Comparison of trends of iceberg scour marks with iceberg trajectories and evidence of paleocurrent trends on Saglek Bank, northern Labrador Shelf

High-resolution seismic and sidescan sonar surveys on Saglek Bank indicate extensive areas of iceberg-scoured sea bottom and provide data for an analysis of 6075 iceberg scour marks in 537 samples, each of 0.25 km by 2.0 km area.The general trends of iceberg scours, measured on sidescan sonographs, are comparable to iceberg trajectories, which are mostly controlled by currents. On Saglek Bank, iceberg-scour and iceberg-drift directions are generally northwest–southeast.Straight scours predominate on the shelf edge, reflecting the influence of unidirectional oceanic (Labrador) currents. Bank-top scours are commonly curved, reflecting the influence of slower moving water more subject to the effects of rotary tidal currents and storms. This difference in dispersion of scour trends between the bank top and shelf edge is due to the relative strengths of variable tidal and storm-driven currents and unidirectional oceanic currents. Pack-ice forces may also influence iceberg movement.Modern icebergs scour the shelf to about 220 m water depth, locally to 280 m, and can change draft by about 25 m. Scarps in excess of 25 m vertical relief appear to redirect icebergs offslope or along slope.Relict scours were observed in the 220–300 m depth range and were differentiated from recent scours on the basis of greater width, discordant orientation, or advanced degree of degradation. Relict scours near water depths of 220 m are superimposed by modern scours and in shallower water are completely obliterated. Those scours remaining below 220 m show evidence of paleoceanographic conditions, which, in places, are similar to present conditions such as at northeast Saglek Bank. In other places, currents flowed in a different direction from those at present, as indicated by east–west scour trends in Okak Trough. Thus paleoscour directions may be useful in the reconstruction of paleocurrent trends.

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Detection of Objects Buried in the Sea Bottom with the Use of Parametric Echosounder

Archives of Acoustics ◽

10.2478/aoa-2013-0012 ◽

2013 ◽

Vol 38 (1) ◽

pp. 99-104 ◽

Cited By ~ 7

Author(s):

Eugeniusz Kozaczka ◽

Grazyna Grelowska ◽

Sławomir Kozaczka ◽

Wojciech Szymczak

Keyword(s):

Low Frequency ◽

Point Of View ◽

Acoustic Energy ◽

Sidescan Sonar ◽

Main Task ◽

Sound Sources ◽

Sea Bottom ◽

Detection Of Objects ◽

Beam Patterns

Abstract The paper contains results of a in situ research main task of which was to detect objects buried, partially or completely, in the sea bottom. Object detecting technologies employing acoustic wave sources based on nonlinear interaction of elastic waves require application of parametric sound sources. Detection of objects buried in the sea bottom with the use of classic hydroacoustic devices such as the sidescan sonar or multibeam echosounder proves ineffective. Wave frequencies used in such devices are generally larger than tens of kHz. This results in the fact that almost the whole acoustic energy is reflected from the bottom. On the other hand, parametric echosounders radiate waves with low frequency and narrow beam patterns which ensure high spatial resolution and allows to penetrate the sea bottom to depths of the order of tens of meters. This allows to detect objects that can be interesting, among other things, from archaeological or military point of view.

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A globally fragmented and mobile lithosphere on Venus

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2025919118 ◽

2021 ◽

Vol 118 (26) ◽

pp. e2025919118

Author(s):

Paul K. Byrne ◽

Richard C. Ghail ◽

A. M. Celâl Şengör ◽

Peter B. James ◽

Christian Klimczak ◽

...

