Uncertainties in the projected patterns of wave-driven longshore sediment transport along a non-straight coastline

This study quantifies the uncertainties in the projected changes in potential longshore sediment transport (LST) rates along a non-straight coastline. Four main sources of uncertainty, including the choice of emission scenarios, Global Circulation Model-driven offshore wave datasets (GCM-Ws), LST models, and their non-linear interactions were addressed through two ensemble modelling frameworks. The first ensemble consisted of the offshore wave forcing conditions without any bias correction (i.e., wave parameters extracted from eight datasets of GCM-Ws for baseline period 1979–2005, and future period 2081–2100 under two emission scenarios), a hybrid wave transformation method, and eight LST models (i.e., four bulk formulae, four process-based models). The differentiating factor of the second ensemble was the application of bias correction to the GCM-Ws, using a hindcast dataset as the reference. All ensemble members were weighted according to their performance to reproduce the reference LST patterns for the baseline period. Additionally, the total uncertainty of the LST projections was decomposed into the main sources and their interactions using the ANOVA method. Finally, the robustness of the LST projections was checked. Comparison of the projected changes in LST rates obtained from two ensembles indicated that the bias correction could relatively reduce the ranges of the uncertainty in the LST projections. On the annual scale, the contribution of emission scenarios, GCM-Ws, LST models and non-linear interactions to the total uncertainty was about 10–20, 35–50, 5–15, and 30–35%, respectively. Overall, the weighted means of the ensembles reported a decrease in net annual mean LST rates (less than 10% under RCP 4.5, a 10–20% under RCP 8.5). However, no robust projected changes in LST rates on annual and seasonal scales were found, questioning any ultimate decision being made using the means of the projected changes

First recorded case of leucism in the velvet belly lantern shark Etmopterus spinax (Squaliformes: Etmopteridae)

The capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, North-eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considerate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae. A comprehensive updated review of published literature on albinism and leucism in chondrichthyans is also provided.En prens

Controls of Multimodal Wave Conditions in a Complex Coastal Setting

Coastal hazards emerge from the combined effect of wave conditions and sea level anomalies associated with storms or low-frequency atmosphere-ocean oscillations. Rigorous characterization of wave climate is limited by the availability of spectral wave observations, the computational cost of dynamical simulations, and the ability to link wave-generating atmospheric patterns with coastal conditions. We present a hybrid statistical-dynamical approach to simulating nearshore wave climate in complex coastal settings, demonstrated in the Southern California Bight, where waves arriving from distant, disparate locations are refracted over complex bathymetry and shadowed by offshore islands. Contributions of wave families and large-scale atmospheric drivers to nearshore wave energy flux are analyzed. Results highlight the variability of influences controlling wave conditions along neighboring coastlines. The universal method demonstrated here can be applied to complex coastal settings worldwide, facilitating analysis of the effects of climate change on nearshore wave climate.This work was funded by the U.S. Geological Survey (USGS) Coastal and Marine Geology Program. The authors thank Jorge Perez, IH Cantabria, for providing the GOW wave hindcast and for assistance with wave spectra, and Sean Vitousek, University of Chicago, for a helpful review. This material is based upon work supported by the U.S. Geological Survey under grant/cooperative agreement GI5AC00426. A. R., J. A. A. A., and F. J. M. acknowledge the support of the Spanish “Ministerio de Economía y Competitividad” under grant BIA2014-59643-R. J. A. A. A. was funded by the Spanish “Ministerio de Educación, Cultura y Deporte” FPU (Formación del Profesorado Universitario) studentship BOE-A-2013-12235. Reanalyses of ocean data are available for research purposes through IH Cantabria (contact [email protected]). Southern California Bight look-up table data are available at https://doi.org/10.1594/PANGAEA.880314. Related Southern California nearshore wave data can be found at http://dx.doi.org/10.5066/F7N29V2V

First recorded case of leucism in the velvet belly lantern shark Etmopterus spinax (Squaliformes: Etmopteridae)

Poster presentado en el SIBIC 2022 IX Iberian Congress of IchthyologyThe capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, North-Eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considérate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae

The microwave spectrum, ab initio analysis, and structure of the fluorobenzene–hydrogen chloride complex

