Basin, the Fram Strait, the Barents Sea shelf edge and deep basins of the western Greenland Sea. Complementary picture emerges from Argo floats deployed since 2009 – the ones launched in the neighborhood of the Bear Island circulate close to the southern tip of Spitsbergen and then following the topography rapidly flow farthest north and mostly recirculate south of the Fram Strait. Otherwise, they get under the ice and transmission ends. Both the trajectories and the properties measured by floats successfully circulating in the Greenland Sea indicate eddies activity and existence of larger structures such as jets and gyres.


Temperature signature of high latitude Atlantic boundary currents revealed by marine mammal-borne sensor and Argo data

Jeremy P. Grist1*, Simon A. Josey1, Lars Boehme2, Michael P. Meredith3, Fraser J. M. Davidson4, Garry B. Stenson5, Mike O. Hammill5

* Presenting author

1) National Oceanography Centre, UK
2) Sea Mammal Research Unit, St. Andrews University , UK
3) British Antartic Survey & Scottish Association of Marine Science, UK
4) Fisheries and Oceans Canada (Newfoundland and Labrador), Canada
5) Maurice Lamontage Institute, Fisheries and Oceans Canada, Canada

A key step towards understanding North-West Atlantic variability is a reliable determination of the mean temperature characteristics to serve as a baseline against which changes can be robustly determined. This is particularly important in the context of high-resolution ocean-only model studies: these are typically initiated from a temperature-salinity basic state and relaxed back to this state during the course of an integration to eliminate excessive drift. However, the global climatologies used most frequently for this purpose have a limited depiction of important coastal currents and consequently may inadvertently promote, rather than restrict, model drift. This shortcoming in the climatologies is partly due to the absence of Argo profiling floats from the shelf regions, as well as the fact that data acquired by research vessels in these regions are strongly seasonal in nature due to the challenges of working in ice-infested waters. In this work we address this challenge by combining data from 13,000 temperature profiles from Argo floats with that 48,000 profiles from marine mammal borne sensors to greatly enhance shelf region coverage where Argo floats are absent. Our analysis reveals distinctive boundary current related temperature minima in the Labrador Sea (-1.1 C) and at the east Greenland coast (1.8 C), largely absent in the widely-used Levitus’09 and EN3v2a datasets. Furthermore the 0-500 m average temperature is lower than Levitus’09 and EN3v2a by up to 3 C locally. Our results clearly reveal the value of combining data from marine mammal-borne sensors with Argo floats for an improved description of the North-West Atlantic at a time of rapid change.


Data Quality Assessment of in situ and altimeter observations through two-way intercomparison methods

Stéphanie Guinehut1, Michael Ablain1, Marie-Hélène Rio1, Guillaume Valladeau1, Jean-François Legeais1, Gilles Larnicol1, Christine Boone1*

* Presenting author

1) CLS, Space Ocean Division, France

Intercomparison methods also called multi-observations CalVal (Calibration/Validation) methods are widely used between in situ and satellite data to assess the quality of the latest. The stability of the different altimeter missions is, for example, commonly assessed by comparing altimeter sea surface height measurements with those from arrays of independent tide gauges [Mitchum, 2000; Valladeau et al., 2012]. Other examples include the validation of altimeter velocity products with drifting buoys observations provided by the Global Drifter Program (GDP) [Bonjean and Lagerloef, 2002; Pascual et al., 2009] that are also used for the systematic validation of satellite SST thanks to their in situ surface temperature measurements. In turn, comparison of in situ and altimeter data can also provide an indication of the quality of the in situ measurements [Guinehut et al., 2009; Rio et al, 2012].
This talk presents an overview of the two-way intercomparison activities performed at CLS for both space and in situ observation agencies and why this activity is a required step to obtain accurate and homogenous data sets that can then be used together for climate studies or in assimilation/validation tools. We first describe the work performed in the frame of the SALP program to assess the stability of altimeter missions through SSH comparisons with tide gauges (GLOSS/CLIVAR network). Then, we show how the SSH comparison between the Argo array and altimeter time series allows the detection of drifts or jumps in altimeter (SALP program) but also for some Argo floats (Ifremer/Coriolis center). Lastly, we describe how the combined use of altimeter and wind observations helps the detection of drog loss of surface drifting buoys (GDP network) and allow the computation of a correction term for wind slippage.


Using Eulerian and Lagrangian time-series data to improve models of ocean biogeochemistry

John C. P. Hemmings1*, Peter G. Challenor2

* Presenting author

1) National Oceanography Centre, Marine Systems Modelling, UK
2) University of Exeter, College of Engineering Mathematics and Physical Sciences, UK

Time-series data comprising physical and biogeochemical observations are essential for assessing the fidelity of biogeochemical model response to physical drivers. Models are typically semi-empirical constructs representing our understanding of dominant plankton ecosystem processes in the cycling of key elements such as carbon and nitrogen. Such models necessarily rely on many adjustable parameters to compensate for un-modelled biological complexity and incomplete ecological knowledge. Bio-Argo data promise to improve constraints on these parameters leading to more reliable predictions of environmental change. However, uncertainty in the physical environment to which the ecosystem responds raises particular challenges for model calibration and assessment, implying an external source of error in trial simulations. The expected simulation error must be taken into account in model-data comparison if reliable inferences are to be made.

Recent advances are enabled by the development of a new water-column simulation tool for plankton model analysis: the Marine Model Optimization Testbed. MarMOT supports multi-column ensemble simulations and parameter optimization in a realistic 3-D context. 1-D analysis allows computational effort to be focussed on data-rich locations such as time-series sites or Argo float tracks. MarMOT has been used to demonstrate, in experiments with synthetic data, that plausible patterns of environmental uncertainty can lead to strong temporal and spatial variability in the expected simulation error of observable biogeochemical properties. A new calibration scheme that uses this information in weighting residuals gives a marked improvement in parameter estimates when tested against established methods. The results motivate efforts to better characterize real-world uncertainties, including those associated with the effects of lateral advection or shear flow as well as those due to vertical transport processes.

A statistical modelling strategy for the environmental input data is described. Ideally, simulations for a trial model would represent its response to a perfect 3-D circulation so that advective tendencies depended on real-world currents and upstream tracer gradients for a hypothetical simulation. Gradient distributions can be provided by 3-D biogeochemical simulations and constrained by satellite SST gradients on the basis of modelled relationships. Satellite products also provide constraints for near-surface currents. In-situ measurements can be used to constrain physical properties of the water column. Where physical observations are unavailable, statistics must rely on model results and their uncertainties inferred from validation data. High levels of uncertainty mean that only weak parameter constraints can realistically be obtained from syntheses of data from individual sites or Argo floats. The size of the data set and its representativeness of the global ocean are key to obtaining good constraints for global models.


