Submarine Mountain Research Articles

Modeling the barotropic tidal dynamics of the Kuril region

A 3D boundary-value problem for computation barotropic tidal dynamics is solved at Kuril region, including southern part of the Okhotsk Sea, the Kuril Straits and its continental slope. The model is realised in statement for the contravariant components of velocity vector of the Programmed Complex “Cardinal”. Modeling the tidal dynamics of the straits of the Kuril Сhain and its continental slope is of particular importance due to the high geostrategic prestige of the region. The exceptional complexity of the relief of the area containing dozens of underwater volcanoes requires solving the problem in a complete non-hydrostatic formulation; this necessitates a multiprocessor implementation of the model with a high grid resolution for model representativity. An efficient methods for tidal dynamic reproduction at the 2D vertical cross-cuts domain is described. A statement of boundary problem at vertical cross-cuts is considered both in non-hydrostatic formulation and hydrostatic approximation. The results of computation contain the field of level tidal currents generated by the dominant wave K1 and summary wave in the synodic period; results of comparison the bottom vertical velocity at submarine mountain and on sharp depth changes in the hydrostatic and non-hydrostatic statements, result related to structure vertical velocity at cross-cut, the frequency spectrum and energy of tidal currents.

“Firefly” of the Submarine Mountains: New Data on Physiculus cynodon (Moridae, Teleostei) from Emperor Seamounts and Northwestern Hawaiian Ridge

Physiculus cynodon is a member of the Moridae family and possesses a ventral bioluminescent organ. Although it has been captured by commercial vessels for decades, our understanding of its biology and ecology remains fragmented. This paper provides data on the species’ spatial and vertical distributions; age and growth; size, age, sex compositions; and sex ratio in the waters around the Emperor Seamounts and the northwestern Hawaiian Ridge. This information is based on the analysis of multi-year Russian data obtained from scientific surveys and observations on commercial fishing vessels. The northernmost capture of this species has been recorded at Nintoku Seamount. Additionally, this species was regularly encountered at depths ranging from 53 to 900 m on seamounts such as Lira (Annei), Koko, Milwaukee (Yuryaku and Kammu), Colahan, and C-H of the Emperor Seamounts and Hancock, Zapadnaya, and Academician Berg of the northwestern Hawaiian Ridge. Catch rates of P. cynodon gradually decreased in a southeastern direction. Notably, the relative abundance of this species in bottom trawl catches significantly surpasses that in pelagic catches. The age of the fish in the catch varied from 9 to 37 years, and its growth is described by the VBGF equation with the following coefficients: L∞ = 858.6, k = 0.030, t0 = 3.5. While the growth patterns for males and females were similar, it is worth mentioning that males rarely survive beyond the age of 25 years.

Linear stability of monopolar vortices over isolated topography

The linear instability of circular vortices over isolated topography in a homogeneous and inviscid fluid is examined for the shallow-water and quasi-geostrophic models in the $f$ -plane. The eigenvalue problem associated with azimuthal disturbances is derived for arbitrary axisymmetric topographies, either submarine mountains or valleys. Amended Rayleigh and Fjørtoft theorems with topographic effects are given for barotropic instability, obtaining necessary criteria for instability when the potential vorticity gradient is zero somewhere in the domain. The onset of centrifugal instability is also discussed by deriving the Rayleigh circulation theorem with topography. The barotropic instability theorems are applied to a wide family of nonlinear, quasi-geostrophic solutions of circular vortices over axisymmetric topographic features. Flow instability depends mainly on the vortex/topography configuration, as well as on the vortex size in comparison with the width of the topography. It is found that anticyclones/mountains and cyclones/valleys may be unstable. In contrast, cyclone/mountain and anticyclone/valley configurations are stable. These statements are validated with two numerical methods. First, the generalised eigenvalue problem is solved to obtain the wavenumber of the fastest-growing perturbations. Second, the evolution of the vortices is simulated numerically to detect the development of linear perturbations. The numerical results show that for unstable vortices over narrow topographies, the fastest growth rate corresponds to mode $1$ , which subsequently forms asymmetric dipolar structures. Over wide topographies, the fastest perturbations are mainly modes $1$ and $2$ , depending on the topographic features.

