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Pere Puig - One of the best experts on this subject based on the ideXlab platform.
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numerical modeling of bottom trawling induced sediment transport and accumulation in la fonera Submarine Canyon northwestern mediterranean sea
Marine Geology, 2017Co-Authors: Jacobo Martín, Pere Puig, Miquel Canals, Marta Payopayo, Ricardo Silva Jacinto, Galderic Lastras, Marina Rabineau, Nabil SultanAbstract:Bottom trawling leads to recurrent sediment resuspension events over fishing grounds. Recent studies have shown how bottom trawling can drive seascape reshaping at large spatial scales and enhance sediment transport in Submarine Canyons, which subsequently impacts deep-sea ecosystems. Present knowledge on the transfer and accumulation of sediment flows triggered by bottom trawling is based on localized and infrequent measurements whilst a more complete picture of the process is needed. The present work focuses on the modeling of sediment transport and accumulation resulting from trawling activities in La Fonera Submarine Canyon, northwestern Mediterranean Sea, thus contributing to an improved assessment of trawling impacts. Based on mooring data within a Canyon gully, we use an inverse model to retrieve the unknown time series of resuspension due to trawling over the fishing grounds. This resuspension is later used as forcing for the direct problem: we simulate trawling-induced flows through the Canyon and provide a 3D visualization of potential trawling impacts on sediment dynamics, including the identification of the propagation patterns of sediments resuspended by trawling. Flows coming from shallower fishing grounds are funneled through Canyon flank gullies towards the Canyon axis, with part of the resuspended sediment reaching the continental rise out of the Canyon across the open continental slope. Trawling-induced sediment flows promote sediment accumulation beyond the Canyon mouth. Given the wide geographical distribution of bottom trawling, our results have far-reaching implications that go much beyond La Fonera Submarine Canyon. Our study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins.
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Submarine Canyon dynamics - Executive Summary
2015Co-Authors: S. Ceramicola, Pere Puig, Frédéric BriandAbstract:Ceramicola, S. ... et al.-- Submarine Canyon Dynamics in the Mediterranean and Tributary Seas - An integrated geological, oceanographic and biological perspective, 15-18 April 2015, Sorrento, Italy.-- 14 pages, 6 figures, 1 table
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increasing sediment accumulation rates in la fonera palamos Submarine Canyon axis and their relationship with bottom trawling activities
Geophysical Research Letters, 2015Co-Authors: Pere Puig, Jacobo Martín, Pere Masqué, Albert PalanquesAbstract:Previous studies conducted in La Fonera (Palamos) Submarine Canyon (NW Mediterranean) found that trawling activities along the Canyon flanks cause resuspension and transport of sediments toward the Canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same Canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr−1 (compared to ~0.25 cm yr−1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in Submarine Canyon environments.
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space for time substitution and the evolution of a Submarine Canyon channel system in a passive progradational margin
Geomorphology, 2014Co-Authors: Pere Puig, Miquel Canals, Galderic Lastras, Aaron Micallef, Marta Ribo, Xavier TubauAbstract:Abstract Space-for-time substitution is a concept that has been widely applied, but not thoroughly tested, in some fields of geomorphology. The objective of this study is to test whether the concept of space-for-time substitution is valid in reconstructing the evolution of a Submarine Canyon–channel system in a passive progradational margin. We use multibeam echosounder data and in situ measurements from the south Ebro Margin to analyse the morphology and morphometry of a sequence of Submarine valleys ordered in terms of increasing valley thalweg length. The morphological model of Submarine valley evolution that we can propose from this analysis is very similar to established models in the literature, which leads us to conclude that time can be substituted by space when reconstructing the evolution of Submarine Canyon and channel systems in the south Ebro Margin. By extracting morphometric information from the application of the space-for-time substitution model to our data, we identify a series of morphological patterns as a Submarine Canyon evolves in a passive progradational margin. These include the geometric similarity of Canyon planform shape, an increase in Canyon draining efficiency and in the influence of flank slope failures, and an evolution towards equilibrium between Canyon form and imposed water and sediment load without net erosion or deposition taking place. We also observe that Canyon elongation is higher downslope and that the Canyon undergoes an early stage of rapid incision similar to the process of “erosion narrowing” reported in terrestrial rivers. We demonstrate that the conclusions of our study are not limited to Submarine valleys in the south Ebro Margin but are applicable to other margins around the world.