Hydrographic properties of the Cretan Sea derived from an Argo float profiles and buoy data measurements during 2010-2012

Dimitris Kassis1*, Karina Von Schuckmann2, Gerasimos Korres1

* Presenting author

1) Hellenic Centre for Marine Research, Institute of Oceanography, Greece
2) Ifremer, LER/LOS, France

The Cretan Sea is characterized as a transitional area with complex hydrology. Water masses formed in the Levantine, Aegean and Adriatic Seas, meet here and interact with water masses deriving from the Western Mediterranean Sea and entering through the Sicily straits. We examine hydrographic characteristics of the Cretan Sea using profile data derived from the first Argo float deployed in the area during June 2010 within the framework of the Greek Argo program. The 75 profiles measured by the float, covering a 2-year period, are analyzed and combined with time series data recorded from the E1M3A multi-parametric instrumentation platform operating in the area since 2007. Spatial analysis reveals significant variability at subsurface layers with strong, alternating signals of Modified Atlantic Water and Levantine Intermediate Water. Intermediate water formation events in the basin are revealed while data also suggests evidence for deep convection events occurring after a series of pre-conditioning signals. These preliminary results reveal the dynamic and variable hydrological regimes in the sub-surface, intermediate, and deep layers of the Cretan Sea basin.


The Deep Arvor : technology and results from the first deployment

Serge LE RESTE1*, Vincent DUTREUIL1, Xavier ANDRE1, Coralie TRAUTMANN1, Virginie THIERRY2

* Presenting author


Monitoring the deep ocean below 2000 meters is one of the main foreseen evolutions of Argo. There is a strong requirement from the ocean and climate research community to have floats able to go deeper than 2000 m in order to observe large-spatial scale variability and change in temperature and salinity on timescales of a decade and longer. However target and requirements for a deep argo array are still not clear; pilot experiments, at least for several years, are necessary for acquiring information needed both for array design and to determine the cost-feasibility of global sampling.
In order to address this challenge, Ifremer has designed and tested the Deep Arvor. The work has been carried out in the framework of Euro-Argo preliminary phase and NAOS ( Novel Argo Ocean observing System - project. The Deep Arvor is an extension of the 2000m depth version of Arvor. It has been designed to achieve more than 150 cycles at 3500m depth with CTD (continuously pumped) and oxygen measurements. The self-ballasting feature and the light weight of Arvor have been maintained in a cost effective solution. Several improvements have been done like transmission of high sampling profiles with Iridium communication, filament winding housing to save weight, new technical parameters for diagnostic to better monitor the float behavior. Sub assemblies have undergone intensive tests in pressure tanks. This year, the industrial float will be extended to a 4000m operating depth by using a higher range pressure sensor.
Two deep Arvor (3500 m) have been tested in 2012. One prototype was deployed in the Bay of Biscay and has been retrieved due to a decrease of the antenna performance. This float should be re-deployed soon. The second prototype, which cycled every 2 days in mid-Atlantic Ocean from August 2012 to January 2013, performed 60 cycles at 3500m depth. It was deployed in an area where the water masses are stable in order to assess the quality and behaviour of the sensors in deep (greater than 2000 db) layers. Results from this deployment will be presented.


Seasonal to interannual variability of temperature and salinity in the Nordic Seas: heat and freshwater budgets

Katrin Latarius1*

* Presenting author

1) University of Hamburg, Institut für Meereskunde Hamburg (IFM), Germany

Eleven years of autonomous profiling float data from the Nordic Seas are used to detect changes in temperature and salinity of the water column on time scales from seasonal to decadal. The measurements concentrate on the deep Norwegian Basin, Lofoten Basin and Greenland Sea Basin and the somewhat shallower Icelandic Plateau. Time series of temperature and salinity are dominated by the seasonal cycle in the upper 500 to 750 m. But also the longer-term development is detected. The heat and freshwater budgets reveal a similar structure for all basins: The effect of ocean-atmosphere and internal ocean fluxes on heat and freshwater is largely confined to the upper 500 m. They import heat laterally from the boundary currents below 50 m and export heat to the atmosphere and to a minor degree laterally in the upper 50 m. Freshwater is imported into the basins laterally in the upper 50 m and to a minor degree from the atmosphere. Below 50 m freshwater is exported laterally. Thus the water mass conversion from inflowing Atlantic waters to dense overflow waters in the basins is underestimated by taking only atmospheric fluxes into account. The net contribution of the basins to the water mass conversion in the Arctic Mediterranean on the whole is about 15 % although they account for only 4 % of the total area. The contribution from the eastern basins is of greater importance than the one from the western basins.


New PROVOR float dedicated to challenging sensors and complex missions: opportunities for arctic deployments

Edouard Leymarie1*, Christophe Penkerc\'h1, Christophe Schaeffer2, Claudie Marec3, Arnaud David2, Antoine Poteau1, Patrice Brault2, Hervé Claustre1, Marcel Babin3

* Presenting author

1) CNRS/UPMC, LOV, France
2) NKE, Instrumentation, France
3) U. Laval/CNRS, TAKUVIK, Canada

For more than a decade, the Argo program has proved its usefulness for physical measurements within the ocean. More recently, floats developed for this program have been used independently for a large number of other applications, from biogeochemical measurements to rainfall estimation. New programs, like remOcean and NAOS projects, have already succeeded in merging a significant number of sensors on the same float named ProvBioII (NKE). This float is perfectly suitable for a large range of “BioArgo” applications, and merging of sensors provides scientific benefits and cost reductions. Now new challenging sensors, such as imaging, chemical or acoustic sensors, are already planned to be implemented on floats. These new applications will need improved capacities of the float, in particular the electronic which manages sensors, and also increased flexibility of the float missions to accommodate all the potentials scientific applications. All these new capacities make this new float well adapted for arctic deployments, which require an avoidance of sea-ice and a large storage of data.
We present here a prototype version of a new NKE float which implements the so-called “double electronic boards” architecture. This scheme is based on one navigation board to drive the float and one acquisition board to drive sensors. This architecture is used to secure vital functions of the float and allows easier and safer integration of new challenging sensors. The new float prototype is equipped with a new navigation board developed by NKE, named APMT. This board allows script-based mission and is able to exchange data and receive navigation commands from an acquisition board. This allows retroactive programming of the float’s mission based on scientific measurements, which could be extremely useful for a large number of applications including arctic deployments (avoidance of sea-ice) or adapted sampling of biogeochemical events. In addition, this new APMT board has large memory capacities as well as advanced remote control options. A new acquisition board developed by the LOV and OSEAN Company has been interfaced with the float. This new low power acquisition board is able to accommodate a large range of sensors (including news sensor for sea-ice detection) and perform in real time complex processing of collected data (FFT, Wavelet decomposition or statistical identification).
Descriptions of specifications, laboratory validations and first deployments of this new float will be presented here, as well as new opportunities for scientific applications. There will be a special focus on the technical solutions provided by this new float to arctic needs.
Acknowledgements: This project is founded thanks to remOcean (ERC advanced grant N°246777), NAOS (ANR-10-EQPX-40) and ProVal (CNES-TOSCA) projects.


