4,176 results
Search Results
2. Assessing and Planning for the Impacts of Storms, Flooding and Sea Level Rise on Vulnerable Gulf of Mexico Coastal Communities: A White Paper
- Author
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Lynn Donelson Wright, Robert Weiss, Kiki Caruson, Gary A. Zarillo, Jerry Draayer, Christopher F. D'Elia, and Reid Nichols
- Subjects
geography ,geography.geographical_feature_category ,Continental shelf ,business.industry ,Flooding (psychology) ,Threatened species ,Environmental resource management ,Vulnerability ,Climate change ,Storm surge ,Storm ,business ,Sea level - Abstract
Vulnerable coastal communities in low-lying and flood-prone areas are subject to water-borne health hazards that often linger well after the storm subsides. Risk-informed decision making is crucial, but for the resulting information to be actionable, it must be effectively and promptly communicated to planners, decision makers and emergency managers in readily understood terms and formats. Projections of human and physical factors that affect community vulnerability are essential to support long-range planning for climate change and sea level rise. The states of Florida, Alabama, Mississippi, Louisiana and Texas all have extensive Low Elevation Coastal Zones (LECZ) bordering the Gulf of Mexico where the wide, shallow and low-gradient continental shelf causes pronounced amplification of storm surges. These surges are often accompanied by heavy rains and compound flooding and are superimposed on a background of rising sea level and land subsidence. In some cases, long-range plans require relocation of entire communities. The strategies required to resettle, or protect, threatened or displaced communities and help them adapt to change requires highly informed and careful communication.
- Published
- 2020
3. Northern Hemisphere permafrost extent: Drylands, glaciers and sea floor. Comment to the paper: Obu, J., et al. 2019. Northern Hemisphere permafrost map based on TTOP modeling for 2000–2016 at 1 km2 scale, Earth Science Reviews, 193, 299–316
- Author
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Wojciech Dobiński
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Dry land ,Continental shelf ,Earth science ,Northern Hemisphere ,Glacier ,010502 geochemistry & geophysics ,Permafrost ,01 natural sciences ,General Earth and Planetary Sciences ,Ice sheet ,Scale (map) ,Geology ,Seabed ,0105 earth and related environmental sciences - Abstract
The article published by Obu et al. (2019) estimating the occurrence of permafrost over a Northern Hemisphere. The results published differ from those presented in previous works. This comment highlights the errors introduced in that study, and in a positive note, its cause and proposed solution. The problem remains beyond capabilities of computed models or empirical research. Its solution lies in using the correct categories and land classifications, and clearly defining the medium subjected to freezing. In particular, the correct classification of ice plays a decisive role here. To provide a full picture of the occurrence of permafrost on the Earth surface, three different media must be considered: 1) exposed land, traditionally understood as “dry land”, 2) glaciers and ice sheets together with its bed and 3) the sea floor (continental shelves). The biggest weakness of the published study is not including glaciated areas in their estimations. The authors do not take either a clear position in this crucial matter, despite a radical divergence of opinions has emerged in recent years. Whether and in what way Greenland or other glaciated areas are covered by permafrost remains a pressing issue, as the final determination of the range of the permafrost worldwide depends on it. Until then, any criteria or benchmark used will continue to be ambiguous and open to discussion, maintaining the discrepancy at millions of square kilometers.
- Published
- 2020
4. Widespread erosion and mass failure from the ∼51 Ma Montagnais marine bolide impact off southwestern Nova Scotia, Canada 1This article is one of a series of papers published in this CJES Special Issue on the theme of Mesozoic–Cenozoic geology of the Scotian Basin. 2Earth Sciences Sector Contribution 20120241
- Author
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D. Calvin Campbell and Mark E. Deptuck
- Subjects
Sedimentary depositional environment ,Paleontology ,geography ,geography.geographical_feature_category ,Impact crater ,Continental shelf ,Abyssal plain ,General Earth and Planetary Sciences ,Mesozoic ,Fault scarp ,Cenozoic ,Geology ,Cretaceous - Abstract
The ∼51 Ma Montagnais impact crater on the outer Scotian Shelf is well known, but the potential effects from the impact event on the slope and rise seaward of the crater have, until now, remained poorly understood. Through detailed seismic stratigraphic correlation and ties to available wells, we define a threefold seismic stratigraphic subdivision for Upper Cretaceous to Eocene strata on the shelf and slope, calibrated to the most recent biostratigraphic results. Using this framework, we identify a number of depositional and erosional products that are temporally consistent with a late Ypresian impact event (within the limits of seismic and biostratigraphic resolution). We link a series of prominent failure scarps on the outer shelf and upper slope to a single widespread mass-transport deposit (MTD) on the lower continental slope, rise, and abyssal plain. Failed material amassed in a large debris field referred to here as the “Montagnais MTD”. It covers an area of ∼93 000 km2 and travelled up to 580 km from the impact site where its distal termination onlaps the New England Seamounts, making it one of the largest known debris avalanches on Earth. We interpret these deposits, and the associated pattern of erosion landward of them, as products of widespread margin collapse caused by a combination of ground shaking and ensuing tsunamis triggered by the Montagnais impact event. This study provides insight into the potential effects of outer-shelf marine impact events immediately downslope from impact sites, and their diminished effects with increasing distance along the margin.
- Published
- 2012
5. Geomorphology of a thermo-erosion gully, Bylot Island, Nunavut, Canada1This article is one of a series of papers published in this CJES Special Issue on the theme of Fundamental and applied research on permafrost in Canada.2Polar Continental Shelf Project Contribution 043-11
- Author
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E. Godin and Daniel Fortier
- Subjects
Hydrology ,geography ,geography.geographical_feature_category ,Water flow ,Continental shelf ,Sinkhole ,Erosion ,General Earth and Planetary Sciences ,Glacier ,Drainage ,Permafrost ,Snow ,Geology - Abstract
A thermo-erosion gully has been monitored in the valley of glacier C-79 on Bylot Island since 1999. The main channel of the gully reached 390 m in length a few months after its initiation and grew between 38 and 50 m/year over the following decade, for an overall approximated average of 75 m/year. In 2009, the total gully length and area, including the main and relict channels, were 2500 m and 25 000 m2, respectively. Gullies affect snow accumulation, and therefore ground temperature, local water flow, and drainage. Sinkholes, gully heads, pools, baydzherakhi, tunnels, and collapses were grouped as a function of time since gully formation in that area. Sinkholes and tunnels were formed every year after gully inception, and baydzherakhi were found in 3–10 year old sections of the gully. Stabilization of the gully floor and sides took about a decade.
- Published
- 2012
6. Impact of melting of the Laurentide Ice Sheet on sediments from the upper continental slope off southeastern Canada: evidence from Sm–Nd isotopesThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network
- Author
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Claude Hillaire-Marcel, Ross Stevenson, and X. W. Meng
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geography ,geography.geographical_feature_category ,Proterozoic ,Continental shelf ,Geochemistry ,Last Glacial Maximum ,Isotopic signature ,chemistry.chemical_compound ,Oceanography ,chemistry ,General Earth and Planetary Sciences ,Carbonate ,Glacial period ,Ice sheet ,Polar climate ,Geology - Abstract
We present new Sm–Nd isotope data for sediments from a core located on the continental slope of the St. Pierre Bank of Canada’s east coast. The Nd analyses indicate that the sediments were derived from two principal sources: the North American Shield that yields an average early Proterozoic isotopic signature and a younger Proterozoic signature attributed to Appalachian crustal sources. The Appalachian-sourced sediments predominated during the last glacial maximum (LGM) and were associated with low sedimentation rates (
- Published
- 2008
7. Exploration and economics of the petroleum industry: new ideas, new methods, new developments. Volume 4. [Indexing was entered in the data base for selected papers]
- Published
- 1966
8. Review paper: Instrumentation for marine magnetotelluric and controlled source electromagnetic sounding.
- Author
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Constable, Steven
- Subjects
- *
MAGNETOTELLURICS , *ELECTROMAGNETIC fields , *MAGNETOMETERS , *INDUCTION coils , *CONTINENTAL shelf , *SEAWATER , *OCEAN bottom - Abstract
ABSTRACT We review and describe the electromagnetic transmitters and receivers used to carry out magnetotelluric and controlled source soundings in the marine environment. Academic studies using marine electromagnetic methods started in the 1970s but during the last decade these methods have been used extensively by the offshore hydrocarbon exploration industry. The principal sensors (magnetometers and non-polarizing electrodes) are similar to those used on land but magnetotelluric field strengths are not only much smaller on the deep sea-floor but also fall off more rapidly with increasing frequency. As a result, magnetotelluric signals approach the noise floor of electric field and induction coil sensors (0.1 nV/m and 0.1 pT) at around 1 Hz in typical continental shelf environments. Fluxgate magnetometers have higher noise than induction coils at periods shorter than 500 s but can still be used to collect sea-floor magnetotelluric data down to 40-100 s. Controlled source transmitters using electric dipoles can be towed continuously through the seawater or on the sea-bed, achieving output currents of 1000 A or more, limited by the conductivity of seawater and the power that can be transmitted down the cables used to tow the devices behind a ship. The maximum source-receiver separation achieved in controlled source soundings depends on both the transmitter dipole moment and on the receiver noise floor and is typically around 10 km in continental shelf exploration environments. The position of both receivers and transmitters needs to be navigated using either long baseline or short baseline acoustic ranging, while sea-floor receivers need additional measurements of orientations from compasses and tiltmeters. All equipment has to be packaged to accommodate the high pressure (up to 40 MPa) and corrosive properties of seawater. Usually receiver instruments are self-contained, battery powered and have highly accurate clocks for timekeeping, even when towed on the sea-floor or in the water column behind a transmitter. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
9. Method for Delineating the Formula Limit of the Continental Shelf under the Maximum Area Principle Constraint.
- Author
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Xie, Tian, Dong, Jian, Tang, Lulu, Ma, Mengkai, and Wang, Dong
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CONTINENTAL shelf ,UNITED Nations Convention on the Law of the Sea (1982) ,OPTIMIZATION algorithms ,CONTINENTAL slopes ,AZIMUTH - Abstract
In current practices of determining continental shelf area, the measured sediment thickness data do not effectively reflect the distribution of sediments across the area due to its dispersed nature. This issue raises potential limitations in unknown optimal survey line layout strategies for maximizing the posterior determination area. This paper adopts the binary search algorithm, relies on existing sediment thickness grid data, and uses geodetic formulas to build an ellipsoidal surface grid distance calculation model. This model quickly screens potential areas for the 1% sediment thickness line candidate points set. By constraining the azimuth parameter values during the construction process of the ellipsoidal point feature buffer zones, efficiently select the candidate points set for the 1% sediment thickness line. Furthermore, by elucidating the essential meanings of points on the formula limit and combining the candidate points set of the foot of the continental slope (FOS)+60 n mile line, the polygon minimal convex hull construction technique and a baseline points optimization algorithm with a length threshold are used to efficiently select points on formula limit. Experimental results demonstrate that this method can effectively assist coastal states in optimizing the determination of continental shelf area to the fullest extent under the length threshold requirements of the United Nations Convention on the Law of the Sea. Experiments have proven that compared to the traditional intersection method, the method presented in this paper can help coastal countries delineate a larger continental shelf area. In typical application scenarios, the gain in area can reach 77,278,427 m
2 accounting for 0.51% of the total area. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
10. Validation of the NEMO-ERSEM operational ecosystem model for the North West European Continental Shelf.
- Author
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Edwards, K. P., Barciela, R., and Butenschon, M.