Keyword(s):

Mantle Convection ◽

Convective Motion ◽

Tectonic Plates ◽

Flow Models ◽

Long Wavelength ◽

Surface Mobility ◽

Pack Ice ◽

Show Evidence ◽

Globally Distributed ◽

Acting In Concert

Venus has been thought to possess a globally continuous lithosphere, in contrast to the mosaic of mobile tectonic plates that characterizes Earth. However, the Venus surface has been extensively deformed, and convection of the underlying mantle, possibly acting in concert with a low-strength lower crust, has been suggested as a source of some surface horizontal strains. The extent of surface mobility on Venus driven by mantle convection, however, and the style and scale of its tectonic expression have been unclear. We report a globally distributed set of crustal blocks in the Venus lowlands that show evidence for having rotated and/or moved laterally relative to one another, akin to jostling pack ice. At least some of this deformation on Venus postdates the emplacement of the locally youngest plains materials. Lithospheric stresses calculated from interior viscous flow models consistent with long-wavelength gravity and topography are sufficient to drive brittle failure in the upper Venus crust in all areas where these blocks are present, confirming that interior convective motion can provide a mechanism for driving deformation at the surface. The limited but widespread lithospheric mobility of Venus, in marked contrast to the tectonic styles indicative of a static lithosphere on Mercury, the Moon, and Mars, may offer parallels to interior–surface coupling on the early Earth, when global heat flux was substantially higher, and the lithosphere generally thinner, than today.

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Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer

Biogeosciences ◽

10.5194/bg-15-7315-2018 ◽

2018 ◽

Vol 15 (23) ◽

pp. 7315-7332 ◽

Cited By ~ 1

Author(s):

Jørgen Bendtsen ◽

Katherine Richardson

Keyword(s):

North Sea ◽

Vertical Mixing ◽

Euphotic Zone ◽

Bottom Layer ◽

Depth Range ◽

Shelf Edge ◽

Nutrient Inputs ◽

New Production ◽

Edge Zone ◽

The North

Abstract. New production, i.e. that driven by allochthonous nutrient inputs, is the only form of primary production that can lead to net increases in organic material and is, therefore, important for understanding energy flow in marine ecosystems. The spatial distribution of new production is generally, however, not well known. Using data collected in July 2016, we analyse the potential for vertical mixing to support new production in the upper layers of the northeastern portion of the North Sea. Relatively large (up to >0.5 mmol N m−2 d−1) nitrate fluxes due to turbulent vertical mixing into the euphotic zone were found at some stations over the shelf edge, while low values (< 0.1 mmol N m−2 d−1) were found in the deeper open area north of the shelf edge. The low vertical mixing rates (dissipation rates of turbulent kinetic energy below 10−8 W kg−1, corresponding to vertical turbulent diffusion coefficients of 10−6–10−5 m2 s−1) implied f ratios of <0.02 in the open waters north of the shelf edge. In the shallow (<50 m) southern and central part of the study area, inorganic nutrients were low and nitrate undetectable, suggesting negligible new production here, despite relatively high concentrations of chlorophyll a being found in the bottom layer. Thus, high rates of new production seem to be concentrated around the shelf-edge zone and in association with localized features exhibiting enhanced vertical mixing. We find that the nutricline depth is significantly deeper at the shelf edge and interference with increased mixing in this deeper depth range can explain the increased diapycnal nitrate fluxes. Overall, this suggests that the shelf-edge zone may be the major nutrient supplier to the euphotic zone in this area during the period of summer stratification.

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KONDISI GEOMORFOLOGI DAN KARAKTERISTIK SEDIMEN DASAR LAUT DI WILAYAH PERAIRAN SEBAGIN UNTUK EVALUASI TAPAK PLTN DI BANGKA SELATAN

Jurnal Pengembangan Energi Nuklir ◽

10.17146/jpen.2015.17.2.2597 ◽

2015 ◽

Vol 17 (2) ◽

pp. 97

Author(s):

Yuliastuti Yuliastuti ◽

Heni Susiati ◽

Yarianto Sugeng Budi Susilo

Keyword(s):

