Underwater Canyon Research Articles

What was the source of the nonseismic tsunami that occurred in Toyama Bay during the 2024 Noto Peninsula earthquake

In recent years, there have been worldwide reports of massive tsunamis, drawing attention to how tsunamis are intensified by submarine landslides triggered by earthquakes. However, precise data on tsunamis caused by submarine landslides are scarce, leading to insufficient information for a thorough discussion of the characteristics of such tsunamis. On the other hand, during the Noto Peninsula earthquake (Mw7.5) that occurred in Japan on January 1, 2024, a nonseismic tsunami distinct from those originating from fault ruptures were observed. To investigate its characteristics, we analyzed tide/wave gauge records, video footage, and tsunami trace heights along the coast of Toyama Bay. Furthermore, we validated scenarios capable of reproducing the observed records using an integrated landslide–tsunami model. It was found that assuming the existence of 5 submarine landslides along the underwater canyons of Toyama Bay enabled the precise explanation of multiple types of data. Additionally, our study revealed that submarine landslides occurred approximately 50 s after the earthquake, coinciding with the peak ground shaking in Toyama Bay. Compared to the seismic tsunami originating solely from the Noto Peninsula offshore fault rupture, the subsequent tsunami triggered by submarine landslides amplified the tsunami height by approximately 30% along Toyama Bay.

Encounter rate and relative abundance of eight cetaceans off the central Catalan coast (Northwestern Mediterranean sea)

This study provides information on cetacean occurrence in the central Catalan coast (NE Iberian Peninsula), an area characterised by an underwater canyon system. Encounter rates (ER), relative abundances (RA) and seasonality were assessed for eight species. This information was combined with physiographic features of the seafloor to understand their influence on cetacean distribution. Data were collected along 189 surveys from January 2017 to December 2022. In total, 479 sightings of eight species of cetaceans were recorded. Striped, bottlenose and Risso's dolphins and fin whales were the most frequently sighted. ER and RA were similar or higher than in other areas of the Mediterranean Sea. Species were distributed differently according to physiographic features: bottlenose dolphins in coastal waters and Risso's dolphins and fin whales above the Garraf underwater canyon system. These results highlight the importance of the central Catalan coast, particularly the underwater canyon system, for at least four species of cetaceans.

UNDERWATER CANYONS OF THE SOUTHWESTERN OUTSKIRTS OF SOUTHERN BAIKAL AS PRESUMABLE TRANSITERS OF TECHNOGENIC MATERIALS TO THE ABYSSAL SURFACE

Numerous publications by domestic and foreign authors deal with a significant role of underwater canyons in transit of loose material from the littoral to the abyssal surfaces of the seas. Lake Baikal fully corresponds in its hydrodynamic and bathymetric parameters to sea water basins, and the Baikal canyons are similar in their morphological and morphometric factors to sea canyons. A digital elevation model of the southwest underwater tip of the lake, generated based on a large array of bathymetric data, allowed identifying clearly defined valleys of the Shamanka and Slyudyanka canyons. The data obtained during the study of the canyon-valley area, carried out using special geophysical measuring instruments – Kongsberg EM710S multibeam echosounder and Knudsen CHIRP 3260 profilograph, – and analysis of the published materials showed a rather high degree of confindness of coarse debris to the canyon valleys and alluvial fans which implies their significant role in sediment transit. It has been shown that high seismicity of the Baikal basin and active wave conditions give rise to the formation of movable loose sediment masses and to the occurrence of gravity flows in the canyon valleys. Climate changes over the last decades contribute also to permafrost decomposition in the Baikal basin and to new-sediment transport into the lake. It is implied that an intensive development of the coastline leads to the coastal accumulation of a large amount of industrial and municipal contaminants which can move through the canyons to different distances into the lake water area. To date, there is no definite answer to the question about an actual role of underwater canyons in the transit of technogenic wastes to the abyssal lake surface. This requires organized large-scale specialized fieldwork with the use of high-precision geological-geophysical measuring instruments, and systematic sampling and thorough analysis of the bottom material.

Canyon Vortices: Application of the Theory of Topographic Vortices to the Phenomenon of Ice Rings in Baikal

A phenomenon of ice rings in Lake Baikal is considered. A hydrodynamic theory is proposed according to which geostrophic vortices form under ice in the area near the ice rings. These vortices are due to bed relief, namely, underwater canyons; therefore, they are referred to as canyon vortices. It is shown that a divergent ring vortex forms under ice in the ring domain at the crossing of a vertical cylindrical Stewartson layer on the lateral surface of the canyon geostrophic vortex and under-ice horizontal Ekman layer in the form of a horizontal vortex torus, and the melting of ice below in the form of a ring is due to the formation of this vortex torus.