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effect of commercial trawling on the deep sedimentation in a mediterranean Submarine Canyon
Marine Geology, 2008Co-Authors: Jacobo Martín, Pere Puig, Albert Palanques, Pere Masqué, Jordi GarciaorellanaAbstract:Abstract In order to study sediment accumulation rates in the Palamos Submarine Canyon (Northwestern Mediterranean) during the last century, three sediment cores were extracted from the Canyon axis at depths of 450, 1200 and 1750 m respectively, where instrumented moorings were previously located. Estimated sedimentation rates based on 210 Pb and 137 Cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the Canyon may be different from secular trends. During the seventies, a two-fold increase of the sediment accumulation rate took place at the 1750 m depth site. This change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies. The surroundings and rims of Submarine Canyons are frequently targeted by commercial trawling fisheries, an activity that may enhance the input of resuspended particles into Canyons, and eventually trigger sediment gravity flows. Our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds, eventually extending to bathyal depths. Hence the anthropogenic influence on the sedimentary budget of some deep Submarine environments may be more important than previously thought.
James T. Liu - One of the best experts on this subject based on the ideXlab platform.
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effects of a major typhoon on sediment accumulation in fangliao Submarine Canyon sw taiwan
Marine Geology, 2012Co-Authors: R P Hale, James T. Liu, Charles A Nittrouer, Richard G Keil, Andrea S OgstonAbstract:Abstract The Fangliao Submarine Canyon cuts across the shelf and slope of southwest Taiwan. Unlike other Canyons along this margin, there is no obvious connection to an individual fluvial sediment source on land. Two recent cruises to Fangliao Canyon provide insight into sedimentation associated with a major typhoon. Box and piston cores were retrieved from Fangliao Canyon in early January 2007, after a local earthquake and an extended period of low-to-moderate river flow in streams that are suspected of contributing sediment to the Canyon. Similar cores were collected from the Canyon in early October 2009, following one of the largest typhoons to hit Taiwan in the past several decades. Typhoon Morakot delivered several meters of rain to Taiwan, with the largest river floods occurring in the south and southwest regions. In addition, the coastal ocean environment was energized by significant wave heights (> 12 m). Comparisons of textural, radioisotopic, and geochemical data reveal likely sediment transport and depositional processes within and surrounding Fangliao Canyon. Typhoon Morakot caused a layer ~ 10 cm thick (and greater) throughout the Canyon. X-radiographs of the 2007 cores show limited physical structure in most cases, and the 2009 radiographs display obvious changes in sediment density relative to the underlying sediment, as well as distinct physical lamination. Examining signals from different geochemical and radiochemical tracers for terrestrial sediment source indicates that the flood layer deposited by Typhoon Morakot came from several small mountainous rivers. By comparing the results of the 2007 cruise with those from 2009, we gain significant insight to the close linkage between a line source of fluvial sediment and deposition in a Submarine Canyon, as well as the role that tropical-storm events can play in delivering sediment to these environments.
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Cyclone-induced hyperpycnal turbidity currents in a Submarine Canyon
Journal of Geophysical Research: Oceans, 2012Co-Authors: James T. Liu, Yu-huai Wang, Rick J. Yang, Ray T. Hsu, Shuh-ji Kao, Hui-ling Lin, Fang Hsu KuoAbstract:[1] Density currents such as turbidity currents are major transport agents in various terrestrial, lacustrine, and marine environments worldwide. However, a gap exists between those who study the deposits by turbidity currents (turbidite) on a field scale, and those who study turbidity currents using small-scale laboratory experiments and theoretical/numerical models. We report two typhoon-triggered hyperpycnal turbidity current events observed in a Submarine Canyon. Our findings verify turbidite sequences with the characteristics of suspended sediment carried by passing turbidity currents that displayed distinct waxing and waning phases. Our study also confirms the direct link between typhoon-triggered hyperpycnal flows in a small mountainous river and turbidity currents in a nearby Submarine Canyon that transport sediment to the deep-sea efficiently.
