High-Resolution Observations in the Western Mediterranean Sea:
The REP14-MED Experiment

Onken, Reiner; Fiekas, Heinz-Volker; Béguery, Laurent; Borrione, Ines; Funk, Andreas; Hemming, Michael; Heywood, Karen J.; Kaiser, Jan; Knoll, Michaela; Poulain, Pierre-Marie; Queste, Bastien Y.; Russo, Aniello; Shitashima, Kiminori; Siderius, Martin; Küsel, Elizabeth T.

doi:10.5194/os-2016-82

Cited by 13 publications

(20 citation statements)

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“…Murphy (1993) defines three types of "goodness": consistency, quality, and value. Concerning the latter, it is rather difficult to rate the value for the "end users" because REP14-MED was planned solely for scientific purposes -see the objectives defined in Onken et al (2018). Amongst others, a special aim was the comparison of different methods for data assimilation.…”

Section: Discussionmentioning

confidence: 99%

“…Observational data were selected from the REP14-MED experiment which took place over the period 6-25 June; for a complete overview of all observations, see Onken et al (2018). Some details are as follows:…”

Section: Observational Datamentioning

confidence: 99%

“…In this study, ROPS was implemented for the waters west of Sardinia (western Mediterranean Sea) within the framework of the REP14-MED experiment (Onken et al, , 2018.…”

Section: Introductionmentioning

confidence: 99%

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Forecast skill score assessment of a relocatable ocean prediction system, using a simplified objective analysis method

Onken

2017

Ocean Sci.

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Abstract. A relocatable ocean prediction system (ROPS) was employed to an observational data set which was collected in June 2014 in the waters to the west of Sardinia (western Mediterranean) in the framework of the REP14-MED experiment. The observational data, comprising more than 6000 temperature and salinity profiles from a fleet of underwater gliders and shipborne probes, were assimilated in the Regional Ocean Modeling System (ROMS), which is the heart of ROPS, and verified against independent observations from ScanFish tows by means of the forecast skill score as defined by Murphy (1993). A simplified objective analysis (OA) method was utilised for assimilation, taking account of only those profiles which were located within a predetermined time window W . As a result of a sensitivity study, the highest skill score was obtained for a correlation length scale C = 12.5 km, W = 24 h, and r = 1, where r is the ratio between the error of the observations and the background error, both for temperature and salinity. Additional ROPS runs showed that (i) the skill score of assimilation runs was mostly higher than the score of a control run without assimilation, (i) the skill score increased with increasing forecast range, and (iii) the skill score for temperature was higher than the score for salinity in the majority of cases. Further on, it is demonstrated that the vast number of observations can be managed by the applied OA method without data reduction, enabling timely operational forecasts even on a commercially available personal computer or a laptop.

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Section: Discussionmentioning

confidence: 99%

Section: Observational Datamentioning

confidence: 99%

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Forecast skill score assessment of a relocatable ocean prediction system, using a simplified objective analysis method

Onken

2017

Ocean Sci.

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“…In situ observing systems, when combined with satellite data and advanced numerical simulations can provide a full description of the physical and biogeochemical variability at the meso-and submesoscale (Bouffard et al, 2012;Pascual et al, 2013;Tintoré et al, 2013;Shcherbina et al, 2015;Troupin et al, 2015;Cotroneo et al, 2016;Onken et al, 2016;Krug et al, 2017;Morrow et al, 2017;Ohlmann et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

