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Phytoplankton plays a major role in the ocean, being the basis of the marine food web and controlling the biogeochemical cycles. Numerical simulation have shown that finescale structures such as fronts are often suitable places for the generation of vertical velocities, transporting subsurface nutrients to the euphotic zone and thus modulating phytoplankton abundance and community structure. Since several years, observations have concentrated on nutrient fluxes along these structures. Instead, direct in situ estimations of the phytoplankton growth rates are much less numerous; although difficult to obtain, they provide a precious information on the ecosystem functioning. Here, we consider the case of a front separating two water masses characterized by several phytoplankton groups with different abundances, in the southwestern Mediterranean Sea. In order to estimate possible differences in growing rates, we used an adaptive and Lagrangian sampling strategy to measure the phytoplankton diurnal cycle in these two water masses. The use of a size-structured population model was then applied to these data to estimate the growth and division rates for each phytoplankton groups identified by flow cytometry, showing that these two population parameters are significantly different on the two sides of the front, and consistent with the relative abundances. Our results introduce a general method for estimating growth rates at frontal systems, paving the way to in situ exploration of finescale biophysical scenarios. [ABSTRACT FROM AUTHOR]

The study of extreme weather events and their impact on ocean physics and biogeochemistry is challenging due to the difficulty of collecting in situ data. Yet, recent research pointed out the major influence of such physical forcing events on microbiological organisms. Moreover, such violent event occurrences may rise in the future in the context of global change. In May 2019, an intense storm occurred in the Ligurian Sea (north-western Mediterranean Sea) and was captured during the FUMSECK cruise. In situ multi-platform measurements (vessel-mounted ADCP, thermosaligraph, fluorometer, flow cy-tometer, a Moving Vessel Profiler equipped with a multi-sensor towed vehicle, and glider) along with satellite data and a 3D atmospherical model were used to characterise the fine-scale dynamics occurring in the impacted oceanic zone. The most affected area was marked by a lower water temperature (1°C colder), and an increase by a factor two in surface chlorophyll-a and seven in nitrate concentrations, exhibiting strong gradients with respect to the surrounding waters. Our results show that this storm led to a deepening of the mixed layer depth from 15 to 50 m and a dilution of the deep chlorophyll maximum. As a result, the surface phytoplankton biomass of most groups identified by automated flow cytometry increased by up to a factor of two. Conversely, the phytoplankton carbon-chlorophyll ratio of most groups dropped down by a factor of two, evidencing significant changes in the phytoplankton cell composition. These results suggest that the role of storms on the biogeochemistry and ecology of the Mediterranean open sea may be underestimated and highlight the need for high-resolution measurements coupling physics and biology during these events. [ABSTRACT FROM AUTHOR]

The biogeochemical role of phytoplanktonic organisms strongly varies from one plankton type to another, and their relative abundance and distribution have fundamental consequences at the global and climatological scales. In situ observations find dominant types often associated to specific physical and chemical water properties. However, the mechanisms and spatiotemporal scales by which marine ecosystems are organized are largely not known. Here we investigate the spatiotemporal organization of phytoplankton communities by combining multisatellite data, notably high-resolution ocean-color maps of dominant types and altimetry-derived Lagrangian diagnostics of the surface transport. We find that the phytoplanktonic landscape is organized in (sub-)mesoscale patches (10-100 km) of dominant types separated by physical fronts induced by horizontal stirring. These physical fronts delimit niches supported by water masses of similar history and whose lifetimes are comparable with the timescale of the bloom onset (few weeks). The resonance between biological activity and physical processes suggest that the spatiotemporal (sub-)mesoscales associated to stirring are determinant in the observation and modeling of marine ecosystems. biogeochemical cycles | chaotic stirring | marine biogeography | marine ecology | phytoplankton functional types doi/ 10.1073/pnas.1004620107

The Lyapunov diffusivity is used to investigate local isentropic mixing events in the upper troposphere-lower stratosphere (UTLS) region. The diagnostic highlights the seasonal cycle of the longitudinally varying mixing properties, in particular those associated with the monsoon circulations and the westerly ducts in the subtropics. The results are broadly consistent with studies of Rossby wave-breaking frequencies. The mixing structure is shown to be modulated by modes of atmospheric variability. El Nino-Southern Oscillation (ENSO) is found to strongly influence the mixing structure throughout the tropics and subtropics. The subtropical jet is associated with longitudinal bands of mixing minima (isentropic mixing barriers) separated by synoptic-scale regions of strong mixing activity. The greatest ENSO modulation in December-February is confined to the Pacific sector, where the barriers associated with the subtropical jets extend farther into the eastern Pacific, and in the western Pacific a barrier is found at the equator during the positive phase. During June-August, the influence is seen to extend beyond the Pacific region, with the barrier at the subtropical jet in the Southern Hemisphere increasing in strength at all longitudes and with an increase in strength (and isolation of) monsoon-related mixing over Asia and North America. The local influence of the North Atlantic Oscillation in wintertime is investigated. During the positive phase, a double-barrier structure is associated with the subtropical jet, the northern branch crosses the Atlantic toward Scandinavia, and the southern branch tends toward North Africa. The Antarctic Oscillation is shown to influence whether the subvortex region is isolated from midlatitudes. DOI: 10.1175/2009JAS2983.1

