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The outcomes from the survey research in distribution of the giant grenadier Coryphaenoides pectoralis at different stages of development in the Northwest Bering Sea over 1963–2020 have been reported. The data for 37 thousand catches performed with the bottom and multi-depth trawls at the depths between 0–1200 m are processed. It has been revealed that the species fish tend to spawn throughout the year, with two periods of peak spawning activity in the second half of a spring season and from the late summer season to the first half of an autumn season. The female fish ready to spawn migrate down the water column, keeping deeper than 600 m, where the males ready to spawn are concentrated. After spawning, they come back to the feeding areas of less water depths. The juvenile giant grenadier less than 30 cm in length can be encountered in the mesopaelagic and upper bathypelagic zones, which do not appear to form dense aggregations. The majority of the specimens less than 30–40 cm in length and smaller commonly leave this water column layer to occupy the bottom water layers along the continental shelf. Such differentiation between the juvenils and the sexually mature specimens can provide the opportunity to avoid cannibalism and to use the habitat food sources efficiently. [ABSTRACT FROM AUTHOR]

This study investigates the influence of along‐front wind forcing on chlorophyll‐a (Chl‐a) at the Otago Shelf Break (OSB) in southeast Aotearoa/New Zealand using remotely‐sensed and in situ data. Summer wind stress over the OSB was shelf‐aligned, oscillating between upfront and downfront. Surface Chl‐a concentrations along the OSB were shown to increase episodically (≤10 days duration) following upfront wind stress. This response occurred over most of the 350 km long shelf break, and was most intense north of the Otago Peninsula. Peak Chl‐a enhancement at the shelf break occurred following periods of upfront winds, exhibiting a lagged response of approximately 5 days. Moored thermistor data indicated that upfront wind events were followed by increased thermal stratification over the mid‐shelf, whereas downfront wind events were followed by a well‐mixed water column. In situ temperature, salinity, and nutrient measurements suggested an offshore movement of the surface expression of the front following upfront winds, and a reduction in nitrate over the shelf break. From these observations a model of Ekman restratification driven by upfront winds is proposed for this system, wherein off‐shelf Ekman transport converts strong horizontal isopycnal gradients at the shelf break front into vertical stratification. This stratification holds phytoplankton in the upper water column, allowing increased access to light, which is marked by the increased drawdown of nitrate at the shelf break. Downfront winds break down this stratification, move the shelf break front onshore, and mix phytoplankton through the water column, reducing the surface expression of chlorophyll. Plain Language Summary: The southeast coast of Aotearoa/New Zealand has a relatively near‐shore "shelf break," the area where shallow continental shelf seas (<200 m) slope steeply toward the deeper ocean (>1,000 m). Here lighter shelf waters meet more‐dense off‐shelf waters, forming a "shelf break front." Satellite images show large phytoplankton blooms occurring over the whole shelf break front in summer months, but researchers have not yet explored the factors that cause these short‐lived events. Understanding phytoplankton patterns and the ocean processes driving them is key to our knowledge of this ecosystem, which is home to endangered marine species and commercial fisheries. This study uses satellite images of chlorophyll‐a and winds, in tandem with in‐person ship and mooring data to explore how winds influence chlorophyll‐a at this front. Winds that are aligned with the shelf break (here southwest/northeast) are focused on due the cross‐shelf movement they can generate. This study finds that northeast winds cause increases in chlorophyll‐a at the front, which we believe to result from increased water column stability when light waters move over dense waters. This stratification provides a near‐surface layer with abundant light. During southwest winds, this stability is believed to be broken down, mixing phytoplankton away from the surface. Key Points: Remotely‐sensed summer chlorophyll‐a concentrations are enhanced at the southeast shelf break of Aotearoa/NZ following upfront wind stressSurface chlorophyll‐a was reduced at the shelf break following downfront wind stress, despite relatively elevated nitrate concentrationsEkman restratification by upfront wind stress is proposed as a likely mechanism for episodic summer shelf break chlorophyll‐a enhancements [ABSTRACT FROM AUTHOR]