Zooplankton community associated with mesophotic coral reefs in the Colombian Caribbean Sea

The morphological, phenological and ecological characteristics of shallow coral reefs have been widely studied, but only recently have mesophotic corals begun to be studied. Very little is known about these ecosystems and their associated communities, such as the zooplankton community, which constitutes a food source for reefs and for the organisms that inhabit them. In the present study, changes in zooplankton composition were characterised during two hydroclimatic periods in a mesophotic environment of the submarine mountain Bajo Frijol, in Corales de Profundidad National Natural Park, Colombia. Zooplankton was collected using a portable pumping device, which contained three collectors of differing mesh sizes; this allowed the capture of zooplankton ranging in size from 45 to 300 μm. Temperature, conductivity, oxygen and pH were obtained and complemented with MODIS AQUA satellite information. In this ecosystem, the zooplankton organisms with the greatest richness and abundance were small-sized copepods, radiolarians and tintinnids. The oceanography of the area results in greater zooplankton abundance, richness, and diversity in June when the coastal current allows greater chlorophyll-a concentrations in the area and smaller organisms are favoured by greater retention within the corals of the mesophotic system. The biodiversity reported for Bajo Frijol is the first detailed approach to the community of mesophotic coral reefs in the Colombian Caribbean Sea, contributing to new records to the Global Biodiversity Information Facility.

A parallel, non-spatial iterative, and rotational pressure projection method for the nonlinear fluid-fluid interaction

In this paper, a parallel, non-spatial iterative, and rotational pressure projection method for the coupled Navier-Stokes equations is proposed and developed. As for each Navier-Stokes equation, one elliptic equation and one Possion equation at each time step determine the values of the velocity and pressure, respectively. Moreover, we only need to solve four simple linear equations, and the computational time of the whole system is greatly reduced. The rotational pressure projection method achieves the same accuracy as the traditional decoupled fractional time-stepping method. Furthermore, we apply the presented method, the rotational pressure projection method and the linear decoupled fractional time-stepping method to the submarine mountain problem. Compared to the streamline diagrams of these three methods from two aspects of accuracy and CPU times, we obtain that the presented method has good parallelism and is the most efficient method, the rotational pressure projection method is more efficient than the traditional decoupled fractional time-stepping method. Finally, numerical results verify that our proposed method has the high efficiency.

Submarine mountains can subdue earthquakes

Submarine mountains can subdue earthquakes

Influence of the conical seamount on underwater sound propagation in a 3D shallow sea environment

The sound field of a 3D shallow sea environment with a conical submarine mountain is simulated and calculated using the finite element method. To verify the accuracy of the finite element calculation results, the effects of submarine mountain height and sound source depth on sound-propagation characteristics are evaluated. The simulation results indicate that owing to the reflection and concentration of acoustic energy due to the submarine mountain, before the sound wave reaches the subsea mountain, the impact of subsea mountain on the acoustic energy can reach 10 dB. In addition, the sound energy is hindered by the seamount. Therefore, the sound energy loss after the sound wave reaches the subsea mountain is higher than the sound energy loss in the absence of the seamount under the same circumstance, and the maximum is up to 20 dB. The larger the seamount height and sound source depth, the more significant the blocking and accumulation of the sound energy.

Associated fauna of Sponge grounds in the Cantabrian Sea. SponGES Project. Crustacea Decapoda. Expansion of distribution and new records of unusual species.

Associated fauna of Sponge grounds in the Cantabrian Sea. SponGES Project. Crustacea Decapoda. Expansion of distribution and new records of unusual species.

ОСОБЕННОСТИ СТРОЕНИЯ ВЕРХНЕЙ ЧАСТИ ОСАДОЧНОГО ЧЕХЛА И ОПОЛЗНЕВЫЕ СТРУКТУРЫ В СЕВЕРО-ЗАПАДНОЙ ЧАСТИ ТИХОГО ОКЕАНА И БЕРИНГОВА МОРЯ ПО ДАННЫМ СЕЙСМОАКУСТИЧЕСКОГО ПРОФИЛИРОВАНИЯ

The authors studied geology-geophysical data that had been obtained during German RV «Sonne» Cruise in NW Pacific organized in frames of the Russian-German Project KALMAR («Kurile-Kamchatka and Aleutian Marginal sea-island arc systems: geodynamic and climate interaction in space and time»). The profiling was carried out using PARASOUND P70 system, including narrow-beam system and sub-bottom profiler. The study showed that besides undisturbed sedimentation, landside processes are widely spread in open areas of the ocean and the Bering Sea as well as deposits caused by strong submarine currents. Landslides were revealed on the slopes of the Emperor Ridge in the NW Pacific and the Shirshov Ridge submarine mountains, in canyons near Eastern Kamchatka coasts and apparently in many other areas.