China's little-known efforts to protect its marine ecosystems safeguard some habitats but omit others.

China’s stature as the world’s major producer and consumer of seafood is legendary, but its long-standing tradition of protecting marine life domestically is virtually unknown. We present the most comprehensive database on area-based marine conservation in China including 326 sites that conserve 12.98% of China’s seas and address 142 conservation objectives. Twenty-two percent of shallow habitats (<10 meters) were fully or highly protected and 20% of waters 10 to 50 meters deep were conserved to some degree. Ecosystems in deeper waters (>50 meters) are critical to protect, yet <5% of these waters in China were conserved, primarily in areas with the highest chlorophyll-α concentrations. Habitats such as underwater canyons and seamounts beyond the continental shelf had no area-based protection. While China has made progress in marine protection within its boundaries, there is more work to be done to ensure that the full suite of marine life is safeguarded.

РАСПРЕДЕЛЕНИЕ ГИДРОЛОГИЧЕСКИХ ПАРАМЕТРОВ НАД ПЛОЩАДКОЙ МЕТАНОВЫХ ПУЗЫРЬКОВЫХ ГАЗОВЫДЕЛЕНИЙ В ГОЛУБОЙ БУХТЕ (ЧЕРНОЕ МОРЕ) - СВЯЗЬ С СУБМАРИННОЙ ПРЕСНОВОДНОЙ РАЗГРУЗКОЙ

The vertical distribution of temperature ( T ), salinity ( S ), dissolved oxygen (O2) concentration, flow velocity ( U ) in the underwater canyon over the gas seepage site in the Golubaya Bay (the Black Sea) is studied. A significant decrease in the O2 concentration in the bottom water layer over the seep site as compared to the background site is shown, with a minimum of 0.2 mg/l, which was kept during the entire measurement period. The minima at the bottom were also revealed in the distribution of salinity in the first dataset; in the second dataset, desalination lenses were registered at a depth of 4, 10, and 8 m for three consecutive soundings. Such distribution potentially indicates a pulsed freshwater discharge, during which the desalination lenses gradually rise to the surface. The bottom current in the canyon was on average two times weaker than at the background station, where its velocity varied within 0.04-0.09 m/s. The described features of the distribution of hydrological parameters are associated with the gas bubble seepage and geomorphology of the study area.

A 2D Optimal Path Planning Algorithm for Autonomous Underwater Vehicle Driving in Unknown Underwater Canyons

This research aims to solve the safe navigation problem of autonomous underwater vehicles (AUVs) in deep ocean, which is a complex and changeable environment with various mountains. When an AUV reaches the deep sea navigation, it encounters many underwater canyons, and the hard valley walls threaten its safety seriously. To solve the problem on the safe driving of AUV in underwater canyons and address the potential of AUV autonomous obstacle avoidance in uncertain environments, an improved AUV path planning algorithm based on the deep deterministic policy gradient (DDPG) algorithm is proposed in this work. This method refers to an end-to-end path planning algorithm that optimizes the strategy directly. It takes sensor information as input and driving speed and yaw angle as outputs. The path planning algorithm can reach the predetermined target point while avoiding large-scale static obstacles, such as valley walls in the simulated underwater canyon environment, as well as sudden small-scale dynamic obstacles, such as marine life and other vehicles. In addition, this research aims at the multi-objective structure of the obstacle avoidance of path planning, modularized reward function design, and combined artificial potential field method to set continuous rewards. This research also proposes a new algorithm called deep SumTree-deterministic policy gradient algorithm (SumTree-DDPG), which improves the random storage and extraction strategy of DDPG algorithm experience samples. According to the importance of the experience samples, the samples are classified and stored in combination with the SumTree structure, high-quality samples are extracted continuously, and SumTree-DDPG algorithm finally improves the speed of the convergence model. Finally, this research uses Python language to write an underwater canyon simulation environment and builds a deep reinforcement learning simulation platform on a high-performance computer to conduct simulation learning training for AUV. Data simulation verified that the proposed path planning method can guide the under-actuated underwater robot to navigate to the target without colliding with any obstacles. In comparison with the DDPG algorithm, the stability, training’s total reward, and robustness of the improved Sumtree-DDPG algorithm planner in this study are better.

Modeling propagation in shallow water with the range-dependent sea surfaces and fluid seabeds using the equivalent source method.