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turbulent mixing and internal tides in gaoping kaoping Submarine Canyon taiwan
Journal of Marine Systems, 2009Co-Authors: Ihuan Lee, James T. Liu, Renchieh Lien, Wenssn ChuangAbstract:Abstract Turbulent overturning on scales greater than 10 m is observed near the bottom and in mid-depth layers within the Gaoping (formerly spelled Kaoping) Submarine Canyon (KPSC) in southern Taiwan. Bursts of strong turbulence coexist with bursts of strong sediment concentrations in mid-depth layers. The turbulence kinetic energy dissipation rate in some turbulence bursts exceeds 10 − 4 W kg − 1 , and the eddy diffusivity exceeds 10 − 1 m 2 s − 1 . Within the Canyon, the depth averaged turbulence kinetic energy dissipation rate is ~ 7 × 10 − 6 W kg − 1 , and the depth averaged eddy diffusivity is ~ 10 − 2 m 2 s − 1 . These are more than two orders of magnitude greater than typical values in the open ocean, and are much larger than those found in the Monterey Canyon where the strong turbulent mixing has also been. The interaction of tidal currents with the complex topography in Gaoping Submarine Canyon is presumably responsible for the observed turbulent overturning via shear instability and the breaking of internal tides and internal waves at critical frequencies. Strong 1st-mode internal tides exist in KPSC. The depth averaged internal tidal energy near the Canyon mouth is ~ 0.17 m 2 s − 2 . The depth integrated internal tidal energy flux at the mouth of the Canyon is ~ 14 kW m − 1 , propagating along the axis of the Canyon toward the Canyon head. The internal tidal energy flux in the Canyon is 3–7 times greater than that found in Monterey Canyon, presumably due to the more than 10 times larger barotropic tide in the Canyon. Simple energy budget calculations conclude that internal tides alone may provide energy sufficient to explain the turbulent mixing estimated within the Canyon. Further experiments are needed in order to quantify the seasonal and geographical distributions of internal tides in Gaoping Submarine Canyon and their effects on the sediment flux in the Canyon.
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from suspended particles to strata the fate of terrestrial substances in the gaoping kaoping Submarine Canyon
Journal of Marine Systems, 2009Co-Authors: James T. Liu, Ray T. Hsu, Hui-ling Lin, Jiajang Hung, Chihan Huh, Chonlin Lee, Yawen Huang, Joel C ChuAbstract:Abstract The river–sea system consisting of the Gaoping (new spelling according to the latest government's directive, formerly spelled Kaoping) River (KPR), shelf, and Submarine Canyon (KPRSC) located off southern Taiwan is an ideal natural laboratory to study the source, pathway, transport, and fate of terrestrial substances. In 2004 during the flood season of the KPR, a system-wide comprehensive field experiment was conducted to investigate particle dynamics from a source-to-sink perspective in the KPRSC with the emphasis on the effect of particle size on the transport, settling, and sedimentation along the pathway. This paper reports the findings from (1) two sediment trap moorings each configured with a Technicap PPS 3/3 sediment trap, and an acoustic current meter (Aquadopp); (2) concurrent hydrographic profiling and water sampling was conducted over 8 h next to the sediment trap moorings; and (3) box-coring in the head region of the Submarine Canyon near the mooring sites. Particle samples from sediment traps were analyzed for mass fluxes, grain-size composition, total organic carbon (TOC) and nitrogen (TN), organic matter (OM), carbonate, biogenic opal, polycyclic aromatic hydrocarbon (PAH), lithogenic silica and aluminum, and foraminiferal abundance. Samples from box cores were analyzed for grain-size distribution, TOC, particulate organic matter (POM), carbonate, biogenic opal, water content, and 210 Pb ex . Water samples were filtered through 500, 250, 63, 10 µm sieves and 0.4 µm filter for the suspended sediment concentration of different size-classes. Results show that the river and shelf do not supply all the suspended particles near the Canyon floor. The estimated mass flux near the Canyon floor exceeds 800 g/m 2 /day, whose values are 2–7 times higher than those at the upper rim of the Canyon. Most of the suspended particles in the Canyon are fine-grained (finer than medium silt) lithogenic sediments whose percentages are 90.2% at the upper rim and 93.6% in the deeper part of the Canyon. As suspended particles settle through the Canyon, their size-composition shows a downward fining trend. The average percentage of clay-to-fine-silt particles (0.4–10 µm) in the water samples increases from 22.7% above the upper rim of the Canyon to 56.0% near the bottom of the Canyon. Conversely, the average percentage of the sand-sized (> 63 µm) suspended particles decreases downward from 32.0% above the Canyon to 12.0% in the deeper part of the Canyon. Correspondingly, the substrate of the Canyon is composed largely of hemipelagic lithogenic mud. Parallel to this downward fining trend is the downward decrease of concentrations of suspended nonlithogenic substances such as TOC and PAH, despite of their affinity to fine-grained particles. On the surface of the Canyon, down-core variables (grain size, 210 Pb ex activity, TOC, water content) near the head region of the Canyon show post-depositional disturbances such as hyperpycnite and turbiditic deposits. These deposits point to the occurrences of erosion and deposition related to high-density flows such as turbidity currents, which might be an important process in Submarine Canyon sedimentation.
