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Geomorphic features map of the world's oceans. Dotted black lines mark boundaries between major ocean regions. Basins are not shown.
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We present the first digital seafloor geomorphic features map (GSFM) of the global ocean. The GSFM includes 131,192 separate polygons in 29 geomorphic feature categories, used here to assess differences between passive and active continental margins as well as between 8 major ocean regions (the Arctic, Indian, North Atlantic, North Pacific, South A...
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Context 1
... integration of the base layers, classification layers and discrete feature layers presented above a new global seafloor geomorphic fea- tures map (GSFM) has been created comprised of 131,192 separate polygons (Fig. 4). Although there are numerous possible approaches to assess the GSFM, we focus here on two perspectives of the integrated results to quantify geomorphic differences between passive and active continental margins (Fig. 2), and between the eight different ocean re- gions selected for detailed ...
Similar publications
Submarine canyons are the major channels for the migration of terrigenous sediments towards deep seas and an important geomorphological unit in continental shelves/slopes. With the development of multibeam bathymetry technology, a method of quickly identifying and accurately extracting the characteristics of submarine canyons from large datasets is...
Citations
... Our area of interest is the Norwegian continental margin, which spans 26°of latitude and approximately 3000 km between the North Sea and the Arctic Ocean north off Svalbard (Fig. 1). The formerly glaciated Norwegian continental margin is characterised by a deep shelf break and a continental shelf that is frequently incised by glacial troughs, which are characterised by depths of over 100 m and an overdeepened longitudinal profile that reaches a maximum depth inboard of the shelf break 24 . We use machine-learning methods to make spatial predictions of dry bulk density, organic carbon content and sediment accumulation rates and quantify the uncertainty in these predictions. ...
... Further, we have demonstrated that glacial troughs are the main centres of organic carbon accumulation on the Norwegian continental margin, with accumulation rates significantly higher than in other geomorphological units. Globally, glacial troughs are found on the formerly glaciated continental margins of North America, Eurasia, south America, and Antarctica, covering 3.66 million km 2 of the seabed 24 . If we assumed that the rate of organic carbon accumulation in glacial troughs of 9.29 ± 6.89 g C m −2 yr −1 (Fig. 5a) is representative for glacial troughs globally, then these geomorphological features would accumulate 9-59 Tg C yr −1 (based on mean value and standard deviation), which is in the same order of magnitude as fjords (21-25 Tg C yr −1 ) 42 , seagrass meadows (11.1-27.1 Tg C yr −1 ) 13 , mangroves (17.5-23.1 Tg C yr −1 ) 56 , and saltmarshes (8.5 -9.0 Tg C yr −1 ) 13 . ...
... Our area of interest (Fig. 1) comprises the Norwegian continental shelf and slope 24 , which we define here as the Norwegian continental margin. We also include the shallowest parts of the abyss (deep sea) within 50 km distance from the seaward boundary of the slope to make best use of existing data. ...
The role of continental margin sediments in the carbon cycle and the associated management potential for climate mitigation are currently poorly understood. Previous work has indicated that margin sediments store significant amounts of organic carbon, but few studies have quantified the rates at which organic carbon is accumulated. Here, we use machine learning to make spatial predictions of the organic carbon stocks and accumulation rates of sediments on the Norwegian continental margin. We show that surface sediments (upper 10 cm) store 814 Tg and accumulate 6 Tg yr⁻¹ of organic carbon. Shelf-incised glacial troughs account for 39% of the stocks and 48% of the accumulation, with the main accumulation hotspot located in the Skagerrak. Continental margin sediments accumulate organic carbon at scales much larger than vegetated coastal ecosystems in Norway because of their larger extent. Future studies should explore to what extent management interventions could increase accumulation rates, e.g., by minimising anthropogenic disturbance of seafloor sediments.
... We also included the predictor Month in our models to account for the seasonality of the movement behaviour of pygmy blue whales (Table 1). We used the layers of geomorphology of the Australian margin and adjacent seafloor [32] and [40] to overlay predicted suitable habitat over shelf, slope, and ocean basin bathymetric features within Australian waters and the Southeast Asia region, respectively, and calculated the percentage of suitable habitat within each bathymetric feature. ...
... S) (Fig. 3b). Using the geomorphology layer [32,40], suitable habitat occurred almost exclusively on slope (91% of suitable habitat), with a small amount of suitable habitat in deep ocean floor (7%) and minimal suitable habitat on the shelf (2%) (Fig. 3b). However, spatial Kappa and spatial AUC values had a large variation indicating that the model performed better at some areas than others (Fig. 3c, d). ...