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CONTINENTAL shelf ,HYDRODYNAMICS ,MARINE ecological models ,REMOTE-sensing images ,CHLOROPHYLL ,CLIMATOLOGY - Abstract
This paper details updates to the Met Office's operational coupled hydrodynamicecosystem model from the Medium-Resolution Continental Shelf - POLCOMSERSEM (MRCS-PE) system (Siddorn et al., 2007) to the 7km Atlantic Margin Model NEMO-ERSEM (AMM7-NE) system. We also provide a validation of the ecosystem component of the new operational system. Comparisons have been made between the model variables and available in situ, satellite and climatological data. The AMM7-NE system has also been benchmarked against the MRCS-PE system. The transition to the new AMM7-NE system was successful and it has been running op erationally since March 2011 and has been providing products through MyOcean (http://www.myocean.eu.org) since July 2011. The results presented herein show the AMM7-NE system performs better than the MRCS-PE system with the most improvement in the model nutrient fields. The problem of nutrient accumulation in the MRCSPE system appears to be solved in the new AMM7-NE system with nutrient dynamics improved throughout the domain. Improvements in model chlorophyll are also seen but are more modest. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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11. Modeling the Number of Bids Received for Outer Continental Shelf Leases by Poisson-Type Models (includes associated papers 12296, 12297. 12338, 12369, 12570 and 12710 )
- Author
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Lawrence A. Bruckner and Christopher J. Nachtsheim
- Subjects
geography ,geography.geographical_feature_category ,Continental shelf ,Strategy and Management ,Energy Engineering and Power Technology ,Bidding ,Poisson distribution ,Competition (economics) ,symbols.namesake ,Fuel Technology ,Commerce ,Lease ,Continental margin ,Industrial relations ,symbols ,Econometrics ,Economics - Abstract
Summary Since 1954, the U.S. federal government has held hydrocarbon lease sales for areas on the Outer Continental Shelf (OCS). The U.S. DOE is charged with developing lease sale policies designed to increase competition on the offered tracts, Increased competition has been assumed synonymous with increased number of bids (NOB). To study the influence of alternative bidding systems on the number of bids received, a mixed Poisson-type model has previously been employed. Here we show why this model is not statistically supportable. A truncated model is proposed and is shown to be statistically justified for the number of solo bids over all sales and marginally supported for the number of joint bids on sales before the joint-bidding ban. Introduction Since 1954 the federal government has held hydrocarbon lease sales for areas in the OCS region of the U.S. In a typical sale, from 75 to 300 tracts were offered and 30 to 90% of these tracts received bids. The number of sealed bids received by tracts varied from 0 to 18 with approximately exponentially decaying frequency. The U.S. DOE is charged with developing bidding systems that will increase competition on the offered tracts. At present, if one sale generates a larger average number of bids per tract than another sale, the first sale is considered to have been more competitive. Dougherty and Lohrenz rightly question the efficacy of judging different bidding alternatives "by comparing the average number of bids per lease" alone. Their paper attempts to address this inadequacy by developing a model for the number of bids received considering classes of differing" bidder interest." (A related model has been developed independently by Engelbrecht- Wiggans.) Unfortunately, the Dougherty-Lohrenz model was not properly tested for goodness of fit. In the next section of this paper we statistically evaluate and reject the mixed Poisson model as proposed. Then, in the ensuing sections, a number of departures from the previous approach are considered. Solo and joint bidding patterns are examined separately. Then, certain ambiguities regarding the interpretation of the number of tracts that were offered but received no bids are discussed. The removal of such tracts from consideration led to the formation of a new, truncated Poisson-type model that provided some significant improvements in goodness of fit. Later we examine the effects on the distribution of NOB of the 1975 ban on joint bidding among major oil companies. The Dougherty-Lohrenz Model Dougherty and Lohrenz proposed a Poisson-type model of the following form to fit the number of bids (NOBS) on offered tracts. Pk=F1 k+F2P(N=k/ 2)+F3P(N=k/ 3), ........................ (1) JPT P. 1263^
- Published
- 1983
12. Validation and Application of the Accu-Waves Operational Platform for Wave Forecasts at Ports.
- Author
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Makris, Christos, Papadimitriou, Andreas, Baltikas, Vasilis, Spiliopoulos, Giannis, Kontos, Yiannis, Metallinos, Anastasios, Androulidakis, Yannis, Chondros, Michalis, Klonaris, Georgios, Malliouri, Dimitra, Nagkoulis, Nikolaos, Zissis, Dimitris, Tsoukala, Vasiliki, Karambas, Theophanis, and Memos, Constantine
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BUOYS ,OCEAN circulation ,FORECASTING ,CONTINENTAL shelf ,OCEAN waves ,SEVERE storms - Abstract
This paper presents a recently developed Operational Forecast Platform (OFP) for prevailing sea conditions at very important ports worldwide (Accu-Waves). The OFP produces reliable high-resolution predictions of wave characteristics in and around ocean ports. Its goal is to support safer navigation, predict possible port downtime, assist vessel approaching, enhance management of towing services, and bolster secure ship maneuvering in busy ports around the globe. Accu-Waves OFP is based on integrated, high-resolution wave modelling over the continental shelf and in coastal areas that incorporates data from global- and regional-scale, open-sea wave and ocean circulation forecasts as boundary conditions. The coupling, nesting, calibration, and implementation of the models are reported and discussed in this paper, concerning 50 selected areas near and inside significant port basins. The detailed setup of the Accu-Waves OFP and its sub-system services is also provided regarding three-day forecasts at three-hourly intervals. The validation of the wave forecast system against in situ observations from wave buoys in coastal areas of the USA, Belgium, and Spain, as well as other model predictions by established OFPs, seems very promising, with performance skill scores ranging from adequate to very good. An exceptional case of stormy seas under severe marine weather conditions with very high wave maxima (>10 m) in the port of Algeciras is further discussed, confirming the good performance of the Accu-Waves OFP. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
13. A resilient ice cover over the southernmost Mendeleev Ridge during the late Quaternary.
- Author
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Song, Tengfei, Hillaire‐Marcel, Claude, de Vernal, Anne, and Liu, Yanguang
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ICE shelves ,ICE sheets ,SEDIMENT transport ,SEA level ,CONTINENTAL shelf ,CHRONOSTRATIGRAPHY - Abstract
The presence of a late Quaternary ice sheet/ice shelf over the East Siberian Sea has been proposed in several papers. Here, we further document its duration/resilience based on the sedimentary, bulk mineralogical, and geochemical (organic matter content and its stable isotopic composition, U‐Th series) properties of a core raised from the southernmost Mendeleev Ridge. The chronostratigraphy of the studied core was mainly built from the 230Th excess (230Thxs) distribution and decay downcore. At the core‐top, peaking 230Thxs values during the early MIS 3 and mid‐MIS 1 encompassing an MIS 2 hiatus were observed. As documented in several papers, these peaks suggest seasonally open ice conditions over proximal continental shelves. Below, the interval spanning MIS 4 and possibly MIS 5d records major ice‐rafting events illustrated by overall high coarse‐fraction contents. Underlying MIS 5e, down to MIS 11, the sediment depicts relatively low sand (1.7±2.5 dw%), high clay (33.5±4.7 dw%), and very low organic carbon (0.10±0.06 dw%) contents, and low δ13Corg values (−24.3±0.9‰). This section is interpreted as recording fine sediment transport by deep currents and/or meltwater plumes below a resilient ice cover, only interrupted by a few short‐duration events. These events include (i) detrital carbonate pulses assigned to deglacial events along the NW Laurentide Ice Sheet margin (Termination (T) III), and (ii) intervals with some planktonic foraminifer occurrences, likely relating to their advection from open areas of the Arctic Ocean (MIS 5e, 9 and 11). All Terminations, but TII and the early MIS 3, show peaking Mn/Al values linked to the submergence of Arctic shelves under a rising sea level. We conclude that the resilient ice cover, likely an ice shelf, has been present over the southern Mendeleev Ridge during most of the interval after the Mid‐Pleistocene Transition and was favoured by the low summer insolation of the MIS 14 to 10 interval. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
14. Pleistocene sediment offloading and the global sulfur cycle.
- Author
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Markovic, S., Paytan, A., and Wortmann, U. G.
- Subjects
PLEISTOCENE Epoch ,SULFUR cycle ,SEA level ,QUATERNARY Period ,SEDIMENTS ,CONTINENTAL shelf - Abstract
Quaternary sea level fluctuations have greatly affected the sediment budgets of the continental shelves. Previous studies suggested that this caused a considerable increase in the net loss of shelf sediments. Since sediment accumulation and erosion are closely tied to the formation and re-oxidation of pyrite, we use a high resolution record of sulfur isotope ratios (
34 S=32 S) of marine sulfate to evaluate the implications of the so called "shelf sediment offoading" on the global sulfur cycle. Modeling of our δ34 S record suggests that erosion during sea level lowstands was only partly compensated by increased sedimentation during times of rising sea level and sea level highstands. Furthermore, our data suggests that shelf systems reached a new equilibrium state about 700 kyr ago, which considerably slowed or terminated shelf sediment offoading. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
15. Influence of terrestrial inputs on continental shelf carbon dioxide.
- Author
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Jiang, L.-Q., Cai, W.-J., Wang, Y., and Bauer, J. E.
