Long‐Distance/Time Surf‐Zone Tracer Evolution Affected by Inner‐Shelf Tracer Retention and Recirculation

Abstract

The transport and dilution of shoreline released tracers, such as pathogens (e.g., Boehm, 2003) or larvae (e.g., Morgan et al., 2018), is important to coastal ecosystems and human health (Boehm et al., 2017). The surf-zone can entrain shoreline released tracers and discharges from small-scale and low-flow rivers, estuaries and out-falls (Kastner et al., 2019;Rodriguez et al., 2018;Wong et al., 2013). Surf-zone released tracers have been detected in coastal community aerosols (Pendergraft et al., 2021), indicating potential for pathogen and toxin exposure without direct coastal water contact (e.g., Kirkpatrick et al., 2010). On alongshore uniform beaches, surf-zone alongshore (y) currents, driven by obliquely incident surface gravity wave forcing (e.g.,

Performance of a One-Dimensional Model of Wave-Driven Nearshore Alongshore Tracer Transport and Decay with Applications for Dry Weather Coastal Pollution

“…The second linear loss parameter k P represents the cross-shelf tracer exchange between the nearshore region and the inner shelf. The k P parameter may be thought of as an exchange velocity, u ex , divided by the cross shore distance from the shoreline to boundary between the nearshore and the shelf, L . , This cross-shelf exchange is often driven by rip currents in observations ,− and models. ,, Here exchange between the surf zone and inner shelf was parametrized as a monotonic decay of nearshore tracer. We calculated k P by subtracting k B from the total rate of dye loss, i.e.…”

“…The coastline of the San Diego Bight has over 30 km of mostly straight, sandy beach with bathymetric irregularities only near the Tijuana River Estuary (TJRE) (Figure ). On a straight coastline, pollution point sources along the beach can contaminate nearshore waters tens of kilometers away because tracer, i.e., passively transported material, is transported alongshore efficiently and exported offshore slowly. − …”

“…A plume tracker model advects particles released from the TJRE mouth, PB, and the South Bay ocean outfall using high-frequency radar (HFR) currents to make daily water quality predictions . Among other issues, HFR does not sample within 1 km of shore, where pollution plumes are often located. , HFR therefore cannot resolve the relevant nearshore processes to accurately estimate plume transport . A hydrodynamic model of the coastal ocean near San Diego, USA, and Tijuana, MX, that resolves both the shelf and the nearshore and tracks plumes from both TJRE and PB (hereafter “SD Bight model”) was built by coupling an ocean model to a wave model using the COAWST framework. , However, the SD Bight model is computationally expensive (a year of model output requires weeks of runtime on a supercomputer cluster) and currently exists as a hindcast.…”

“…Alongshore forcing is dominated by wave-breaking which can be estimated from an offshore wave buoy. − Previous nearshore water quality models have reduced the problem to 1D wave-driven advection on an alongshore-uniform grid by cross-sectionally averaging tracer concentrations and alongshore transport. The models from these studies were tuned to recreate observations to derive mixing parameters and scales of biological and physical controls on water quality. ,,, Pathogen decay and offshore transport are represented as tracer loss from the 1D domain . Operationally, such models are many orders of magnitude faster than a full 3D hydrodynamic regional model, which is able to produce a year of model output in seconds.…”

The strategies preventing particle transportation into the inlets of nuclear power plants: Mechanisms of physical oceanography

“…To date, the windage effect has most commonly been expressed in particle-tracking simulations as a simplified term, which is proportional to the local wind speed (e.g., Breivik et al, 2011;Duhec et al, 2015). Turbulence movement takes place at such a small scale that it is hard to reproduce it accurately in current models; it is highly random, but could be important to particle transport related to the mixing process (Steinbuck et al, 2011;Grimes et al, 2021). In particle-tracking simulations, turbulence movement is usually parameterized as a random walk term associated with the local diffusivity.…”