... Values of spatial Kappa and AUC indicated Fig. 6 Habitat suitability predicted from the gradient boosted model and spatial accuracy maps for whales in the Southeast Asia region (May-October). Shown is a continuous (0-1) relative habitat suitability; b thresholded suitable habitat (pink) and validated suitable habitat (red; suitable habitat restricted to areas with spatial AUC and, spatial Kappa > 0.4) overlaid with geomorphologic features [40], c spatial distribution of model accuracy (spatial Kappa) and d spatial distribution of model accuracy (spatial AUC). Black dotted contours represent the 200 m bathymetry (shelf break). ...
Background
Accurate predictions of animal occurrence in time and space are crucial for informing and implementing science-based management strategies for threatened species.
Methods
We compiled known, available satellite tracking data for pygmy blue whales in the Eastern Indian Ocean (n = 38), applied movement models to define low (foraging and reproduction) and high (migratory) move persistence underlying location estimates and matched these with environmental data. We then used machine learning models to identify the relationship between whale occurrence and environment, and predict foraging and migration habitat suitability in Australia and Southeast Asia.
Results
Our model predictions were validated by producing spatially varying accuracy metrics. We identified the shelf off the Bonney Coast, Great Australian Bight, and southern Western Australia as well as the slope off the Western Australian coast as suitable habitat for migration, with predicted foraging/reproduction suitable habitat in Southeast Asia region occurring on slope and in deep ocean waters. Suitable foraging habitat occurred primarily on slope and shelf break throughout most of Australia, with use of the continental shelf also occurring, predominanly in South West and Southern Australia. Depth of the water column (bathymetry) was consistently a top predictor of suitable habitat for most regions, however, dynamic environmental variables (sea surface temperature, surface height anomaly) influenced the probability of whale occurrence.
Conclusions
Our results indicate suitable habitat is related to dynamic, localised oceanic processes that may occur at fine temporal scales or seasonally. An increase in the sample size of tagged whales is required to move towards developing more dynamic distribution models at seasonal and monthly temporal scales. Our validation metrics also indicated areas where further data collection is needed to improve model accuracy. This is of particular importance for pygmy blue whale management, since threats (e.g., shipping, underwater noise and artificial structures) from the offshore energy and shipping industries will persist or may increase with the onset of an offshore renewable energy sector in Australia.
... Submarine canyons are narrow, V-shaped valleys incised into lithified rock or sediment that typically 49 occur on upper continental slopes and connect directly to the shelf edge (Daly, 1936;Shepard, 1972;50 Wynn et al., 2007;Fildani, 2017). They are globally important as conduits that transfer vast amounts of 51 sediment and pollutants from continents to deep-marine basins (Harris et al., 2014;Amaro et al., 2016;52 Mountjoy et al., 2018;Zhong and Peng, 2021), as efficient sites of organic carbon burial (Masson et al.,53 The latter transition to a compressional stress regime was characterised by reverse faulting and uplift, 154 followed by batholith emplacement and subsequent unroofing. ...
Submarine canyon-fills comprise substantial volumes of thin-bedded successions deposited by sediment gravity flows that are either stripped or overspill from adjacent channels into highly confined, topographically complex overbank settings. Here, we document the Punta Baja Formation, a rare example of an exhumed canyon-confined overbank succession with good 3D constraints from the Mesozoic Peninsular Ranges Forearc, Mexico. High-resolution sedimentary logging and drone-captured photogrammetric models reveal that the overbank was a highly dynamic environment, where different bed types point to a variety of flow transformations and complex topographical interactions that evolved through time. The lower overbank is characterised by variable bed thicknesses, grain-sizes and palaeocurrent directions, which point to a wide range of unfiltered flows that overspilled from channels. Thick sandstone beds contain distinct hummock-like bedforms, representing high energy combined flows that repeatedly deflected and reflected against the high relief canyon margin, suggesting complete confinement within the conduit. Locally, thinner beds are disrupted by slides, debrites and scour surfaces on the canyon floor. As the canyon system matured, constituent channels migrated laterally and aggraded. Here, the character of the overbank changes, developing distinct fining- and thinning-upward packages that decay in thickness and grain-size away from the channel axis. Packages are more mud-rich and beds contain mixed grain-size bedforms indicating smaller magnitude, rapidly decelerated transitional flows that failed to interact with the canyon margin. In more quiescent parts of the upper overbank, beds containing rhythmic bundles of silt-rich, mud-draped bedforms are interpreted to be the product of sediments reworked by internal tides. This is the first detailed study of fine-grained fills in an ancient ocean-facing submarine canyon. Canyon-confined overbanks offer a more diverse fill, with flow transformations that demonstrate a complex balance between erosion and deposition, and an absence of discrete internal levée or depositional terrace elements that have been identified in more distal confined overbank settings.
