Wind‐driven upwelling promotes the onshore transport of dense slope waters onto the continental shelf. New observational evidence suggests that the propagation of coastal trapped waves (CTWs) over a submarine canyon can also cause upwelling within the canyon, independent of the wind forcing. Here, we use idealized numerical experiments to assess the role of CTWs in promoting the onshore transport of deeper waters onto the continental shelf. The experiments are forced with a 7‐days period CTW. Overall, there is accumulated upwelled water in time with increased onshore transport during the low sea level phase of the CTWs. Most of the onshore flow is spread over the upwave side of the canyon during the low sea level phase, but it is advected further downwave during the subsequent high sea level phase. As a result, a dense pool of upwelled water is spread over the shelf extending primarily in the downwave direction.

The exchanges of water, nutrients, and oxygen between the coastal and open ocean are key components of on-shelf nutrient budgets and biogeochemical cycles. On a regional scale, submarine canyons enhance physical processes such as shelf–slope mass exchange and mixing. There is good understanding of the flow around upwelling submarine canyons; however, the flux of biologically relevant tracers is less understood. This work investigates the impact of submarine canyons on the cross-shelf exchange of tracers and water, taking into account the impact of locally enhanced mixing within the canyon, and develops a scaling estimate for canyon-induced upwelling of tracers, proportional to local concentration, vertical diffusivity, and previously scaled upwelling flux. For that purpose, we performed numerical experiments simulating an upwelling event near an idealized canyon, adding a passive tracer with an initially linear profile. We varied the geographic distribution of vertical eddy diffusivity and its magnitude, the initial stratification, the Coriolis parameter, and the strength of the incoming flow. We find that a canyon of width 5% of the along-shelf length of the shelf upwells between 25% and 89% more tracer mass onto the shelf than shelfbreak upwelling. Locally enhanced vertical diffusivity has a positive effect on the tracer that is advected by the upwelling flow and can increase canyon-upwelled tracer flux by up to 27%.

Submarine canyons enhance cross‐shelf mass exchanges, which are a key component of on‐shelf nutrient budgets and biogeochemical cycles. Previous studies assume that canyon‐induced tracer flux onto the shelf only depends on canyon‐induced water upwelling. This paper investigates the validity of this dependence for nutrients, carbon, and dissolved gasses. To estimate the canyon‐induced tracer upwelling flux and its spatial distribution on the shelf, we performed numerical experiments simulating an upwelling event near an idealized canyon, adding 10 passive tracers with initial profiles representing nutrients, carbon, and dissolved gasses. This paper presents a scaling estimate for canyon‐induced tracer upwelling and for the on‐shelf distribution of a given tracer. We find that tracer upwelling depends on the vertical local mean of the initial vertical tracer gradient within the canyon, the depth of upwelling and the upwelling flux. We identify a pool of low oxygen and high nutrient concentration, methane, dissolved inorganic carbon, and total alkalinity on the shelf bottom, downstream of the canyon. The downstream extension of the pool of low oxygen water depends on the onshore flux of water through the canyon and the oxygen profile. This canyon‐induced distribution of tracers has the potential to impact demersal and benthic ecosystems by lowering dissolved oxygen levels and spreading corrosive waters along the shelf.

The mixed layer depth (MLD) is critical for understanding ocean-atmosphere interactions and internal ocean dynamics. Traditional methods for determining the MLD commonly rely on hydrographic thresholds that vary spatially and temporally with local oceanographic conditions, limiting their global consistency and applicability. To address this, we propose an energy-based methodology that defines the MLD as the depth at which the work done by buoyancy (WB) reaches 20 J m^-3. Based on the structural change in WB, the MLD criterion identifies the upper ocean's well-mixed layer in energetic terms. This approach provides a robust criterion based on physical principles, which is globally and temporally consistent and easy to implement. Our methodology aligns with turbulent boundary layer dynamics while maintaining quasi-homogeneity in density and temperature for most of the global ocean throughout the year. A global monthly MLD climatology derived from this method demonstrates its reliability across diverse oceanic conditions and its accuracy in regions and seasons where conventional methods struggle. Our study advances the development of MLD energy-based methodologies by providing a single energy value to define the MLD globally during all months. This energy-based approach could offer significant potential for advancing the study of dynamic, and thermodynamic processes, including heat content and vertical exchanges. It could also serve as a robust tool for validating ocean circulation models and to support intercomparison studies in initiatives such as the Ocean Model Intercomparison Project (OMIP) and the International Coupled Model Intercomparison Project (CMIP). Future research will explore its applicability to high-frequency processes and regional variability, further enhancing its utility for understanding and modeling oceanic phenomena.

The mixed layer depth (MLD) is critical for understanding ocean-atmosphere interactions and internal ocean dynamics. Traditional methods for determining the MLD, commonly relying on constant temperature and density thresholds, may not adequately address spatial and temporal variations in local oceanographic conditions, thereby limiting their global consistency and applicability. An energy-based definition of the mixed layer could be a more physically consistent alternative to address this issue. We propose a physically derived and energy-based methodology that defines the mixed layer as the energetically homogeneous upper ocean layer in which water parcels can move with little or no buoyancy work. The threshold in buoyancy work, which determines the mixed layer globally throughout the year, was carefully investigated. An energy-based global monthly MLD climatology demonstrated the reliability of the methodology across diverse ocean conditions and its usefulness for studies spanning seasonal to climate time scales, from regional to large spatial scales. Our easy-to-implement MLD methodology provides a robust criterion that is globally and temporally consistent, maintaining quasi-homogeneity in energy, density, and temperature year-round for most of the global ocean. This study promotes the development of MLD energy-based methodologies that could offer significant potential for advancing the study of dynamic and thermodynamic processes, including heat content and vertical exchanges. Our methodology could also serve as a robust tool for validating ocean circulation models and supporting intercomparison studies in initiatives such as the Ocean Model Intercomparison Project (OMIP) and the International Coupled Model Intercomparison Project (CMIP). Future research will explore its applicability to high-frequency processes and regional variability, further enhancing its utility for understanding and modeling oceanic phenomena.