Previous studies about tectonic events in the Ulleung Basin have been performed using diverse methods, but the deformation history of the Ulleung Basin is still controversial. In the Ulleung Basin, the Dolgorae and Gorae I structures were formed by basin deformation I (northwest-southeast compression) and the Gorae V structure was formed by basin deformation II (east-west compression). Since the quality of seismic data of the Dolgorae structures is not good, it is more difficult to reveal the basin deformation history through structural analysis of the seismic data. Thus, we traced the change in paleo-shelf breaks and studied provenance using image logs as indirect tectonic evidence and analyzed the growth strata of the Dolgorae and Gorae structures using seismic data for analyzing basin deformation. The shape of the paleo-shelf break has changed from linear to curved shape since 12.5 Ma, and the progradation rate of the paleo-shelf break was the fastest during 10.6–12.5 Ma. Before 12.5 Ma, sediments were supplied in the southwest direction, but after 12.5 Ma, they were supplied in the southeast direction originated from uplifted Dolgorae thrust fault zone. This evidence imply that basin deformation occurred in 12.5 Ma. During basin deformation I, the Gorae I structure was formed later than the Dolgorae structures due to the propagation of compression, and during basin deformation II, the Gorae V structure was formed from 5.33 Ma based on analysis of growth strata. [ABSTRACT FROM AUTHOR]

Based on interpretation and inversion of high‐resolution seismic data, a previously undocumented occurrence of pore‐filled gas hydrates that are associated with a submarine canyon system was discovered in the shelf break of the north‐east Qiongdongnan Basin (QDNB) in the northern South China Sea (SCS). Continuous bottom simulating reflections (BSRs) were recognized in the submarine striking NW‐SE ridges along the shelf break. The two‐way travel times (TWTs) of the BSRs are about 200–250 ms below the sea floor and the burial depths are mapped at ~180–225 mbsf after time‐depth conversion. The distribution of the enhanced reflections (ERs) and acoustic blanking zone overlying the BSRs indicate possible pore‐filled gas hydrate enrichment. ERs have been commonly observed immediately below the BSRs, indicating the accumulation of free gas, which exhibits distinct amplitude versus offset (AVO) anomalies. The acoustic impedance inversion results show that the gas hydrate saturation is 20–50%, and the thickness of the gas hydrate‐bearing layers is usually ~10–40 m, with a maximum thickness of up to ~90 m in local regions. Large‐scale listric faults originating from the deep sag connect the hydrocarbon source region and the shallow gas hydrate stability zone (GHSZ) and act as migration pathways for biogenic gas and potentially thermogenic gas. In addition, hydrocarbons may also be transported into the GHSZ along the sidewalls of the canyon. Canyon incision is believed to cause the increase in the burial depth of the BSRs on the flank of the ridge toward the base of the channel and thereby to trap the hydrocarbons migrating along the sidewall in permeable beds due to the decrease in permeability caused by the gas hydrate accumulation, resulting in the occurrence of ERs immediately below the BSRs. It is speculated that in the channel‐levee system, the coarse‐grained sediments should be deposited within the GHSZ, and the reservoir's physical properties are conducive to the wide distribution and enrichment of pore‐filled gas hydrates in the shelf break of the northern QDNB. [ABSTRACT FROM AUTHOR]

The Risso's dolphin, Grampus griseus, is widely distributed in temperate and tropical ocean waters around the world. Despite the known occurrence along the Brazilian coast, information regarding the spatial distribution of the species is scarce. Here we evaluated the distribution pattern of Risso's dolphins using records obtained through 200 h of dedicated aerial surveys for marine mammals off the slope and outer continental shelf of Southeast Brazil, conducted between March and May 2012. A total of 16 groups of Risso's dolphins was recorded with a median group size of 35 individuals (range = 1-300). Environmental variables (i.e., depth, slope, distance to the coast and to the shelf break, and sea surface temperature) associated with the Risso's dolphin groups recorded indicate an oceanic distribution pattern, occurring close to the shelf break, what is probably related with foraging activity. This study provides new information about the distribution of Risso's dolphins in Brazilian waters, and could be used as basis to plan conservation actions. [ABSTRACT FROM AUTHOR]

