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Abstract The ocean is home to many different submesoscale phenomena, including internal waves, fronts, and gravity currents. Each of these processes entail complex nonlinear dynamics, even in isolation. Here we present shipboard, moored, and remote observations of a submesoscale gravity current front created by a shoaling internal tidal bore in the coastal ocean. The internal bore is observed to flatten as it shoals, leaving behind a gravity current front that propagates significantly slower than the bore. We posit that the generation and separation of the front from the bore is related to particular stratification ahead of the bore, which allows the bore to reach the maximum possible internal wave speed. After the front is calved from the bore, it is observed to propagate as a gravity current for ≈4 hours, with associated elevated turbulent dissipation rates. A strong cross-shore gradient of along-shore velocity creates enhanced vertical vorticity (Rossby number ≈ 40) that remains locked with the front. Lateral shear instabilities develop along the front and may hasten its demise. 

After a relaxation of the regional southward, upwelling‐favorable winds along the central California coast, warm water from the Santa Barbara Channel propagates northward as a buoyant plume. As the plume transits up the coast, it causes abrupt temperature changes and modifies shelf stratification. We use temperature and velocity data from 35 moorings north of Pt. Arguello to track the evolution of a buoyant plume after a wind relaxation event in October 2017. The moorings were deployed September–October 2017 and span a ∼30 km stretch of coastline, including nine cross‐shelf transects that range from 17 to 100 m water depth. The high spatial resolution of the data set enables us to track the spatiotemporal evolution of the plume, including across‐front temperature difference, cross‐shore structure, and propagation velocity. We observe an alongshore current velocity signal that takes ∼10 hr to propagate ∼25 km alongshore (∼0.7 m/s) and a temperature signal that takes ∼34 hr to propagate the same distance (∼0.2 m/s). The plume cools as it transits northward, leading to a decrease in the cross‐front temperature difference and the reduced gravity (g’). The plume’s propagation velocity is nonuniform in space and time, with accelerations and decelerations unexplained by the alongshore reduction ing’or advection by tidal currents. As the plume reaches the northernmost part of the mooring array, its temperature variability is obscured by internal waves, a prominent feature in the region. We focus on one relaxation event but observe five other similar events over the 2 months record.