The Vaccarès Lagoon System, located in the central part of the Rhône Delta (France), is a complex shallow coastal lagoon, exposed to a typical Mediterranean climate and a specific hydrological regime affected by man-controlled exchanges with the sea and agricultural drainage channels. In this article, we report the results obtained by a series of monitoring programs, with different spatial and temporal resolutions. Long-term datasets from 1999 to 2019 with data collected on a monthly basis and a high spatial resolution highlighted the significant spatial heterogeneity in salinity regimes, and helped to determine the long-term evolution of the total mass of dissolved salt. High-frequency surveys allowed to characterize the water levels and salinity dynamics seasonal response to (i) the exchanges with the Mediterranean Sea, (ii) the exchanges with agricultural drainage channels, and (iii) the rain and evaporation. In addition, wind effects on salinity variations are also explored. This work shows how different spatial and temporal monitoring strategies provide complementary information on the dynamic of such a complex system. Results will be useful and provide insight for the management of similar lagoon systems, accommodating for both human activities and ecological stakes in the context of global change.

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The submarine Istanbul-Silivri fault segment, within 15 km of Istanbul, is the only portion of the North Anatolian Fault that has not ruptured in the last 250 years. We report first results of a seafloor acoustic ranging experiment to quantify current horizontal deformation along this segment and assess whether the segment is creeping aseismically or accumulating stress to be released in a future event. Ten transponders were installed to monitor length variations along 15 baselines. A joint least squares inversion for across-fault baseline changes, accounting for sound speed drift at each transponder, precludes fault displacement rates larger than a few millimeters per year during the 6 month observation period. Forward modeling shows that the data better fit a locked state or a very moderate surface creep—less than 6 mm/yr compared to a far-field slip rate of over 20 mm/yr—suggesting that the fault segment is currently accumulating stress.

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Based on new U-Th ages of corals drilled offshore Barbados, Abdul et al. (2016) have confirmed the existence of the abrupt stratigraphic feature called meltwater pulse 1B (MWP-1B), which they interpret as being due to a very large and global sea level step change dated at about 11.3 kyr before present (approximately 15 m and equivalent to twice the amount of water stored in the present Greenland ice sheet). This contrasts with the Tahiti record, in which MWP-1B is essentially absent or very small, as Carlson and Clark (2012) and Lambeck et al. (2014) also conclude in their recent reviews of deglacial sea levels at the global scale. However, the evidence provided by Abdul et al. and their main conclusions are not convincing as they are affected by the following three main problems, which may explain the apparent discrepancies: Problem #1/Barbados is located in a subduction zone, which was also active throughout the Late Glacial period. Furthermore, the Barbados cores studied by Abdul et al. were drilled on both sides of the extension of a tectonic feature identified at the southern tip of Barbados (South Point) as underlined by several studies of the Barbados stratigraphy. Problem #2/Fossil samples of Acropora palmata may not be reliable sea level markers during rapid and large sea level rises. Indeed, the asexual reproduction strategy of this species may not be optimal to keep up when the water depth is increasing very rapidly. This may in part explain why the living depth of A. palmata at Barbados was significantly greater than 5 m during some periods of the last deglaciation, notably between 14.5 and 14 kyr B.P. and possibly between 14 and 11.5 kyr B.P. Problem #3/The slow glacio-isostatic adjustment and the rapid responses due to gravitational changes of ice and water masses complicate the interpretation of individual relative sea level (RSL) records at specific locations. Therefore, the Barbados and Tahiti record cannot be compared directly in terms of absolute sea level values as done by Abdul et al. In addition, different glaciohydroisostatic adjustments at the two sites may also have contributed to the observed discrepancy between their deglacial RSL records.

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