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a Submarine Canyon conduit under typhoon conditions off southern taiwan
Deep Sea Research Part I: Oceanographic Research Papers, 2006Co-Authors: James T. Liu, Hui-ling Lin, Jiajang HungAbstract:Abstract The function of a Submarine conduit under typhoon conditions is examined. The study site is the Kao-ping river, shelf, and Submarine Canyon (KPRSC) system located off southern Taiwan on a wave-dominated microtidal coast. The head of the Canyon is located approximately 1 km off the river mouth. Two comprehensive 1-month field experiments were carried out in 2000 and 2002 during the flood season of the river. Both experiments encountered typhoons that generated significant river discharge and wave resuspension events. Particle samples collected in 2000 by sediment-traps were analyzed for coarse fraction by the wet sieving method. Among the coarse fraction, foraminiferal species and their abundance were recorded as a tracer for biogenic particles of marine origin. Stable isotopes of carbon (δ 13 C) of organic particles of sediment-trap samples were analyzed as a tracer for particles of terrestrial origin. All the measured flow and particle concentration records were analyzed by conventional time-series analytical methods. Simultaneously observed records of suspended sediment concentration at the river mouth and the volume concentration of suspended particles near the Canyon floor were compared. Instantaneous flux and cumulative transport of suspended particles near the Canyon floor were estimated during the deployment period. Results show that Kao-ping Submarine Canyon is a multi-level and process-dependant two-way conduit for particles of terrestrial and marine origins. In general, terrestrial signals are stronger than the marine signals in sediment-trap samples near the head of the Canyon. During typhoon events, in the early distal phase of their influence nonlithogenic and biogenic marine sources are enhanced; in the later proximal phase signals of locally generated terrestrial lithogenic sources are enhanced. An episode of momentary downCanyon flushing of suspended particles near the Canyon floor is observed during one typhoon occurrence. This flushing suggests nondeposition during the typhoon at the locale of deployment despite increased input of particles to the Canyon floor. It also suggests a mechanism by which turbidity currents could be triggered. Yet, this flushing phenomenon is not observed in another typhoon occurrence, suggesting it is not universal in the Canyon's response to the typhoon.
Albert Palanques - One of the best experts on this subject based on the ideXlab platform.
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increasing sediment accumulation rates in la fonera palamos Submarine Canyon axis and their relationship with bottom trawling activities
Geophysical Research Letters, 2015Co-Authors: Pere Puig, Jacobo Martín, Pere Masqué, Albert PalanquesAbstract:Previous studies conducted in La Fonera (Palamos) Submarine Canyon (NW Mediterranean) found that trawling activities along the Canyon flanks cause resuspension and transport of sediments toward the Canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same Canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr−1 (compared to ~0.25 cm yr−1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in Submarine Canyon environments.
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effect of commercial trawling on the deep sedimentation in a mediterranean Submarine Canyon
Marine Geology, 2008Co-Authors: Jacobo Martín, Pere Puig, Albert Palanques, Pere Masqué, Jordi GarciaorellanaAbstract:Abstract In order to study sediment accumulation rates in the Palamos Submarine Canyon (Northwestern Mediterranean) during the last century, three sediment cores were extracted from the Canyon axis at depths of 450, 1200 and 1750 m respectively, where instrumented moorings were previously located. Estimated sedimentation rates based on 210 Pb and 137 Cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the Canyon may be different from secular trends. During the seventies, a two-fold increase of the sediment accumulation rate took place at the 1750 m depth site. This change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies. The surroundings and rims of Submarine Canyons are frequently targeted by commercial trawling fisheries, an activity that may enhance the input of resuspended particles into Canyons, and eventually trigger sediment gravity flows. Our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds, eventually extending to bathyal depths. Hence the anthropogenic influence on the sedimentary budget of some deep Submarine environments may be more important than previously thought.