A Multiplatform Experiment to Unravel Meso- and Submesoscale Processes in an Intense Front (AlborEx)

et al. 2017

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The challenges associated with meso-and submesoscale variability (between 1 and 100 km) require high-resolution observations and integrated approaches. Here we describe a major oceanographic experiment designed to capture the intense but transient vertical motions in an area characterized by strong fronts. Finescale processes were studied in the eastern Alboran Sea (Western Mediterranean) about 400 km east of the Strait of Gibraltar, a relatively sparsely sampled area. In-situ systems were coordinated with satellite data and numerical simulations to provide a full description of the physical and biogeochemical variability. Hydrographic data confirmed the presence of an intense salinity front formed by the confluence of Atlantic Waters, entering from Gibraltar, with the local Mediterranean waters. The drifters coherently followed the northeastern limb of an anticyclonic gyre. Near real time data from acoustic current meter data profiler showed consistent patterns with currents of up to 1 m/s in the southern part of the sampled domain. High-resolution glider data revealed submesoscale structures with tongues of chlorophyll-a and oxygen associated with the frontal zone. Numerical results show large vertical excursions of tracers that could explain the subducted tongues and filaments captured by ocean gliders. A unique aspect of AlborEx is the combination of high-resolution synoptic measurements of vessel-based measurements, autonomous sampling, remote sensing and modeling, enabling the evaluation of the underlying mechanisms responsible for the observed distributions and biogeochemical patchiness. The main findings point to the importance of fine-scale processes enhancing the vertical exchanges between the upper ocean and the ocean interior.

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“…The latter objective was perhaps the most relevant to the deployment of the UEA glider. A more indepth overview of the REP14-MED trial, its objectives, and the collected observational data is described by Onken et al (2016).…”

Section: Introductionmentioning

confidence: 99%

Measuring pH variability using an experimental sensor on an underwater glider

et al. 2017

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Abstract. Autonomous underwater gliders offer the capability of measuring oceanic parameters continuously at high resolution in both vertical and horizontal planes, with timescales that can extend to many months. An experimental ionsensitive field-effect transistor (ISFET) sensor measuring pH on the total scale was attached to a glider during the REP14-MED experiment in June 2014 in the Sardinian Sea in the northwestern Mediterranean. During the deployment, pH was sampled at depths of up to 1000 m along an 80 km transect over a period of 12 days. Water samples were collected from a nearby ship and analysed for dissolved inorganic carbon concentration and total alkalinity to derive the pH for validating the ISFET sensor measurements. The vertical resolution of the pH sensor was good (1 to 2 m), but stability was poor and the sensor drifted in a non-monotonous fashion. In order to remove the sensor drift, a depth-constant time-varying offset was applied throughout the water column for each dive, reducing the spread of the data by approximately two-thirds. Furthermore, the ISFET sensor required temperature-and pressure-based corrections, which were achieved using linear regression. Correcting for this decreased the apparent sensor pH variability by a further 13 to 31 %. Sunlight caused an apparent sensor pH decrease of up to 0.1 in surface waters around local noon, highlighting the importance of shielding the sensor from light in future deployments. The corrected pH from the ISFET sensor is presented along with potential temperature, salinity, potential density anomalies (σ θ ), and dissolved oxygen concentrations (c(O 2 )) measured by the glider, providing insights into the physical and biogeochemical variability in the Sardinian Sea. The pH maxima were identified close to the depth of the summer chlorophyll maximum, where high c(O 2 ) values were also found. Longitudinal pH variations at depth (σ θ > 28.8 kg m −3 ) highlighted the variability of water masses in the Sardinian Sea. Higher pH was observed where salinity was > 38.65, and lower pH was found where salinity ranged between 38.3 and 38.65. The higher pH was associated with saltier Levantine Intermediate Water, and it is possible that the lower pH was related to the remineralisation of organic matter. Furthermore, shoaling isopycnals closer to shore coinciding with low pH and c(O 2 ), high salinity, alkalinity, dissolved inorganic carbon concentrations, and chlorophyll fluorescence waters may be indicative of upwelling.

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High-Resolution Observations in the Western Mediterranean Sea: The REP14-MED Experiment

Cited by 13 publications

References 1 publication

Forecast skill score assessment of a relocatable ocean prediction system, using a simplified objective analysis method

Forecast skill score assessment of a relocatable ocean prediction system, using a simplified objective analysis method

A Multiplatform Experiment to Unravel Meso- and Submesoscale Processes in an Intense Front (AlborEx)

Measuring pH variability using an experimental sensor on an underwater glider

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