This paper describes a shallow water range-dependent propagation model (RPM) based on the equivalent source method (ESM). The proposed model allows both the sea surface and fluid seabed to vary with the propagation range. The proposed equivalent source method-based range-dependent propagation model (ESM-RPM) utilizes three sets of equivalent sources, placed above the sea surface, below the seabed, and above the seabed, which replace the sea surface reflection, seabed reflection, and seabed transmission, respectively. The unknown strengths of the equivalent sources can be determined by solving an inverse problem based on the boundary conditions. The capability of the ESM-RPM for propagation in refractive water is demonstrated by evaluating the Green's function using a modal projection method. Numerical simulations are conducted in iso-velocity and refractive shallow water with an underwater canyon and corrugated surface waves, including two-dimensional (2-D) propagation across the canyon and three-dimensional (3-D) propagation along the canyon. Further simulations demonstrate the 2-D across-canyon and 3-D along-canyon propagations with random rough sea surfaces. The results show that the proposed ESM-RPM provides efficient, benchmark-quality numerical solutions that accurately capture the mode coupling associated with the varying cross section of the waveguide. Thus, the model has great potential to be applied in benchmarking propagation in shallow water with the varying sea surface and seabed.

Insights on the Indian Ocean Tectonics and Geophysics Supported by GMT.

This paper presented analyzed and summarized data on geological and geophysical settings about the tectonics and geological structure of the seafloor of the Indian Ocean by thematic visualization of the topographic, geophysical and geological data. The seafloor topography of the Indian Ocean is very complex which includes underwater hills, isolated mountains, underwater canyons, abyssal and accumulative plains, trenches. Complex geological settings explain seismic activity, repetitive earthquakes, and tsunami. Understanding and prognosis of the disastrous and catastrophic geological events is strongly based on correct data analysis, modelling and visualization. An important feature of this paper is mapping multi-source high-resolution data by GMT. Data include raster grids in NetCDF and GRD formats: ETOPO1, geologic and marine free-air gravity data, EGM96, age, spreading rates, and spreading asymmetry of the ocean crust by NOAA, total sediment thickness. Data were visualized by GMT modules to compare and analyze geophysical and geological settings of the Indian Ocean. Visualization reveled correlations between high bathymetric variations of the oceanic seafloor, distribution of main geological seafloor fabric: Southwest, Southeast, Mid and Carlsberg ridges. Tectonic maps were plotted to perform comparative analysis of several variables: crust age, spreading half rates (mm/yr), asymmetries in crustal accretion on conjugate ridge flanks (%), variations in the geopotential and gravimetric models. Being the warmest of the world’s ocean, Indian Ocean has specific climatic conditions (repetitive monsoons, tsunamis, cyclones and storms), complex geologic seafloor structure with triple junction and unique geographic settings. Presented paper contribut ed to the regional studies of the Indian Ocean.

On Adiabatic Sound Propagation in a Shallow Sea with a Circular Underwater Canyon

An idealized problem of sound propagation in a shallow sea with a curved underwater canyon is considered. The canyon is a circular feature of the bottom relief which causes horizontal refraction of acoustic waves. The sound field computation method for a waveguide with an inhomogeneity of this type is considered, and the geometry of horizontal rays trapped by the canyon is studied. The computation method is based on the separation of variables in the equation for the mode amplitudes and representation of the solution in the form of a double series. This technique is rather general in nature, because it can be used to compute the field in any problem where the waveguide has rotational symmetry. Furthermore, it is also shown which terms of the series correspond to horizontal rays trapped by the canyon.

Wide-angle mode parabolic equations for the modelling of horizontal refraction in underwater acoustics and their numerical solution on unbounded domains

The modelling of sound propagation in the ocean by the solution of mode parabolic equations is discussed. Mode parabolic equations can be obtained as the one-way approximation to horizontal refraction equations for modal amplitudes. Their wide-angle capabilities depend on the order of the Padé approximation of the involved pseudo-differential operators. Various aspects of numerical solution methods for wide-angle mode parabolic equations are considered in detail, including artificial domain truncation and Cauchy initial data for the point source field approximation. The capabilities of the discussed numerical approaches are demonstrated in several important test cases, including the problems of sound propagation in a penetrable wedge and in a sea with an underwater canyon.