Bajo Espitritu Santo; biological abundance hotspot off Bahia de La Paz

Bajo Espí­ritu Santo (EBES) is a submarine mountain located 9 nautical miles from the northern end of the Espí­ritu Santo archipelago, outside Bahia de La Paz. It is considered as a hotspot of biodiversity and biomass that has motivated studies to understand the processes that make it an area of high biological activity. Processes that enrich the EBES are advection and vertical transport, mainly caused by tides and currents that collide with the mountain. Also, there is retention of organisms, particularly zooplankton, which favors a biological enrichment. A review on hydrography, dynamics and biology is presented, complemented with time series analysis of satellite information on sea surface temperature, surface chlorophyll, net primary productivity, and euphotic zone depth, to identify the variability of seasonal and interannual processes affecting the mountain. The main processes that enrich EBES are mixture due to the vertical cut of the currents; the vertical transport caused by tidal currents that collide with the mountain; advection by jet currents originating in the interior of the bay and/or eddies from the Gulf of California; the retention of zooplankton organisms in the vicinity of the mountain. Two periods of productivity, one in spring and the other at late summer indicate a bimodal regime with dominant periods of 12 and 6 months respectively. Additionally, there is an inter-annual variability dominated by periods of 5 and 7.5 years associated with ENSO. Combination of these factors give EBES its ability for nutrient and plankton enrichment throughout the year, which attracts secondary consumers and top predators, turning it into a point of great biological activity.

Samaretta perexilis, a new genus and new species of samarid flatfish (Pleuronectiformes: Samaridae) from the South Pacific

A new genus of righteye flounder, Samaretta gen. nov., is described from two specimens (one female and one juvenile) collected in deep waters (470–512 m) from submarine mountains of the southern eastern Pacific. The type species of the new genus, Samaretta perexilis, is characterized by unremarkable (i.e., not elongated) anterior dorsal fin rays, four pectoral fin rays, six parapophyses, reduced lateral line canals, a very slender body, large head and eyes, and minute scales. An updated key to the samarid genera is presented.

Composition, structure, origin, and evolution of off-axis linear volcanic structures of the Brazil Basin, South Atlantic

The paper considers the conditions and mechanisms of the formation of linear volcanic structures in the Brazil Basin, South Atlantic. Among these objects, those related to the ascent of deep mantle plumes predominate. It is shown that the ascent of melts from plume sources leads to the formation of (a) hot spot tracks in the form of linear volcanic ridges and (b) active hot lines in the form of submarine mountain chains with trends differing from those of hot spot tracks and with a more variable character of the age distribution of volcanic rocks. Fault tectonics affects the character of plume activity. In addition, plume material from a hot spot area is dragged by a moving plate as a flow or a sublithospheric lens, which leads to the long-term existence of particular independent segments of linear structures and sometimes to late volcanism reactivation within their limits. Decompression melting of the asthenospheric mantle in zones where thin lithosphere undergoes tension causes the formation of passive hot lines. The main mantle source for the considered volcanic rocks was a mixture of DMM and HIMU mantle components, with the latter abruptly dominating. In marginal oceanic regions, the EM1 component is also present (the EM2 component is found more rarely) within fragments of tectonically delaminated continental mantle that was trapped by the oceanic mantle during the breakup of Gondwana.

Tidal influence on particulate organic carbon export fluxes around a tall seamount

