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

A simple model of a water column applied to the deep water formation in the Northern Catalan Sea

In this paper an attempt to reproduce the evolution of the thermal structure of water columns by a simple one-dimensional model is presented. The model is based on the heat balance between the sea and the atmosphere and it is specially sensitive to air temperature and wind speed. The model is used to study the influence of these atmospheric forcings on the deep water formation process in the Northern Catalan Sea. It is applied using meteorological and oceanographic data collected during the ALPEX Special Observation Period (SOP) and the results are compared to temperature profiles obtained during the CARON 82 cruise (MEDALPEX)Publicado

Influence of the NAO on the northwestern Mediterranean wave climate

RESUMEN. Influencia de la nao en el clima marítimo del Mediterráneo noroccidental. – El presente trabajo estudia las teleconexiones entre la Oscilación del Atlántico Norte (NAO ) y el clima marítimo en el Mediterráneo noroccidental, definido por la media mensual de la altura significante (SWH) y la media mensual de la altura significante correspondiente al percentil 95 (percentil 95 SWH), en el período comprendido entre 1958 y 2001. Los datos analizados corresponden al retroanálisis de 44 años de datos atmosféricos, dentro del marco del proyecto HIPOCAS . Estos datos han sido codificados en forma de EOF s para obtener la variabilidad espacio-temporal asociada a la NAO . Los datos utilizados han sido previamente blanqueados para evitar correlaciones ficticias entre las series, mediante el ajuste a un modelo autorregresivo de orden p. Los resultados muestran como el clima marítimo del Mediterráneo noroccidental está influenciado a escala mensual por las distintas fases de la NAO . Cuando la NAO está en su fase positiva, podemos observar anomalías positivas en la altura significante media mensual, así como en la altura de ola correspondiente al percentil 95, estas anomalías aparecen en la zona comprendida entre las Islas Baleares, el Golfo de León y la costa catalana.ABSTRACT. This study examines teleconnections between the North Atlantic Oscillation (NAO ) and the wave climate of the northwestern Mediterranean Sea (NWM), defined by the monthly mean significant wave height (SWH) and the 95th percentile significant wave height (95th percentile SWH), in the period ranging from 1958 to 2001. The data analyzed comes from the multidecadal hindcast over Europe carried out during the HIPOCAS project. In order to avoid fictitious cross-correlations, data were prewhitened by fitting a p-order autoregressive model. To split the temporal and spatial variability, an EOF encoding technique was applied to residuals before searching for teleconnections. We found the northwestern Mediterranean wave climate to be influenced by the North Atlantic Oscillation (NAO ) with an instantaneous response. When the NAO is in its positive phase, positive anomalies in the SWH and the 95th percentile SWH appear in the area between the Balearic Islands, the Gulf of Lions and the Catalonian coast

density front in NW Mediterranean

www.ocean-sci.net/10/657/2014/ doi:10.5194/os-10-657-201

Tracking the global reduction of marine traffic during the COVID-19 pandemic

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: Stringency index data are available from the Oxford COVID-19 Government Response Tracker (www.bsg.ox.ac.uk/covidtracker). Raw AIS data are available from SOCIB and exactEarth Ltd. Anonymized and aggregated data from terrestrial AIS are available (https://doi.org/10.6084/m9.figshare.12667256). Density maps of satellite AIS were purchased from exactEarth Ltd., are used under license, and cannot be publicly shared by the authors. We make the global difference maps publicly available (https://doi.org/10.6084/m9.figshare.12676070).Code availability: All analyses were coded in R version 3.6.067. Code which is available from Github at https://github.com/dmarch/covid19-ais and https://doi.org/10.5281/zenodo.4582712.The COVID-19 pandemic has resulted in unparalleled global impacts on human mobility. In the ocean, ship-based activities are thought to have been impacted due to severe restrictions on human movements and changes in consumption. Here, we quantify and map global change in marine traffic during the first half of 2020. There were decreases in 70.2% of Exclusive Economic Zones but changes varied spatially and temporally in alignment with confinement measures. Global declines peaked in April, with a reduction in traffic occupancy of 1.4% and decreases found across 54.8% of the sampling units. Passenger vessels presented more marked and longer lasting decreases. A regional assessment in the Western Mediterranean Sea gave further insights regarding the pace of recovery and long-term changes. Our approach provides guidance for large-scale monitoring of the progress and potential effects of COVID-19 on vessel traffic that may subsequently influence the blue economy and ocean health.European Union Horizon 2020Natural Environment Research Council (NERC)Department for Environment, Food & Rural Affairs (Defra

Las playas de Menorca: naturaleza y distribución

[spa]La costa de Menorca acoge 114 sistemas de playa que representan el 9,9% de la línea de costa de Menorca. Ubicadas en un ambiente micromareal y expuestas a oleajes que raras veces superan los 3m de altura significante, la mayoría de las playas menorquinas se caracterizan por presentar arenas biogénicas de medias a gruesas, estando su distribución y naturaleza condicionadas, principalmente, por el contexto morfoestructural de la isla. Tanto en lo tocante a la configuración fisiográfica de las playas y su espacio de acomodación como a la naturaleza y tipología del sedimento. En general, la tasa de evolución media de las playas de Menorca no presenta grandes problemas y se caracteriza por la estabilidad, una estabilidad reforzada por el carácter protegido o semi-protegido de las ensenadas que acogen a las playas o porque las playas más expuestas coinciden las acumulaciones de cantos y bloques al pie de acantilados[eng]The Menorcan coast contains 114 beach systems, which occupy 9,9% of the coastline. Menorcan beaches are characterized by a microtidal and a moderate wave energy environment where, at annual scale, in few occasions significant wave heights attend values larger than 3m. Biogenic medium to coarse sands beaches are the dominant feature, although the island morphostructure controls both: the type of beach and the sediment nature and/or texture. In average, the shoreline change rate for the island beaches shows a stability scenario reinforced by the large number of embayed and pocket beaches along the Menorcan coast. The beaches exposed to the most energetic waves tend show cobble-boulder beaches at the cliff-toe

Capabilities of Global Ocean Programmes to Inform Climate Services

AbstractClimate services are identified as a means of providing the information that is needed to support decision makers in assessing the impacts of climate change on the oceans. We discuss the current observation programs to support these services, and their capacity to provide the information needed to monitor and address key science questions. An analysis of the current oceanographic observation programs is shown to be undersubscribed from their original plans. There are vulnerabilities in the current observing programs, particularly in relation to satellite measurements. The interaction of climate services with the research community, with policy makers and stakeholders and operational centres is outlined and leads to four recommendations. The key recommendations are for the more pervasisve development of climate services and for a modest increment in the observing program informed by the recommendations of the OceanObs’09 conference

Autonomous underwater gliders monitoring variability at "choke points" in our ocean system: a case study in Western Mediterranean Sea

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