- Subjects
CONTINENTAL shelf ,CARBON dioxide ,SALT marshes ,ATMOSPHERIC temperature ,COASTS - Abstract
Air-sea carbon dioxide (CO
2 ) fluxes have recently been reported for the US South Atlantic Bight (SAB), a low-latitude shallow continental shelf bordered landward by abundant salt marshes and rivers. In this study, influences of terrestrial inputs on sea surface partial pressure of CO2 (pCO2 ) in the SAB are quantified. After re- moving pCO2 variations due to the annual temperature cycle and air-sea gas ex- change from the in situ pCO2 , temperature and gas exchange corrected (TG-corrected) pCO2 is derived. Contributions from the river, marsh, and continental shelf to the TG-corrected pCO2 are then calculated. Findings show that CO2 contributions from the river [ΔpCO2 (river)] are highest close to the coast and decrease with distance off-shore. For example, ΔpCO2 (river) was up to 30 µatm on the inner shelf but averaged only 0--3 µatm on the outer shelf during January and March 2005. CO2 contributions from salt marshes [ΔpCO2 (marsh)] show similar spatial and seasonal distributions as ΔpCO2 (river), with the magnitude of ΔpCO2 (marsh) being about three times as high as that of ΔpCO2 (river). CO2 contributions from within the shelf [ΔpCO2 (shelf)] are highest among the three components. Compared to ΔpCO2 (river) and ΔpCO2 (marsh), ΔpCO2 (shelf) show the smallest onshore-offshore gradients. Despite large uncertainties, this study clearly demonstrates the importance of terrestrial impacts on coastal ocean CO2 distribution. [ABSTRACT FROM AUTHOR]- Published
- 2012
- Full Text
- View/download PDF
16. Differential responses of seabirds to inter-annual environmental change in the continental shelf and oceanic habitats of southeastern Bering Sea.
- Author
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Yamamoto, T., Kokubun, N., Kikuchi, D. M., Sato, N., Takahashi, A., Will, A., Kitaysky, A. S., and Watanuki, Y.
- Subjects
SEA birds ,GLOBAL environmental change ,CONTINENTAL shelf ,HABITATS - Abstract
Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to the inter-annual change in environmental conditions. Between the study years, winter ice retreated earlier and summer water temperatures were warmer in 2014 compared to those in 2013. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf, but showed a relatively higher use of the shelf break and oceanic basin in the colder year, 2013. The foraging distances from the colony peaked at 250-300 km in 2013 and, bimodally, at 150-250 and 300-350 km in 2014 for RLKI, and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between years in RLKI, but differed in TBMU, showing higher levels of physiological stress incurred by murres during the colder year, 2013. d
13 N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU, while d13 C (a proxy of prey origin) were lower in 2014 than in 2013 in both species, suggesting possible differences in influx of oceanic prey items into foraging areas. These results suggest that the response of ecosystem dynamics to climate variability in the southeast Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those habitats for foraging. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
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17. Real-time quality assurance and quality control for a high frequency radar network.
- Author
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Roarty, Hugh, Updyke, Teresa, Nazzaro, Laura, Smith, Michael, Glenn, Scott, and Schofield, Oscar
- Subjects
QUALITY control ,QUALITY assurance ,MARINE biodiversity ,CONTINENTAL shelf ,OIL spills ,RADAR - Abstract
This paper recommends end to end quality assurance methods and quality control tests for High Frequency Radar Networks. We focus on the network that is operated by the Mid Atlantic Regional Association Coastal Ocean Observing System (MARACOOS). The network currently consists of 38 radars making real-time measurements of the surface currents over the continental shelf for a variety of applications including search and rescue planning, oil spill trajectory modelling and providing a transport context for marine biodiversity observing networks. MARACOOS has been delivering surface current measurements to the United States Coast Guard (USCG) since May 2009. Data quality is important for all applications; however, since the USCG uses this surface current information to plan life-saving missions, delivery of the best quality data is crucial. We have mapped the components of the HF radar data processing chain onto the data levels presented in the NASA Earth Science Reference Handbook and have applied quality assurance and quality control techniques at each data level to achieve the highest quality data. There are approximately 400 High Frequency radars (HFRs) deployed globally and the presented techniques can provide a foundation for data quality checks and standardization of the data collected by the large number of systems operating today. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
18. Formation of Abnormal Gas-Geochemical Fields and Dissolved Gases Transport at the Shallow Northeastern Shelf of Sakhalin Island in Warm Season: Expedition Data and Remote Sensing.
- Author
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Syrbu, Nadezhda, Kholmogorov, Andrey, Stepochkin, Igor, Lobanov, Vyacheslav, and Shkorba, Svetlana
- Subjects
REMOTE sensing ,CONTINENTAL shelf ,ISLANDS ,GASES ,SEASONS - Abstract
Our paper deals with gas-geochemical measurements of CH
4 and CO2 , as well as the first measurements of dissolved H2 and He in the waters of the eastern shelf of Sakhalin Island, obtained during cruise 68 on the R/V Akademik Oparin (OP68) on 12–18 August 2023. The shallow eastern shelf has high concentrations of dissolved methane and helium in the water. The combined anomalies of methane and helium indicate the presence of an ascending deep fluid. The sources of methane in the studied area are the underlying oil- and gas-bearing rocks extending to the coast of the island. The deep faults of the region and the minor discontinuities that accompany them along the eastern coast of Sakhalin Island create a fluid-permeable geological environment both on the shallow shelf and on the coastal part of the island. East Sakhalin current and counter-current influence gases that migrate from lithospheric sources; these currents form a special hydrological regime that ensures high solubility of the gases released and their transfer under the lower boundary of the seasonal pycnocline to the east, where they are involved in the general circulation of the Sea of Okhotsk. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
19. Sedimentary characteristics, lithofacies, and paleogeography of the Middle–Lower Cambrian in the Tarim Basin, NW China.
- Author
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Ji, Tianyu, Yang, Wei, Wu, Xueqiong, Li, Dejiang, Liu, Mancang, Song, Chengpeng, and Chen, Xi
- Subjects
PALEOGEOGRAPHY ,LITHOFACIES ,CONTINENTAL shelf ,SEDIMENTARY facies (Geology) ,FACIES ,DOLOMITE ,SEDIMENTS - Abstract
The Cambrian pre-salt dolomite sequence in the Tarim Basin is a target zone of great strategic significance for hydrocarbon exploration in the basin. Using the results of the interpretation of 3D seismic data from Lunnan and 2D seismic data covering the whole basin, and based on a synthesis of outcrop data, drilling data, well logs, core data, and thin-section data, and the findings from previous studies, this paper studies the characteristics of the facies of the Middle–Lower Cambrian in the platform area in the Tarim Basin, the formation and evolution of platform margins, and the sedimentary characteristics, lithofacies, and paleogeographic characteristics of the Middle–Lower Cambrian series. Based on the types of lithofacies and the seismic facies analysis, the sedimentary facies of the Middle–Lower Cambrian strata can be classified into the five types. From bottom to top, the Middle–Lower Cambrian have experienced several development stages, including the deposition of continental shelf sediments of the Yuertusi Formation, gently sloping non-rimmed platform margin sediments of the Xiaoerbulake Formation, weakly rimmed platform margin sediments of the Wusongger and Shayilike formations, and strongly rimmed platform margin sediments of the Awatage Formation. In each stage, the platform margin shifted further east relative to its location in the previous stage. Based on these results and previous studies, the lithofacies and paleogeography maps of the Middle–Lower Cambrian in the Tarim Basin are modified, and the implications for hydrocarbon exploration in this area are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
20. Halocline water modification and along slope advection at the Laptev Sea continental margin.
- Author
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Bauch, D., Torres-Valdes, S., Polyakov, I., Novikhin, A., Dmitrenko, I., McKay, J., and Mix, A.
- Subjects
CONTINENTAL margins ,OXYGEN isotopes ,CONTINENTAL slopes ,CONTINENTAL shelf ,ADVECTION - Abstract
A general pattern in water mass distribution and potential shelf-basin exchanges is revealed at the Laptev Sea continental slope based on hydrochemical and stable oxygen isotope data from summers 2005-2009. Despite considerable interannual variations, a frontal system can be inferred between shelf, continental slope and central Eurasian Basin waters in the upper 100m of the water column along the continental slope. Net sea-ice melt is consistently found at the continental slope; however the sea-ice meltwater signal is independent from the local retreat of the ice cover and appears to be advected from upwind locations. In addition to the along-slope frontal system at the continental shelf break a strong gradient is identified on the Laptev Sea shelf between 122 and 126° E with an eastward increase of riverine and sea-ice related brine water contents. These waters cross the shelf break at ~140° E and feed the Low Salinity Halocline Water (LSHW, salinity S <33) in the upper 50m of the water column. Extremely high silicate concentrations in Laptev Sea bottom waters may lead to speculation on a link to the local silicate maximum found within the salinity range of ~33 to 34.5, typical for the Lower Halocline Water (LHW) at the continental slope. But brine signatures and nutrient ratios from the central Laptev Sea differ from those at the continental slope. Thus a significant contribution of Laptev Sea bottom waters to the LHW at the continental slope can be excluded. The silicate maximum within the LHW at the continental slope may be formed locally or at the outer Laptev Sea shelf. Similar to the advection of the sea-ice melt signal along the Laptev Sea continental slope the nutrient signal at 50-70m water depth within the LHW might also be fed by advection parallel to the slope. Thus, our analyses suggest that advective processes from upwind locations play a significant role in the halocline formation in the northern Laptev Sea. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
21. On the shelf resonances of the English Channel and Irish Sea.
- Author
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Webb, D. J.
- Subjects
CONTINENTAL shelf ,MATHEMATICAL models of oceanography ,TIDES ,OCEAN circulation - Abstract
The resonances of the English Channel and Irish Sea are investigated using the methods of Webb (2012) together with an Arakawa C-grid model of the region under study. In the semi-diurnal tidal band, the high tides of the Bristol Channel and Gulf of St. Malo are shown to be due to two shelf resonances which strongly couple the two regions. In the diurnal band, the response is complicated by the presence of continental shelf waves. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
22. Modeling the seasonal cycle of the oxygen minimum zone over the continental shelf off Concepción, Chile (36.5° S).
- Author
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Charpentier, J., Mediavilla, D., and Pizarro, O.