As tall seamounts may be ‘stepping stones’ for dispersion and migration of deep open ocean fauna, an improved understanding of the productivity at and food supply to such systems needs to be formed. Here, the 234Th/238U approach for tracing settling particulate matter was applied to Senghor Seamount – a tall sub-marine mountain near the tropical Cape Verde archipelago – in order to elucidate the effects of topographically-influenced physical flow regimes on the export flux of particulate organic carbon (POC) from the near-surface (topmost⩽100m) into deeper waters. The comparison of a suitable reference site and the seamount sites revealed that POC export at the seamount sites was ∼2–4 times higher than at the reference site. For three out of five seamount sites, the calculated POC export fluxes are likely to be underestimates. If this is taken into account, it can be concluded that POC export fluxes increase while the passing waters are advected around and over the seamount, with the highest export fluxes occurring on the downstream side of the seamount. This supports the view that biogeochemical and biological effects of tall seamounts in surface-ocean waters might be strongest at some downstream distance from, rather than centred around, the seamount summit. Based on measured (vessel-mounted ADCP) and modelled (regional flow field: AVISO; internal tides at Senghor: MITgcm) flow dynamics, it is proposed that tidally generated internal waves result in a ‘screen’ of increased rates of energy dissipation that runs across the seamount and leads to a combination of two factors that caused the increased POC export above the seamount: (1) sudden increased upward transport of nutrients into the euphotic zone, driving brief pulses of primary production of new particulate matter, followed by the particles’ export into deeper waters; and (2) pulses of increased shear-driven aggregation of smaller, slower-settling into larger, faster-settling particles. This study shows that, under certain conditions, there can be an effect of a tall seamount on aspects of surface-ocean biogeochemistry, with tidal dynamics playing a prominent role. It is speculated that these effects can control the spatiotemporal distribution of magnitude and nutritional quality of the flux of food particles to the benthic and benthic-pelagic communities at and near tall seamounts.

CLIMATIC TYPES OF MOUNTAINS

The main types of mountains forming in the different climatic zones or under altitudinal zonality are described: humid tropics and monsoon; alpine type and subglacial mountains, submarine mountains and coral erections as their subtype. Peculiar climatic properties of mountains influence the young tectonics of upper lithosphere.

No place to retreat: Heavy extinction and delayed recovery on a Pacific guyot during the Paleocene–Eocene Thermal Maximum

Modern global change threatens alpine ecosystems by forcing species to migrate to higher elevations and potentially eliminating alpine habitat altogether. Here we show that an analogous restriction of suitable habitat operates on submarine mountains. During the Paleocene–Eocene Thermal Maximum (PETM, ca. 55.96 Ma), ostracodes underwent local extinction on the crest of Allison Guyot in the central Pacific Ocean, which lost 64% of its ostracode species richness (14 species reduced to three species) and as much as 94% of ostracode abundance for ∼1.1 m.y., before recolonization rebuilt biodiversity and abundance over the next 200 k.y. Biotic changes may reflect an increase in current speeds, acidification, and a decrease in food supply owing to a temperature-driven increase in metabolic rates. Notably, continental margin ostracodes also underwent extinction during the PETM (25%–38% loss) but, unlike Allison Guyot faunas, could quickly repopulate the continental slope. The absence of refugia for isolated seamounts prolonged the reduction in biodiversity initiated by the PETM, a pattern that may be expected for modern seamount faunas in an era of future global change.

Horizontal and vertical motions of barotropic vortices over a submarine mountain

AbstractThe evolution of barotropic vortices over a topographic, axisymmetric mountain in a homogeneous rotating fluid is studied experimentally. The aim is to identify the main physical processes observed in (i) a horizontal plane of motion, perpendicular to the rotation axis of the system, and (ii) a vertical plane across the diameter of the mountain. The vortices are monopolar cyclones initially generated near or over the topography. Initially, the vortices drift towards the mountain due to the $\ensuremath{\beta} $-effect associated with the topographic slope. On arriving, they turn around the obstacle in an anticyclonic direction, whilst anticyclonic vorticity is generated over the summit. The long-term vorticity distribution is dominated by the original cyclone elongated around the topographic contours and the generated anticyclone over the tip of the topography. In the vertical plane an oscillatory uphill–downhill flow is generated, which is directly related to the drift of the cyclone around the mountain. Depending on the vortex characteristics, the period of the oscillation ranges from 4 to 10 times the rotation period of the system. The horizontal and vertical flow fields are reproduced numerically by using a shallow-water formulation, which allows a detailed view of the vertical motions, hence facilitating the interpretation of the experimental results. In addition, the cyclone–anticyclone pair over the mountain is compared with analytical solutions of topographically trapped waves. A general conclusion is that vertical motions persist for several days (or rotation periods), which implies that this mechanism might be potentially important for the vertical transport over seamounts.