Challenging deployment of biogeochemical ARGO floats in Arctic ice edges : need for an efficient sea-ice detection system.

Claudie MAREC1*, Marcel BABIN1, Edouard LEYMARIE2, Christophe PENKERC\'H2, Guislain BECU1

* Presenting author


The main objective of the oceanographic component of Takuvik is to analyze the impacts of climate change and anthropogenic activities on Arctic ecosystems.
The Arctic ice edge is a location with high biological production in the spring and summer months. Phytoplankton blooms are often observed there (ice edge blooms). While ocean colour remote sensing provides valuable information on trends in biogeochemical processes of the Arctic Ocean, its use is limited to the ocean surface. According to studies based on ocean colour remote sensing, it is estimated that ice-edge blooms may represent more than a half of the total Arctic deep primary production.
Consequently, to support and complement the group’s remote-sensing and modelling activities, Takuvik plans to deploy ARGO floats with a bio-optical payload in the ice-edge zone of the Arctic, especially in Baffin Bay.
However, deploying profiling floats in the Arctic poses a major challenge due to the difficulty in adapting the floats to the icy conditions of the Arctic Ocean. While the target is the deployment of the floats in the seasonal-ice zone in open waters rather than under the ice pack, ice detection is necessary to avoid ice floes, thus allowing successful surface emersion for positioning and communication.

Under the framework of a CERC (Chairholder M. Babin), Takuvik plans to deploy biogeochemical Argo floats funded by a Canada Foundation for Innovation grant (CFI).
In parallel, Takuvik, one of the 9 partners in the french NAOS project, is responsible for WP4: deployment of biogeochemical floats in Arctic (to start in 2014).
This new generation of NKE floats are designed under the NAOS project. In addition to the biogeochemical payload, they will have enhanced characteristics (described by E.Leymarie LOV, poster).

Descriptions of the needs of spring ice-bloom observations, specifications of the bio-optical float, strategies for deployment (location, tactical pattern, etc…) will be presented here.
A special focus on unavoidable sea-ice detection systems is done, especially on optical sea-ice detection under development by Takuvik.

Acknowledgements: This project is founded thanks to CERC (FCI#30124), NAOS (ANR-10-EQPX-40)


The Pole-to-Pole Atlantic Ocean main pycnocline from Argo data

Guillaume Maze1*, Virginie Thierry1, Herlé Mercier2

* Presenting author

1) Ifremer, LPO, France
2) CNRS, LPO, France

At mid-latitudes, the oceanic vertical structure of density is characterized by a permanent highly stratified layer: the pycnocline. The pycnocline is the transition layer between surface water masses ventilated every winter when penetrated locally by the mixed layer and deeper water masses which have been ventilated at high latitudes and circulate equatorward.
The pycnocline thus reflects a large scale balance between the penetration of local air-sea interactions and the re-emergence of remote ones.
The overall question we want to address is whether and to which extent the variability of the pycnocline properties (depth, thickness and thermohaline characteristics) are influenced by those of air-sea interactions.
To this end, we first developed a new method to characterize the permanent pycnocline properties from Argo data. We then applied this method to study the pycnocline in the Atlantic Ocean.
We will present the first results of this analysis: the climatological (over the Argo observational period) and seasonal variability of the pycnocline properties.


Oceanic fluxes and storage of freshwater and heat in the North Atlantic using Argo data

Elaine L. McDonagh1*, Brian A. King1, Harry L. Bryden1

* Presenting author

1) National Oceanography Centre, Southampton,

A North Atlantic temperature and salinity field is generated every 10-days from the early 2000’s. These fields are generated using Argo data that has been optimally interpolated on density surfaces. Temperature and salinity anomalies from the hydrobase climatology are interpolated without making the widely used assumption that the anomalies have a zero mean. In addition to the temperature and salinity fields, uncertainty estimates in each field are quantified.

We use the optimally interpolated Argo fields in conjunction with full-depth coast-to-coast hydrography and information from the RAPID-MOCHA mooring array at 26°N in the Atlantic to quantify the variability in the oceanic freshwater flux at this latitude. Including the information (from hydrography and Argo) within the interior of the subtropical gyre reduces the southward freshwater flux by 0.1Sv (mean total freshwater flux is 0.35 Sv southward; 1Sv = 106 m3 s-1). The variability of this interior component is quantified using Argo data. The optimally interpolated Argo fields are examined to quantify variability in the oceanic heat and salt content to the north and south of 26°N and this is related to the variability in the freshwater and heat flux observed at 26°N. The focus of this analysis is on the Atlantic Meridional Overturning Circulation slow-down event observed by the 26°N mooring array in 2009-2010.


Variability of the meridional overturning circulation at the Greenland–Portugal Ovide section from 1993 to 2010

Herle Mercier1*, Pascale Lherminier2, Artem Sarafanov3, Fabienne Gaillard2, Nathalie Daniault4, Damien Desbruyeres1, Anastasia Falina3, Bruno Ferron1, Claire Gourcuff1, Thierry Huck1, Virginie Thierry2

* Presenting author

1) CNRS, Laboratoire de Physique des Océans, France
2) Ifremer, Laboratoire de Physique des Océans, France
3) Shirshov Institute of Oceanology, Russia
4) UBO, Laboratoire de Physique des Océans, France

The meridional overturning circulation (MOC) in the North Atlantic transports heat from the subtropics to high latitudes and hence plays an important role in the Earth’s climate. A region crucial for the MOC is the northern North Atlantic and the adjacent Nordic Seas, where waters transported northward in the MOC upper limb progressively cool, gain density and eventually sink. Here we discuss the variability of the gyre circulation, the MOC and heat flux as quantified from a joint analysis of hydrographic and velocity data from six repeats of the Greenland to Portugal Ovide section (1997–2010), satellite altimetry and Argo float measurements. For each repeat of the Ovide section, the full-depth absolute circulation and transports were assessed using an inverse model constrained by ship-mounted Acoustic Doppler Current Profiler data and by an overall mass balance. The obtained circulation patterns revealed remarkable transport changes in the whole water column and evidenced large variations (up to 50% of the lowest value) in magnitude of the MOC computed in density coordinates (MOCσ). The extent and time scales of the MOCσ variability in 1993–2010 were then evaluated using a monthly MOCσ index built upon altimetry and Argo. The MOCσ index, validated by the good agreement with the estimates from repeat hydrographic surveys, shows a large variability of the MOCσ at Ovide on monthly to decadal time scales. The intra-annual variability is dominated by the seasonal component with peak-to-peak amplitude of 3.3 Sv. On longer time scales, the MOCσ index varies from less than 15 Sv to about 25 Sv. It averages to 18.1 ± 1.4 Sv and shows an overall decline of 2.5 ± 1.4 Sv (95% confidence interval) between 1993 and 2010. The estimates from repeat hydrographic surveys indicate that the heat flux across the Ovide section is linearly related to the MOCσ intensity (0.054Sv/PW).


