Review of lessons learned after five years of shallow water autonomous underwater vehicles (AUV) operations

The Unidad de Tecnología Marina (UTM) acquired in 2010, due to the wide scientific requirement to obtain high quality images of the seafloor, a couple of AUV´s for shallow waters applications with the aim to support marine research operations in coastal waters. The vehicles has been used as a routine science vehicle but also for technical development. During these years a valuable experience has been gained for future operation on either, coastal and open waters with new and more performant platforms.Peer Reviewe

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

SOCIB: the impact of new marine infrastructures in understanding and forecasting the coastal oceans: some examples from the Balearic Islands in the Mediterranean Sea

New monitoring technologies are being progressively implemented in coastal ocean observatories. As an example, gliders allow high resolution sampling, showing the existence of new features, such as submesoscale eddies with intense vertical motions that significantly affect upper ocean biogeochemical exchanges, an issue of worldwide relevance in a climate change context. SOCIB, is one of such systems, a new facility of facilities (covering from the coast to the open sea, and including among others a nearshore beach monitoring facility, HF radar, gliders and AUV’s, moorings, satellite, drifters and ARGO profilers, modelling), a scientific and technological infrastructure which is providing free, open, quality controlled and timely streams of oceanographic and coastal data and also modelling services. SOCIB takes profit of the strategic position of the Balearic Island at the Atlantic/Mediterranean transition area, one of the ‘hot spots’ of biodiversity in the world’s oceans. As an example of on-going SOCIB operations, since January 2011 sustained glider operations are in place in the Ibiza and Mallorca channels. The data centre is the core of SOCIB. The data management system created for gliders is an example of the new informatics capabilities for real time definition of mission planning, including adaptive sampling and real time monitoring using a Web tool that allows quick visualization and download. This type of new infrastructures, combined with new technologies and careful scientific analysis will allow new ways of international cooperation leading to major science breakthroughs in the very near future and new ways of science based coastal and ocean management.Peer Reviewe

Ocean currents measurement using an ADCP mounted on an Autonomous Underwater Vehicle

2 pages, figuresAutonomous Underwater Vehicles (AUVs) are gradually being adopted by ocean observing systems as versatile platforms for high resolution autonomous underwater sampling. A large variety of sensors can be mounted on these vehicles, allowing for multi-parametric characterization of water masses, seafloor acoustic/optical exploration or any other investigation requiring instrument autonomy, high spatiotemporal data resolution (~1m, 1Hz) in relatively long transects (~30 km) and good underwater positioning accuracy. One of the sensors that is common to most AUVs is the DVL (Doppler Velocity Log), which, mounted facing downward, uses the Doppler Effect to calculate the AUV’s velocity with respect to the ground (i.e. bottom tracking), provided it is within the DVL’s range. This is a key sensor to obtain accurate positioning as the Global Positioning System (GPS) becomes useless underwater. Most DVLs have also the capability to perform as an ADCP (Acoustic Doppler Current Profiler), turning the AUV into a potential ocean currents measurement instrument. However, a lack of standardization, thorough comparison with more assimilated technologies and the added data processing difficulty intrinsic to a 3D moving instrument provoke that, nowadays, one can hardly find oceanographic studies where the currents measurement task relies on autonomous platforms. The speaker will present the results of a field experiment comparing the AUV currents measures with those of a moored AWAC as well as the data processing techniques used to obtain the currents. The main purpose of the talk is to interact with oceanographers in order to comment on the obtained results and also to establish the requirements for an AUV water currents processing tool (Python scripts) that is to be developed soonPeer Reviewe

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

Evaluation of AUV-borne ADCP measurements in different navigation modes

OCEANS 2017, 19-22 June 2017, AberdeenMost Autonomous Underwater Vehicles (AUVs) mount an Acoustic Doppler Current Profilers (ADCP). Data from this sensor are rarely used in scientific studies due to the complexity of its processing and the lack of validation. Aside of that, AUV operators lack a set of guidelines regarding the optimal navigation modes and AUV-borne ADCP configurations to obtain the most accurate data possible. This study compares 12.6 hours of AUV-borne ADCP currents measurements, taken in different AUV navigation modes and ADCP configurations, to those of a moored AWAC. Results show RMS errors of 5 cm/s for U (East) and V (North) measures and of 2 cm/s for vertical currents measures for most of the navigation modes. Cell size is found to be the most influential parameter in data accuracy and yo-yo type of surveys are proved to be as accurate as constant depth onesPeer Reviewe

Operational use of gliders at ICTS SOCIB

Comunicación presentada en EOF2012, II Encuentro de la Oceanografía Física Española, celebrada del 14 al 16 de noviembre de 2012 en Madrid (España)Peer Reviewe

Las grandes infraestructuras de investigación, motor de conocimiento, de transferencia de productos tecnológicos y de tecnologías de gestión para el sector público y privado

Trabajo presentado en ForoTec2011, III Foro Tecnológico de las Islas Baleares, celebrado el 24 y 25 de noviembre de 2011 en Palma de Mallorca (España), y organizado por la Dirección General de Universidades, Investigación y Transferencia del Conocimiento del Govern de las Illes Balears, la Universitat de les Illes Balears y el Instituto de Innovación Empresarial de les Illes BalearsPeer Reviewe

SOCIB: The Balearic Islands Coastal Ocean Observing and Forecasting System Responding to Science, Technology and Society Needs

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