Modeling the morphodynamic response of tidal embayments to sea-level rise

Sea-level rise has a strong influence on tidal systems, and a major focus of climate change effect studies is to predict the future state of these environmental systems. Here, we used a model to simulate the morphological evolution of tidal embayments and to explore their response to a rising sea level. The model was first used to reproduce the formation of channels and intertidal flats under a stable mean water level in an idealised and initially unchannelled tidal basin. A gradual rise in sea level was imposed once a well-developed channel network had formed. Simulations were conducted with different sea-level rise rates and tidal ranges. Sea-level rise forced headward erosion of the tidal channels, driving a landward expansion of the channel network and channel development in the previously non-inundated part of the basin. Simultaneously, an increase in channel drainage width in the lower part of the basin occurred and a decrease in the overall fraction of the basin occupied by channels could be observed. Sea-level rise thus altered important characteristics of the tidal channel network. Some intertidal areas were maintained despite a rising sea level. However, the size, shape, and location of the intertidal areas changed. In addition, sea-level rise affected the exchange of sediment between the different morphological elements. A shift from exporting to importing sediment as well as a reinforcement of the existing sediment export was observed for the simulations performed here. Sediment erosion in the inlet and the offshore transport of sediment was enhanced, resulting in the expansion of the ebb-tidal delta. Our model results further emphasise that tidal embayments can exhibit contrasting responses to sea-level rise.<br/

A Comparison of Global Estimates of Marine Primary Production From Ocean Color

The derivation of oceanic primary production using satellite measurements of ocean color (PP models) has great potential for biogeochemical studies. The Primary Production Algorithm Round Robin 3 (PPARR3) aims to compare existing PP models. It is a continuation of previous PPARR exercises, which compared in situ carbon14 uptake rates with an estimate of primary production using satellite-accessible data. PPARR2 found that modeled primary production would be within a factor of two of the in situ rates if systematic offsets were corrected. PPARR3 aims to provide a forum to compare model output, improve parameterization, and help identify the source of biases. This community project presently counts with over twenty modeling groups who estimate primary production for input fields provided by the organizers. The PPARR3 exercise consists of three stages, the first stage is a comparison of monthly global primary production fields generated by the different algorithms. Stage 2 is a step-by-step sensitivity study of the different algorithms tracking the derivation of sub-products in a series of point value estimates. The third stage is similar to PPARR1 and PPARR2 and is a blind comparison to the quality-controlled data base of carbon-14 measurements in the equatorial Pacific. We present here the results of the first stage, which compares the output of the models throughout an annual cycle, as well as two different years. Early results of the sensitivity analysis of Part 2 will also be shown.JRC.H.5-Rural, water and ecosystem resource