- Subjects
MATHEMATICAL models ,OXYGEN ,CONTINENTAL shelf ,HYDROGRAPHY ,PRECIPITATION variability ,TRANSPORT theory - Abstract
We analyze the seasonal dynamics of oxygen concentrations in the southernmost part of the Eastern South Pacific oxygen minimum zone (ESP's OMZ), offshore of Concepcion, Chile (∼ 37° S). We use data from a time series over the continental shelf off Concepcion, as well as other hydrographic data and measurements from moored instruments and ocean gliders to evaluate temporal and spatial variability in this region. We identify two extreme modes (winter and summer) that characterize the seasonal variability. A simple model that account for the main physical and biological processes that influences the oxygen concentration was developed. According to our results, the seasonal variability of the dissolved oxygen in the study region is mainly driven by lateral (advective and diffusive) transport that connect the waters over the shelf with poorly oxygenated water from the slope, which is in turn, advected southward by the Peru-Chile Undercurrent. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
23. The 2007 record of the International Court of Justice
- Author
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Bekker, Pieter H.F.
- Subjects
Paper mills ,Paper industry ,Courts ,Continental shelf ,Sound recordings ,Corporations ,Coasts ,International relations ,Law ,United Nations. International Court of Justice -- International relations - Published
- 2008
24. Bryozoan diversity on a whale bone: an uncommon substrate from the continental shelf off NW Spain
- Author
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Oscar Reverter-Gil and Javier Souto
- Subjects
Colonization ,Original Paper ,010506 paleontology ,geography ,geography.geographical_feature_category ,biology ,Continental shelf ,Whale ,Ecology ,Range (biology) ,Biodiversity ,Aquatic Science ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Baleen ,Habitat ,Escharella ,biology.animal ,Whale fall ,Whale-falls ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Invertebrate - Abstract
Carcasses and bones of whales are interesting yet poorly understood habitats for invertebrates and microbial communities. Nevertheless, bryozoans have never before been reported in this particular habitat at the present day. Here, we present the first study on a bryozoan community colonizing a whale bone from the continental shelf off NW Spain at 128 m depth. Thirty-three species of bryozoans were identified, representing 50% of the known bryozoan diversity from this area and depth range. Despite this high biodiversity, no potential whale-fall specialists were detected: all the species are already known in the area, with several being more frequent in shallower or deeper waters. Our results support the hypothesis that the number of specialist taxa on whale-fall habitats decreases drastically on whale remains at depths of less than 260 m. These results also support the theory that whale-falls can serve as intermediate habitats where no other suitable substrate is present, facilitating habitat colonization. Supplementary Information The online version contains supplementary material available at 10.1007/s12526-021-01189-6.
- Published
- 2021
25. Biogeochemical characterization of the riverine organic matter transferred to the NW Mediterranean Sea.
- Author
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Higueras, M., Kerherve, P., Sanchez-Vidal, A., Calafat, A., Ludwig, W., Verdoit-Jarraya, M., Heussner, S., and Canals, M.
- Subjects
BIOGEOCHEMISTRY ,RIVERINE operations ,ORGANIC compounds ,CONTINENTAL shelf ,HYDRODYNAMICS ,STABLE isotope analysis - Abstract
A large amount of terrestrial organic matter is annually delivered by rivers to the continental shelf, where this material is either buried or transferred to the deep sea by hydrodynamic processes such as storms. The relative amount of terrestrial organic matter in the marine sediments is often determined by analyzing the stable isotopes (δ
13 C and δ15 N) and the C/N ratio of organic matter because the various particulate organic matter (POM) sources have distinct isotopic compositions. With the objective to refine and better interpret POM sources in the marine environment, we have monthly characterized terrestrial POM delivered by eight rivers discharging to the NW Mediterranean Sea: Rhone, Herault, Orb, Aude, Têt, Fluvià, Ter and Tordera rivers. These rivers were simultaneously sampled from November 2008 to December 2009 and the concentrations of total suspended matter (TSM), particulate organic carbon (POC) and nitrogen (PN), as well as their stable isotopic ratios (δ13 C and δ15 N) were determined. During the survey, three rainstorm events with winds coming from the E-NE and the S-SE impacted the NW Mediterranean. Depending on the direction of incoming winds, the fluvial response (amount of water discharge and TSM) was different. Rivers draining the Alps (Rhône River) and Central Massif (Hérault, Orb, and Aude rivers) were mostly impacted by rainstorms associated with winds coming from the S-SE, while rivers draining the Pyrenees (Têt, Fluvià, and Ter rivers) and the Montseny Massif (Tordera River) were impacted by rainstorms associated with winds coming from the E-NE. In addition, the spatial evolution of water discharges shows different hydro-logical regime of the Rhone River, with relatively constant and high water stages and TSM concentrations when compared to coastal rivers, characterized by long periods of low water stages. TSM concentrations are positively correlated to water discharges (high water flows resuspended riverbed sediments) but show an inverse relationship with POC and PN relative contents (mostly due to dilution and by low availability of light in river waters during flood events). TSM in most of the coastal rivers have in average 2.5-3 times higher POC and PN mean contents than the Rhone River (8.5% and 1.5%, respectively for coastal rivers against 3.6% and 0.5%, respectively for the Rhône River). This discrepancy may be caused by the long drought periods in small coastal Mediterranean watersheds that enhance the eutrophication in studied coastal rivers. The δ13 C ratios of organic matter reflect also this discrepancy between high and low water stages with values ranging from -33.2‰ to -24.5‰. The enriched C values (-26.3±0.4‰ for the Rhône River and -26.9±1.2‰ for coastal rivers), measured during high water stages, express mostly a mixture of terrestrial source (plant remains and soils) whereas depleted13 C values (~ -30‰) associated with low water stages exhibit a source with predominant freshwater algae. The high δ15 N mean values (> 8‰) found in Tet, Ter and Tordera rivers underline the importance of denitrification processes as a consequence of the eutrophication and anthropogenic impact. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
26. "Air-sea exchanges of CO2 in world's coastal seas".
- Author
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Chen, C.-T. A., Huang, T.-H., Chen, Y.-C., Bai, Y., He, X., and Kang, Y.
- Subjects
OCEAN-atmosphere interaction ,TERRITORIAL waters ,CONTINENTAL shelf ,SALINITY ,ESTUARIES ,CARBON dioxide in water ,BIOGEOCHEMISTRY ,WATER temperature - Abstract
The air-sea exchanges of CO
2 in the world's 165 estuaries and 87 continental shelves are evaluated. Generally and in all seasons, upper estuaries with salinities of less than two are strong sources of CO2 (39±56 mol Cm-2 yr-1 , negative flux indicates that the water is losing CO2 to the atmosphere); mid-estuaries with salinities of between 2 and 25 are moderate sources (17.5±34 mol Cm-2 yr-1 ) and lower estuaries with salinities of more than 25 are weak sources (8.4±14 mol Cm-2 yr-1 ). With respect to latitude, estuaries between 23.5 and 50 °N have the largest flux per unit area (63±101 mmol Cm-2 d-1 ); these are followed by mid-latitude estuaries (23.5- 0°S: 44±29 mmol Cm-2 d-1 ; 0-23.5 °N: 39±55 mmol Cm-2 d-1 ), and then regions north of 50°N (36±91 mmol Cm-2 d-1 ). Estuaries south of 50°S have the smallest flux per unit area (9.5±12 mol Cm-2 d-1 ). Mixing with low-pCO2 shelf waters, water temperature, residence time and the complexity of the biogeochemistry are major factors that govern the pCO2 in estuaries but wind speed, seldom discussed, is critical to controlling the air-water exchanges of CO2 . The total annual release of CO2 from the world's estuaries is now estimated to be 0.10 PgC yr-1 , which is much lower than published values mainly because of the contribution of a considerable amount of heretofore unpublished or new data from Asia and the Arctic. The Asian data, although indicating high in pCO2 , are low in sea-to-air fluxes because the wind speeds are lower than previously determined values, which rely heavily on data from Europe and North America, where pCO2 is lower but wind speeds are much higher, such that the CO2 fluxes are higher than in Asia. Newly emerged CO2 flux data in the Arctic reveal that estuaries there mostly absorb, rather than release CO2 . Most continental shelves, and especially those at high latitude, are under-saturated in terms of CO2 and absorb CO2 from the atmosphere in all seasons. Shelves between 0° and 23.5°S are on average a weak source and have a small flux per unit area of CO2 to the atmosphere. Water temperature, the spreading of river plumes, upwelling, and biological production seem to be the main factors in determining pCO2 in the shelves. Wind speed, again, is critical because at high latitudes, the winds tend to be strong. Since the surface water pCO2 values are low, the air-to-sea fluxes are high in regions above 50°N and below 50°S. At low latitudes, the winds tend to be weak, so the sea-to-air CO2 flux is small. Overall, the world's continental shelves absorb 0.4 PgC yr-1 from the atmosphere. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
27. Trace metal/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions.
- Author
-
Groeneveld, J. and Filipsson, H. L.
- Subjects
TRACE metals ,FORAMINIFERA ,HYPOXIA (Water) ,CONTINENTAL shelf ,AQUATIC habitats ,COASTS ,GLOBAL warming ,EUTROPHICATION - Abstract
Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing global warming and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g. stable isotopes and trace metal/Ca ratios, which are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are completely different or as conditions change a-typical compared to the open-ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW-Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected it can be excluded that any diagenetic coatings have affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values from the literature but display much larger variation than would be expected from the annual temperature change of less than 2°C. An additional impact of the difference in the carbonate ion saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios on Globobulimina turgida potentially record variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens which lived deeper in the sediment than those that lived near the surface. Globobulimina turgida samples from the lower oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations but care needs to be taken to constrain the carbonate system. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
28. Oceanic controls on the primary production of the northwest European continental shelf under recent past and potential future conditions.
- Author
-
Holt, J., Butenschön, M., Wakelin, S. L., Artioli, Y., and Allen, J. I.