... Wessel & Smith 1996). We also obtained a digital map of global seafloor geomorphic features (GSFM) created by Harris et al. (2014). GSFM is a collection of GIS vector maps of oceanic regions generated by the analysis of bathymetric contours derived from the Shuttle Radar Topography Mapping (SRTM30_plus) database (Becker et al. 2009). ...
The newly recognized Rice’s whale Balaenoptera ricei is among the most endangered large whale species in the world and primarily occupies a region near the continental shelf break in the northeastern Gulf of Mexico (GoMex). We analyzed visual line-transect survey data collected throughout the northern GoMex from 2003-2019 and developed spatially explicit density maps using a density surface modeling approach to examine relationships between Rice’s whale density and bathymetric and oceanographic features. We identified water depth, surface chl a concentration, bottom temperature, and bottom salinity as key parameters that define the Rice’s whale habitat. This is consistent with upwelling of cold, high-salinity water along the continental shelf break and seasonal input of high-productivity surface water originating from coastal sources. The dominant circulation patterns in the GoMex, including the presence of Loop Current eddies, lead to increased productivity and likely play a role in maintaining high densities of forage species needed to support Rice’s whales. Extrapolation of the model suggests additional regions in Mexican waters of GoMex that may be suitable for Rice’s whales. This study informs the designation of critical habitat as defined by the US Endangered Species Act and will assist in marine spatial planning activities to avoid additional anthropogenic impacts to Rice’s whales associated with the development of wind energy and aquaculture.
... To validate the scaling relationship between length and area obtained from laboratory scale, we compared the labora-tory data with field data (Fig. 12). The obtained results show that the length-to-area relationship obtained from laboratoryscale submarine canyons and hanging-wall fans is consistent with the field-scale submarine canyon length to fluvial drainage area analyzed in S2S studies (n = 9477, Harris et al., 2014). Our data also aligns with modern metadata of submarine canyons configuration in active margins (n = 35) and passive margins (n = 36) (Bührig et al., 2022a, their Fig. 8). ...
Tectonics play a significant role in shaping the morphology of submarine canyons, which form essential links in source-to-sink (S2S) systems. It is difficult, however, to investigate the resulting morphodynamics over the long term. For this purpose, we propose a novel experimental approach that can generate submarine canyons and hanging-wall fans on continuously evolving active faults. We utilize morphometric analysis and morphodynamic models to understand the response of these systems to fault slip rate (Vr) and inflow discharge (Q). Our research reveals several key findings. Firstly, the fault slip rate controls the merging speed of submarine canyons and hanging-wall fans, which in turn affects their quantity and spacing. Additionally, the long profile shapes of submarine canyons and hanging-wall fans can be decoupled into a gravity-dominated breaching process and an underflow-dominated diffusion process, which can be described using a constant-slope relationship and a morphodynamic diffusion model, respectively. Furthermore, both experimental and simulated submarine canyon–hanging-wall fan long profiles exhibit strong self-similarity, indicating that the long profiles are scale independent. The Hack's scaling relationship established through morphometric analyses serves as an important link between different scales in S2S systems, bridging laboratory-scale data to field-scale data and submarine-to-terrestrial relationships. Lastly, for deep-water sedimentary systems, we propose an empirical formula to estimate fan volume using canyon length, and the data from 26 worldwide S2S systems utilized for comparison show a strong agreement. Our geomorphic experiments provide a novel perspective for better understanding of the influence of tectonics on deep-water sedimentary processes. The scaling relationships and empirical formulas we have established aim to assist in estimating volume information that is difficult to obtain during long-term landscape evolution processes.
... Relief data was retrieved from the GEBCO_2022 Grid (https://www.gebco.net/). Shelf classification based on vertical relief from the SRTM30 plus v7 global bathymetric model yielded three classes: low-(<10 m), medium-(10-50 m), and high-relief (>50 m) shelves (after Harris et al., 2014). The shelf can be divided into three major sectors: Sao Paulo Bight, Florianopolis-Mostardas, and Rio Grande Cone (after Zembruscki, 1979). ...