Bending deformations of plates in the model of strong subduction earthquakes

The model of elastic rebound of thin plates is considered to account for GPS-inferred surface deformation of plates during subduction earthquakes on the example of the M9 earthquake that occurred in Japan in 2011. Due to the fact that the oceanic plate moves together with a great mass of the convective mantle, it dips into the mantle at constant velocity all the time, both during the earthquakes and in the periods between them, although its coupling with the continental plate changes. The edge of the continental plate behaves as an elastic plate that permanently bends under the action of the friction force on contact with the diving oceanic plate. The bent plate unbends after the earthquake. This leads to its thrusting over the subducting oceanic plate. As a result, the island plate moves towards the ocean, its island part sinks, and the oceanic plate uplifts leading to a tsunami. The coordinates and magnitudes of the rise and subsidence correspond to the universal relations in the elastic plate model. The breaking of coupling of the continental plate with the submarine mountains and a basaltic plateau of the dipping plate is considered as a possible explanation of the anomalous properties of the strongest earthquakes. The main earthquake can be produced by partial destruction of a plateau or a large mountain. After this, the locked plates become free along a great area in an avalanche-like manner, and the friction of rest gives place to sliding friction.

ORE CRUSTS OF NORTHERN SUBMARINE MOUNTAINS OF THE EMPEROR RIDGE (PACIFIC OCEAN)

The author considers the ore formations of the submarine mountains in the northern part of the Emperor Ridge (Pacific Ocean) as iron-manganese crusts of high Co, Ni, Mo contents. The forming conditions, chemical composition, spatial distribution to the post volcanic active zones were established. According the data of the manned submarine vehicles, the highest ore element concentrations are observed on the submarine mountains in the latitudes 37–41 NL.

Evolution of intrathermocline eddies moving over a submarine hill

Anticyclonic and cyclonic mediterranean eddies are formed on continental slopes of the Iberian Peninsula. Cyclonic eddies commonly live for 0.5–1 year at most. Anticyclonic eddies (meddies) live for 4–5 years, on average, but there are eddies of 7–8 years in age drifting at the distance of up to 6000 km from the region of its formation. According to the results of observations, in some regions of the Atlantic Ocean, the meddies are destructed partially or completely after contact with submarine mountains. However, it is impossible to trace evolution of the lens moving over the submarine obstacle by the field data. We studied the modeled influence of variable-height submarine hills on movement of cyclonic and anticyclonic intrathermocline eddies by the contour dynamics method. The evolution of lenses appeared to be quite sensitive to variations in hill height. Cyclonic and anticyclonic lenses interact with the hill in different ways. The data of unique field observations of Mediterranean lenses in the North Atlantic are confirmed by the results of our model experiments. Hence, it is possible to predict basic, similar to real, scenarios of interaction of intrathermocline eddies under conditions of complex bottom relief in the context of the three-layered ocean model.

Conserving pelagic habitats: seascape modelling of an oceanic top predator

Summary1. Currently pelagic ecosystems are changing significantly due to multiple threats. An important management policy is to establish marine protected areas, until now overlooked due to the difficulty of declaring ‘high seas’ protected areas, obtaining long‐term distribution data on indicator species and the dynamic nature of these ecosystems.2. Within this framework, we developed predictive habitat suitability models of an oceanic predator, the vulnerable wandering albatross Diomedea exulans, in the highly dynamic Southern Ocean. Based on a long‐term tracking database (1998–2008), we estimated three quantitative ecological indices that complementarily describe the hierarchical habitat use of the species at multiple spatial scales: where the species (i) spent more time (the seascape, based on the time spent per area), (ii) searched for prey (the foraging habitat, based on zones of increased foraging intensity using first passage time), and (iii) fed (the feeding habitat, based on prey capture data).3. Predictive habitat models reasonably matched the observed distribution patterns and described albatross multi‐scale habitat use as a hierarchical arrangement: albatrosses foraged over topographic features in subtropical waters, nested within the wider seascape due to the constraint imposed by the colony effect, whereas feeding occurred nested over the continental shelf and seamounts in areas of low oceanographic variability within the Polar Frontal Zone.4. Within the current oceanographic conditions, the location of key pelagic habitats for albatrosses breeding in the southern Indian Ocean encompassed certain topographic features such as pelagic areas surrounding main breeding sites, seamounts and submarine mountain ranges. The placement of these pelagic hotspots depends on the current sea surface temperature conditions.5. Synthesis and applications. The present study provides two key conservation and management tools. First, we provide the first map to support the development of a prospective network of priority conservation zones across the southern Indian Ocean based on habitat predictions of an oceanic indicator species. This could be used not only to support conservation of top predators but also the underlying biodiversity associated with pelagic key habitats. Secondly, the developed habitat modelling procedure is widely applicable and could be used to track changes in species distribution in both marine and terrestrial environments within the current global change scenario.