- Subjects
CONTINENTAL shelf ,OCEAN-atmosphere interaction ,OCEAN circulation ,ATMOSPHERIC models ,ATMOSPHERIC chemistry ,PERTURBATION theory ,EXPERIMENTS - Abstract
In this paper we clearly demonstrate that changes in oceanic nutrients are a first order factor in determining changes in the primary production of the northwest European continental shelf on time scales of 5-10 yr. We present a series of coupled hydrodynamic ecosystem modelling simulations, using the POLCOMS-ERSEM system. These are forced by both re-analysis data and a coupled ocean-atmosphere general circulation model (OA-GCM) representative of possible conditions in 2080-2100 under an SRES A1B emissions scenario, along with the corresponding present day control. The OA-GCM forced simulations show a substantial reduction in surface nutrients in the open-ocean regions of the model domain, comparing future and present day time-slices. This arises from a large increase in oceanic stratification. Tracer transport experiments identify a substantial fraction of on-shelf water originates from the open-ocean region in the south of the domain, where this increase is largest, and indeed the on-shelf nutrient and primary production are reduced as this water is transported on shelf. This relationship is confirmed quantitatively by comparing changes in winter nitrate with total annual nitrate uptake. The reduction in primary production by the reduced nutrient transport is mitigated by on-shelf processes relating to temperature, stratification (length of growing season) and recycling. Regions less exposed to ocean-shelf exchange in this model (Celtic Sea, Irish Sea, English Channel, and southern North Sea) show a modest increase in primary production (of 5-10 %) compared with a decrease of 0-20% in the outer shelf, central and northern North Sea. These findings are backed up by a boundary condition perturbation experiment and a simple mixing model. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
29. Metazoan zooplankton in the Bay of Biscay: a 16-year record of individual sizes and abundances obtained using the ZooScan and ZooCAM imaging systems.
- Author
-
Grandremy, Nina, Bourriau, Paul, Daché, Edwin, Danielou, Marie-Madeleine, Doray, Mathieu, Dupuy, Christine, Forest, Bertrand, Jalabert, Laetitia, Huret, Martin, Le Mestre, Sophie, Nowaczyk, Antoine, Petitgas, Pierre, Pineau, Philippe, Rouxel, Justin, Tardivel, Morgan, and Romagnan, Jean-Baptiste
- Subjects
IMAGING systems ,ZOOPLANKTON ,WEB-based user interfaces ,OCEAN bottom ,CONTINENTAL shelf ,METADATA - Abstract
This paper presents two metazoan zooplankton datasets obtained by imaging samples collected on the Bay of Biscay continental shelf in spring during the PELGAS (PELagique GAScogne) integrated surveys over the 2004–2019 period. The samples were collected at night with a 200 µm mesh-size WP2 net fitted with a Hydrobios (back-run stop) mechanical flowmeter and hauled vertically from the sea floor to the surface, with the maximum depth set at 100 m when the bathymetry was deeper than this. The first dataset originates from samples collected from 2004 to 2016 and imaged on land with the ZooScan and is composed of 1 153 507 imaged and measured objects. The second dataset originates from samples collected from 2016 to 2019 and imaged onboard the R/V Thalassa with the ZooCAM and is composed of 702 111 imaged and measured objects. The imaged objects are composed of zooplankton individuals, zooplankton pieces, non-living particles and imaging artefacts ranging from 300 µm to 3.39 mm in equivalent spherical diameter which were individually imaged, measured and identified. Each imaged object is geolocated and associated with a station, a survey, a year and other metadata. Each object is described by a set of morphological and grey-level-based features (8 bit encoding, 0 = black, 255 = white), including size, that were automatically extracted from each individual image. Each object was taxonomically identified using the web-based application Ecotaxa with built-in random-forest and CNN-based semi-automatic sorting tools, which was followed by expert validation or correction. The objects were sorted into 172 taxonomic and morphological groups. Each dataset features a table combining metadata and data at individual-object granularity from which one can easily derive quantitative population and community descriptors such as abundances, mean sizes, biovolumes, biomasses and size structure. Each object's individual image is provided along with the data. These two datasets can be used in combination for ecological studies, as the two instruments are interoperable, or they can be used as training sets for ZooScan and ZooCAM users. The data presented here are available at the SEANOE dataportal: 10.17882/94052 (ZooScan dataset, Grandremy et al., 2023c) and 10.17882/94040 (ZooCAM dataset, Grandremy et al., 2023d). [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
30. Geohazard features of the Tyrrhenian Calabria.
- Author
-
Casalbore, Daniele, Conforti, Alessandro, Budillon, Francesca, Martorelli, Eleonora, Morelli, Eleonora, Pierdomenico, Martina, Bosman, Alessandro, De Falco, Giovanni, Di Martino, Gabriella, Falese, Francesco Giseppe, Innangi, Sara, Tonielli, Renato, Adami, Chiara, Foderà, Isabella, Lai, Erika, Lodi, Mariangela Diana, Presti, Valeria Lo, Marsella, Ennio, Montanaro, Cristian, and Sposato, Andrea
- Subjects
OCEANOGRAPHIC maps ,MARINE debris ,CONTINENTAL shelf ,CONTINENTAL margins ,MAP collections ,LANDSLIDES - Abstract
This paper accompanies the Maps of Geohazard features of the Cilento and the Calabro- Tyrrhenian continental margin in the southern Tyrrhenian Sea (Italy). The main geohazardrelated features were derived from extensive seafloor mapping through the collection of high-resolution multibeam data acquired during several oceanographic cruises. They encompass many fluids seepage features, fault scarps, landslides scars, gullies, channels, and canyons. Hazards related to coastal landslides and shelf-indenting canyons are very high in these sectors (especially in southern Calabria) due to active seismicity coupled with rapid uplift, high sedimentation rates and narrow or totally absent continental shelf, thus promoting a direct connection between steep slopes and coastal areas. In this setting, masswasting features can directly impact coastal or submarine infrastructures or indirectly create local tsunami waves, as observed in historical times. Moreover, this physiographic setting of the margin facilitates the transfer of marine litter toward deep-sea areas. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. Geohazard features of the Aeolian Island slopes and the North-Eastern Sicily offshore.
- Author
-
Gamberi, Fabiano, Casalbore, Daniele, Marani, Michael, Rovere, Marzia, Bosman, Alessandro, Calarco, Marilena, Valle, Giacomo Dalla, Leidi, Elisa, Martorelli, Eleonora, Mercorella, Alessandra, Pierdomenico, Martina, Romagnoli, Claudia, Adami, Chiara, Falese, Francesco Giuseppe, Fascetti, Andrè, Ferrante, Valentina, Ingrassia, Michela, Lai, Erika, Montanaro, Cristian, and Sposato, Andrea
- Subjects
OCEANOGRAPHIC maps ,CONTINENTAL shelf ,LANDSLIDES ,CANYONS ,SEAMOUNTS - Abstract
The MaGIC project (Marine Geohazard along the Italian Coasts) had the aim of mapping the geohazard in the Italian seas and resulted in the production of numerous maps covering parts of the Italian Seas. In this paper, we present the maps: 'The submerged portions of the Aeolian volcanic islands and the north-eastern Sicilian margin', located in the south-eastern Tyrrhenian Sea. Both areas are affected by active geological processes, which represent important geohazards elements. Inthe submarine parts of the Stromboli volcanoremobilization of volcaniclastic deposits occur along the Sciara del Fuoco, where small-scale instabilities may represent a source of geohazard. Hydrothermal activity occurs on Enarete and Enaretino conical seamounts. The north-eastern Sicilian margin has a narrow continental shelf. Numerous canyon heads indent the shelf and, sometimes, reach close to the coast. Canyons have often a retrogradational trend and further eventual landward shift through sliding can iendangeri coastal or offshore infrastructures. Many of the canyons connect with leveed channels with widespread sediment instability. In the Gioia Basin, some of the channels connect to form the Stromboli slope Valley. Volcanic unrest or local and regional earthquakes are proven to have caused submarine landslides and tsunamis. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
32. Chelidonichthys lucerna (Linnaeus, 1758) Population Structure in the Northeast Atlantic Inferred from Landmark-Based Body Morphometry.
- Author
-
Ferreira, Inês, Schroeder, Rafael, Mugerza, Estanis, Oyarzabal, Iñaki, McCarthy, Ian D., and Correia, Alberto T.
- Subjects
PHENOTYPIC plasticity ,FISH morphology ,MORPHOMETRICS ,GEOGRAPHICAL distribution of fishes ,CONTINENTAL shelf ,FISH populations - Abstract
Simple Summary: This is the first study to investigate the spatial distribution and population structure of the tub gurnard (Chelidonichthys lucerna) in different regions of the northeast Atlantic. To analyze fish body shape, a morphometry-based method, which helps identify variations in fish body shape that may exist due to genetic factors or environmental adaptability, was used. This study relied on C. lucerna individuals captured in the following three fishing areas: Conwy Bay (United Kingdom), Biscay Bay (Spain) and Matosinhos (Portugal). The findings indicate the existence of significant regional differences in fish bodies, thus highlighting the existence of distinct fish populations in the three regions. Results also suggest that the Spanish and British populations may inhabit similar habitats, as some similarities in body shape were found. To confirm these findings, we recommend future research using a holistic approach with alternative and complimentary stock assessment tools. The study of geometric morphometrics among stocks has proven to be a valuable tool in delineating fish spatial distributions and discriminating distinct population units. Variations in fish body morphology can be linked to genetic factors or to phenotypic adaptability in response to environmental variables. The tub gurnard (Chelidonichthys lucerna) is a demersal species that usually lives in the bottom of the continental shelf, being widely distributed along the northeast Atlantic, Mediterranean and Black seas. Worldwide interest in the species has increased since 2006, when ICES recognized its potential for commercial exploitation. However, despite its broad geographic occurrence, to date, research on C. lucerna population structure at large spatial scales is still lacking. In this paper, body geometric morphometrics, using a landmark-based truss network, was applied in order to discriminate C. lucerna populations caught in three different fishery grounds areas along the northeast Atlantic: Conwy Bay (United Kingdom), Biscay Bay (Spain) and Matosinhos (Portugal). The results obtained in this study revealed a high overall relocation success (95%) of samples to their original locations, thus demonstrating the existence of significant regional differences and indicating that we are dealing with different fish population units. Moreover, the data revealed a partial overlap between individuals from Spain and United Kingdom, suggesting that in geographically distant areas these populations may inhabit similar environments. However, to corroborate these findings, future works using a holistic approach with alternative and complimentary stock assessment tools (e.g., genetic and phenotypic natural tags) are highly recommended. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. An hypoxia-tolerant flatfish: consequences of sustained stress on the slender sole Lyopsetta exilis (Pleuronectidae) in the context of a changing ocean
- Author
-
Verena Tunnicliffe, Nicole Soderberg, Francis Juanes, Ryan Gasbarro, Jackson W. F. Chu, and Jessica Qualley
- Subjects
0106 biological sciences ,Saanich Inlet ,Climate Change ,NE Pacific Ocean ,Population ,Population Dynamics ,population change ,Flounder ,growth response ,Aquatic Science ,010603 evolutionary biology ,01 natural sciences ,Otolithic Membrane ,Stress, Physiological ,Regular Paper ,Animals ,Body Size ,14. Life underwater ,Sex Ratio ,education ,Hypoxia ,Planktivore ,oxygen stress ,Ecology, Evolution, Behavior and Systematics ,Ecosystem ,geography ,education.field_of_study ,geography.geographical_feature_category ,Pacific Ocean ,biology ,British Columbia ,Continental shelf ,010604 marine biology & hydrobiology ,fungi ,Regular Papers ,Hypoxia (environmental) ,Water ,Ichthyoplankton ,biology.organism_classification ,Oxygen tension ,Oxygen ,Oceanography ,otoliths ,Groundfish ,Slender sole - Abstract
Slender sole Lyopsetta exilis is an abundant groundfish on the continental shelf and inner waters of British Columbia, Canada, where it reaches a maximum standard length of 44 cm. Benthic image surveys coupled with oxygen measurements in Saanich Inlet document a dense population in bottom conditions near anoxia (0.03 ml l−1 oxygen) where diel migrating zooplankton intersect the bottom; we confirm this species is a planktivore, which limits its depth range to the base of the migration layer. In a comparison with slender sole from a nearby well‐oxygenated habitat, several probable effects of living in severe hypoxia emerge: both sexes are significantly smaller in Saanich and the sex ratio is male‐skewed. Otoliths from the Saanich fish were difficult to read due to many checks, but both sexes were smaller at age with the largest female (20 cm) from the hypoxia zone registering 17 years. Hypoxia appears to have a direct consequence on growth despite good food supply in this productive basin. Hyperventilation, a low metabolic rate and a very low critical oxygen tension help this fish regulate oxygen uptake in severely hypoxic conditions; it will be particularly resilient as the incidence of hypoxia increases on the continental shelf. Data from small‐mesh bottom‐trawl surveys over four decades reveal an increase in mean annual catch per unit effort in southern regions of the province, including the outer shelf and the Strait of Georgia. The California Cooperative Oceanic Fisheries Investigations (CalCOFI) ichthyoplankton database records a general decline in fish larvae on the Oregon–California shelf since 1990, but slender sole larvae are increasing there, as they are in the Strait of Georgia. We project that the slender sole will gain relative benefits in the future warming, deoxygenated northeast Pacific Ocean.