The main factors of the origin and morphology evolution of underwater canyons in the Southern and Middle basins of the Baikal depression

We present the results of morphological analysis of the bottom topography in the Southern and Middle basins of Lake Baikal based on the high-precision bathymetric survey. There is a dominant influence of the fault tectonics at the origin of underwater canyons. Turbidity currents play a great role in the further evolution of the underwater valley. They intensify during abrupt seismic shocks or storm injections into the canyon heads. In cases when canyon heads are close to the river estuaries, terrestrial rivers have a significant impact on the speed of the formation of the canyon valleys. The topography of the original surface often determines the morphological features of the valleys. Climate change in the Pleistocene and fluctuations in the water level of the lake also could initiate the formation of some canyons in Lake Baikal. The studies have indicated the high morphological and genetic similarity of Baikal canyons with marine ones.

Engineering a dream workspace.

A sediment scientist rebuilt his entire lab to model how water shapes underwater canyons. A sediment scientist rebuilt his entire lab to model how water shapes underwater canyons.

Computing and Plotting Correlograms by Python and R Libraries for Correlation Analysis of the Environmental Data in Marine Geomorphology

The geomorphology of the Mariana Trench, the deepest ocean trench on the Earth, has a complex character: its transverse profile is asymmetric, the slopes are higher on the side of the Mariana island arc. The shape of the Mariana Trench is a strongly elongated, arched in plan and lesser rectilinear depression. The slopes of the trench are dissected by deep underwater canyons with various narrow steps on the slopes of various shapes and sizes, caused by active tectonic and sedimentation processes. Understanding of factors that may affect the shape of the geomorphology of such complex structure requires advanced methods of numerical computing. Current research is focused on the analysis of the geomorphology of the Mariana Trench by application of statistical libraries embedded in Python and R programming languages for the data analysis. Workflow algorithms include processing a data set by analysis, computing and visual plotting of the graphs. The research aims is to understand the environmental interactions affecting submarine geomorphology of the Mariana Trench by statistical data analysis. Technically, used algorithms included libraries of Python (Seaborn, Matplotlib, Pandas, SciPy and NumPy) and libraries of R ({hexbin}, {ggally}, {ggplot2}). Technically, following types of the statistical analysis were tested for computing and plotting: correlograms, histograms, strip plots, ridgeline plots and hexagonal diagrams for the bathymetric and geomorphic analysis. Python, being a high-level language, shown more straightforward approach for the statistical data analysis, while R implies more power in the data visualization. The results of the geospatial data modelling show detected correlation between various factors (geology, bathymetry, tectonics) affecting submarine geomorphology that reveal unevenness in its structure. Both programming languages demonstrated significant functionality for the spatial data analysis. The effective and accurate geospatial data visualization demonstrated by Python and R proves high potential of their application in the geomorphological studies.

Asymptotic solution for the problem of sound propagation in a shallow sea with the bathymetry described by a parametric quadratic function.

A wide class of three-dimensional sound propagation problems in shallow water where the bathymetry can be locally approximated by a parametric quadratic function is considered. Relevant examples of such bathymetry functions include underwater canyons and ridges. Asymptotic solution for this class of problems is derived under the adiabaticity assumption. The solution is based on mode parabolic equation theory and group-theoretical disentanglement formulas for operator exponentials. Two examples are considered (a ridge and a bottom with quadratic slope), and respective wavefront geometry is studied.

МОРФОСТРУКТУРНА ОРГАНІЗАЦІЯ ПІВНІЧНО-ЗАХІДНОЇ ЧАСТИНИ ШЕЛЬФУ ЧОРНОГО МОРЯ

The article is devoted to the investigation of the morphostructure organization of the northwestern part of the Black Sea shelf and the connection of morphostructural elements with underwater canyons. In the presented material is considered the issue of the origin of underwater canyons. The valleys of the Danube, the Dnieper, the Dniester, and the Southern Bug are followed on the north-western shelf at a considerable distance from the shore (approximately 100-120 km). The question of the origin of the underwater canyons remains controversial. Since the underwater canyons in their main part are the continuation of large rivers, the question arises of their paleogeographic origin, but at the same time if the underwater canyons are former river valleys, then how did they find themselves at the bottom of the sea at depths of 2000 m? Consequently, we need incredible tectonic processes to hide the riverbed at such a depth. All this contradicts the formation of the Earth in Tertiary and Quaternary time. Consequently, there are reasons to believe that the underwater canyons are based on tectonic forms of relief. The analysis of the tectonic discontinuity of the Baltic Shield and other areas shows that when the shields are raised, radial split systems are formed and concentrically located to the center of the lift. This hypothesis is consistent with the theory of tectonic plates. It is likely that the same system of splits should also be formed when immersing the edge of the main platform. Thus, the most scientific one can be considered a tectonic hypothesis. The characteristic of morphostructures, analysis of their interconnection, expression in the relief, connection with underwater canyons is carried out. It was investigated that all large underwater canyons of the Black Sea shelf coincide with the isolated linear morphostructures, and, consequently, have tectonic origin.

