While estuarine salt plugs can develop worldwide in estuaries adjacent to buoyant coastal currents, their formation has been scarcely documented. This study aims to generalize a mechanism for salt plug formation that does not invoke evaporation processes but involves a buoyant coastal current modified by wind stresses. A numerical model, Delft3D, is used to simulate two idealized bays, one with a single inlet and another with two inlets. The numerical experiments are inspired by recent observations and simulate nine different scenarios of wind and tidal forcings under the influence of an along-shelf buoyant current. Results show that the salt plug induces an inverse circulation at the inlet with inflow at the surface and outflow underneath. This circulation is modified by wind action. The persistence of the salt plug depends on tidal flushing, as well as wind intensity and direction. A yearlong numerical experiment with non-stationary buoyant currents and non-stationary winds indicate that: (i) onshore winds transport oceanic waters into the bay, while offshore winds export estuarine water to the ocean; (ii) onshore winds enhance the inverse circulation at the inlet, while offshore winds stall it. The ratio between wind-driven and density-induced accelerations, given by the Wedderburn number, determines the dominant contribution to the along-estuary circulation in an along-estuary transect. In general, baroclinicity dominates over wind-stress at the inlet, while wind-stress governs the circulation along the estuary. This study represents the first attempt to identify the role of wind and buoyant coastal currents on the dynamics of salt plug formation.

Hurricane Irma affected the Florida peninsula in September 2017. The east coast of the peninsula was hit particularly hard: the city of Jacksonville flooded around the St. Johns River estuary with non-tidal water levels that exceeded 1.5 m and precipitation that surpassed 20 cm in 24 hours. This study used observations such as water and wind velocities, river discharge, and conductivity data to determine whether compounding forcings influenced flood levels. Results show that flooding was initiated by a pulse from the ocean and then exacerbated by high river discharge. The 1-2 punch from the ocean and then the river caused record flooding, with impacts that lasted through the rest of September. Peak water levels occurred while hurricane winds were receding, and river discharge was increasing. Compound flood models should consider the phase lag between driving processes, as the individual peaks may not occur simultaneously, yet exacerbate flooding.

Intertidal creeks (<5m width) weave through salt marshes, delivering water, nutrients, and sediments into the marsh interior and alter spatial heterogeneity in plant and animal distributions. Despite their global prevalence, creek connectivity, and the mechanisms controlling cross-marsh hydrodynamics, remain poorly resolved. In this study, we measured flow and total suspended solids (TSS) transport in three intertidal creeks within a confined drainage basin in a Georgia, USA salt marsh. We discovered that the effective drag is 3 to 12 times greater than bed drag, reaching levels similar to those observed in coral reefs. Furthermore, the drag between tidal flood and ebb phases differ, suggesting a non-symmetric drag. Analyses of along-channel momentum reveal that the friction O(10E-3 - 10E-2 ) and pressure gradient O(10E-3 - 10E-2) dominate creek momentum balance. Divergence in tidal and TSS transport between adjacent creeks reveals opposing tidal asymmetries within this confined basin. We suggest that these differences may mediate the eco-geospatial evolution of salt marshes and their response to sea level rise.

Inter-annual sea-level variations of up to 20 mm are superimposed upon the global average sea-level rise (~3 mm/yr) from human-caused global warming. These variations affect the degree of coastal flooding, and related damage, during the highest annual tides. Along the Atlantic coast of the United States, such inter-annual sea-level variations have been attributed to several atmospheric and oceanographic processes. In the present analysis, detrended tide gauge data isolate inter-annual interannual variations that can be reconstructed using Fourier analysis of a limited number of coefficients based on frequencies of lunar orbit ( and precessions) combined with . Although a causal relationship between such forcings and extreme sea levels remains elusive, the reconstructions may provide an effective method for projections of occurrence of extreme sea levels. Two reconstructions project that anomalously high sea levels may occur in the late 2020s, mid 2050s, early 2060s, early 2070s and late 2090s.