- Published
- 2019
34. THE CONSTITUTIONAL POSITION OF CONTINENTAL SHELF IN MALAYSIA: THE CASE OF THE MALAY STATES.
- Author
-
Fauzi Wan Husain, Wan Ahmad
- Subjects
CONTINENTAL shelf ,TERRITORIAL waters ,PETROLEUM production ,LOCAL government ,SOVEREIGNTY ,RIGHTS - Abstract
The Malay states remain sovereign from the pre-Federation of Malaya in 1957 until today. They acquired external sovereignty through international recognition via membership of Malaya in the United Nations. International law recognises Malaysia's continental shelf, a federation comprising a few coastal states under UNCLOS 1982. A local issue close to this subject is the Malay states’ rights in the Federation of Malaysia over petroleum production within the continental shelf adjacent to their territorial waters. Hence, this paper examines a Malay state's rights over Malaysia's continental shelf. This study is a qualitative legal analysis using a case study design promoting the method of watanic jurisprudence. Therefore, the Federal Constitution, UNCLOS 1982, and various statutes are analysed to answer many related issues beforehand. This paper has found that the territorial waters of the Malay states cannot be limited to three nautical miles from the low tide line in pursuance of the Territorial Sea Act 2012 without strict compliance with Article 2 of the Federal Constitution. The legitimacy of the territorial limits of the Malay states' waters is essential as it determines their rights to the continental shelf and its petroleum production. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
35. A 3D numerical diagnostic simulation for the general circulation in the Gulf of Lion (France)
- Author
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Nguyen, Kim Dan, Araki, H., editor, Ehlers, J., editor, Hepp, K., editor, Kippenhahn, R., editor, Ruelle, D., editor, Wedenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Beiglböck, W., editor, and Morton, K. W., editor
- Published
- 1990
- Full Text
- View/download PDF
36. Recent Papers on the Coast of England and Wales
- Author
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J. A. Steers
- Subjects
Shore ,geography ,geography.geographical_feature_category ,Continental shelf ,Geography, Planning and Development ,Interglacial ,Erosion ,Cliff ,Flandrian interglacial ,Glacial period ,Archaeology ,Earth-Surface Processes ,Coastal erosion - Abstract
A considerable amount of interest has been taken in the coast and adjacent sea-floor of Great Britain s c the w r. It seems therefore worthwhile to call attention to papers concerned more particularly with the geographical and geological aspects of coastal morphology, which are scattered through very different types of journals, and so may easily escape the notice of those for whom they are intended. In our own Journal Miss M. A. Arber gave an account of the cliff profiles in Devon and Cornwall,1 and thus extended the observa? tions made known by her father in fThe Coast Scenery of North Devon' (1911). Recently W. G. V. Balchin, continuing his work on Cornwall has given us a paper on the high level surfaces and their relation to the coast of North Devon. J. Challinor added a chapter to his earlier work on the Cardigan coast in the form of a note on convex erosion slopes in North Cardiganshire,2 and E. H. Brown 3 has analysed comprehensively the erosion surfaces of the same area. These three papers are however only incidentally concerned with the coast. C. A. Cotton 4 discusses our south-western coasts, and thinks the morvan theory, slightly modified, explains their structure better than the fault theory outlined by Suess. He regards the English and St. George's Channels as old features. The deepening of the valleys, later drowned by the Flandrian transgression, took place in times of glaciation. He thinks the tempo of coastal erosion has been slow owing to the great width of the continental shelf. Thus shoreline details survive from an interglacial age. His explanation of the bevelled form of some of the cliffs depends on two cycles of erosion, and so differs from Miss Arber who regards the distribution of bevelled cliffs as being controlled by structure, especially jointing. Other differences of opinion arise over the rate of cliff retreat in relation to valley truncation and the preservation of raised beaches.5 Cotton also alludes to The Needles of the Isle of Wight 6 and regards them as the surviving remnants of a plunging cliff which has been subjected to lateral erosion by the sea. Cotton's treatment of these two problems is theoretical, and scarcely takes local details sufficiently into consideration.
- Published
- 1953
37. Exceptional dense water formation on the Adriatic shelf in the winter of 2012.
- Author
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Mihanović, H., Vilibić, I., Carniel, S., Tudor, M., Russo, A., Bergamasco, A., Bubić, N., Ljubešić, Z., Viličić, D., Boldrin, A., Malačič, V., Celio, M., Comici, C., and Raicich, F.
- Subjects
CONTINENTAL shelf ,GEOLOGICAL basins ,CLIMATE change ,MERIDIONAL overturning circulation ,WATER masses - Abstract
We document dense water formation (DWF) throughout the Adriatic shelf and coastal area in January/February 2012, resulting in record-breaking densities observed during and after the event. The unprecedented dense water generation was preconditioned by a dry and warm year which resulted in a significant reduction of coastal freshwaters, superimposed on a long-term basin-wide salinity increase. The final event that triggered the DWF was an extended period of cold weather with strong and severe winds. Record-breaking potential density anomalies (above 30 kgm
-3 ) were measured at several DWF sites. Accumulated surface net heat and water losses in some coastal regions exceeded 1.5GJm-2 and 250 kgm-2 over 21 days, respectively. Excessiveness, importance of shelf-type DWF, effects on the thermohaline circulation and deep aquatic systems, and connection with climate change are discussed. [ABSTRACT FROM AUTHOR]- Published
- 2012
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38. Sea Country: Plurality and knowledge of saltwater territories in Indigenous Australian contexts.
- Author
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Kearney, Amanda, O'Leary, Michael, and Platten, Spencer
- Subjects
INDIGENOUS Australians ,HUMAN geography ,INDIGENOUS peoples ,SALINE waters ,OCEAN bottom ,CONTINENTAL shelf ,ORAL tradition - Abstract
There are distinct bodies of cultural knowledge attached to the sea. In this paper we orient the focus towards the nature and extent of cultural framings of sea territories, as inclusive of submerged landscapes, for Indigenous maritime peoples in northern Australia. This approach is distinguished by a pluralist methodology and reorients the primal focus of a human geography and broader geographical scholarship concerning submerged landscapes to begin with an Indigenous perspective. Engaging ethnographic accounts of Indigenous Australian knowledges of Sea Country, as inclusive of ancient pre‐inundation landscapes that lie out‐of‐sight on Australia's continental shelves, highlights the potential for a more expansive vision of human connections to the past and present continental landmass of Australia. Indigenous oral traditions, Dreaming Ancestor narratives and songlines provide extensive detail to assist in understanding these parts of the greater Australian landmass and in this paper are brought into relation with recent sea floor mapping efforts which operate to draw back the water and reveal commensurable geographies upon which to envision possibilities for socialised realms of human emplacement. Both bodies of knowledge generate information of submerged landscapes that call for an expansion of thinking on where the land ends and the sea begins and how submerged terrestrial landscapes are understood across cultures as part of human geography. The approach outlined here calls for a habit of bringing principled systems of understanding to stand together as part of an explanatory schema for a world populated by and yet differentially known by people. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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39. Canada's maritime frontier: the science legacy of Canada's extended continental shelf mapping for UNCLOS.