Use of a Bio-Argo dataset to investigate the onset of the sub-polar North Atlantic spring bloom.

Alexandre Mignot1*, Raffaele Ferrari1, Herve Claustre2

* Presenting author

1) Massachusetts Institute of Technology, EAPS, USA
2) CNRS, Université Pierre et Marie Curie, Laboratoire d\\\'Océanographie de Villefranche

The sub-polar North Atlantic Bloom, one of the largest in the global ocean, supports major fisheries and contributes significantly to global photosynthesis and ocean carbon uptake. There is an ongoing debate as to what conditions trigger the onset of the bloom. The traditional explanation formalized by Sverdrup sixty years ago is that the bloom starts when the mixed layers shoals above a 'critical depth' in late winter, early spring. Recently Behrenfeld suggested that blooms may start early in the winter when the mixed layer is deepening, because the dilution of biomass limits the encounter rates of phytoplankton and zooplankton thereby reducing grazing pressure on phytoplankton. Taylor and Ferrari, building on work of Huisman, finally proposed that blooms can also start when ocean cooling subsides at the end of winter and turn into surface heating, resulting in a shutoff of vertical mixing and growth phytoplankton in the euphotic layer. Progress in testing these different hypothesis has been hampered by the lack of appropriate observations. In situ observations are rare and cover few bloom events. Satellite measurements of ocean color provide a global picture, but they are limited to the surface ocean and the persistent cloudy region of the North Atlantic limits severely the data coverage in winter. We will present bio-optical data from 5 bio-Argo floats deployed in the northern sector of the sub-polar North Atlantic, together with estimates of air-sea net heat fluxes and sea-surface irradiance. Our observations suggest that the onset of the sub-polar North Atlantic spring bloom appears to be triggered by the increase of light at the sea-surface above a critical value. There is no clear evidence of a trigger by changes in mixed layer depth or air-sea heat fluxes. Hence light intensity appears to exert a stronger control on bloom onset, much like on land, at least at latitudes above 60 degrees in the North Atlantic.


World Ocean general circulation


* Presenting author


Combining an absolute mean velocity field at 1000 m depth, obtained from Argo displacements, with the mean velocity vertical shear from the WOA09 hydrographic database, one obtains the absolute geostrophic ocean circulation everywhere (except near the Equator and close to land masses). Western boundary currents, eastern boundary “slope” currents are nevertheless satisfactorily sampled.
The method provides an independent absolute mean sea level surface derived only from oceanographic data. Geostrophic flow patterns at greater depths show directly the mean circulation of the World Ocean illustrated at 2000m, 3000m and 4000m. Finally basin-wide heat, salinity and mass fluxes are estimated.


Vertical thermohaline structure of mesoscale eddies in the four major Eastern Boundary Systems

Cori Pegliasco1*, Alexis Chaigneau1, Rosemary Morrow1, Yves Morel1

* Presenting author

1) Laboratoire d'Etudes en Océanographie et Géophysique Spatiales (LEGOS), UMR 5566, France

The four major Eastern Boundary Upwelling Systems (EBUS) are characterized by the presence of numerous mesoscale eddies. They are preferentially formed along the continental coasts and then propagate westward to the open ocean where they progressivly dissipate. Thus, mesoscale eddies actively participate to the zonal redistribution of physical and biogeochemical properties from near-coastal upwelling regions to the open ocean. Although the main eddy caracteristics (size, duration, formation areas, propagation, etc) have been largely studied in the four EBUS, little is known about their physical vertical structure and the associated heat and salt contents. The main goal of this study is to merge 12 years (2000-2012) of satellite altimetry data with temperature and salinity profiles acquired by Argo floats in order to describe the vertical thermohaline structure of mesoscale eddies in the four EBUS.
In each EBUS, eddies are detected on sea-level altimetry maps and all available Argo profiles are classified into 3 categories depending whether they surface in anticyclonic eddies, cyclonic eddies or outside eddies. The vertical temperature and salinity anomalies associated with both anticyclonic and cyclonic eddies are depicted for each EBUS, showing clear differences in terms of eddy-core position and intensity. For instance, eddy vertical temperature anomalies in the Peru-Chile Upwelling System presents an anticyclonic eddy-core in subsurface (~300m) and a cyclonic eddy-core centered in the thermocline (~100m depth) ; in the California Upwelling System, both types of eddies are centered in the thermocline ; in the Canary Upwelling System, eddy-cores exhibit on average a deeper vertical extent and the signature of Meddies can sometimes be observed between 1100 m and 1600 m ; in the Benguela Upwelling Sytem, the maximum anomalies are found between 100 and 600 m, influenced by the passage of Agulhas Rings carrying Indian Ocean water in relatively deep layers. Furthermore, each EBUS is divided in subregions, where vertical temperature and salinity anomalies can be related to several processes and mecanisms such as large-scale water-mass distribution, front locations, wind-induced vorticity or near-coastal dynamics.


Performance of the recent Argo floats in the Black Sea. Data quality control procedures and lessons learned.

Elisaveta L. Peneva1*, Emil V. Stanev1, Milena S. Milanova1, Violeta H. Slabakova2

* Presenting author

1) Sofia Univerity "St. Kliment Ohridski", Department of Meteorology and Geophysics, Bulgaria
2) Institute of Oceanology, Bulgaria

Since 2009 several Argo floats have been deployed in the Western Black Sea in the frame of the Euro-Argo preparation phase (1 float), the Bulgarian Argo program (3 floats) and the Italian Argo program (4 floats). The data are quality validated taking into account the specific Black Sea regional characteristics. The quality control (QC) includes control of specific range of the measurements, comparison with climatological profiles, comparison with other Argo floats data, temperature and salinity gradients’ check, check of the stability of vertical stratification. Standard QC flags are assigned to each profile. The data measured by the float with the oxygen sensor are still under validation. The new data appeared helpful to describe the main elements of the Black Sea circulation - the Rim current and the coastal anticyclonic eddies. An important fact came from the temperature profiles: the Cold Intermediate Layer in the period 2009-2012 was almost absent, but re-appeared again in the winter in 2012 due to the very cold winter conditions.