Sorting out submarine canyons

Marine Geology Submarine canyons, often found directly off the coastline, are common but understudied features of Earth. Despite their prevalence, what determines their location and morphology remains a mystery. Smith et al. used a massive data set from the entire western coast of the United States to determine what variables best correlated with underwater canyon formation. They found that the distribution of rock type and sediment flux were the most important factors for explaining the location of submarine canyons. Geophys. Res. Lett. 10.1002/2017GL075139 (2017).

Toward estimating ocean temperature through passive acoustics

In this paper, we analyze the noise recorded in two drifting vertical line arrays (VLAs) deployed 1 km apart, in the area of the Setubal’s underwater canyon off the west coast of Portugal during RADAR’07 sea trial. Automatic Information System (AIS) recordings for this period reveal a major tanker passing by the area, whose acoustic signature is clearly seen in the spectrogram. The influence of the underwater canyon in the recorded spectrograms is discussed by simulations. By cross-correlating and spatially filtering (beamforming) the signals received at the VLAs, a wave front structure is obtained with coherent information from propagating paths traversing both VLAs and respective arrival times. This work is a contribution for application in a passive ocean acoustics framework to the estimation of sound speed perturbations in the water column.

New deep ocean Iravadiidae of the genus Ceratia (Caenogastropoda: Truncatelloidea) from an underwater canyon and adjacent regions of the southwestern Atlantic (northeastern Brazil).

Previous studies on the mollusks from Brazilian underwater canyons have addressed the record and description of new species of aplacophorans, bivalves, scaphopods and/or gastropods (Leal & Simone 2000; Absalão 2010; Corrêa et al. 2014). Leal & Simone (2000) described a new bathyal gastropod of the family Pseudococculinidae collected from the continental slope and Doce River Canyon (960 m) off the state of Espírito Santo (southeastern Brazil). Absalão (2010) reported a number of species of gastropods, bivalves and scaphopods from Campos Basin off the state of Rio de Janeiro (southeastern Brazil). It is likely that some of these species reported by Absalão (2010) were collected from underwater canyons in the northern portion of the Campos Basin. Corrêa et al. (2014) recorded two species of aplacophorans of the genus Falcidens Salvini-Plawen, 1968 obtained from the continental slope and underwater canyons of Campos Basin. Certainly more species of mollusks were studied from Brazilian underwater canyons, but not duly mentioned in publications (i.e., the region of canyons may have been referred to as the continental slope or deep sea).

Seasonal spatial patterns in seabird and marine mammal distribution in the eastern Chukchi and western Beaufort seas: Identifying biologically important pelagic areas

The Chukchi and Beaufort seas are undergoing rapid climate change and increased human activity. Conservation efforts for upper trophic level predators such as seabirds and marine mammals require information on species’ distributions and identification of important marine areas. Here we describe broad-scale distributions of seabirds and marine mammals. We examined spatial patterns of relative abundance of seabirds and marine mammals in the eastern Chukchi and western Beaufort seas during summer (15 June–31 August) and fall (1 September–20 November) from 2007 to 2012. We summarized 49,206km of shipboard surveys for seabirds and 183,157km of aerial surveys for marine mammals into a grid of 40-km×40-km cells. We used Getis-Ord Gi∗ hotspot analysis to test for cells with higher relative abundance than expected when compared to all cells within the study area. We identified cells representing single species and taxonomic group hotspots, cells representing hotspots for multiple species, and cells representing hotspots for both seabirds and marine mammals. The locations of hotspots varied among species but often were located near underwater canyons or over continental shelf features and slopes. Hotspots for seabirds, walrus, and gray whales occurred primarily in the Chukchi Sea. Hotspots for bowhead whales and other pinnipeds (i.e., seals) occurred near Barrow Canyon and along the Beaufort Sea shelf and slope. Hotspots for belugas occurred in both the Chukchi and Beaufort seas. There were three hotspots shared by both seabirds and marine mammals in summer: off Wainwright in the eastern Chukchi Sea, south of Hanna Shoal, and at the mouth of Barrow Canyon. In fall, the only identified shared hotspot occurred at the mouth of Barrow Canyon. Shared hotspots are characterized by strong fronts caused by upwelling and currents, and these areas can have high densities of euphausiids in summer and fall. Due to the high relative abundance of animals and diversity of taxa, these sites are clearly important areas of congregation for seabirds and marine mammals that should be prioritized in the development of management and conservation plans.