Formation of coastal fog was observed near the southern tip of Nova Scotia when warm, humid air was advected towards the shore over an area of colder water. The sea-surface temperature in the colder and higher salinity patch near the coast was below 14 °C compared to that of the surrounding sea of ≈ 17–18 °C. Measurements of stratification, currents, and the dissipation rate of turbulence kinetic energy (ε) on the Nova Scotia shelf, shelf break, and continental slope revealed the frequent occurrence of shear instability in the pycnocline. The probability of the gradient Richardson number (R i) being less than a critical value of R i cr = 0.25 in the depth range 30–90 m exceeded 50% on the shelf and over the slope, and it was above 75% along the shelf break, while in the open ocean pycnocline the probability of R i < 0.25 is below 5%. The cumulative distribution functions of the dissipation rate in the pycnocline south-east of Nova Scotia followed the Burr probability model with median values from 7.9 × 10 - 9 W kg−1 on the slope to 1.9 × 10 - 8 W kg−1 at the shelf break. The eddy diffusivity ( K N ) estimates follow a generalized extreme value distribution with a high median value of K N = 5.8 × 10 - 5 m2 s−1 at the shelf break. The diffusivity K N depended on Ri in general agreement with the parametrization previously suggested by Lozovatsky and Fernando (Philos Trans R Soc A 371:20120213, 2013) but with a higher level of mixing at R i > 1 . This could be relevant to the nature of turbulence generation near the shelf break by random wave instabilities in the pycnocline at high Richardson and high Reynolds numbers. [ABSTRACT FROM AUTHOR]

Seabirds modify their behavior during the breeding season as they transition from incubation (self-feeding) to chick-rearing (self-feeding + chick provisioning) periods, which affects parental foraging patterns and distribution. However, it is less clear how much flexibility parents have to modulate their behavior when environmental conditions are unusually poor. Using GPS loggers and time depth recorders, we examined the foraging flexibility of common murres (Uria aalge) at Southeast Farallon Island as adjustments were made between breeding phases and across consecutive years (2019 and 2020) with contrasting oceanographic conditions (i.e. prominent marine heatwave in 2019). Foraging trips were longer during the incubation period (2019: 31.7 ± 20.1 h; 2020: 23.5 ± 7.2 h) compared to the chick provisioning period (2019: 12.2 ± 9.9 h; 2020: 7.5 ± 8.3 h). Moreover, parents generally ventured farther from the colony during incubation (2019: 34.7 ± 17.6 km; 2020: 30.1 ± 11.5 km) than when foraging to provision chicks (2019: 22.6 ± 17.1 km; 2020: 14.1 ± 15.0 km) in each year. Nevertheless, overall foraging ranges had a high degree of overlap (> 60%) within breeding phases and across years, suggesting that murres at this colony are constrained by the habitats primarily based on foraging range. Murres dove deeper during incubation compared to chick-rearing in 2020 (36.0 ± 24.4 vs 19.5 ± 15.2 m), but there were no other differences within or across years in diving behavior, suggesting that diving effort was less affected by breeding stage. Interannual differences in foraging behavior only occurred during chick-feeding trips and were likely driven by the prey species present. For example, rockfish were more common in chick diets in 2020, when ocean temperatures were cooler compared to 2019. Despite similarities in trip parameters between years, breeding productivity was much lower in 2019 compared to both long-term averages and the 2020 season, suggesting a potential constraint on murre behavioral flexibility when oceanographic variation occurs. These results emphasize the importance of examining behavior on multiple time scales to gain a better understanding of how predators respond to changes in their environment. • Common murres foraging behavior differs during incubation and chick-rearing phases. • Murres venture further and are out to sea longer during incubation. • Chick-rearing murres display bimodal foraging behavior, with long and short trips. • Overall foraging ranges have high degree of overlap between breeding phases. • Murres at Southeast Farallon Island may be limited in the habitat they can exploit. [ABSTRACT FROM AUTHOR]