An Autonomous Profiling Explorer for the deep ocean – APEX Deep

Ernest Petzrick1*, James Truman2, Dan Ryan0

* Presenting author

1) Teledyne Webb Research, APEX, USA
2) Teledyne Webb Research, APEX, USA

Profiling float technology is maturing faster than ever before in its history. New sensors are rapidly being fielded and research demands are expanding to new areas. The Argo program, with its fleet of over 3,500 profiling floats, has provided insights and understandings of our oceans that would never have been achieved if researchers were limited to research vessels alone. Until recently this fleet of profiling vehicles has been limited to a maximum depth of 2,000 meters. Responding to requests from researchers around the world, Teledyne Webb Research designed an Autonomous Profiling Explorer (APEX) capable of reaching 6,000 meters in a cost effective, robust, system.
Taking advantage of sister company, Teledyne Benthos’ expertise in glass sphere floatation and instrument housings, Teledyne Webb Research engineers designed a vehicle using the 17 inch glass sphere as the pressure hull. Glass spheres have long been used for deep floatation. But there was a concern about the effects of multiple cycles and hull penetrations. Together the Teledyne Webb Research and Benthos engineers conducted a series of pressure cycle tests to 10,000 psi and explored optimized hull penetration patterns. After successfully cycling a prototype hull to 10,000 psi over 500 times, it was clear that glass would work.
Teledyne Webb Research has also designed the next generation profiling float controller, the APF-11. Originally this controller was intended as the replacement for the aging APF-9. But the robust design and flexibility of the APF-11 allow it to easily command the APEX Deep. This novel controller enhances the user programming features and incorporates superior diagnostics for improved overall performance while continuing Teledyne Webb Research’s effort to manufacture environmentally friendly systems; the APF-11 is a lead free controller board. The APF-11 incorporates a highly scalable architecture and a real-time operating systems enabling more sensor and battery configurations. User functionality is enhanced to include easy mission reconfiguration and Z modem data compression. Ease of use features includes a more friendly activation mode with an audible activation feedback alert, giving improved, easy to interpret state of the float including launch readiness
The APF-11 integrates improved self-diagnostics. A separate vacuum sensor is dedicated to internal pressure and a humidity sensor aids in leak detection. Another important addition is the introduction of a Coulomb counter to track energy consumption. The Coulomb counter allows operators to track energy consumption and estimate remaining energy and thus APEX lifetime This is particularly important as floats employ increasingly expensive sensors, making retrieval (for re-battery & re-deployment) economically more realistic. .New hardware features also include a scalable MICRO SD card and GPIO expansion connector.
Overall, the new APF-11 controller will provide a leap-ahead system that is better equipped to the demanding missions expected as profiling floats expand from their initial physical oceanographic requirements to biogeochemical science and beyond.
Hull and controller were then combined with a completely redesigned pump and bladder system with novel valve controls that take advantage of ambient pressure to reduce the energy required for some operations.
On October 30 and 31, 2012 two APEX Deeps, Hull 002 and 003 were deployed off Hawaii’s Big Island as part of the spiral 1 demonstration. Both floats exceeded 4,000 meters and provided data that allowed Teledyne Webb Research to merge spirals 2 and 3 into a successful 6,000 meter demonstration in the Puerto Rico trench. On 26/27 February 2013, APEX Deep hull 004 dove to over 6,000 meters and continue on to provide multiple CTD profiles.


Bio-Argo: qualification of sensors and evaluation of their factory calibrations.

Antoine Poteau1*, Hervé Claustre1, Fabrizio D\'Ortenzio1, Christophe Penkerc\'h1, Edouard Leymarie1, Grigor Obolensky1, Florent Besson1

* Presenting author

1) UMPC / CNRS, Laboratoire d'Océanographie de Villefranche, France

Biogeochemical sensors now implemented on profiling floats have reached a sufficient degree of maturity allowing the establishment of a Bio-Argo network to become reality. Data quality control procedures are being developed, in phase with the procedures created for classical T and S Argo. To complement these emerging “good practices” it appears essential to undertake in parallel the evaluation of sensor performances. This is a key requirement for the future with the objective of developing homogeneous and consistent databases of biogeochemical parameters. Here the various procedures that were developed and tested to control and cross-compare a set of (or subsets of) 40 bio-optical (Chlorophyll a, CDOM, backscattering, radiometry) and biogeochemical (nitrate) sensors are described. The first procedure makes use of the System of Inter-calibration of Bio-Optic sensors (SIBO) developed at the LOV and allows 6 sensors (not implemented on the floats) to be simultaneously cross-compared (or 5 sensors compared with a “gold” sensor) as part of a set of in situ profiles. The second procedure relies on the intercomparison of measurements performed by sensors onboard floats, either in pools (limited to 20m depth) or deployed as an ensemble of floats. In this presentation, the results of these various tests will be presented and their respective pros and cons will be discussed.


ProvBioII: biogeochemical floats become more flexible

Antoine Poteau1*, Hervé Claustre1, Edouard Leymarie1, Florent Besson1, Christophe Penkerc\'h1, Fabrizio D\'Ortenzio1

* Presenting author

1) UPMC / CNRS, Laboratoire d'Océanographie de Villefranche, France

A major improvement has recently been made with the development of a new version of the ProvBio float, the now so-called ProvBioII. The LOV has been deeply involved in expressing specific requirements to the manufacturer in order to fulfill a number of scientific goals, (in the frame of two main projects: “remOcean” and “NAOS”). The float now presents much more flexible possibilities regarding the programming of the mission. For instance, navigation is now better adapted to science purposes, and allows a “multi-profiles” mode (up to ten per day). In particular, floats can rise at a predetermined time which would be suitable for ocean color validation. The data acquisition is now highly adaptive. Five different sampling zones are available within which, the powering of the various sensors as well as the data acquisition resolution can be optimized (to balance science needs versus energy costs). This float prototype was validated a few months ago and ten ProvBioII floats have now already been deployed. The new potentialities of ProvBioII will be illustrated through data from a set of floats deployed in the north and south Atlantic sub-tropical gyres as well as in the Mediterranean Sea. Visualization tools will also be presented.


Argo floats in the Arctic: contribution of the IAOOS project. First results.

Christine Provost1, Jean-Claude Gascard 1*, Nathalie Sennéchael1, Mehrad Rafizadeh 1, Fernanda Jardon1, Michel Calzas2, Christine Drezen2, Antoine Guillot2, Alain Desautez3, Patrice Brault4, Christophe Schaeffer4, Michel Jouannic4

* Presenting author

1) UPMC and CNRS, LOCEAN, France
2) CNRS, DT-INSU, France
3) IPEV, IPEV, France
4) NKE-Instrumentation, France

IAOOS (Ice, Atmosphere, Ocean Observing System) is a 9-year ANR-funded project (2011-2019) (ANR-10-EQPX-32-01), whose objective is to provide and maintain an integrated observing system (40 platforms in total) over the Arctic Ocean to collect synoptic and near real time information related to the state of the ocean, the atmosphere and the sea ice. Each platform comprises instrumentation for vertical soundings through the ocean, the atmosphere and the sea ice.
Oceanic profilers in IAOOS are derived from ARGO floats. They are tethered to a vertical cable along which they profile from 5 down to 800m depth. A new float body was designed and realized. A bidirectional inductive transmission between the surface buoy and the float enables transmission of information to and from land based stations via satellites.
Results from the first deployments at the North Pole (2012 and 2013) are presented. Possibilities to build on this technology to add a suite of biogeochemical sensors are discussed.