Chirp profiles collected on the southern Brazilian shelf were combined with sedimentological and hydrodynamic data to characterize shelf geomorphology, focusing on the development of outer shelf bedforms and their genetic links with major oceanic currents. Outer shelf sediment accumulations are interpreted as two scales of bedforms, such as dunes and sand ridges. In the São Paulo Bight, cuspate bedforms are bounded landward by a geomorphological scarp. The sector between Florianopolis and Mostardas also exhibits frequent asymmetric bedforms, whereas the inner- middle shelf is covered by semitransparent sheets. The southern Rio Grande Cone is characterized by stratified deposits covering vast outer shelf areas. Surficial sediment samples reveal a dominantly muddy composition and relatively high carbonate contents. Hydrodynamic data indicate a major influence of the Brazil Current over the São Paulo Bight. The prolific bedform outer-shelf environment is assumed to be mostly relict formed in a transgressive shallow-water setting. The sand ridges are believed to have evolved from a moribund stage characterized by morphological degradation to a relict stage, with preservation enhanced by fine-grained winnowing, coarse sediment armoring, and early cementation. Bedform migration seems to be occurring on the São Paulo Bight due to the presence of a nearly permanent meander of the Brazil Current. Over most of the inner shelf, the northward advection of sediments mainly led by the Brazilian Coastal Current has formed extensive fine-grained deposits. The occurrence of a relict shelf scarp may have conditioned the formation of the outer-shelf bedform environment. The vast spatial distribution of bedforms over most of the outer shelf seems comparable with other shelf areas, such as the south African shelf, dominated by the influence of unidirectional oceanic currents. Dune dimensions are lower on the Brazilian shelf, due to their relict character, the geomorphological configuration of the margin, and the scarcity of sand sources.
... The seabed morphology on continental margins, including western and eastern boundaries, is diverse and exhibits intricate topographic features [12,13], including seamounts (raised), canyons (concave), terraces (wide), etc. Understanding how these topographic changes interact with multi-scale oceanic processes and, consequently, affect the structure and dynamics of mid-deep circulations has attracted considerable attention [14][15][16][17]. However, the scarcity of observational data has seriously impeded the advancement of our understanding [18]. ...
As a key component of meridional overturning circulation, mid-deep circulation plays a crucial role in the vertical and meridional distribution of heat. However, due to a lack of observation data, current knowledge of the dynamics of mid-deep circulation currents moving through basin boundaries and complicated seabed topographies is severely limited. In this study, we combined oceanic observation data, bathymetric data, and numerical modeling of the northwest continental margin of the South China Sea to investigate (i) the main features of mid-deep circulation currents traveling through the central depression belt and (ii) how atmospheric-forcing (winds) mesoscale oceanic processes such as eddies and current-topography interactions modulate the mid-deep circulation patterns. Comprehensive results suggest that the convergence of different water masses and current-topography interactions take primary responsibility for the generation of instability and enhanced mixing within the central depression belt. By contrast, winds and mesoscale eddies have limited influence on the development of local circulation patterns at mid-deep depths (>400 m). This study emphasizes that the intensification and bifurcation of mid-deep circulation; specifically, those induced by a large depression belt morphology determine the local material cycle (temperature, salinity, etc.) and energy distribution. These findings provide insights for a better understanding of mid-deep circulation structures on the western boundary of ocean basins such as the South China Sea.
... Holocene sea level fluctuations yield unique datasets of earth's climate and ice sheet evolution. Those fluctuations were responsible for changes in patterns of sedimentary accumulation as the sea invaded ancient fluvial plains and flooded coastal areas that became the modern continental shelves (Blum et al., 2013;Harris et al., 2014). This period is characterized by global warming, the end of the last glaciation, and an increase of the sea level around the ocean basins. ...
Along the coast of the state of Pernambuco, NE Brazil, the presence of coastal outcrops aligned with the shoreline and distributed above and below the mean sea level is remarkable. These outcrops were sampled, and petrological, isotopic, and geochronological analyses were integrated to investigate the local effects of the Holocene sea-level fluctuations. The results indicate that the rocks are recent (< 8ka), formed by cementation of beach sands (magnesian calcite cement, predominance of quartz and presence of marine bioclasts, signs of compaction, fractures, and dissolution), in a tropical climate and warm waters, which allows to classify them as typical examples of beachrocks. The carbonate cement consisted of Mg-rich calcite with values ranging from −1.1‰ to 3.5‰ for δ¹³C and from −0.9‰ to 0.5‰ for δ¹⁸OVPDB. These isotopic values are typical of marine carbonate cemented deposits in shallow marine environments under freshwater influence (meteoric vadose environment). In these conditions, the cementing processes occurred in the intertidal zones, which reinforce the use of these data as indicators of ancient sea levels. The sea level fluctuations could be divided, in chronological order, into three different phases, starting with a rapid sea level rise followed by a relative stabilization at a maximum level and, finally, a decreasing phase. Recent sea level fluctuations in Pernambuco are represented by beachrocks with ages between 8 ka and 800 years and a maximum level of 2 to 3 meters above the present mean level. In scenarios of a near future with a general global sea level rise pattern, significant local geomorphological changes may occur, which means a great future challenge to society.