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anthropogenic trace metals in the sedimentary record of the llobregat continental shelf and adjacent foix Submarine Canyon northwestern mediterranean
Marine Geology, 2008Co-Authors: Albert Palanques, Pere Puig, Pere Masqué, J A Sanchezcabeza, M Frignani, Francesca AlvisiAbstract:Abstract Anthropogenic trace-metal concentrations and inventories were studied on the Llobregat continental margin, from the Llobregat river mouth to the Foix Submarine Canyon. A prodelta sedimentary depocentre was identified along with a previously known Canyon depocentre. Significant upward increases in trace-metal contents were detected in sediment cores of the prodelta and upper part of the Canyon (down to 860 m depth). Metal enrichment factors ranged between 1.8 and 10 on the continental shelf and between 1.2 and 2.7 in the Submarine Canyon. These metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the Barcelona area and the consequent anthropogenic metal inputs. Maximum trace-metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the Foix upper Canyon as a consequence of efficient shelf–Canyon sediment and metal transfer. Deeper in the Canyon, at 1370 m depth, no metal enrichments were detected, probably because of particle dispersion and dilution with uncontaminated sediment within the Canyon. This study shows that, in some Mediterranean sedimentation systems, anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf, but also the adjacent continental slope sediments through Submarine Canyons.
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deep slope currents and suspended particle fluxes in and around the foix Submarine Canyon nw mediterranean
Deep Sea Research Part I: Oceanographic Research Papers, 2000Co-Authors: Pere Puig, Albert Palanques, Jorge Guillen, Emilio GarcialadonaAbstract:Abstract Deep slope currents and particulate matter concentrations were studied on the Barcelona continental margin in and around the Foix Submarine Canyon from May 1993 to April 1994. This year-long moored experiment revealed that near-bottom slope currents are strongly influenced by the bottom topography, being oriented along isobaths and along the Canyon axis. The deep slope current fluctuations are controlled by the local inertial motion (18.3 h) and also by low-frequency oscillations at periods of 6–10 days, related to the passage of atmospheric pressure cells. Particulate matter concentrations recorded during the experiment do not show a clear seasonal variability, except outside the Canyon, where significant peaks of particulate matter concentrations were recorded only during the winter-fall deployment. In addition, the temporal evolution of suspended particulate matter concentration is not linked to changes in the cross-slope or along-slope current components and did not show a clear relationship with river avenues or wave storm events. This suggests that suspended particulate matter exported from the shelf is dispersed on the slope by advective processes, which attenuate the signal of the shelf-slope sediment transfer. Mean particulate matter concentrations differed among sampling sites, but the magnitude of the mean horizontal suspended particle flux reflects a quite similar value in the whole study area, ranging from 2.53 to 4.05 mg m −2 s −1 . These horizontal suspended particle fluxes are 27 (Canyon head) to 360 (open slope) times higher than the settling particle fluxes measured at the same sampling sites, indicating that the suspended particulate transport on the Barcelona continental slope dominates over the settling particle fluxes, even inside the Foix Submarine Canyon.
Glenn S. Carter - One of the best experts on this subject based on the ideXlab platform.
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mixing in stratified turbulent layers on the steep sloping walls of monterey Submarine Canyon
Challenger Society Marine Science Conference, 2014Co-Authors: Danielle J Wain, Rob A. Hall, Renchieh Lien, Michael C Gregg, Matthew H Alford, Glenn S. CarterAbstract:Strong internal tide generated currents and rough topography lead to intense mixing at the bottom and the sloping sidewalls of Monterey Submarine Canyon. Estimates of mixing were made from measurements with SWIMS3, a depth-cycling towed body, at eleven cross-Canyon transects and two along Canyon-transects in upper Monterey Canyon (at thalweg depths 10^(-3) m^2/s) over the Canyon bottom, ranging from 70 m thick during neap tide to 300 m thick during spring tide over topographic features. The regions of elevated mixing extend up the Canyon sidewalls, diminishing in thickness and magnitude of mixing as the shelf is approached. These sidewall boundary layers generated by the internal tide may be important for sediment resuspension and other transport processes in the Canyon.