- Author
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Mosher, David C., Dickson, Mary-Lynn, Shimeld, John, Jackson, H. Ruth, Oakey, Gordon N., Boggild, Kai, Campbell, D. Calvin, Travaglini, Paola, Rainey, Walta-Anne, Murphy, Alain, Dehler, Sonya, and Ells, John
- Subjects
GEOMORPHOLOGY ,CONTINENTAL shelf ,UNITED Nations Convention on the Law of the Sea (1982) ,GEOSTROPHIC currents ,SUBMARINE fans ,CONTINENTAL slopes ,CONTINENTAL margins - Abstract
Canada ratified the United Nations Convention on the Law of the Sea (UNCLOS) in 2003. With that ratification is an obligation to submit data and information to the U.N. pertaining to the limits of the country's extended continental shelf (ECS); the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of Canadian scientists, managers, and legal experts that included representation from three Federal Departments (Natural Resources Canada, Fisheries and Oceans Canada, and Global Affairs Canada) with additional support from other departments, spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada's seaward most maritime limit. The submission has the potential to provide Canada with 2.4 million km
2 of additional submarine landmass in the Atlantic and the Arctic oceans over which Canada exercises sovereign rights for the purpose of exploring and exploiting its natural resources. Specific information such as the tectonic framework of the continental margin, the geomorphology of the margin and in particular the continental slope, the geologic nature of adjoined ridges, rises, and plateaux, and sediment thickness within adjacent basins are examples of fundamental pieces of geoscientific information needed to substantiate Canada's outermost maritime limits. This paper highlights a number of segments of Canada's continental margins to showcase this scientific evidence and how it is applied in the UNCLOS context. In doing so, the paper demonstrates the geologic complexity of Canada's margins as illustrated in scientific publications that have resulted from these new data collections, while at the same time presenting new scientific evidence and interpretations. This collection of data and information provides a wealth of new knowledge in Canada's offshore regions. The massive data compilation in the Atlantic led to conception of continental margins, in a source-to-sink scenario, as having an equilibrium base level or graded form, comparable to river systems. Departures from this shape relate to the interplay of sedimentary processes and in particular to those processes that do not fit the source-to-sink paradigm. For example, a significant part of the Atlantic margin is shown to be heavily influenced by along-slope geostrophic currents that generated massive contourite drift deposits. These deposits reflect lateral transport of sediment that had a significant impact on the morphology of the margin. The role of mass transport processes in shaping continental margins is also highlighted, and in particular the collapses of entire segments of the margin were observed. The prominent role mass failure processes play in delivering sediment to the adjacent abyssal plain is also critical in the ECS context. These observations challenge the entrenched notion of a continental margin comprising a shelf, slope, and rise and in particular the concept of the "continental rise". Prior to 2006, regions of the Arctic Ocean seaward of the Canadian landmass had fewer than 5000 km of seismic reflection data. The massive efforts of Arctic coastal States to map their margins for ECS purposes have led to a leap in technological advances to acquire data in ice-covered seas and have led to a wealth of new geoscientific knowledge. Perhaps foremost amongst this knowledge is demonstration that Canada Basin is indeed a fully developed ocean basin, albeit significantly infilled with sediment. Based on this knowledge and identification of related structures, new realistic tectonic scenarios for opening of the Amerasia Basin are proposed that include a significant component of transform or strike-slip motions. With seismic velocity and rock sample information, the continental nature of Alpha and Mendeleev ridges has been substantiated. Even bathymetric data were lacking in the Arctic and new editions of seafloor maps now support grids of 500 m spacing; although some regions remain sparse. Once thought to be relatively stagnant, sedimentary processes such as found in many ocean basins were discovered in the Arctic Ocean. Evidence of geostrophic currents, sediment mass failures, and deep-sea turbidity current channels were found to be ubiquitous, even in the deepest parts of the Arctic's basins. [ABSTRACT FROM AUTHOR]- Published
- 2023
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- View/download PDF
40. The stoichiometric ratio during biological removal of inorganic carbon and nutrient in the Mississippi River plume and adjacent continental shelf.
- Author
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Huang, W.-J., Cai, W.-J., Powell, R. T., Lohrenz, S. E., Wang, Y., Jiang, L.-Q., and Hopkinson, C. S.
- Subjects
STOICHIOMETRY ,BIOLOGICAL nutrient removal ,CARBON ,CONTINENTAL shelf ,BIOTIC communities ,BIOGEOCHEMICAL cycles ,GEOCHEMICAL modeling ,SALINITY - Abstract
The stoichiometric ratios of dissolved inorganic carbon (DIC) and nutrients during biological removal have been widely assumed to follow the Redfield ratios (especially the C/N ratio) in large river plume ecosystems. However, this assumption has not been systematically examined and documented because DIC and nutrients are rarely studied simultaneously in a river plume area, a region in which they can be affected by strong river-ocean mixing as well as intense biological activity. We examined stoichiometric ratios of DIC, total alkalinity (TA), and nutrients (NO
3 , Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. and Si(OH)4 ) data during biological removal in the Mississippi River plume and adjacent continental shelf in June 2003 and August 2004 with biological removals defined as the difference between measured values and values predicted on the basis of conservative mixing determined using a multi-endmember mixing model. Despite complex physical and biogeochemical influences, relationships between DIC and nutrients were strongly dependent on salinity range and geographic location, and influenced by biological removal. Lower C/Si and N/Si ratios in one nearshore area were attributed to a potential silicate source induced by water exchange with coastal salt marshes. When net biological uptake was separated from river-ocean mixing and the impact of marshes and bays excluded, stoichiometric ratios of C/N/Si were similar to the Redfield ratios, thus supporting the applicability of the Redfield-type C/N/Si ratios as a principle in river-plume biogeochemical models. [ABSTRACT FROM AUTHOR]- Published
- 2012
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- View/download PDF
41. RESULTS FROM THE 2003 AUSCAN CRUISE OFFSHORE KANGAROO ISLAND AND THE VERACITY OF THE RECORDS OF TWO DEEP-SEA CORES OBTAINED DURING THE CRUISE, WITH A DISCUSSION ON THE HOLOCENE HISTORY OF THE RIVER MURRAY ESTUARY.
- Author
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De Deckker, Patrick and Murray-Wallace, Colin V.
- Subjects
HOLOCENE Epoch ,CONTINENTAL slopes ,SEDIMENTATION & deposition ,CONTINENTAL shelf ,ISLANDS - Abstract
A brief account of the achievements of the AUSCAN cruise is presented together with an extensive list of published papers resulting from this cruise. Many of these papers provide considerable detail about the link between marine and continental records, many of which span the entire last glacial cycle (MIS 5e - MIS 1). The second part of the paper argues that a large estuary to the north of the River Murray mouth during the early Holocene, postulated by Helfensdorfer et al. (2019, 2020) requires scrutiny because their postulated sealevel reconstruction is flawed. In addition, the extensive deposition of sediments dammed near the mouth of the River Murray thought by these authors to have prevented the dispersal of fluvial sediments to the continental shelf and slope is unfounded. [ABSTRACT FROM AUTHOR]
- Published
- 2021
42. North Atlantic Current and European Slope Current Circulation in the Rockall Trough Observed Using Moorings and Gliders.
- Author
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Fraser, Neil J., Cunningham, Stuart A., Drysdale, Lewis A., Inall, Mark E., Johnson, Clare, Jones, Sam C., Burmeister, Kristin, Fox, Alan D., Dumont, Estelle, Porter, Marie, and Holliday, N. Penny
- Subjects
OCEANOGRAPHIC observations ,GLIDERS (Aeronautics) ,GULF Stream ,CONTINENTAL shelf ,OCEAN currents ,REMOTE submersibles - Abstract
The Rockall Trough (RT) accommodates the warmest and saltiest branch of the North Atlantic Current, which delivers water from the Gulf Stream into the marine environment around western Europe. In addition, the European Slope Current (ESC) carries warm water northward along the eastern boundary of the RT, and exchange between the ESC and the continental shelf is a dominant factor in determining the oceanographic conditions around the British Isles. However, the picture of the mean circulation and variability in the RT is still emerging, with a continuous observational campaign still in its relative infancy. The ESC, in particular, is poorly constrained by ship‐based, mooring, and satellite observations. In this paper, we examine the RT circulation and volume transport using a temporally extended and spatially expanded observing network. Six years of continuous mooring occupation reveal that a large‐amplitude, basin‐scale freshening event, previously detected south of Iceland around 2015, impacted the RT around 2017. Geostrophic transport was greatly reduced during this period, driven by a concurrent subsurface temperature increase at the western boundary. The circulation regained strength during the latter part of the record. We gathered 110 glider transects over 22 months which capture the ESC velocity field in unprecedented detail. The data are sufficient to characterize both the mean state and the emergent seasonal variability of the ESC, and reveal the year‐round presence of a southward countercurrent at depth. Variability in the strength and structure of this previously unstudied feature modulates net northward transport in the eastern boundary current system. Plain Language Summary: The Rockall Trough (RT) is a key pathway for warm and salty water flowing northward, a process which plays a key role in dictating the western European climate. However, the amount of water flowing northward, and how it changes over time, is still rather uncertain. In particular, the narrow boundary current in the eastern RT has previously proven difficult to measure. In this paper, we use 6 years of continuous oceanographic observations in the RT to monitor the flow. We also used underwater robots, called gliders, to focus on the narrow current in the eastern boundary. The data gathered give the best description of the ocean currents in the region to date. The study period coincided with a period of profound change across the subpolar North Atlantic, with a strong freshwater signal detected in the RT around 2017. The glider observations give a detailed view of the narrow eastern boundary current and how it varies seasonally, and also revealed the presence of a southward‐flowing current at depth. Key Points: Eastern boundary current system captured in unprecedented detail using 22 months of near‐continuous glider observationsLarge‐scale freshening event in subpolar North Atlantic impacted Rockall Trough (RT) around 2017Interannual variability in poleward transport driven by subsurface temperature anomalies at the western flank of the RT [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
43. A comparative study of biological production in eastern boundary upwelling systems using an artificial neural network.
- Author
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Lachkar, Z. and Gruber, N.
- Subjects
COMPARATIVE studies ,BIOLOGICAL productivity ,UPWELLING (Oceanography) ,ARTIFICIAL neural networks ,ENVIRONMENTAL impact analysis ,CONTINENTAL shelf ,CLIMATE change - Abstract
Eastern Boundary Upwelling Systems (EBUS) are highly productive ocean regions. Yet, substantial differences in net primary production (NPP) exist within and between these systems for reasons that are still not fully understood. Here, we explore the leading physical processes and environmental factors controlling NPP in EBUS through a comparative study of the California, Canary, Benguela, and Humboldt Current systems. The identification of NPP drivers is done with the aid of an artificial neural network analysis based on self-organizing-maps (SOMs). We show that in addition to the expected NPP enhancing effect of stronger alongshore wind, three factors have an inhibiting effect: (1) strong eddy activity, (2) narrow continental shelf, and (3) deep mixed layer. The co-variability of these 4 drivers defines in the context of the SOM a continuum of 100 patterns of NPP regimes in EBUS. These are grouped into 4 distinct classes using a Hierarchical Agglomerative Clustering (HAC) method. Our objective classification of EBUS reveals important variations of NPP regimes within each of the four EBUS, particularly in the Canary and Benguela Current systems. Our results show that the Atlantic EBUS are generally more productive and more sensitive to upwelling favorable winds because of a weaker factors inhibiting NPP. Perturbations of alongshore winds associated with climate change may therefore lead to contrasting biological responses in the Atlantic and the Pacific EBUS. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
44. Impact of seasonal oxygen deficiency on the phosphorous geochemistry of surface sediments along the Western Continental Shelf of India.