The fluorobenzene–hydrogen chloride π-hydrogen-bonded complex has been studied by high resolution microwave spectroscopy and ab initio calculations. Rotational spectra of the C6H5F–H35Cl,C6H5F–H35Cl, C6H5F–H37Cl,C6H5F–H37Cl, and C6D5F–H35ClC6D5F–H35Cl isotopomers were assigned using pulsed molecular beam techniques in a Fourier-transform microwave spectrometer. The spectra are consistent with a structure of the complex in which the HCl is above the fluorobenzene ring near the ring center, similar to the benzene–HCl prototype dimer. An analysis of the inertial data and the chlorine quadrupole coupling tensor results in two mathematically possible locations for the HCl subunit with respect to the fluorobenzene arising from sign ambiguities in interpreting the spectral constants. One structure has the HCl nearly perpendicular to the aromatic ring; the other has the HCl pointing toward the fluorine end of the ring. Spectral intensities for the μaμa and μbμb transitions favor the former configuration. Ab initio calculations (MP2/6-311++G(2df,2pd)+BSSE corrections) indicate that the position of the HCl is driven by electrostatic interactions with the π electrons of the benzene ring. HCl is shifted by 0.16 Å from the center of the ring toward the para-C atom, where the π density is significantly higher. In the equilibrium form, HCl is tilted by δ=14° from perpendicular to the ring with the hydrogen end toward the para-C atom. The H atom can perform an internal rotation or at least a half-circular libration (barriers smaller than 100 cm−1). An average δ value of 0.7° is estimated in reasonable agreement with the derived vibrationally averaged value of 3.8°. The complex binding energy ΔEΔE calculated at the CCSD(T)/6-311++G(2df,2pd)+CP(BSSE) level of theory is 2.8 kcal/mol, suggesting a lower ΔEΔE value for benzene–HCl than previously reported. Fluorobenzene–HCl possesses some charge transfer character; however, just 5.5 melectron are transferred from the benzene ring to HCl. In view of this, π–H bonding in fluorobenzene–HCl is predominantly electrostatic rather than covalent in character contrary to claims made in connection with benzene–HCl. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71342/2/JCPSA6-118-20-9278-1.pd

A multiscale climate emulator for long-term morphodynamics (MUSCLE-morpho)

Interest in understanding long-term coastal morphodynamics has recently increased as climate change impacts become perceptible and accelerated. Multiscale, behavior-oriented and process-based models, or hybrids of the two, are typically applied with deterministic approaches which require considerable computational effort. In order to reduce the computational cost of modeling large spatial and temporal scales, input reduction and morphological acceleration techniques have been developed. Here we introduce a general framework for reducing dimensionality of wave-driver inputs to morphodynamic models. The proposed framework seeks to account for dependencies with global atmospheric circulation fields and deals simultaneously with seasonality, interannual variability, long-term trends, and autocorrelation of wave height, wave period, and wave direction. The model is also able to reproduce future wave climate time series accounting for possible changes in the global climate system. An application of long-term shoreline evolution is presented by comparing the performance of the real and the simulated wave climate using a one-line model.Keywords: climate variability, long-term, morphodynamics, multivariate wave climate emulator, statistical downscaling, climate changeKeywords: climate variability, long-term, morphodynamics, multivariate wave climate emulator, statistical downscaling, climate chang

Sentinels of Seabed (SoS) indicator: Assessing benthic habitats condition using typical and sensitive species

Indicators are key tools used to assess the ecological status of the environment for ecosystem based management. Anthropogenic disturbances produce changes to habitat condition, which include modifications in species composition and their functions. Monitoring a group of sentinel species (from a taxonomic and functional point of view) provides useful insights into benthic habitat condition. Here, a new indicator, Sentinels of the Seabed (SoS) is proposed to assess state of benthic habitats using “sentinel” species (species which are characteristic of a habitat and sensitive to a given pressure). The selection of these sentinel species has two stages. First, a ‘typical species set’ is computed using intra-habitat similarity and frequency under reference conditions. Second, the ‘sentinel species set’ is generated by selecting the most sensitive species from the typical species set. This selection is made using specific indexes able to assess species sensitivity to a particular pressure. The SoS indicator method was tested on six case studies and two different pressure types (trawling disturbance and pollution), using data from otter trawl, box-corer and Remote Operate Vehicle images. In each scenario, the SoS indicator was compared to the Shannon-Wiener diversity index, Margalef index and total biomass, being the only metric, which showed the expected significant negative response to pressure in all cases. Our results shows that SoS was highly effective in assessing benthic habitats status under both physical and chemical pressures, regardless of the sampling gear, the habitat, or the case study, showing a great potential to be a useful tool in the management of marine ecosystems.Versión del editor2,69

