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The capacity to monitor suspended sediment concentrations (SSCs) in the ocean, from surface to bottom, using data acquired by the future Meteosat Third-Generation (MTG)/flexible combined imager (FCI) satellite sensor has been quantified by observing system simulation experiments (OSSEs). The “true” ocean state for these experiments is based on a 15-month numerical simulation of hydrodynamic and sediment transport, configured to represent the highly dynamical waters of the English Channel under the influences of tides and waves. Simulated MTG/FCI hourly averaged acquisitions at a given location near the Isle of Wight have been processed via hidden Markov model combined with a statistical classification—based on self-organizing maps—of predicted vertical SSC profiles. The resulting experiments demonstrated that MTG/FCI images, despite their high temporal resolution, and because of many gaps due to nights and clouds over the English Channel, still require spatial interpolations to enhance the amount of information available at a given location. For an accurate determination of particle concentrations, time series of the main forcing (wind, tides, and waves) need to be included in the process: 1) as a crucial parameter correlated with the dynamics of large particles (sands) and 2) as an equally important parameter as satellite data themselves in the correlation with the dynamics of fine particles (silts). [ABSTRACT FROM AUTHOR]

Insight on wave regimes along the world's coastlines is important for virtually all coastal and nearshore marine activities, installations, planning and protection. Waves are pervasive and the dominant source of energy driving extreme sea levels, the transport of pollutants and sediments, erosion, and a major contributor to risks of flooding. We quantify the global spatio-temporal wave conditions along the world's coasts and evaluate the needs for coastal Earth Observation strategies, with the aim, notably, that the derived scales of change can contribute to optimisation of these strategies. A global dominant timescale of 30 days is found in coastal wave variability that is, on average, spatially correlated just over the synoptic 5 degrees' regional scale (≈ 550 km at the equator). This regional-scale dimension suggests that the timing and design of traditional field surveys and observations relevant to a vast array of coastal activities, and which may be expensive in terms of human resources, may be complemented by information gained from satellite Earth Observation that throws light on spatio-temporal scales of wave-energy change along the world's coastlines. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the Capbreton canyon head, just off the coast, is investigated using high-resolution multibeam bathymetry datasets, sediment samples and numerical modeling. The HR bathymetry analysis reveals a morphological connection between the longshore trough and the head of the canyon. The analysis of recent sediment samples shows a clear correlation between the sediment of the canyon head and that of the nearshore. Hydrodynamic modeling (a coupled wave-flow model) shows that for high-energy waves, the rotational nature of surf-zone circulation reverses and wave-induced currents have the potential to transport large quantities of nearshore sands toward the canyon head. All these arguments support the assumption that the canyon head captures a part of the sand transported by longshore drift. Over the 15years of observation (1998–2013), time-lapse bathymetry shows that the floor of the canyon head and one lateral gully network experienced significant morphological reworking. In terms of hazards, despite this strong activity, the position of the canyon head and the profile of its longitudinal slope remained stable and appear as a comforting factor. However, the activity of unusual lateral erosions needs to be monitored. [Copyright &y& Elsevier]

Abstract: In order to define the nature and distribution of the organic matter (OM) preserved in the modern Ogooué deep sea turbidite system (Gabon), bulk geochemical techniques (Rock-Eval pyrolysis, elemental and isotopic analyses) and palynofacies were applied to three piston cores collected in the Cape Lopez Canyon and lobe and on the continental slope, north of the canyon. The hemipelagic sedimentation in the study area is characterized by high accumulations of well-preserved OM (∼2–3 wt. TOC %). Bulk geochemical and palynofacies analysis indicate both a marine and terrestrial origin of the OM. Contribution of the marine source is higher on the slope than in the canyon and lobe. OM accumulation in turbidites is strongly controlled by the combined influence of the Cape Lopez Canyon and littoral drift. In the canyon and lobe, turbidites show generally low TOC content (0.5 wt. %) and OM is oxidized. The origin of the OM is interpreted as both marine and terrestrial, with a higher contribution of continental source versus marine source. The low TOC contents are due to the large siliciclastic fraction transported by the littoral drift and diverted in the Cape Lopez Canyon during high energy processes (e.g. storms) which tend to dilute the OM in the turbidites. Transport by long-shore currents and/or turbiditic flows leads to oxidation of the OM. On the continental slope located north of the Cape Lopez Canyon, large amounts of OM are deposited in turbidites (up to 14 wt. %). The OM is predominantly derived from terrestrial land plants and has not been subjected to intense oxidation. These deposits are characterized by high hydrocarbon potential (up to 27 kg HC/t rock), indicating a good potential as gas-prone source rock. Because Cape Lopez Canyon captures a significant part of the sediment transported by the littoral drift, the siliciclastic sedimentary flux is reduced north of the canyon; OM is thus concentrated in the turbidites. Variation in TOC content within turbidite laminae can be explained by the burst and sweep deposition process affecting the boundary layer of the turbulent flow. This study confirms that gravity flows play a preponderant role in the accumulation and preservation of OM in deep water and that deep sea turbidite systems could be regarded as an environment where organic sedimentation occurs. [Copyright &y& Elsevier]