A fully satellite-driven workflow for hydrodynamic modeling in data-scarce coastal systems: integrating ICESat-2, Sentinel-2, SWOT and reanalysis models

The rapid rise and fall of coastal sea level due to tides and storm surge complicates the application of hydrodynamic models that use constant lateral boundaries in the region where sea level change falls within the tidal range or between the negative and positive surge extremes. In order to enable a hydrodynamic model for use in tidal or surge zones, an inundation and drying scheme must be incorporated into the hydrodynamic model. In this study, a mass-conserving inundation (wetting) and draining (drying) scheme is incorporated into a three-dimensional hydrodynamic model (the Princeton Ocean Model, often referred to as POM) for coastal ocean and estuarine systems. This coupled hydrodynamic and inundation modeling system is tested in an idealized lake/estuarine setting. The results show that: 1) incorporation of the inundation/drying scheme into the POM enabled its application in shallow water systems with time-dependent coastal boundaries; 2) the mass conservation constraint used in the inundati...

In South Africa, gracilarioid red algae have been collected as wash-up to be dried and sold for agar extraction for at least 50 years. Despite much research, there is currently no commercial mariculture of the algae locally although this has been carried out in neighboring Namibia for a number of years. The industry is traditionally confined to Saldanha Bay on the west coast, although small wash-ups of Gracilariopsis longissima have been collected in nearby St Helena Bay. In Saldanha Bay, wash-ups of Gracilaria. gracilis have been very sporadic over the last few decades, with human alteration of the bay configuration possibly responsible for an initial major decline in 1974. This unpredictability in the amounts of wash-up has made the industry unstable and increasingly unprofitable. We compiled the results of previous surveys (some unpublished) of gracilariod populations in St Helena Bay and the Saldanha-Langebaan sytem, and re-surveyed these populations to examine long-term fluctuations. In Saldanha Bay and Langebaan Lagoon, standing stock of G. gracilis was estimated at 538 tons fresh weight and 71 tons fresh weight respectively. Less than 4 tons of gracilarioids are estimated to remain in St Helena Bay. We discuss the fluctuations in biomass and distribution of these South African gracilarioid populations.

It is impractical to create gridded numerical models of coastal circulation with sufficient resolution around small topographic features, such as submarine canyons, and still have the alongshore boundaries placed beyond the decay distance of coastal trapped waves. Two solutions to this problem are to make the alongshore boundaries either open or periodic. Numerical simulations were performed with upwelling and downwelling winds to compare the effects of these different choices for boundary conditions. Several open boundary formulations were tried and three are discussed in detail. The offshore boundary was specified as “no gradient” for all variables with no serious effect. The “modified” Orlanski radiation condition is used for all variables at the alongshore boundaries, except the vertically integrated flow that has the strongest effect on the model solution. An alongshore pressure gradient, opposing the wind, develops in the model if the modified Orlanski radiation condition is applied to the barotropic flow, causing slower currents near the surface and deep undercurrents away from the shelf. The other cases, which combined either a radiation or a relaxation boundary condition with a local solution of the barotropic equations on the boundary, were at least initially similar to the periodic case but with slower alongshore flow. The initial impact of these differences on the circulation within the canyon was small. The models with the open boundaries were more stable (did not develop strong flow meanders) than the cases with periodic conditions as initial transients are not trapped, and amplified, within the domain. Thus, open cases, especially with the upwelling winds, could run for extended times.

