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Most of the ocean kinetic energy is contained in the large scale currents and the vigorous geostrophic eddy field, at horizontal scales of order 100 km. To achieve equilibrium the geostrophic currents must viscously dissipate their kinetic energy at much smaller scale. However, geostrophic turbulence is characterized by an inverse cascade of energy towards larger scale, and the pathways of energy toward dissipation are still in question. Here, we present a mechanism, in the context of the Gulf Stream, where energy is transferred from the geostrophic flow to submesoscale wakes through anticyclonic vertical vorticity generation in the bottom boundary layer. The submesoscale turbulence leads to elevated local dissipation and mixing outside the oceanic boundary layers. This process is generic for boundary slope currents that flow in the direction of Kelvin wave propagation. Topographic generation of submesoscale flows potentially provides a new and significant route to energy dissipation for geostrophic flows.

I present 2 noteworthy foraging observations of a Lesser Yellow-headed Vulture (Cathartes burrovianus) and a Turkey Vulture (C. aura) in Crooked Tree Wildlife Sanctuary and Cockscomb Basin Wildlife Sanctuary, Belize, respectively. 1 observed a Lesser Yellowheaded Vulture successfully capture a live fish from the water and a Turkey Vulture feeding on feces of neotropical otter (Lontra longicaudis) along a river, To my knowledge, these observations represent novel reports for each species, and contribute to the understanding of the breadth of foraging behavior of cathartid vultures. Received I April 2020. Accepted I October 2021. Key words: behavior, Cathartidae, diet, fishing, foraging. Observaciones de alimentacion de las auras Cathartes aura y C, burrovianus en Belice Presento 2 observaciones notables de forrajco de las auras Cathartes hurrovianus y C. aura en las reserves Crooked Tree Wildlife Sanctuary y Cockscomb Basin Wildlife Sanctuary, rcspectivamentc. Observe un C. hurrovianus capturando cxitosamente un pez vivo del agua y a un C. aura alimentandose de heces de la nutria Lontra longicaudis a lo largo de un rio. Segun mi conocimiento. ambas observaciones representan reportes novedosos para cada especic y contribuyen a entendcr la amplitud de comportamientos de forrajco en catartidos. Palabras clave: Cathartidae, comportamiento, dieta, forrajeo, pesca., Vultures of the genus Cathartes are well known for their exceptional olfactory abilities in locating carrion (Stager 1964; Houston 1986, 1988, 1994; Coleman and Fraser 1987; Grigg et al. 2017), [...]

Submesoscale flows (0.1–10 km) are often associated with large vertical velocities, which can have a significant impact on the transport of surface tracers, such as carbon. However, global models do not adequately account for these small‐scale effects, which still require a proper parameterization. In this study, we introduced a passive tracer into the surface mixed layer (ML) of a northern Atlantic Ocean simulation based on the primitive‐equation model CROCO, with a horizontal resolution of Δx = 800 m, aiming to investigate the seasonal submesoscale effects on vertical transport. Using surface vorticity and strain rate criteria, we identified regions with submesoscale fronts and quantified the associated subduction, that is the export of tracer below the ML depth. The results suggest that the tracer vertical distribution and the contribution of frontal subduction can be estimated from surface strain and vorticity. Notably, we observed significant seasonal variations. In winter, the submesoscale fronts contribute up to 40% of the total vertical advective transport of tracer below the ML, while representing only 5% of the domain. Conversely, in summer, fronts account for less than 1% of the domain and do not contribute significantly to the transport below the ML. The findings of this study contribute to a better understanding of the seasonal water subduction due to fronts in the region. Plain Language Summary: Oceanic fronts are dynamical structures characterized by enhanced gradients of variables such as temperature or density. These structures are prominent and ubiquitous at the ocean surface and can reach particularly small scales, down to a few kilometers. They are known to play an important role in the vertical exchange of carbon, nutrients or heat between the surface and the ocean interior. Due to their small scale and short lifecycle, they have not been extensively sampled and a systematic quantification of their impact is missing. In this study, we set up a numerical simulation of the ocean circulation in the North Atlantic that resolves small‐scale fronts. We release a tracer in upper layer of the ocean and analyze how it is transported at depth. Using criteria based on the flow velocity, we quantify the fraction of the ocean surface covered by fronts. We find that the average depth at which the tracer is injected depends on the prevalence of fronts, which itself shows a strong seasonality. In winter, fronts cover less than 5% of the surface area, but contribute up to 40% of the tracer vertical transport. Conversely, in summer, fronts cover less than 1% of the area and have no significant effect on tracer vertical transport. This study helps to better understand the seasonal role of fronts in vertical water transport. This paves the way for addressing questions related to how tracers such as carbon are distributed in the world's oceans. Key Points: Surface strain and vorticity criteria can be used to identify submesoscale frontsThe tracer depth injection correlates with the surface fraction of fronts, regardless of the mixed layer depth evolutionThe submesoscale fronts contribute to ∼40% of the total tracer vertical advective subduction in winter, and less than 1% in summer [ABSTRACT FROM AUTHOR]

The ocean's biological carbon pump plays a major role in climate and biogeochemical cycles. Photosynthesis at the surface produces particles that are exported to the deep ocean by gravity. Sediment traps, which measure deep-carbon fluxes, help to quantify the carbon stored by this process. However, it is challenging to precisely identify the surface origin of particles trapped thousands of meters deep due to the influence of ocean circulation on the sinking path of carbon. In this study, we conducted a series of numerical Lagrangian experiments in the Porcupine Abyssal Plain region of the North Atlantic and developed a machine learning approach to predict the surface origin of particles trapped in a deep-ocean sediment trap. Our numerical experiments support the predictive performance of the machine learning approach, and surface conditions appear to provide valuable information for accurately predicting the source area, suggesting a potential application with satellite data. We also identify factors that potentially affect prediction efficiency, and we show that the best predictions are associated with low kinetic energy and the presence of mesoscale eddies above the trap. This new tool could provide a better link between satellite-derived sea surface observations and deep-ocean sediment trap measurements, ultimately improving our understanding of the biological-carbon-pump mechanism. [ABSTRACT FROM AUTHOR]

Turbulent mixing in the ocean exerts an important control on the rate and structure of the overturning circulation. However, the balance of processes underpinning this mixing is subject to significant uncertainties, limiting our understanding of the overturning's deep upwelling limb. Here, we investigate the hitherto primarily neglected role of tens of thousands of seamounts in sustaining deep-ocean upwelling. Dynamical theory indicates that seamounts may stir and mix deep waters by generating lee waves and topographic wake vortices. At low latitudes, stirring and mixing are predicted to be enhanced by a layered vortex regime in the wakes. Using three realistic regional simulations spanning equatorial to middle latitudes, we show that layered wake vortices and elevated mixing are widespread around seamounts. We identify scalings that relate mixing rate within seamount wakes to topographic and hydrographic parameters. We then apply such scalings to a global seamount dataset and an ocean climatology to show that seamount-generated mixing makes an important contribution to the upwelling of deep waters. Our work thus brings seamounts to the fore of the deep-ocean mixing problem and urges observational, theoretical, and modeling efforts toward incorporating the seamounts' mixing effects in conceptual and numerical ocean circulation models. [ABSTRACT FROM AUTHOR]