Pushing the boundaries: the first time use of an ARGO-float in the Baltic Sea

Tero M.T. Purokoski1*, Eemeli Aro2, Aleksi Nummelin1, Petra E. Roiha1, Simo-Matti Siiriä1

* Presenting author

1) Finnish Meteorological Institute, Finland
2) Aalto University, Automation and Systems Technology, Finland

In 2012 the Finnish Meteorological Institute (FMI) successfully operated an ARGO-float for over a half a year in the shallow and low salinity Baltic Sea. To our knowledge this was the first time the ARGO-float was used in the Baltic Sea. We believe that our project has pushed the limits as to the environment the ARGO-floats have been deployed in and thus, we would like to share our experiences and our future deployment/development plans with the ARGO-community.

The project was started a couple of years ago when the Finnish Meteorological Institute decided to test the suitability of ARGO-floats for the Baltic Sea. This was motivated by the need to get more data in an economical way from sea areas which were not visited so often by a research vessel. The data was needed for environmental monitoring and for model development. The specific sea area chosen for the tests was the Gulf of Bothnia (average depth less than 100 m). After contacting the float manufacturers it became evident that no-one else was using the floats in the Baltic Sea like environment i.e. in a shallow and low-salinity sea.

Two Apex-floats made by Teledyne Webb Research were purchased. In May 2012, after a couple of short test dives to assess the diving dynamics of the floats, one float was deployed for a longer mission. The optimistic goal was to keep it in water till September, but there was a concern that it would drift to shore much earlier. However, it turned out that the float exceeded all the expectations operating flawlessly until December when it was recovered by a coast guard helicopter. During its 6 1/2 month mission the float transmitted over 200 daily vertical CTD-profiles.

Since the diving control algorithm of the ARGO-floats was developed for deep oceans, it is generally too slow for the shallow Baltic Sea. Therefore, a joint development project with the Aalto University was carried out with the aim to modify the other float’s firmware and thus enabling it to settle to the target dive depth quicker. These modifications were also successfully tested in summer 2012.

The experience gained so far indicates that ARGO-floats are useful and valuable tools for monitoring the Baltic Sea. However, their operation requires much more operator involvement and active commanding of the floats than float operations in the oceanic environment. To address this some mission control tools will be developed to assist the float operator to choose the most useful diving parameters in terms of receiving the best possible data without sacrificing the safety of the mission (i.e. to stay away from the bottom).

These new tools will be put to use this coming summer as we will be expanding our operations. In addition to current Baltic floats two new ones with oxygen and bio-optical sensors will be deployed. Besides environmental monitoring and model development the floats will also be used for specific measurement campaigns.


Towards a 3D global Chlorophyll-a climatology based on merged historical and bio-Argo database in situ fluorescence profiles

Raphaëlle Sauzède1*, Hervé Claustre1, Cédric Jamet2, Julia Uitz1, Héloïse Lavigne1, Alexandre Mignot3, Fabrizio D\'Ortenzio1

* Presenting author

1) CNRS, Université Pierre et Marie Curie, Laboratoire d\'Océanographie de Villefranche
2) CNRS, Laboratoire d'Océanologie et de Géosciences, UMR 8187
3) , Massachussets Institute of Technology, USA

In vivo fluorescence of Chlorophyll-a, a proxy of Chlorophyll a concentration ([Chl]), is one of the most routinely measured biological properties in the ocean. Several thousands of such profiles are indeed available from historical databases. With the advent of autonomous platforms and in particular of bio-optical floats it is expected that the acquisition of fluorescence profiles will dramatically increase in the near future. All these data (past and future) could be exploited within a single reference database which would represent an essential source of information of [Chl]. However, a common exploitation of these data is currently impossible because of their heterogeneity. In particular, most of the historical data are badly, if at all, calibrated into [Chl]. We therefore developed a method for converting raw fluorescence profiles into [Chl] profiles based on the sole knowledge of the shape of the fluorescence profiles. This method is based on a statistical iterative learning method of artificial neural networks (multi-layered perceptron). The “learning” was performed on a large database containing concomitant profiles of fluorescence and HPLC-determined (the reference method) [Chl], collected in a wide variety of oceanic regions. In a second step, and using the developed method, our goal was to assemble a global database of fluorescence profiles calibrated into [Chl] profiles. Prior to this calibration, a rigorous quality control procedure was systematically applied. The resulting database (around 40,000 [Chl] profiles) can be considered as an initial phase in view of producing a 3D climatology of [Chl] for the global ocean. Furthermore, this database could also be used for developing quality control applications of [Chl] acquired by autonomous platforms (in the same way that temperature and salinity databases are used for quality controlling Argo float data). Finally, and over a longer term, such a database could also be used to identify possible trends in the temporal evolution of [Chl] in the context of global climate change.


Heat and Freshwater Budget of the Labrador Sea

Lena M. Schulze1*, Eleanor Frajka-Williams1, Sheldon Bacon1

* Presenting author

1) National Oceanography Center Southampton, Ocean and Earth Science, UK

The Labrador Sea is an important site for the formation of intermediate deep water due to its seasonally recurring deep convection. The heat loss during deep mixing is balanced by heat import/gain to the region through the oceanic circu- lation. On an annual cycle, spring-summer freshening of the interior counteracts the buoyancy loss in fall and winter. The recent changes in the rate of melting of the Greenland ice sheet and the Arctic sea ice will impact the formation of deep water, if the freshwater reaches the region of deep convection. An understanding of freshwater and heat exchange between Labrador basin and boundary domain, par- ticularly on interannual timescales, is crucial in order to determin how increasing freshwater fluxes from the Arctic will influence deep convection patterns. A 10-yr (2002 – 2012) timeseries of heat and freshwater content in the interior, obtained from ARGO floats, is used to determine interannual variability. The deep-layer (800 – 2000 m) of the interior shows a trend towards warmer and more saline wa- ter, while a significant freshening of the surface layer (0-200 m) can be observed. However, separating the interior into key regions (e.g. an area of high eddy kinetic energy and an area of highest convection activity) reveals pronounced differences in these variations. Furthermore the areas are characterised in terms of interan- nual variability of surface, lateral heat and freshwater fluxes. This work sets the frame for determining the mechanisms and locations responsible for the exchange between cold, fresh water from the boundary currents and the water from the interior.