In chapter 8, a general overview was provided on the dominant sources of organic matter in estuarine systems. In general, estuarine organic matter is derived from a multitude of natural and anthropogenic allochthonous and autochthonous sources that originate across a freshwater to seawater continuum. Knowledge of sources, reactivity, and fate of organic matter are critical in understanding the role of estuarine and coastal systems in global biogeochemical cycles (Simoneit, 1978; Hedges and Keil, 1995; Bianchi and Canuel, 2001). Due to a wide diversity of organic matter sources and the dynamic mixing that occurs in estuarine systems, it remains a significant challenge in determining the relative importance of these source inputs to biogeochemical cycling in the water column of sediments. Temporal and spatial variability in organic matter inputs adds further to the complexity in understanding these environments. In recent years there have been significant improvements in our ability to distinguish between organic matter sources in estuaries using tools such as elemental, isotopic (bulk and compound/class specific), and chemical biomarker methods. This chapter will provide a general overview of the biochemistry of dominant organic compounds in organic matter and the techniques used to distinguish them in estuarine systems. The abundance and ratios of important elements in biological cycles (e.g., C, H, N, O, S, and P) provide the basic foundation of information on organic matter cycling. For example, concentrations of total organic carbon (TOC) provide the most important indicator of organic matter since approximately 50% of most organic matter consists of C. As discussed in chapter 8, TOC in estuaries is derived from a broad spectrum of sources with very different structural properties and decay rates. Consequently, while TOC provides essential information on spatial and temporal dynamics of organic matter it lacks any specificity to source or age of the material. When bulk C information is combined with additional elemental information, as in the case of the C-to-N ratio, basic source information can be inferred about algal and terrestrial source materials (see review, Meyers, 1997). The broad range of C:N ratios across divergent sources of organic matter in the biosphere demonstrate how such a ratio can provide an initial proxy for determining source information.

Summary Average major and trace element data are reported for recent sediments from Saldanha Bay and Langebaan Lagoon. Chemically, the sediments are composed mainly of SiO2 and CaCO3 (SiO2 + CaCO3 > 93 %). The sediments are considered to be a three-component mix of quartz, calcite and a granitic fraction presumed to be derived from local granitic rocks.

Relative growth rates (RGRs), yields and agar characteristics of threegracilarioid isolates (Gracilariopsis sp. from St. Helena Bay, and Gracilaria gracilis isolates from Langebaan Lagoon and Saldanha Bay) weremeasured to assess the suitability of a site in St. Helena Bay for suspendedcultivation. The gracilarioids were grown on polypropylene ropes and`netlon' lines, and the RGRs were 4.0–11.0% d-1 and 5.0–7.0%d-1, respectively. The RGR of the Langebaan isolate of G. gracilis grown on ropes was significantly higher than the RGR of otherisolates. The mean net yield for the Langebaan isolate grown on `netlon'lines was 2.6 ± 0.9 kg wet wt m-2 30 day-1. Thecultured gracilarioids were extracted for native and alkali treated agars. Themean native agar yield over the entire period was 39.0% dry wt. Alkalipretreatment reduced the yield by 55%, but significantly increased gelstrength. High gel strengths (>750 g cm-2) were measured inagars from Gracilariopsis sp. and Saldanha Gracilaria gracilis inmid-summer and winter. The dynamic gelling and melting temperatures ofnative and alkali treated agars varied among the gracilarioids. The meangelling and melting temperatures of agars were about 39.0 °C and86.0 °C, respectively. The 3,6-AG content ranged from 29% to38% for native agars and 34–45% for alkali treated agars. While theseresults indicate that this site is suitable for gracilarioid cultivation, occasionallow-oxygen events in St. Helena Bay lead to production of hydrogensulphide in the sea water (`black tides'). Such events killed most inshorebiota (including seaweeds) in 1994 and 1998. This frequency (on average1–2 per decade) and duration (maximum 2 weeks) would have to beconsidered in planning commercial seaweed farming in St. Helena Bay.

Non-linear interactions between sea-level rise, tides, and geomorphic change in the Tamar Estuary, Australia

The influence of baroclinity on tidal ranges in the North Sea

A complex hydrodynamic and thermodynamic method for modeling of hydrothermal systems was developed. At the first stage, the hydrodynamic model is calculated, and the results of this calculation serve as the initial data for the second stage (the thermodynamic model). This method was used to compute the model of a convective hydrothermal system in a mid-ocean ridge. The results are consistent with the natural observations concerning the expansion of secondary mineral associations in the oceanic crust.

