Ocean Circulation Over North Atlantic Underwater Features in the Path of the Mediterranean Outflow Water: The Ormonde and Formigas Seamounts, and the Gazul Mud Volcano

Abstract

Seamounts constitute an obstacle to the ocean circulation, modifying it. As a result, a variety of hydrodynamical processes and phenomena may take place over seamounts, among others, flow intensification, current deflection, upwelling, Taylor caps, and internal waves. These oceanographic effects may turn seamounts into very productive ecosystems with high species diversity, and in some cases, are densely populated by benthic organisms, such corals, gorgonians, and sponges. In this study, we describe the oceanographic conditions over seamounts and other underwater features in the path of the Mediterranean Outflow Water (MOW), where populations of benthic suspensions feeders have been observed. Using CTD, LADPC and biochemical measurements carried out in the Ormonde and Formigas seamounts and the Gazul mud volcano (Northeast Atlantic), we show that Taylor caps were not observed in any of the sampled features. However, we point out that the relatively high values of the Brunt-Väisälä frequency in the MOW halocline, in conjunction with the slope of the seamount flanks, set up conditions for the breakout of internal waves and amplification of the currents. This may enhance the vertical mixing, resuspending the organic material deposited on the seafloor and, therefore, increasing the food availability for the communities dominated by benthic suspension feeders. Thus, we hypothesize that internal waves could be improving the conditions for benthic suspension feeders to grow on the slope of seamounts.

A Persistent Deep Anticyclonic Vortex in the Rockall Trough Sustained by Anticyclonic Vortices Shed From the Slope Current and Wintertime Convection

“…The southern RT is in close proximity to the NA subtropical and subpolar gyres boundaries, making the region a key area of interplay between upper and intermediate water masses of both subtropical (Eastern North Atlantic Central Water [ENACW] and Mediterranean Overflow Water [MOW]) and subpolar (Sub‐Arctic Intermediate Water [SAIW] and Labrador Sea Water [LSW]) origins (Figure 1). ENACW is the lightest of the four water masses, falling within the 26.85–27.2 kg m −3 density range (Mosquera Giménez et al, 2019), underlined by SAIW, settled along 27.27–27.3 kg m −3 isopycnals (Wade et al, 1997). MOW occupies the 27.38–27.72 kg m −3 isopycnals (Mosquera Giménez et al, 2019), which overlies the LSW, spreading within the 27.74–27.82 kg m −3 isopycnals (Courtois et al, 2020; Garcia‐Quintana et al, 2019).…”

“…ENACW is the lightest of the four water masses, falling within the 26.85–27.2 kg m −3 density range (Mosquera Giménez et al, 2019), underlined by SAIW, settled along 27.27–27.3 kg m −3 isopycnals (Wade et al, 1997). MOW occupies the 27.38–27.72 kg m −3 isopycnals (Mosquera Giménez et al, 2019), which overlies the LSW, spreading within the 27.74–27.82 kg m −3 isopycnals (Courtois et al, 2020; Garcia‐Quintana et al, 2019). At the RT southern approach, subpolar SAIW and LSW and subtropical ENACW and MOW water masses enter the channel along their respective westward and eastward pathways (Figures 1a, 1c, and 1d).…”

Wave‐influenced deposition of carbonate‐rich sediment on the insular shelf of Santa Maria Island, Azores

“…Tidal currents at Formigas Bank with similar depths to the shelf of Santa Maria Island were predicted by Mosquera Giménez et al . (2019) by modelling to be only 6 to 7 cm s −1 . These speeds of oceanographic and tidal currents are all much smaller than wave‐generated bottom water movements, so their influence can be omitted in the following modelling based on waves.…”

Contrasting hydrodynamic regimes of submerged pinnacle and emergent coral reefs

“…Not least because oceanographic modelling of fine-scale and often transient processes like upwellings and localised eddies requires a measure of vertical flow. Such high-resolution oceanography data, including vertical and horizontal components, is typical in modelling structural flow dynamics and physical properties (density layers, mixing etc) of the water column surrounding seamounts [103][104][105].…”