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mixing in stratified bottom boundary layers on the steep sloping walls of monterey Submarine Canyon
Physical Processes in Natural Waters 2014, 2014Co-Authors: Danielle J Wain, Rob A. Hall, Renchieh Lien, Michael C Gregg, Matthew H Alford, Glenn S. CarterAbstract:Strong internal tide generated currents and rough topography lead to intense mixing at the bottom and the sloping sidewalls of Monterey Submarine Canyon. Estimates of mixing were made from measurements with SWIMS3, a depth-cycling towed body, at eleven cross-Canyon transects and two along Canyon-transects in upper Monterey Canyon (at thalweg depths 10^(-3) m^2/s) over the Canyon bottom, ranging from 70 m thick during neap tide to 300 m thick during spring tide over topographic features. The regions of elevated mixing extend up the Canyon sidewalls, diminishing in thickness and magnitude of mixing as the shelf is approached. These sidewall boundary layers generated by the internal tide may be important for sediment resuspension and other transport processes in the Canyon.
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transition from partly standing to progressive internal tides in monterey Submarine Canyon
Deep-sea Research Part Ii-topical Studies in Oceanography, 2014Co-Authors: Rob A. Hall, Renchieh Lien, Glenn S. Carter, Danielle J Wain, Michael C Gregg, Matthew H Alford, Zhongxiang ZhaoAbstract:Monterey Submarine Canyon is a large, sinuous Canyon off the coast of California, the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward-looking moored ADCPs. The mooring observations measured a near-surface stratification change in the upper Canyon, likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling. This change in near-surface stratification caused a transition in the behaviour of the internal tide in the upper Canyon from a partly standing wave during pre-upwelling conditions to a progressive wave during upwelling conditions. Using a numerical model, we present evidence that either a partly standing or a progressive internal tide can be simulated in the Canyon, simply by changing the initial stratification conditions in accordance with the observations. The mechanism driving the transition is a dependence of down-Canyon (supercritical) internal tide reflection from the Canyon floor and walls on the depth of maximum stratification. During pre-upwelling conditions, the main pycnocline extends down to 200 m (below the Canyon rim) resulting in increased supercritical reflection of the up-Canyon propagating internal tide back down the Canyon. The large up-Canyon and smaller down-Canyon progressive waves are the two components of the partly standing wave. During upwelling conditions, the pycnocline shallows to the upper 50 m of the watercolumn (above the Canyon rim) resulting in decreased supercritical reflection and allowing the up-Canyon progressive wave to dominate.
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mixing on the Canyon walls of upper monterey Submarine Canyon
American Geophysical Union Ocean Sciences Meeting, 2014Co-Authors: Danielle J Wain, Rob A. Hall, Renchieh Lien, Michael C Gregg, Matthew H Alford, Glenn S. CarterAbstract:Strong internal tide generated currents and rough Canyon topography lead to intense mixing at the bottom and the sidewalls of Monterey Submarine Canyon. Estimates of mixing were made from measurements with SWIMS3, a depth-cycling towed body, at eleven cross-Canyon transects and two along Canyon-transects in upper Monterey Canyon (at thalweg depths 10^(-3) m^2/s) over the Canyon bottom, ranging from 70 m thick during neap tide to 300 m thick during spring tide over topographic features. The regions of elevated mixing extend up the Canyon sidewalls, diminishing in thickness and magnitude of mixing as the shelf is approached. These sidewall boundary layers generated by the internal tide may be important for sediment resuspension and other transport processes in the Canyon.