- Author
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Jacob, Josia, Ghosh, Prosenjit, Balchandran, K. K., and George, Rejomon
- Subjects
OXYGEN ,GEOCHEMISTRY ,SEDIMENTS ,CONTINENTAL shelf - Abstract
The intensification of the natural coastal hypoxic zone over the western Indian shelf in the recent years and its impact on the biogeochemistry and marine life is a matter of concern. This study examines the influence of the seasonal oxygen deficiency on the phosphorus geochemistry of the surface sediments along the western continental shelf of India (WCSI). Speciation of phosphorus along with the geochemical characteristics (total organic carbon - TOC, total nitrogen - TN, and total phosphorus - TP) of the surface sediments and the hydrography of the western continental shelf of India (WCSI) were studied, during late summer monsoon (LSM) and spring intermonsoon (SIM). The hydrography of the WCSI revealed upwelling and associated seasonal oxygen deficiency with denitrifying suboxic conditions along the inner shelf and hypoxic conditions along the outer shelf. High concentrations of dissolved phosphate (PO
4 ) and dissolved Iron (Fe) were also observed in the subsurface water of the inner shelf during LSM. The shelf water of the WCSI was oligotrophic and oxygen rich during SIM. A latitudinal enrichment of TOC, TN and TP in the surface sediments was observed at 13-17° N, along the WCSI during LSM, where seasonal suboxia was intense. Authigenic apatite bound phosphorus (Paut ) was the major phosphorus species along the WCSI during LSM whereas detrital flourapatite bound phosphorus (Pdet ) was the major species during SIM. Substantial depletion of reactive iron(III)-bound phosphorus (ΔPFe ) was observed in the surface sediments of the WCSI during LSM which showed significant correlation with the enrichment of PO4 (ΔPO4 ) in the overlying water during LSM compared to SIM. PO4 diffusing into the water column from the sediments by reductive dissolution of PFe probably leads to high dissolved PO4 along the inner shelf water during LSM which agrees with the existing hypothesis. Hence, phosphorus geochemistry of the surface sediments plays a major role in the biogeochemical cycling of phosphorus during periods of seasonal oxygen deficiency along the WCSI. Similar studies carried out along the eastern continental shelf of India (ECSI), where any kind of seasonal oxygen deficiency has not been reported yet, showed an abundance of Pdet (∼50% of TP) and Porg (∼32% of TP) in the surface sediments. The characteristic hydrographical features of the region such as high terrigeneous input, low production in the surface euphotic layers and greater preservation of labile organic matter in the sediments is also reflected in the phosphorus geochemistry of the surface sediments along ECSI. [ABSTRACT FROM AUTHOR]- Published
- 2010
- Full Text
- View/download PDF
45. Southern Ocean polynyas and dense water formation in a high-resolution, coupled Earth system model.
- Author
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Jeong, Hyein, Turner, Adrian K., Roberts, Andrew F., Veneziani, Milena, Price, Stephen F., Asay-Davis, Xylar S., Van Roekel, Luke P., Lin, Wuyin, Caldwell, Peter M., Park, Hyo-Seok, Wolfe, Jonathan D., and Mametjanov, Azamat
- Subjects
POLYNYAS ,WATER masses ,CONTINENTAL shelf ,OCEAN ,EARTH (Planet) ,SEA ice - Abstract
Antarctic coastal polynyas produce dense shelf water, a primary source of Antarctic Bottom Water that contributes to the global overturning circulation. This paper investigates Antarctic dense water formation in the high-resolution version of the Energy Exascale Earth System Model (E3SM-HR). The model is able to reproduce the main Antarctic coastal polynyas, although the polynyas are smaller in area compared to observations. E3SM-HR also simulates several occurrences of open-ocean polynyas (OOPs) in the Weddell Sea at a higher rate than what the last 50 years of the satellite sea ice observational record suggests, but similarly to other high-resolution Earth system model simulations. Furthermore, the densest water masses in the model are formed within the OOPs rather than on the continental shelf as is typically observed. Biases related to the lack of dense water formation on the continental shelf are associated with overly strong atmospheric polar easterlies, which lead to a strong Antarctic Slope Front and too little exchange between on- and off-continental shelf water masses. Strong polar easterlies also produce excessive southward Ekman transport, causing a build-up of sea ice over the continental shelf and enhanced ice melting in the summer season. This, in turn, produces water masses on the continental shelf that are overly fresh and less dense relative to observations. Our results indicate that high resolution alone is insufficient for models to properly reproduce Antarctic dense water; the large-scale polar atmospheric circulation around Antarctica must also be accurately simulated. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
46. Observations de Lege Ferenda
- Author
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Csabafi, Imre Anthony and Csabafi, Imre Anthony
- Published
- 1971
- Full Text
- View/download PDF
47. Migration and Over-Wintering of Red Knots (Calidris canutus rufa) along the Atlantic Coast of the United States
- Author
-
Joanna Burger, Ronald R. Porter, Caleb E. Gordon, Stephanie Koch, Lawrence J. Niles, and Amanda Dey
- Subjects
Fishery ,geography ,Caribbean island ,geography.geographical_feature_category ,Habitat ,Calidris canutus rufa ,Continental shelf ,Range (biology) ,Paper report ,Wildlife refuge ,Animal Science and Zoology ,Bay ,Ecology, Evolution, Behavior and Systematics - Abstract
Surveys and banding records of Calidris canutus rufa indicate that Red Knots migrate mainly north and south through Massachusetts, Delaware Bay, and Virginia, and winter in Florida and South America. We fitted 40 adult Red Knots with geolocators at Monomoy National Wildlife Refuge, Massachusetts, during fall migration (2009), and in this paper report on the locations of migration and wintering along the Atlantic coast of the United States of eight recaptured knots. The knots' migration patterns varied: four birds wintered along the U.S. Atlantic coast, and the rest went to the Caribbean islands or the northern edge of South America. Knots spent 58 to 75 days in Monomoy Refuge before migrating south in November. Seven of the eight stopped along the U.S. Atlantic coast for relatively long periods. For the six with complete yearly cycles, the total time spent along the Atlantic coast averaged 218 days (range 121–269 days). All eight knots crossed the Atlantic outer continental shelf from two to six...
- Published
- 2012
48. How Romania May Benefit from the Natural Gas Resources’ Offshore Exploitation of the Black Sea Romanian Continental Shelf?
- Author
-
Bulearcă, Marius, Chivu, Luminita, editor, Ioan-Franc, Valeriu, editor, Georgescu, George, editor, De Los Ríos Carmenado, Ignacio, editor, and Andrei, Jean Vasile, editor
- Published
- 2024
- Full Text
- View/download PDF
49. Bryozoan zooid size variation across a bathymetric gradient: a case study from the Icelandic shelf and continental slope
- Author
-
Gudmundur Gudmundsson, Malgorzata Krzeminska, Piotr Kuklinski, Maria Włodarska-Kowalczuk, and Anna Stępień
- Subjects
0106 biological sciences ,geography ,Original Paper ,geography.geographical_feature_category ,Zooid ,Community level ,010504 meteorology & atmospheric sciences ,Ecology ,Continental shelf ,010604 marine biology & hydrobiology ,Aquatic Science ,Biology ,Body size ,biology.organism_classification ,01 natural sciences ,Bryozoa ,Bathymetry ,Ecosystem ,Taxonomic rank ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Body size is one of the most important biological characters, as it defines many aspects of organismal functioning at the individual and community level. As body size controls many ecological aspects of species, it is often used as a proxy for the status of the ecosystem. So far no consistent mechanism driving size shift has been proposed. In this study, we investigated bathymetric variability in zooid’s size and shape in aquatic colonial animals, Bryozoa. Although the response of bryozoan zooid size to temperature or food concentration has been experimentally proven, the effects of natural environmental variability on marine bryozoan populations has been much less explored. The presented investigation is aimed to assess the bathymetric patterns and environmental drivers of bryozoan zooid size on continental shelf and slope of southern Iceland. 196 colonies of 11 species representing different colonial forms and taxonomic groups were selected for zooid characteristics measurements. A pattern of depth-related increase in zooid size was documented for Bicellarina alderi, Chartella barleei and Sarsiflustra abyssicola, no statistically significant effects were detected for the other eight species. Two species Bicellarina alderi and Caberea ellisii had significantly longer zooids in deeper water, shape of the remaining species did not change along the bathymetric gradient. Intercolonial coefficient of variation in zooid size did not change across the depth gradient. Temperature differences along studied depth could be responsible for the observed pattern. Electronic supplementary material The online version of this article (doi:10.1007/s00227-017-3231-9) contains supplementary material, which is available to authorized users.
- Published
- 2017
50. Demersal and pelagic species of fish and squid from the Patagonian shelf
- Author
-
Mirtha Noemi Lewis, Maria Rosa Marin, and Elena Beatriz Eder
- Subjects
demersal habitat ,Range (biology) ,Otras Ciencias Biológicas ,elasmobranches ,teleosts ,cephalopods ,occurrence ,Demersal zone ,purl.org/becyt/ford/1 [https] ,Commercial fishing ,Ciencias Biológicas ,Occurrence ,Southwestern Atlantic Ocean ,biology.animal ,lcsh:Zoology ,Patagonia ,lcsh:QL1-991 ,purl.org/becyt/ford/1.6 [https] ,Ecology, Evolution, Behavior and Systematics ,pelagic habitat ,Morphometrics ,Squid ,geography.geographical_feature_category ,biology ,Continental shelf ,Pelagic zone ,Fishery ,Geography ,Benthic zone ,Animal Science and Zoology ,CIENCIAS NATURALES Y EXACTAS ,Data Paper - Abstract
The dataset contains 2007 records of occurrence of 39 species of fish and 2 species of squid distributed on the Patagonian continental shelf and slope. This dataset describes a new and revised version of the original data published through OBIS with individual morphometrics. Specimens are representative of pelagic, demersal, demersal-pelagic, demersal-benthic and benthic habits and they were collected by commercial fishing vessels in autumn (May–June, 2001, 51 catches), winter (July–August, 2001, 38 catches) and summer (January-February, 2002, 112 catches). The sampling was carried out with bottom trawls at a depth range of 73–370 m. The survey was located between 39°–52°S and 55°–65°W. Fil: Eder, Elena Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Marin, Maria Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Lewis, Mirtha Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina
- Published
- 2017
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