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This study explores the spatiotemporal variability in the residual circulation and its dependence on external forces in an interconnected system of intertidal basins. We focus on the Dutch Wadden Sea (DWS), where winds play a major role in water movements and storms significantly affect its short-term characteristics. We make use of realistic three-dimensional high-resolution numerical simulations to model the hydrodynamics in the DWS for the years 2005–2015. First, the ‘empirical orthogonal function’ method is applied to analyze systematically the relative contributions of various forcing mechanisms on the residual (i.e., tidally averaged) volume flow through the inlets and the shallow watersheds delimiting the system and each tidal basin. Then, we compute the tidally averaged flushing frequency of fresh water over the entire period of analysis, and we study its variations at short and long time scales. It is found that over 98% of the residual flow's spatiotemporal variations can be explained by the first three EOF modes, which are highly correlated with the cubic power of the vectorial wind components' speed and the amount of fresh water discharged into the back-barrier system. This study reveals that incidental short-duration events (e.g., storms) occurring at time scales of hours to days, albeit episodic and highly variable, strongly influence the residual transport's inter-annual variability and its long-term typical value in multiple-inlet coastal systems.

Salinity is a key factor affecting biological processes and biodiversity in estuarine systems. This study investigates temporal and spatial changes in salinity at a basin-wide scale for 2005–2015 in the Dutch Wadden Sea. Scan statistics is applied to track salinity variations systematically and to detect potential clusters, i.e., estuarine regions marked by anomalous high-salinity (or low-salinity) values in a certain period (i.e., strong deviations from the expected value in a statistical sense). Clusters’ statistical significance has been assessed via Monte Carlo simulations. Particular attention is devoted to event-driven spatial and temporal patterns characterized by extreme salinity values since these episodes dramatically increase stress levels on organisms living in intertidal areas. Periodic components in the modeled salinity time series are identified using wavelet analysis and eventually removed from the signal before performing scan statistics. Wavelet analysis suggests that tides are the chief agent controlling salinity fluctuations in the system at within-day time scales, whereas no dominant periodicities were detected at longer time scales. Scan statistics reveal long-lasting clusters next to the main freshwater outlets and within the areas characterized by low water exchanges. In contrast, active regions of the estuary can efficiently counteract extreme events and quickly recover their pre-perturbation conditions. Finally, by analyzing the freshwater dispersal in the system, it is found that clusters’ occurrence is related to episodic events characterized by extreme conditions in the southwesterly wind and freshwater discharge. This research demonstrates that scan statistics can be used as a powerful tool for spatiotemporal analyses of marine systems and for identifying data-clustering that may be indicative of emerging environmental hazards (e.g., due to climate change).

This study explores the spatiotemporal variability in the residual circulation and its dependence on external forces in an interconnected system of intertidal basins. We focus on the Dutch Wadden Sea (DWS), where winds play a major role in water movements and storms significantly affect its short-term characteristics. We make use of realistic three-dimensional high-resolution numerical simulations to model the hydrodynamics in the DWS for the years 2005–2015. First, the ‘empirical orthogonal function’ method is applied to analyze systematically the relative contributions of various forcing mechanisms on the residual (i.e., tidally averaged) volume flow through the inlets and the shallow watersheds delimiting the system and each tidal basin. Then, we compute the tidally averaged flushing frequency of fresh water over the entire period of analysis, and we study its variations at short and long time scales. It is found that over 98% of the residual flow's spatiotemporal variations can be explained by the first three EOF modes, which are highly correlated with the cubic power of the vectorial wind components' speed and the amount of fresh water discharged into the back-barrier system. This study reveals that incidental short-duration events (e.g., storms) occurring at time scales of hours to days, albeit episodic and highly variable, strongly influence the residual transport's inter-annual variability and its long-term typical value in multiple-inlet coastal systems.

