Hydrodynamic Variability of an Intermittently Closed Estuary over Interannual, Seasonal, Fortnightly, and Tidal Timescales

Abstract Small low-inflow intermittently closed estuaries are common in Mediterranean climates worldwide; however, despite their important contributions to ecosystem services and coastal resilience, dynamics have been less well studied relative classical (i.e., deeper, persistent freshwater inflow) estuaries. It is known that infragravity wave propagation into these can induce strong currents closures lead stagnating flows declining water quality; how the estuarine circulation (tidal subtidal) dynamically drives responds conditions remains largely unknown. Here we analyze over 4 years of hydrodynamic observations Los Peñasquitos Lagoon, a low-inflow, estuary Southern California, examine estuary, sill accretion, response tidal, fortnightly, seasonal, interannual time scales, providing an unprecedented view as systems respond changing forcing. Wave near inlet show energy inside inlet, which contributes dependent on level height has tidal variation due wave-current interactions. Tidal phase averages during open, pre-closure, spring, neap, highlight large dynamic range experience. During low conditions, stratification consistent with stratification-induced periodic straining subtidal exchange varies fortnightly cycle observed many However, grows, weakens becomes strongly sheared no longer scales theoretical pressure-friction balance.