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internal tides and mixing in a Submarine Canyon with time varying stratification
Journal of Physical Oceanography, 2012Co-Authors: Zhongxiang Zhao, Renchieh Lien, Michael C Gregg, Matthew H Alford, Glenn S. CarterAbstract:AbstractThe time variability of the energetics and turbulent dissipation of internal tides in the upper Monterey Submarine Canyon (MSC) is examined with three moored profilers and five ADCP moorings spanning February–April 2009. Highly resolved time series of velocity, energy, and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring-neap cycles. However, the onset of springtime upwelling winds significantly alters the stratification during the record, causing the thermocline depth to shoal from about 100 to 40 m. The time-variable stratification must be accounted for because it significantly affects the energy, energy flux, the vertical modal structures, and the energy distribution among the modes. The internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals, suggesting more reflection from up Canyon early in the observational record. Turbulence, computed from Thorpe scales, is greatest in the bottom 5...
Jacobo Martín - One of the best experts on this subject based on the ideXlab platform.
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numerical modeling of bottom trawling induced sediment transport and accumulation in la fonera Submarine Canyon northwestern mediterranean sea
Marine Geology, 2017Co-Authors: Jacobo Martín, Pere Puig, Miquel Canals, Marta Payopayo, Ricardo Silva Jacinto, Galderic Lastras, Marina Rabineau, Nabil SultanAbstract:Bottom trawling leads to recurrent sediment resuspension events over fishing grounds. Recent studies have shown how bottom trawling can drive seascape reshaping at large spatial scales and enhance sediment transport in Submarine Canyons, which subsequently impacts deep-sea ecosystems. Present knowledge on the transfer and accumulation of sediment flows triggered by bottom trawling is based on localized and infrequent measurements whilst a more complete picture of the process is needed. The present work focuses on the modeling of sediment transport and accumulation resulting from trawling activities in La Fonera Submarine Canyon, northwestern Mediterranean Sea, thus contributing to an improved assessment of trawling impacts. Based on mooring data within a Canyon gully, we use an inverse model to retrieve the unknown time series of resuspension due to trawling over the fishing grounds. This resuspension is later used as forcing for the direct problem: we simulate trawling-induced flows through the Canyon and provide a 3D visualization of potential trawling impacts on sediment dynamics, including the identification of the propagation patterns of sediments resuspended by trawling. Flows coming from shallower fishing grounds are funneled through Canyon flank gullies towards the Canyon axis, with part of the resuspended sediment reaching the continental rise out of the Canyon across the open continental slope. Trawling-induced sediment flows promote sediment accumulation beyond the Canyon mouth. Given the wide geographical distribution of bottom trawling, our results have far-reaching implications that go much beyond La Fonera Submarine Canyon. Our study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins.
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increasing sediment accumulation rates in la fonera palamos Submarine Canyon axis and their relationship with bottom trawling activities
Geophysical Research Letters, 2015Co-Authors: Pere Puig, Jacobo Martín, Pere Masqué, Albert PalanquesAbstract:Previous studies conducted in La Fonera (Palamos) Submarine Canyon (NW Mediterranean) found that trawling activities along the Canyon flanks cause resuspension and transport of sediments toward the Canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same Canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr−1 (compared to ~0.25 cm yr−1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in Submarine Canyon environments.
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effect of commercial trawling on the deep sedimentation in a mediterranean Submarine Canyon
Marine Geology, 2008Co-Authors: Jacobo Martín, Pere Puig, Albert Palanques, Pere Masqué, Jordi GarciaorellanaAbstract:Abstract In order to study sediment accumulation rates in the Palamos Submarine Canyon (Northwestern Mediterranean) during the last century, three sediment cores were extracted from the Canyon axis at depths of 450, 1200 and 1750 m respectively, where instrumented moorings were previously located. Estimated sedimentation rates based on 210 Pb and 137 Cs profiles suggest that the contemporary trends of sediment transfer and accumulation in the Canyon may be different from secular trends. During the seventies, a two-fold increase of the sediment accumulation rate took place at the 1750 m depth site. This change has been associated to trawling activities and is attributed to the rapid technical development that the local trawling fleet underwent during the seventies. The surroundings and rims of Submarine Canyons are frequently targeted by commercial trawling fisheries, an activity that may enhance the input of resuspended particles into Canyons, and eventually trigger sediment gravity flows. Our results suggest that the effects of trawling over the dynamics of the seafloor may extend further and deeper from the fishing grounds, eventually extending to bathyal depths. Hence the anthropogenic influence on the sedimentary budget of some deep Submarine environments may be more important than previously thought.
