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

 

Abstract Distributed temperature sensing (DTS) uses Raman scatter from laser light pulsed through an optical fiber to observe temperature along a cable. Temperature resolution across broad scales (seconds to many months, and centimeters to kilometers) make DTS an attractive oceanographic tool. Although DTS is an established technology, oceanographic DTS observations are rare since significant deployment, calibration, and operational challenges exist in dynamic oceanographic environments. Here, results from an experiment designed to address likely oceanographic DTS configuration, calibration, and data processing challenges provide guidance for oceanographic DTS applications. Temperature error due to suboptimal calibration under difficult deployment conditions is quantified for several common scenarios. Alternative calibration, analysis, and deployment techniques that help mitigate this error and facilitate successful DTS application in dynamic ocean conditions are discussed.