Bottom Sediment ◽

Water Intake ◽

Depth Range ◽

Sediment Characteristics ◽

Single Beam ◽

Sea Bottom ◽

Sea Bed ◽

The Stability ◽

Result Analysis ◽

Echo Sounder

ABSTRAK KONDISI GEOMORFOLOGI DAN KARAKTERISTIK SEDIMEN DASAR LAUT DI WILAYAH PESISIR PERAIRAN SEBAGIN UNTUK EVALUASI TAPAK PLTN DI BANGKA SELATAN. Telah dilakukan penelitian mengenai kondisi geomorfologi dan karakteristik sedimen dasar laut di wilayah perairan sebagian, Bangka Selatan. Informasi geomorfologi dasar laut sangat berguna dalam hal interpretasi struktur-struktur geologi yang berada di dasar laut. Sedangkan informasi karakteristik sedimen dasar laut bermanfaat untuk memberikan gambaran perlapisan batuan dasar laut dalam kaitannya dengan kestabilan tapak PLTN terkait aspek kegempaan dan penentuan posisi water intake. Penelitian ini bertujuan untuk mengevaluasi kondisi geomorfologi dan karakterisasi sedimen dasar laut di perairan Sebagin, Bangka Selatan. Metodologi yang dipakai untuk mengevaluasi kondisi geomorfologi dasar laut adalah Multi Beam Echo Sounder (MBES) dan Single Beam Echo Sounder (SBES). Sedangkan untuk karakterisasi sedimen dasar laut dilakukan dengan pengukuran seismik refleksi resolusi tinggi menggunakan sub bottom profiling (SBP) dan uji sampel sedimen di daerah penelitian. Hasil penelitian menunjukkan bahwa daerah penelitian merupakan perairan dangkal dengan kedalaman 1- 59 m. Profil geomorfologi dasar laut daerah penelitian cenderung tidak beraturan dan berdasarkan interpretasi seismik tidak ditemukan adanya patahan. Hasil analisis sedimen dasar laut menunjukkan bahwa, distribusi lumpur mendominasi daerah perairan calon tapak PLTN. Kata Kunci : geomorfologi, tapak PLTN, sedimen, sub bottom profile. ABSTRACT GEOMORPHOLOGICAL CONDITION AND SEA BOTTOM SEDIMENT CHARACTERISTICS OF SEBAGIN COAST FOR NPP SITE EVALUATION IN SOUTH BANGKA. Study on geomorphological condition and sea bottom sediment in the coastal area of Sebagin, South Bangka Regency, Bangka Belitung Province has been performed. Geomorphological of the seabed was valuable to identify geological structures that exist on the seabed layers. Whereas, sediments seabed characteristics was useful to provide portrait of seabed layer due to the stability of NPP site concerning the seismic aspect and the determination of water intake position. The objective of the study was to evaluate geomorphological condition and sea bed sediment characteristics in the South Bangka sea. Methodology used for evaluating geomorphological of the sea bed were Multi Beam Echo Sounder (MBES) and Single Beam Echo Sounder (SBES). While for sea bottom sediment characteristics, SBP together with sediment sample analysis were used. The result of the study showed that the study area was a shallow water sea with a depth range of 1-59 m. Geomorphological profile of the sea bed tend to be irregular and based on the seismic interpretation, there were no fault exists. Result analysis on the sea bottom sediment showed that clay distribution dominated the study area. Keywords: geomorphology, NPP site, sediment, sub bottom profile.

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The relative importance of shallow and deep shelf spawning habitats for the South African chokka squid (Loligo reynaudii)

ICES Journal of Marine Science ◽

10.1093/icesjms/fss023 ◽

2012 ◽

Vol 69 (4) ◽

pp. 563-571 ◽

Cited By ~ 12

Author(s):

Michael J. Roberts ◽

Nicola J. Downey ◽

Warwick H. Sauer

Keyword(s):