The Patagonian slope hosts a variety of waves. We used a state‐of‐the‐art ocean reanalysis to examine waves at the shelf break and in the core of the Malvinas Current (MC) at periods larger than 10 days. Statistics over 25 years indicated three types of signals: in phase signals at specific locations of the shelf break to the south of 47°S; fast propagating signals all along the shelf break (phase speed from 140 to 300 cm/s) at periods between 5 and 110 days; and slower signals in the core of the MC (phase speeds from 10 to 30 cm/s) at 20‐day, 60‐day, and 100‐day periods. The large zonal wind stress variations south of 47°S forced in‐phase along‐slope velocity variations and triggered fast propagating waves at distinct sites corresponding to abrupt changes in the shelf‐break orientation. The shelf‐break waves modulated the intensity of the inshore jet, which varied from 0 to 30 cm/s at 100 m depth, and had spatial and temporal structures and scales consistent with those of observed upwelling events. Slow propagating waves in the core of the MC had along‐slope wavelengths between 450 and 1,200 km and were not forced by the local winds. They were tracked back to the Drake Passage and the Malvinas Escarpment. Plain Language Summary: The sinuous Patagonian slope hosts a variety of waves that are yet poorly documented. We examined the waves in a state‐of‐the‐art ocean model assimilating observations. Strong westerly winds forced fast waves at the shelf break. These waves modulated the intensity of the coastal jet of the Malvinas Current (MC) and the shelf‐break upwelling. Slow waves propagating from the Malvinas Escarpment and the Drake Passage modified the velocities of the MC main jet. Key Points: Velocity signals with phase speeds of 140–300 cm/s at the shelf break and 10–30 cm/s in the core of the Malvinas Current (MC) were identifiedAt the shelf break, wind‐forced fast waves modulated the inner MC jet and possibly contributed to upwellingSlowly propagating waves in the core of the MC came from the Malvinas Escarpment or the Drake Passage [ABSTRACT FROM AUTHOR]

On reefless volcanic islands, insular shelves are thought to have formed essentially by the combined effects of wave erosion and glacio-eustatic sea-level oscillations. Subsidence, however, has also been recognized as having an important role in the development of these morphologies. Yet, few studies have quantified the relative contribution of subsidence to shelf generation and development, particularly to shelf width. A better understanding of this contribution, however, is key to understand the long-term evolution of coasts at volcanic islands, particularly given that subsidence may exacerbate the effects of marine erosion. In this study we assess quantitatively the role of subsidence in shelf development by comparing real cross-shore shelf profiles with modeled profiles using varied rates of subsidence. To achieve this, we used shelf bathymetric profiles from Faial and São Jorge islands in the Azores, which we compared with predictions of a numerical model of coastal erosion that has been calibrated previously against other field data. The first set of model runs was made to calibrate the model by determining the values that produced shelves with break depths, widths, and profile shapes that were similar to those observed. The second set of runs, which served to evaluate the contribution of subsidence to shelf widening, revealed that subsidence may have been responsible for increasing shelf widths by almost 2.5 times relative to shelves formed only by the combined effects of wave erosion and glacio-eustatic oscillations. Modeling shelf formation on the same islands but with increased subsidence rates up to 2.2 mm/yr resulted in shelf profiles up to 19 km wide, a value 3 to 6 times greater than observed on these islands. Our study therefore reinforces the idea that subsidence is a key contributor to the generation of broad insular shelves, given its role in enhancing coastal retreat. Our shelf evolution modeling also suggests that, notwithstanding the crucial role subsidence plays in increasing the width of shelves, on islands subjected to energetic wave regimes (as it happens in the Azores and Hawaii), modification by erosion is important enough to result in shelf morphologies that are not constructional in essence, but rather dominantly erosive surfaces. This study therefore contributes to a better understanding of how insular shelves and submarine terraces form and develop by proving important new quantitative insights of the role of subsidence on the generation of these morphologies. [ABSTRACT FROM AUTHOR]