Uncertainties in wave-driven longshore sediment transport projections presented by a dynamic CMIP6-based ensemble

In this study four experiments were conducted to investigate uncertainty in future longshore sediment transport (LST) projections due to: working with continuous time series of CSIRO CMIP6-driven waves (experiment #1) or sliced time series of waves from CSIRO-CMIP6-Ws and CSIRO-CMIP5-Ws (experiment #2); different wave-model-parametrization pairs to generate wave projections (experiment #3); and the inclusion/exclusion of sea level rise (SLR) for wave transformation (experiment #4). For each experiment, a weighted ensemble consisting of offshore wave forcing conditions, a surrogate model for nearshore wave transformation and eight LST models was used. The results of experiment # 1 indicated that the annual LST rates obtained from a continuous time series of waves were influenced by climate variability acting on timescales of 20-30 years. Uncertainty decomposition clearly reveals that for near-future coastal planning, a large part of the uncertainty arises from model selection and natural variability of the system (e.g., on average, 4% scenario, 57% model, and 39% internal variability). For the far future, the total uncertainty consists of 25% scenario, 54% model and 21% internal variability. Experiment #2 indicates that CMIP6 driven wave climatology yield similar outcomes to CMIP5 driven wave climatology in that LST rates decrease along the study area’s coast by less than 10%. The results of experiment #3 indicate that intra- and inter-annual variability of LST rates are influenced by the parameterization schemes of the wave simulations. This can increase the range of uncertainty in the LST projections and at the same time can limit the robustness of the projections. The inclusion of SLR (experiment #4) in wave transformation, under SSP1-2.6 and SSP5-8.5 scenarios, yields only meagre changes in the LST projections, compared to the case no SLR. However, it is noted that future research on SLR influence should include potential changes in nearshore profile shapes

A changing wave climate in the Mediterranean Sea during 58-years using UERRA-MESCAN-SURFEX high-resolution wind fields

This study unravels 58-years (1961–2018) of wind-waves in the Mediterranean Sea (MS). A wave dataset was developed using the wave model WAVEWATCH III forced with the high-resolution (5.5 km) UERRA-MESCAN-SURFEX downscaled wind fields which better contain the imprint of the local geomorphology compared to other, coarser wind datasets used in previous studies. Thus, improving the reliability and characterization of the wind-wave climate in the basin. Validation results revealed a higher performance than previous datasets, particularly on the wave direction (θm), with a bias&lt;1°. Climate variability at seasonal and interannual scales, wind-seas and swells distribution, and long-term trends in storminess and in the mean and extreme regimes were analysed. Results show a slight swell influence over the wind-sea in the hourly spectra at a large portion of the basin, excluding the wave generation areas. We detected that the western MS is the most storminess region with an average of three storms/year. Moreover, the anomalies of the seasonal mean wave direction relative to θm are large (∼60°), with opposing behaviours between the winter and summer. Finally, the long-term trends in the mean and extreme conditions and in storminess are mild with values reaching 6 cm/decade and less than 2% in the absolute value, respectively.</p

Predicting the response of complex systems for coastal management

In recent years, coastal management has been facing new challenges: socio-economic growth and consequent climate change impose new boundary conditions pushing coastal systems towards unseen states. For adaptation and mitigation strategies as well as risk management, the resilience of systems to these projected changes must be tested and quantified using predictive tools, given the scarcity of observations. Process-based models, which limit the number of assumptions, are the preferred tools. However, these models are computationally expensive and therefore unattractive for global sensitivity and uncertainty analyses. Input and model reduction techniques, as well as behavioural empirical models, have been widely used to overcome these computational difficulties. In this paper, we propose a process-based hybrid workflow—that combines statistical and machine learning with a process-based numerical model—to provide sensitivity analyses on complex systems. As an example we explore salt intrusion in estuaries. The novelty of the method presented is the implementation of an adaptive sampling technique of numerical experiments with a process-based hydrodynamic model, and the training of a neural network to augment the set of numerical runs executed. The first uses predictive uncertainty to automatically explore the response of the complex system to varying environmental boundary conditions and geomorphological configurations. The second is trained to provide system responses around the sampled points. This exploration is closed by simulating the extremes in the output space as found by a genetic algorithm. This scheme is shown to be highly efficient in non-linear, heteroscedastic, and highly non-stationary systems.</p