The distribution of larval fishes is influenced by where they hatch and their movements after hatching. In the San Francisco Estuary, the threatened longfin smeltSpirinchus thaleichthysspawns adhesive eggs in fresh to brackish water. Attached eggs hatch and the larvae disperse seaward toward higher-salinity water. Actual locations of spawning and hatching are unknown, and cannot reliably be inferred from distributions of larvae because intense tidal mixing obscures the history of movement. Human interventions such as manipulations and diversions of freshwater flow may contribute to the ongoing decline of this species, and these effects depend on where the fish hatch. We combined movement estimated using hydrodynamic and particle-tracking modeling with trawl data using a Bayesian model to estimate the location and timing of hatching, as well as natural mortality of larvae and losses to freshwater diversions. Results indicate that longfin smelt may hatch further seaward than previously believed, and that estimated direct losses due to diversions were small relative to other sources of mortality. Abundance of this species varies ~100-fold with freshwater flow, but our results suggest that proportional entrainment was practically zero during an extreme wet year and relatively low (2%) in a moderately dry year. This method could be applied to other estuarine and coastal systems where strong mixing reduces the ability of simpler models to predict hatching locations and larval movements.

Hamanako is an economically and culturally important tidal lake on the Pacific coast of Honshu, Japan. Between 1954 and 1973, entrance works were constructed to regulate the channel to the lake. In a previous paper, the tidal records from Maisaka just inside the lake, prior to regulation, were analyzed to explain the responses of the lake to the ocean tide and other water level changes. The present paper compares water level responses with those following regulation of the entrance. The principal differences are that at Maisaka the tidal range increased up to 1965, following the first stages of regulation, but it has been constant since then. In the inner part of the lake, regulation has increased the tidal range but reduced its variability and has reduced the mean water level in the lake. The southern sand shoal divides the lake into two tidal basins, with Maisaka lying in the smaller outer basin. Studies of the inner basin have shown that its tidal range continues to increase. A hydrodynamic model has been used to show that this increase is primarily due to scouring of the inner channel through the southern shoal. The model has also shown that the constancy of the Maisaka tidal amplitude since 1965 is not a static equilibrium, but is a balance between the effects of the outer entrance channel scouring and increasing the Maisaka tide, offset by the inner channel scouring and reducing the Maisaka tide.

Abstract. Precise predictions of storm surges during typhoon events have the necessity for disaster prevention in coastal seas. This paper explores an artificial neural network (ANN) model, including the back propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS) algorithms used to correct poor calculations with a two-dimensional hydrodynamic model in predicting storm surge height during typhoon events. The two-dimensional model has a fine horizontal resolution and considers the interaction between storm surges and astronomical tides, which can be applied for describing the complicated physical properties of storm surges along the east coast of Taiwan. The model is driven by the tidal elevation at the open boundaries using a global ocean tidal model and is forced by the meteorological conditions using a cyclone model. The simulated results of the hydrodynamic model indicate that this model fails to predict storm surge height during the model calibration and verification phases as typhoons approached the east coast of Taiwan. The BPNN model can reproduce the astronomical tide level but fails to modify the prediction of the storm surge tide level. The ANFIS model satisfactorily predicts both the astronomical tide level and the storm surge height during the training and verification phases and exhibits the lowest values of mean absolute error and root-mean-square error compared to the simulated results at the different stations using the hydrodynamic model and the BPNN model. Comparison results showed that the ANFIS techniques could be successfully applied in predicting water levels along the east coastal of Taiwan during typhoon events.

A methodology for defining homogeneous water bodies in estuaries – Application to the transitional systems of the EU Water Framework Directive

The tidal regime of Shark Bay, Western Australia

Coastal systems in transition: From a ‘natural’ to an ‘anthropogenically-modified’ state