A new diagnostic (the 'Lyapunov diffusivity') is presented that has the ability to quantify isentropic mixing in diffusion units and detects local mixing events by describing latitude-longitude variability. It is a hybrid diagnostic, combining the tracer-based effective diffusivity with the particle-based Lyapunov exponent calculation. Isentropic mixing on the 350-K surface shows that there is significant longitudinal variation to the strength of mixing at the northern subtropical jet, with a strong mixing barrier over Asia and the western Pacific, a weaker mixing barrier over the western Atlantic. and active mixing regions at the jet exits over the eastern Pacific and Atlantic. DOI: 10.1175/2009JAS2982.1

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2008.07.014 Byline: Francesco d'Ovidio (a)(b), Jordi Isern-Fontanet (c), Cristobal Lopez (d), Emilio Hernandez-Garcia (d), Emilio Garcia-Ladona (e) Abstract: Transport and mixing properties of surface currents can be detected from altimetric data by both Eulerian and Lagrangian diagnostics. In contrast with Eulerian diagnostics, Lagrangian tools like the local Lyapunov exponents have the advantage of exploiting both spatial and temporal variability of the velocity field and are in principle able to unveil subgrid filaments generated by chaotic stirring. However, one may wonder whether this theoretical advantage is of practical interest in real-data, mesoscale and sub-mesoscale analysis, because of the uncertainties and resolution of altimetric products, and the non-passive nature of biogeochemical tracers. Here we compare the ability of standard Eulerian diagnostics and the finite-size Lyapunov exponent in detecting instantaneous and climatological transport and mixing properties in the south-western Mediterranean. By comparing with sea-surface temperature patterns, we find that the two approaches provide similar results for slowly evolving eddies like the first Alboran gyre. However, the Lyapunov exponent is also able to predict the (sub-)mesoscale filamentary processes occurring along the Algerian current and above the Balearic Abyssal Plain. Such filaments are also observed, with some mismatch, in sea-surface temperature patterns. Climatologies of Lyapunov exponents do not show any compact relation with other Eulerian diagnostics, unveiling a different structure even at the basin scale. We conclude that filamentation dynamics can be detected by reprocessing available altimetric data with Lagrangian tools, giving insight into (sub-)mesoscale stirring processes relevant to tracer observations and complementing traditional Eulerian diagnostics. Author Affiliation: (a) Laboratoire d'Oceanographie et du Climat: Experimentation et Approches Numeriques, IPSL, Paris, France (b) Institute of Complex Systems, Paris Ile-de-France (ISC-PIF), France (c) Laboratoire d'Oceanographie Spatiale, Ifremer, Plouzane, France (d) Instituto de Fisica Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain (e) Institut de Ciencies del Mar, CSIC, Passeig Maritim de la Barceloneta 37-43, E-08003 Barcelona, Spain Article History: Received 25 October 2007; Revised 25 July 2008; Accepted 29 July 2008

Following the introduction of performance management in Italian universities, Business intelligence has become a strategical means to use administrative data in support of governance and decision-making processes. The aim of this paper is to show the important role played by a decision support system inside an organization by evaluating the outcomes of the fair tuition fee policy of the University of Bari, in favour of low-income students, stated as a priority in its mission. A longitudinal analysis is carried out on the cohort of first-year students enrolled in the academic year 2015–2016, searching for a predictive model of their performance given some explicative variables. The usefulness of adopting a periodic monitoring system, investigating data by means of suitable statistical techniques (logistic regression, survival analysis, Cox regression model), allows to early detect those factors to be modified in order to achieve optimal results with respect to student expectations and quality of higher education. [ABSTRACT FROM AUTHOR]

Economic connotation of poverty concerns mainly the level of household's spending and income as privileged indicators. Sometimes, data sources have several lack of information, but such information is available in other data sources related to the same statistical units, or to other households. In order to identify records relating to the same or similar units belonging to two data archives, some methodologies (record linkage in the first case, statistical matching in the latter) are used for integrating data. In this study we illustrate a model of data integration between two surveys conducted by the Italian National Institute of Statistics (Statistics on Income and Living Conditions and Survey on Household Expenses). The construction of an integrated database starting from those two surveys is useful for studying consumer behaviours in relation to specific groups of goods, analysing decisions related to household savings, examining economic and social inequalities, such as studying the impact of public policies through simulations. [ABSTRACT FROM AUTHOR]