Global salinity changes over the ARGO-era

Nikolaos Skliris1*, Robert Marsh1

* Presenting author

1) University of Southampton, Ocean and Earth Science, UK

The EN3 global ocean dataset (1950-2012) is used to investigate global salinity changes over the ARGO-era. Salinity observations over 1950-2000 clearly show an amplification of the global water cycle with the spatial pattern of surface salinity multi-decadal change strongly resembling the climatological mean patterns of both surface salinity and surface freshwater flux. Large salinification of the upper layer North Atlantic subtropical gyre and freshening of the Western Pacific warm pool are highly correlated with the SST increase, and seem to be part of an accentuating contrast between Atlantic and Pacific Oceans water cycle components linked to the broad-scale surface warming. However, results show low correlations between reanalysis-derived surface freshwater flux and EN3 salinity annual variations, especially during the 1950s and 1960s when density of salinity observations is very low. The Argo array of profiling floats, started in 2000, has dramatically increased data coverage for salinity for the global ocean after 2003 allowing for more reliable estimations of global salt content. Over 2000-2012 increasing (decreasing) salinity trends are found in most of evaporation- (precipitation-) dominated regions, indicating a further intensification of the hydrological cycle. Results show robust and spatially coherent correlation patterns between annual precipitation and surface salinity anomaly timeseries in most of the tropical regions. However, as opposed to the long-term multi-decadal trend, the upper layer salinity contrast between Atlantic and Pacific Oceans is reducing over 2000-2012. Furthermore the global average upper ocean salt content is increasing following a global precipitation decrease whilst a reversal of the SST trend and a strong surface cooling take place in large parts of the global ocean. These recent ocean surface changes are shown to be partially associated with inter-decadal variations related to large scale atmospheric modes of natural variability such as the El-Nino - Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO).


Seasonal cycle of pan-Arctic volume - heat and FW fluxes during 2005-2006

Tsubouchi Takamasa1*, Bacon Sheldon1, Naveira Garabato Alberto2

* Presenting author

1) National Oceanography Centre, Southampton, Marine Physics and Ocean Climate
2) University of Southampton, School of Ocean and Earth Science, UK

The Arctic has been changing rapidly over the last decades. The surface air temperature has been risen at more than 2 times faster than the other regions in the globe (IPCC 2007). The September sea ice extent continues to decline at 1% over year (Richter-Menge and Overland 2011). The Greenland ice cap melt rate is increasing (Velicogna 2009). The fresh water (FW) storage in the Arctic Ocean’s upper layers has increased (Rabe et al., 2011). These changes have a potential impact on Meridional Overturning Circulation and eventually future European climate.

Therefore, the importance of monitoring the pan-Arctic heat and FW fluxes and understanding its causes are clear. The pan-Arctic boundary observation system has been maintained since 2004, through Davis Strait (maintained by UW in USA), Fram Strait (maintained by AWI in Germany and NPI in Norway), Barents Sea Opening (maintained by IMR in Norway) and Bering Strait (maintained by UW in USA). However, attempts to gather all data across the four Arctic main gateways, to draw a pan-Arctic picture of heat and FW fluxes, have only just begun (Tsubouchi et al., 2012).

The aim of this study is to estimate the first “observation based” full annual cycle of pan-Arctic volume, heat and FW fluxes during 2005-2006 based on mooring data around the Arctic boundary, and to understand its causes.

As a first step in the analysis, Davis Strait fluxes are estimated based on 9 ADCP, 9 RCM velocity measurements and 21 SBE TS measurements. The estimated volume flux is -1.78±1.11 (Sv), and no clear seasonal cycle has been observed. The associated heat flux is 35.0±9.3 (TW) and FW flux is 88.0±16.8 (mSv). In order to assess the reconstruction scheme of the velocity section, the NEMO 1/12 degree model velocity field across the Davis Strait is "observed" by a virtual mooring array. The reconstructed velocity fields captures most of variability in NEMO 1/12 velocity field, with a bias of 0.34 Sv and R=0.86. In the workshop, the first seasonal cycle of pan-Arctic boundary fluxes of volume, heat and FW fluxes will be presented.


Validation of oxygen data measured by Argo floats equipped with oxygen sensors and preliminary use of those data to estimate mixed layer depth in weakly stratified regions

Virginie Thierry1*, Denis Gilbert2, Herlé Mercier3, Guillaume Maze1

* Presenting author

1) Ifremer, Laboratoire de Physique des Océans, UMR6523 Ifremer/CNRS/IRD/UBO
2) Fisheries and Oceans Canada, Institut Maurice-Lamontagne, Canada
3) CNRS, Laboratoire de Physique des Océans, UMR6523 Ifremer/CNRS/IRD/UBO

Since 2008, we deployed about 30 Argo profiling floats in the North-Atlantic Ocean. These floats (PROVOR-DO) were equipped with Aanderaa optode sensors to measure oxygen concentration in the upper 2000m of the ocean. To assess the overall quality of the oxygen data, we present results from pre-deployment checks in a 20m deep pool at Ifremer, from comparisons with oxygen concentrations measured on discrete samples by Winkler titrations just before the float deployments, and from comparisons of the float time series with the WOA09 climatology. We then present preliminary results on the use of oxygen concentration to help estimate mixed layer depth, especially in weakly stratified regions such as the subpolar gyre of the North Atlantic Ocean.


Impact of Argo data set on an operational 1/4° global ocean forecasting system

Victor Turpin1*, Elisabeth Remy1, Olivier Legalloudec1

* Presenting author

1) Mercator Océan, R&D, France

E-Aims (Euro-Argo Improvement for the GMES Marine Services) aims to assess the whole ARGO chain, from float design to the use of ARGO data by GMES, in order to provide recommendations for the next phase of ARGO. Mercator Ocean leads the global ocean analysis and forecasting system of the GMES Marine Services. As part of E-AIMS, Mercator Ocean will analyze and evaluate the impact of ARGO data in the global ocean forecasting system using OSE (Observing Systems Evaluation). These impacts studies will focus on the contribution of ARGO array in the data assimilation system from sea surface to 2000m. Comparison between different data assimilation experiments with or without ARGO global data set will highlight their impact on the ocean analysis quality. It already appears that ARGO data are crucial to have a good estimation of the 3D structure of the temperature and salinity fields, not only in the ocean interior but also in the mixed layer. Diagnostics quantifying this impact will be shown. The synergy between insitu observing system and satellite observations will also be assessed. These first evaluations are key aspects to prepare OSSE (Observing System Simulation Experiment) and to propose ARGO evolution's advices.