Keywords:
Beachrocks; Sea level fluctuation; Holocene; Radiocarbon dating
... Despite only comprising 15% of the ocean area, continental margins are important sites of organic carbon (OC) storage since they receive organic matter (OM) from both terrestrial and marine sources, and account for the burial of ∼90% of sedimentary OC Harris et al., 2014;Hedges & Keil, 1995). The preservation of OC in marine sediments is highly dependent on its sources (i.e., recently synthesized biospheric marine or terrestrial OM, or petrogenic carbon from eroded bedrock), which often dictate its reactivity given their contrasting chemical composition: while fresh marine OM is more reactive than terrestrial biogenic organic residues derived from plants and soils, petrogenic OC has the most recalcitrant nature Blair & Aller, 2012). ...
As major sites of carbon burial and remineralization, continental margins are key components of the global carbon cycle. However, heterogeneous sources of organic matter (OM) and depositional environments lead to complex spatial patterns in sedimentary organic carbon (OC) content and composition. To better constrain the processes that control OM cycling, we focus on the East Asian marginal seas as a model system, where we compiled extensive data on the OC content, bulk isotopic composition (δ¹³C and Δ¹⁴C), total nitrogen, and mineral surface area of surficial sediments from previous studies and new measurements. We developed a spatial machine learning modeling framework to predict the spatial distribution of these parameters and identify regions where sediments with similar geochemical signatures drape the seafloor (i.e., “isodrapes”). We demonstrate that both provenance (44%–77%) and hydrodynamic processes (22%–53%) govern the fate of OM in this margin. Hydrodynamic processes can either promote the degradation of OM in mobile mud‐belts or preserve it in stable mud‐deposits. The distinct isotopic composition of OC sources from marine productivity and individual rivers regulates the age and reactivity of OM deposited on the sea‐floor. The East Asian marginal seas can be separated into three main isodrapes: hydrodynamically energetic shelves with coarser‐grained sediment depleted in OC, OM‐enriched mud deposits, and a deep basin with fine‐grained sediments and aged OC affected by long oxygen exposure times and petrogenic input from rivers. This study confirms that both hydrodynamic processes and provenance should be accounted for to understand the fate of OC in continental margins.
... Slope-confined canyons, which are also referred to as blind or headless canyons, are commonly observed features along continental margins globally [1][2][3][4][5]. Similar to shelf-indenting canyons, they function as conduits for sediment transport [6,7]. ...
Autonomous Underwater Vehicle (AUV)-based multibeam bathymetry, sub-bottom profiles, and side-scan sonar images were collected in 2009 and 2010 to map the geomorphic features along the axial zone of a canyon (referred to as C4) within the canyon system developed on the northern slope of the South China Sea. These data significantly improved the spatial resolution of acoustic data, leading to a better understanding of the sedimentary processes within the modern canyon system. The bathymetric data reveal that sections across the canyon axis exhibit either asymmetrical or symmetrical characteristics, which differ from the overall asymmetrical pattern of the entire canyon. This suggests that the overall asymmetrical pattern of the canyon is not primarily due to axial incision. Various morphological elements were identified along the canyon axis, including failure scars, undulating features, knickpoints, flat terraces, furrows, and mass transport deposits (MTDs). Landslides, predominantly located in the upper canyon, were formed after at least 5000 years BP. Between the beginning of the canyon and a water depth of approximately 1300 m, there are alternating flat terraces and knickpoints. The large knickpoints’ low slope gradients are likely formed by the presence of undulating features. The internal configurations of undulating features suggest that they are depositional structures rather than sediment deformation. The formation of small-scale furrows below a depth of 1200 m may be associated with occasional gravity flows down the canyon. It is suggested that the canyon was generally inactive during the Holocene but experienced sporadic processes of sediment erosion, transport, and re-deposition in the axial zone that were triggered by landslide events occasionally in the upper canyon.