Salinity is a key factor affecting biological processes and biodiversity in estuarine systems. This study investigates temporal and spatial changes in salinity at a basin-wide scale for 2005–2015 in the Dutch Wadden Sea. Scan statistics is applied to track salinity variations systematically and to detect potential clusters, i.e., estuarine regions marked by anomalous high-salinity (or low-salinity) values in a certain period (i.e., strong deviations from the expected value in a statistical sense). Clusters’ statistical significance has been assessed via Monte Carlo simulations. Particular attention is devoted to event-driven spatial and temporal patterns characterized by extreme salinity values since these episodes dramatically increase stress levels on organisms living in intertidal areas. Periodic components in the modeled salinity time series are identified using wavelet analysis and eventually removed from the signal before performing scan statistics. Wavelet analysis suggests that tides are the chief agent controlling salinity fluctuations in the system at within-day time scales, whereas no dominant periodicities were detected at longer time scales. Scan statistics reveal long-lasting clusters next to the main freshwater outlets and within the areas characterized by low water exchanges. In contrast, active regions of the estuary can efficiently counteract extreme events and quickly recover their pre-perturbation conditions. Finally, by analyzing the freshwater dispersal in the system, it is found that clusters’ occurrence is related to episodic events characterized by extreme conditions in the southwesterly wind and freshwater discharge. This research demonstrates that scan statistics can be used as a powerful tool for spatiotemporal analyses of marine systems and for identifying data-clustering that may be indicative of emerging environmental hazards (e.g., due to climate change).

Salt marshes are valuable ecosystems that must trap sediments and accrete in order to counteract the deleterious effect of sea‐level rise. Previous studies have shown that the capacity of marshes to build up vertically depends on both autogenous and exogenous processes including eco‐geomorphic feedbacks and sediment supply from in‐land and coastal ocean. There have been numerous efforts to quantify the role played by the sediments coming from marsh edge erosion on the resistance of salt marshes to sea‐level rise. However, the majority of existing studies investigating the interplay between lateral and vertical dynamics use simplified modelling approaches and they do not consider that marsh retreat can affect the regional scale hydrodynamics and sediment retention in back‐barrier basins.In this study, we evaluated the fate of the sediments originating from marsh lateral loss by using high‐resolution numerical model simulations of Jamaica Bay, a small lagoonal estuary located in New York City. Our findings show that up to 42% of the sediments released during marsh edge erosion deposits on the shallow areas of the basin and over the vegetated marsh platforms, contributing positively to the sediment budget of the remaining salt marshes. Furthermore, we demonstrate that with the present‐day sediment supply from the ocean the system cannot keep pace with sea‐level rise even accounting for the sediment liberated in the bay through marsh degradation. Our study highlights the relevance of multiple sediment sources for the maintenance of the marsh complex.

Salt marshes are valuable ecosystems that must trap sediments and accrete in order to counteract the deleterious effect of sea‐level rise. Previous studies have shown that the capacity of marshes to build up vertically depends on both autogenous and exogenous processes including eco‐geomorphic feedbacks and sediment supply from in‐land and coastal ocean. There have been numerous efforts to quantify the role played by the sediments coming from marsh edge erosion on the resistance of salt marshes to sea‐level rise. However, the majority of existing studies investigating the interplay between lateral and vertical dynamics use simplified modelling approaches and they do not consider that marsh retreat can affect the regional scale hydrodynamics and sediment retention in back‐barrier basins.In this study, we evaluated the fate of the sediments originating from marsh lateral loss by using high‐resolution numerical model simulations of Jamaica Bay, a small lagoonal estuary located in New York City. Our findings show that up to 42% of the sediments released during marsh edge erosion deposits on the shallow areas of the basin and over the vegetated marsh platforms, contributing positively to the sediment budget of the remaining salt marshes. Furthermore, we demonstrate that with the present‐day sediment supply from the ocean the system cannot keep pace with sea‐level rise even accounting for the sediment liberated in the bay through marsh degradation. Our study highlights the relevance of multiple sediment sources for the maintenance of the marsh complex.