We studied the behavior of chemical substances in the upper 300 m of the water column across the continental shelf-slope interface in the East China Sea off the Okinawa Trough. The behaviors of iron, inorganic nutrients, and humic-like fluorescent dissolved organic matter were strongly influenced by the extensive water exchange between the East China Sea and the Kuroshio Current across the shelf break and slope via upwelling and frontal processes. We attributed the high humic-like fluorescent intensity at the subsurface of the shelf break and slope regions to the lateral supply of humic-like fluorescent dissolved organic matter from the shelf sediments to the outer shelf region due to the intrusion of shelf water into Kuroshio subsurface water. We found that the behavior of iron at the continental shelf-slope was remarkably different from the conservative mixing of inorganic nutrients and humic-like fluorescent dissolved organic matter. In deep and bottom waters at the shelf-slope, high total iron concentrations, which were closely related to water transmittance, possibly resulted from the swept transport of iron-rich resuspended sediments over the shelf floor from the slope by the invading Kuroshio Intermediate Water close to the bottom. [ABSTRACT FROM AUTHOR]

Euphausiids, or krill, often dominate the biomass of zooplankton communities in high latitude marine ecosystems and are recognized as a key component of food webs. Compared to other ecosystems, however, there is scant information regarding the broad-scale distribution of euphausiids in the Northeast U.S. Shelf Large Marine Ecosystem (NEUS-LME). Using long-term (1977–2011) zooplankton survey data, we examine the drivers of the broad-scale spatial distribution and inter-annual variability in euphausiid abundance throughout the entire NEUS-LME. Our results show strong seasonal patterns in both the abundance and spatial distribution of euphausiids, which were commonly associated with waters exceeding 100 m, the continental shelf break (SB), and warmer and more saline bottom waters. Inter-annual patterns in euphausiid abundance were positively correlated with the Atlantic Multidecadal Oscillation (AMO) and bottom salinity, and inter-annual variation was most conspicuous at the outer continental shelf and SB. Assemblage analyses indicated that Euphausia krohnii , Thysanoessa gregaria , T. longicaudata , and Nematoscelis megalops dominated in waters associated with the outer shelf and SB, while Meganyctiphanes norvegica was more important in the Gulf of Maine. These results improve our understanding of the distribution and abundance of euphausiids and provide important information for effective ecosystem-based fisheries management for the NEUS-LME. [ABSTRACT FROM AUTHOR]

Abstract: Observations collected as part of the Cascadia Amphibious Array (Oregon‐Washington coast) show that ocean surface infragravity (IG) waves (periods from 30 to 250 s) in the Pacific Ocean originate from the coastal zone. With the deepest observations at 1909 m, we identify tidal modulation and a dramatic reduction in energy as IG waves cross the shelf break. Observations are consistent with radiation from an isotropic, nearshore source, and provide quantitative verification linking oceanic IG fluctuations with nearshore motions. Our analysis demonstrates that trapping of IG waves on the shelf break strongly reduces energy radiation into ocean basins. Further, for narrow continental shelves (U.S. West Coast), energy levels past the shelf break depend only weakly on shelf geometry. Consequently, oceanic energy levels can be related to coastal sources by scaling relations predicted by geometric optics, simplifying the effort to estimate the impact of radiated IG‐waves on remote sites (e.g., to estimate seismic noise levels or impact on ice shelves). [ABSTRACT FROM AUTHOR]