South African ◽

South Coast ◽

Depth Range ◽

Relative Importance ◽

Shelf Edge ◽

The South ◽

The West ◽

Spawning Grounds ◽

Egg Capsules ◽

Spawning Habitats

Abstract Roberts, M. J., Downey, N. J., and Sauer, W. H. 2012. The relative importance of shallow and deep shelf spawning habitats for the South African chokka squid (Loligo reynaudii). – ICES Journal of Marine Science, 69: 563–571. It is well known that the spawning grounds of chokka squid Loligo reynaudii lie along the shallow inshore regions of South Africa's south coast. However, egg masses have been found in deeper water on the Agulhas Bank, and hydroacoustic targets deemed to be large aggregations of spawning squid have been identified. The aim of this study was to investigate the extent, depth range, and importance of deep spawning. Trawl data collected during demersal research surveys between Port Nolloth on the west and Port Alfred on the south coast were examined for egg capsules. No spawning was found on the west coast. Data showed that chokka squid preferred the eastern Agulhas Bank for spawning. Spawning occurred not only inshore but also on the mid-shelf extending to depths of 270 m near the shelf edge. Squid egg biomass markedly decreased beyond 70 m, suggesting delineation between the inshore and offshore spawning grounds. Total egg biomass calculations for depths shallower and deeper than 70 m indicated the coastal area to be strongly favoured, i.e. 82 vs. 18%. These results contest the commonly accepted notion that L. reynaudii is an inshore spawner and redefine the spawning grounds to extend across the shelf.

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West Florida Shelf: sidescan-sonar and sediment data from shelf-edge habitats in the Northeastern Gulf of Mexico

Open-File Report ◽

10.3133/ofr99589 ◽

1999 ◽

Cited By ~ 2

Author(s):

Peter R. Briere ◽

Kathryn M. Scanlon ◽

Christopher T. Gledhill ◽

Christopher C. Koenig ◽

Gary Fitzhugh

Keyword(s):

Gulf Of Mexico ◽

Sidescan Sonar ◽

Shelf Edge ◽

West Florida Shelf ◽

Florida Shelf ◽

Northeastern Gulf Of Mexico ◽

Sediment Data

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Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer

10.5194/egusphere-egu2020-11427 ◽

2020 ◽

Author(s):

Jørgen Bendtsen ◽

Katherine Richardson

Keyword(s):

North Sea ◽

Vertical Mixing ◽

Euphotic Zone ◽

Bottom Layer ◽

Ecosystem Structure ◽

Depth Range ◽

Shelf Edge ◽

New Production ◽

Edge Zone ◽

Turbulence Measurements

The potential for vertical mixing to support new production in the upper layers of the northeastern portion of the North Sea was analysed from observations obtained during the stratified period in July 2016. Five transects across the shelf edge between the relatively shallow central North Sea and the deep Norwegian trench showed a clear frontal structure in hydrography, turbulent mixing, nutrients and chlorophyll a across the shelf edge. Relatively large (up to >0.5&#8201;mmol&#8201;N&#8201;m&#8722;2&#8201;d&#8722;1) nitrate fluxes due to turbulent vertical mixing into the euphotic zone were found at some stations over the shelf edge, while low values (<&#8201;0.1&#8201;mmol&#8201;N&#8201;m&#8722;2&#8201;d&#8722;1) were found in the deeper open area north of the shelf edge. The low vertical mixing rates implied f ratios less than 0.02 in the open waters north of the shelf edge. In the shallow (<50&#8201;m) southern and central part of the study area, inorganic nutrients were low and nitrate undetectable, suggesting negligible new production here, despite relatively high concentrations of chlorophyll&#160;a being found in the bottom layer. Thus, high rates of new production seem to be concentrated around the shelf-edge zone and in association with localized features exhibiting enhanced vertical mixing. We find that the nutricline depth is significantly deeper at the shelf edge and interference with increased mixing in this deeper depth range can explain the increased diapycnal nitrate fluxes. Overall, this suggests that the shelf-edge zone may be the major nutrient supplier to the euphotic zone in this area during the period of summer stratification. Potential impacts on plankton ecosystem structure are discussed.Reference:Bendtsen, J. and Richardson, K.: Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer, Biogeosciences, 15, 7315&#8211;7332, https://doi.org/10.5194/bg-15-7315-2018, 2018.

