Dispersion of deep-sea hydrothermal vent effluents and larvae by submesoscale and tidal currents

Abstract

Deep-sea hydrothermal vents provide sources of geochemical materials that impact the global ocean heat and chemical budgets, and support complex biological communities. Vent effluents and larvae are dispersed and transported long distances by deep ocean currents, but these currents are largely undersampled and little is known about their variability. Submesoscale (0.1-10 km) currents are known to play an important role for the dispersion of biogeochemical materials in the ocean surface layer, but their impact for the dispersion in the deep ocean is unknown. Here, we use a series of nested regional oceanic numerical simulations with increasing resolution (from δx=6km to δx=0.75km) to investigate the structure and variability of highly-resolved deep currents over the Mid-Atlantic Ridge (MAR) and their role on the dispersion of the Lucky Strike hydrothermal vent effluents and larvae. We shed light on a submesoscale regime of oceanic turbulence over the MAR at 1500 m depth, contrasting with openoceani.e., far from topographic featuresregimes of turbulence, dominated by mesoscales. Highlights► High-resolution numerical simulations shed light on a submesoscale regime of turbulence at the depth of the Mid-Atlantic Ridge. ► Submesoscale and tidal currents enhance the relative dispersion of particles and might augment the likelihood of connectivity between MAR hydrothermal vents. ► Tidal currents and internal tides double the vertical dispersion of particles and help crossing topographic barriers.

Sea Surface Signature of Internal Tides

“…Typical ocean depth ranges between 1,000 m over the ridge and 5,000 m over the abyssal plain, with shallower regions around the Azores Islands. The simulation is a nest of a larger simulation that originates from a North‐Atlantic run (more details are available in Vic et al, ). Tidal forcing interpolated from TPXO7.2 is added to the mesoscale forcing at the boundaries, using the eight most important components.…”

“…The horizontal ( k ‐wise) localization of these patches is representative of the modal structure of the waves and matches roughly the approximate dispersion relation derived from the mean depth of fluid and the mean value of N 2 (white oblique curves in the diagram). In between these tidal peaks, the energy is associated with an internal wave continuum, which is partially resolved within the simulation (Vic et al, ). The latter is probably too weak in the simulation, which lacks near‐inertial waves due to daily winds forcings.…”

Submesoscale Coherent Vortices in the Gulf Stream

“…These SCVs are essential for spreading oxygen-poor and nutrient-rich waters into the interior of gyres (Frenger et al, 2018). More generally, SCVs can be generated by interaction of boundary currents with topography, as in the Beaufort Gyre in the Arctic Ocean (D'Asaro, 1988;Manley & Hunkins, 1985), in the Mediterranean Sea along Sardinia (Bosse et al, 2015), at the tail of the Grand Banks (Bower et al, 2013), and over the Mid-Atlantic Ridge (Vic et al, 2018). They also form from wintertime deep convection, as observed in the Labrador Sea (Clarke, 1984;Lilly & Rhines, 2002) and the northwestern Mediterranean Sea (Bosse et al, 2016(Bosse et al, , 2017Testor & Gascard, 2003) where they are essential for spreading the newly formed deep waters within ocean basins.…”

Mean Structure and Seasonality of the Norwegian Atlantic Front Current Along the Mohn Ridge From Repeated Glider Transects

“…The interaction of the barotropic jet of the PF and tides with numerous seamounts of O(1-10 km) horizontal scales found along the ridge could generate internal waves and turbulent mixing (Nikurashin & Ferrari, 2011). Moreover, the Mohn Ridge is an active hydrothermal vent (Schander et al, 2010), for which small-scale currents and mixing are important (Vic et al, 2018). The mixing generated by the barotropic component of the frontal current and tides is still unknown and needs further investigations.…”