Submarine landslides can be tremendous in scale. They are one of the most important processes for global sediment fluxes and tsunami generation. However, studies of prodigious submarine landslides remain insufficient. In this review paper, we compile, summarize, and reanalyze the results of previous studies. Based on this reanalysis, we discover the giant Baiyun−Liwan submarine slide in the Pearl River Mouth Basin, South China Sea. We describe three concurrent pieces of evidence from ~23 Ma to 24 Ma, the Oligocene−Miocene boundary, for this landslide: the shoreward shift of the shelf break in the Baiyun Sag, the slump deposition to the southeast, and the abrupt decrease in the accumulation rate on the lower continental slope. This landslide extends for over 250 km, and the total affected area of the slide is up to ~35,000−40,000 km2. The scale of the landslide is similar to that of the Storegga slide, which has long been considered to be the largest landslide on earth. We suggest that strike−slip movement along the Red River Fault and ridge jump of the South China Sea caused the coeval Baiyun−Liwan submarine slide. The identification of the giant landslide will promote the understanding of not only its associated geohazards but also the steep rise of the Himalayan orogeny and marine engineering. More attention needs to be paid to areas with repeated submarine landslides and offshore installations.

Generation and propagation of internal waves (IWs) in the coastal waters of the extended shelf of the western Bay of Bengal are investigated for late winter by using the Massachusetts Institute of Technology General Circulation Model (MITgcm). The model is forced with astronomical tides and daily winds. Monthly climatological temperature and salinity fields are used as initial conditions. The simulations are compared with time series observations of temperature and currents from acoustic Doppler current profiler (ADCP) and conductivity-temperature-depth (CTD) moored at three locations south of Gopalpur: two at a local depth of 100 m and another at 400-m depth during 19-21 February 2012. The comparison of the spectral estimates for the time series of temperature from the model and observations are in reasonable agreement for the near-tidal frequency waves. The peak of temperature spectra is always found near the shelf break region which steadily lost its intensity over the continental shelf. The calculation of Richardson number reflected the presence of local mixing due to density overturning in the shelf region. To understand further the generation and propagation of internal tides in the region, energy flux and conversion of barotropic-to-baroclinic M tidal energy are examined. The model simulations suggest that the internal tide is generated all along the shelf slope. The energy flux analysis shows that the internal tides propagate to either side of the generation sites. [ABSTRACT FROM AUTHOR]

The migration history of shelf breaks in the stratigraphy of a basin contains significant information about sediment-budget partitioning into the deep water area, which is thus important in predicting the distribution and quality of deepwater reservoirs. Previous studies primarily focused on the sedimentary-dominated shelf breaks (e.g., progradational-type), which are controlled by sediment supply and relative sea-level changes. The location and migration pattern of structure-controlled shelf breaks are comparatively less well documented. The evolutionary history of shelf breaks in the Pearl River Mouth Basin from 30 Ma to present is examined here. Shelf breaks are picked from 280 2-D depositional dip-oriented seismic profiles in the forced regressive systems tracts of 20 3rd-order sequences (SQ 1-20) in four super sequences (SSQ 1-4). Planview distribution maps indicate these shelf breaks can be divided into two groups of different character. Shelf breaks in SSQ 1 (30–23.8 Ma) have migrated progressively and considerably basinward (∼50 km) along with the progradation of shelf-margin deltas, which were propelled by a very strong sediment supply even under the background of relative sea-level rise. They are consequently classified as sedimentary-dominated types. In contrast, shelf breaks in SSQ 2-4 have stayed fairly close (∼20 km) to the boundary between the Panyu Low Uplift and the Baiyun Sag, which is identified as a tectonic hinge zone across which subsidence rate increased abruptly basinward. Shelf breaks were close to the hinge zone even in SQ 11 and 12, in which the depositional shoreline breaks were located ∼80 km further landward. They are classified as structure-controlled types. Our study indicates that through the evolutionary history of the Pearl River Mouth Basin, the locations and migration pattern of the shelf breaks were mainly sediment-supply controlled during 30–23.8 Ma but changed to structure-controlled (i.e., tectonic hinge zone) during 23.8 Ma-Present. [ABSTRACT FROM AUTHOR]