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The effect of estuarine system on the meiofauna and nematodes in the East Siberian Sea

Scientific Reports ◽

10.1038/s41598-021-98641-1 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Daria A. Portnova ◽

Lesya A. Garlitska ◽

Alexander A. Polukhin

Keyword(s):

Organic Carbon ◽

Total Organic Carbon ◽

Water Temperature ◽

Estuarine System ◽

Depth Range ◽

Sea Bottom ◽

Run Off ◽

East Siberian Sea ◽

Low Diversity ◽

Depth Water

AbstractArctic meiofauna and nematodes were examined at 12 stations in the East Siberian Sea, covering a depth range of 13–59 m and an estuarine-shelf system from the Indigirka and Kolyma rivers to the adjacent shelf. Our data reveal the low diversity of the meiofauna at the East Siberian Sea shelf. The meiobenthos abundance was influenced by river run-off and the sea bottom landscape. The samples comprised a total of 28 families and 72 genera, and the number of genera per station ranged from 15 to 32. The Comesomatidae was the dominant family with genus Sabatieria. Among all factors, depth, water temperature and the total organic carbon appeared to be important variables explaining spatial variations in meiofauna and nematodes abundance. Depth and river run-off were defining in controlling the density of nematodes in the study area.

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Spatio-temporal variability in the distribution pattern of anglerfish species in the Mediterranean Sea

Scientia Marina ◽

10.3989/scimar.04966.11a ◽

2020 ◽

Vol 83 (S1) ◽

pp. 129 ◽

Cited By ~ 2

Author(s):

Elena Barcala ◽

Jose Maria Bellido ◽

Andrea Bellodi ◽

Pierluigi Carbonara ◽

Roberto Carlucci ◽

...

Keyword(s):

Mediterranean Sea ◽

Temporal Distribution ◽

Aegean Sea ◽

Boosted Regression Trees ◽

Trawl Survey ◽

Depth Range ◽

General Terms ◽

Sea Bottom ◽

The Mediterranean ◽

Spatio Temporal

The Mediterranean distributions of two species of anglerfish, the blackbellied anglerfish (Lophius budegassa) and the white anglerfish (Lophius piscatorius), were analysed from trawl survey data (MEDITS project – Spain, France, Italy and Greece) from 2006 to 2015 implementing a Delta model approach with residuals autocovariate boosted regression trees. Sea bottom temperature (SBT), sea bottom salinity (SBS), bathymetry, slope of the seabed and distance to the coast were considered possible predictors. The results show that the locations with a higher presence, abundance and biomass of L. budegassa are those with a depth range between 150 to 300 m, with an SBT range between 17.5 and 18.5°C, and SBS of 37-38 PSU. Similarly, L. piscatorius shows a higher probability of presence, abundance and biomass in location with a bathymetry range of 200-400 m, an SBT of 17.5°C to 18.5°C and an SBS of 36.5 to 37.5. Our results identify preference habitats for the anglerfishes in the Mediterranean Sea such as the Aegean Sea, the Gulf of Lions, south and southeast Spain and the northwestern Ionian Sea. In general terms, these findings enhance our understanding of the differences in the spatio-temporal distribution of these two species, providing useful information that can help their fisheries management and conservation.

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The Cellular Origin in Atheromatous Lesion

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006800x ◽

1970 ◽

Vol 28 ◽

pp. 202-203

Author(s):

T. M. Murad ◽

H. A. I. Newman ◽

K. F. Kern

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Rabbit Aorta ◽

Mixed Population ◽

The Other ◽

Cellular Origin ◽

Ultrastructural Studies ◽

Atherosclerotic Lesions ◽

Show Evidence ◽

Early Lesion

The origin of lipid containing cells in atheromatous lesion has been disputed. Geer in his study on atheromatous lesions of rabbit aorta, suggested that the early lesion is composed mainly of lipid-laden macrophages and the later lesion has a mixed population of macrophages and smooth muscle cells. Parker on the other hand, was able to show evidence that the rabbit lesion is primarily composed of lipid-laden cells of smooth muscle origin. The above studies and many others were done on an intact lesion without any attempt of cellular isolation previous to their ultrastructural studies. Cell isolation procedures have been established for atherosclerotic lesions through collagenase and elastase digestion Therefore this procedure can be utilized to identify the cells involved in rabbit atheroma.

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