Transformation of the Atlantic Water in the West Spitsbergen Current – synoptic observations versus ARGO floats results

Waldemar Walczowski1*

* Presenting author

1) Institute of Oceanology Polish Academy of Sciences, Sopot, Physical Oceanography

The Atlantic Water is the most important water mass conveying oceanic heat northward to high latitudes. The West Spitsbergen Current is one of the main oceanic flows delivering this water to the Arctic Ocean. Cooling of the Atlantic Water during its northward advection along the West Spitsbergen Current pathways results in high heat fluxes to the atmosphere, preconditioning water to convection and deep water masses formation. Between the northern Norway and the Fram Strait the Atlantic Water loses on average 4.4 GJ of heat per each meter of northward flow. Only part of the heat is released to the atmosphere, while the major share is lost due to the processes of advection and mixing with adjacent water masses. Both phenomena are very important for the climate.
Institute of Oceanology Polish Academy of Sciences has investigated the Nordic Seas since 1988. The time series of summer observations in the region between the northern Norway and the Fram Strait has been collected since 2000. The data series obtained from synoptic observation conducted from aboard the Institute’s vessel s/y ‘Oceania’ as well as from moorings will be compared with data gained from the ARGO floats deployed in the Nordic Seas. Spatial and temporal variability of the WSC properties, as well as pathways of currents and mean velocities will be compared.


Reliability of heat storage estimates in the N.Atlantic Ocean from sub-tropical to sub-polar latitudes.

Neil Wells1*, Matthew Couldrey1, Vladimir Ivchenko1

* Presenting author

1) National Oceanography Centre, Ocean and Earth Sciences, United Kingdom

There are a number of heat storage products produced in the global ocean by many different groups. These products are derived from Argo in the last decade, for example XBT and CTD. Here we compare two heat storage estimates one derived solely from Argo data alone whilst the other is derived from Argo and other platforms. Various measures are used to compare the two estimates. Questions arise as to the reliability of these estimates and how may this reliability be best determined.


Impact of Argo data in Mercator Ocean global and regional systems.

Mounir benkiran1*, Elisabeth Remy2, Nicolas Ferry2, Eric Greiner1

* Presenting author

1) cls, Space Oceanography Division, Ramonville
2) Mercator-ocean , Ramonville

Mercator-Ocean has developed a regional forecasting system at 1/12° resolution over the North East Atlantic (IBI: Iberia, Biscay and Irish), taking advantage of the recent developments in NEMO. The model was forced by ERA-interim products (every 3 hours) including the atmospheric pressure. In addition to atmospheric forcing, the model includes astronomical tidal forcing. This regional forecasting system uses boundary conditions from the Mercator-Ocean global reanalysis (GLORYS: GLobal Ocean ReanalYses and Simulations).The assimilation component of the Mercator Ocean system, is based on a reduced-order Kalman filter (the SEEK or Singular Extended Evolutive Kalman filter). An IAU method (Incremental Analysis Updates) is used to apply the increments in the system. The error statistics are represented in a sub-space spanned by a small number of dominant 3D error directions. A 3D-Var scheme corrects for the slowly evolving large-scale biases in temperature and salinity. The data assimilation system allows to constrain the model in a multivariate way with Sea Surface Temperature (AVHRR + Multi-satellite High resolution), together with all available satellite Sea Level Anomalies, and with in situ observations from the CORA-03 data base, including ARGO floats temperature and salinity measurements. The background SLA field accounts for the high frequency signal determined by the model and the forcing by atmospheric pressure. This reanalysis covers the period from January 2002 to December 2009.
In this presentation, results obtained with this reanalysis system (1/12°) are compared to results from GLORYS. A special focus will be made on the methods developed for GLORYS and IBI12 in order to perform an automated quality control of in situ T/S profiles. Around 50% of the observations pointed out by GLORYS’s automated QC were in turn flagged as bad by the CORIOLIS data centre, and QC algorithms developed for these reanalyses will soon be implemented in the Mercator Ocean operational suite.


Interannual variability of global and regional ocean climate indicators from the Argo observing system

Karina von Schuckmann1*, Jean-Baptiste Sallée2, Pierre-Yves Le Traon3, Don Chambers4, Cecile Cabanes5

* Presenting author

1) Ifremer, LER/LOS, France
2) British Anarctic Survey, Open Oceans group, U.K.
3) Ifremer, LOS, France
4) University of South Florida, Faculty of Marine Science, USA
5) Ifremer, LPO, France

One of the Argo Program’s most important contributions to climate science is an improvement in estimations of heat stored by the oceans and its associated volume changes, which is a key factor for the Earth’s energy budget, to gauge global warming and to gain a better understanding of the mechanisms behind rising mean sea level. We present here an analysis of Regional Ocean Indicators (ROIs). We also include an up-dated estimation of Argo Global Ocean Indicators (GOIs) for the period 2005 to 2011 which reveal a 7-year rate of 0.5±0.1 W/m2 (1-standard error) for global ocean heat content, 200±50km3/year for Global Ocean Freshwater Content and (OFC) 0.4±0.2 mm/year for global steric sea level (SSL). Interannual variability of ROIs associated in the tropics to ENSO variability, and in the Northern Ocean to deep reaching events substantially affect Argo global SSL short-term trend estimations and hence, global mean sea level. Data from the global Argo array, from satellite altimetry (AVISO) and satellite derived ocean mass (GRACE) are used here during the period January 2005 to December 2010 to assess the consistency with Argo GOIs. The global sea level budget during the years 2005-2010 is closed within uncertainties, but regional issues remain. We identify a systematic bias introduced by sparse Argo sampling in some parts of the tropical ocean sector, in particular in the Indonesian Archipelago region. However, using sampled altimeter data allows us to reduce this bias and close the regional sea level budget for the tropical ocean. Uncertainties of the observing systems and larger regional variability remain nevertheless too large to allow us to ‘open a window’ toward inferring deep ocean warming changes from the global sea level budget.


Steric sea level variations in the Mediterranean Sea during the last decade

Karina von Schuckmann1*, Giulio Notarstefano2, Pierre-Marie Poulain2, Louis Prieur3, Isabelle Taupier-Letage1

* Presenting author

1) Ifremer, Toulon, France
2) OGS, OCE Trieste, Italy
3) LOV, France

Understanding the regional dominant modes of sea level variability and assessing the potential regional impacts of sea level rise is particularly important in vulnerable populated area such as the Mediterranean basin. Previous studies have shown that a significant part of these regional variations can be explained by the geographical variations of ocean volume changes. We have used a re-qualified in situ data set during the years 2001-2011 to analyze interannual of Mediterranean steric sea level at basin-wide and regional scale. The dataset was built combining the temperature and salinity profiles from Argo floats, and from data collected by recent scientific cruises and historical data belongings to several Mediterranean oceanographic campaigns. A method based on a simple box averaging scheme is developed, where boxes have been defined related to general circulation properties of the Mediterranean basin, including uncertainty estimation. This method is easy to implement and run and can be used to set up a routine monitoring of the Mediterranean basin. We also present examples of Mediterranean steric sea level variations that include the basin-wide mean rise and main patterns of regional variability.