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Dominique Cluzel - One of the best experts on this subject based on the ideXlab platform.
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Chapter 5 The Eocene Subduction–Obduction Complex of New Caledonia
Geological Society London Memoirs, 2020Co-Authors: Pierre Maurizot, Dominique Cluzel, Jeanyves Collot, M Iseppi, Martin Patriat, S. Lesimple, A. Secchiari, Delphine Bosch, A. Montanini, P. MaceraAbstract:AbstractConvergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene Obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouébo Terrane and the Diahot–Panié Metamorphic Complex, before being exhumed at 38–34 Ma. The Obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.
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post Obduction evolution of new caledonia
2020Co-Authors: Brice Sevin, Dominique Cluzel, Pierre Maurizot, E Tournadour, Samuel Etienne, Nicolas Folcher, Julie Jeanpert, Jeanyves Collot, M Iseppi, S MeffreAbstract:The post-Obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Nepoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recovered shallow Miocene sedimentary rocks, indicating substantial Neogene subsidence. Quaternary formations are represented inland by aeolianite, vertisols and calcrete and offshore by the large barrier reef–lagoon complex, the onset of which is dated at c. 400 ka. This chapter discusses the different models proposed for the post-Obduction evolution of Grand Terre.
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chapter 5 the eocene subduction Obduction complex of new caledonia
Geological Society London Memoirs, 2020Co-Authors: Pierre Maurizot, Dominique Cluzel, Jeanyves Collot, M Iseppi, Martin Patriat, S. Lesimple, A. Secchiari, Delphine Bosch, A. Montanini, P. MaceraAbstract:Abstract Convergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene Obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouebo Terrane and the Diahot–Panie Metamorphic Complex, before being exhumed at 38–34 Ma. The Obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.
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U–Pb zircon dating of post-Obduction volcanic-arc granitoids and a granulite-facies xenolith from New Caledonia. Inference on Southwest Pacific geodynamic models
International Journal of Earth Sciences, 2007Co-Authors: Jean-louis Paquette, Dominique CluzelAbstract:In New Caledonia, the occurrence of one of the World’s largest and best-exposed subduction/Obduction complex is a key point for the understanding of the geodynamic evolution of the whole Southwest Pacific region. Within the ophiolite, pre-and post-Obduction granitoids intrude the ultramafic allochthon and provide new time constraints for the understanding of Obduction processes. At 27.4 Ma, a new East-dipping subduction generated the active margin magmatism along the western coast of the island (Saint-Louis massif). At 24.3 Ma, the eastward shift of the magma activity and slightly different geochemical features (Koum-Borindi massif) was either related to the older slab break-off; or alternatively, due to the eastward migration of the mantle wedge following the collision of the eastern margin of the Low Howe rise. Finally, the occurrence of a granulite-facies xenolith in the Koum-Borindi massif with comparable 24.5 Ma U–Pb zircon age and isotopic features (initial ε_Nd = 5.1) suggests that these evolved magmas were generated within the lithospheric mantle beneath a continental crust of normal thickness. Geochronological evidence for continuous convergence during the Oligocene infers an East-dipping Eocene-Oligocene subduction/Obduction system to have existed in the Southwest Pacific from the d’Entrecasteaux zone to the North Island of New Zealand.
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u pb zircon dating of post Obduction volcanic arc granitoids and a granulite facies xenolith from new caledonia inference on southwest pacific geodynamic models
International Journal of Earth Sciences, 2007Co-Authors: Jean-louis Paquette, Dominique CluzelAbstract:In New Caledonia, the occurrence of one of the World’s largest and best-exposed subduction/Obduction complex is a key point for the understanding of the geodynamic evolution of the whole Southwest Pacific region. Within the ophiolite, pre-and post-Obduction granitoids intrude the ultramafic allochthon and provide new time constraints for the understanding of Obduction processes. At 27.4 Ma, a new East-dipping subduction generated the active margin magmatism along the western coast of the island (Saint-Louis massif). At 24.3 Ma, the eastward shift of the magma activity and slightly different geochemical features (Koum-Borindi massif) was either related to the older slab break-off; or alternatively, due to the eastward migration of the mantle wedge following the collision of the eastern margin of the Low Howe rise. Finally, the occurrence of a granulite-facies xenolith in the Koum-Borindi massif with comparable 24.5 Ma U–Pb zircon age and isotopic features (initial eNd = 5.1) suggests that these evolved magmas were generated within the lithospheric mantle beneath a continental crust of normal thickness. Geochronological evidence for continuous convergence during the Oligocene infers an East-dipping Eocene-Oligocene subduction/Obduction system to have existed in the Southwest Pacific from the d’Entrecasteaux zone to the North Island of New Zealand.
Rui Xin Huang - One of the best experts on this subject based on the ideXlab platform.
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ventilation in the south china sea subduction versus Obduction
Deep Sea Research Part I: Oceanographic Research Papers, 2020Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Abstract We investigate ventilation in the South China Sea (SCS) based on a recently developed framework for annual subduction/Obduction in monsoon-dominated oceans. It is found that subduction occur in winter, and it was greatly weakened by ~58% due to the summer monsoon. Furthermore, there is a second Obduction window opened up during the summer monsoon period, besides the winter Obduction window. The winter subduction is concentrated in two narrow regions: one is located in the northern SCS and the other in the eastern SCS from 10°N to 15°N. The winter Obduction distributes widely in two areas: the northeastern SCS and the area south of 10°N, while the summer Obduction occurs primarily near the Vietnam. The key factors regulating subduction/Obduction and their variability at different areas are different: the lateral induction term is the key contributor for subduction in the northern SCS; however, for the subduction in the eastern SCS and the Obduction process, the vertical pumping term is dominant. Furthermore, the subducted (obducted) water in the SCS would penetrate into (come from) the subsurface ocean at the depth ~ 100m after (before) one year.
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Ventilation of a Monsoon‐Dominated Ocean: Subduction and Obduction in the North Indian Ocean
Journal of Geophysical Research: Oceans, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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ventilation of a monsoon dominated ocean subduction and Obduction in the north indian ocean
Journal of Geophysical Research, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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Subduction/Obduction rate in the North Pacific diagnosed by an eddy-resolving model
Chinese Journal of Oceanology and Limnology, 2016Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Ventilation in the North Pacific is examined using data from the eddy-resolving 1/12° global HYbrid Coordinate Ocean Model (HYCOM) and QuikSCAT wind stress data. For the period January 2004 to December 2006 and area 20°–40°N, the total annual subduction rate is estimated at 79 Sv, and the Obduction rate 41 Sv. Resolving the small-scale and high-frequency components of the eddy field can increase the subduction rate by 42 Sv, and Obduction by 31 Sv. Lateral induction is the dominant contributor to enhancement of subduction/Obduction, and temporal change of mixed layer depth has a secondary role. Further analysis indicates that the high-frequency components of the eddy field, especially those with timescale shorter than 10 days, are the most critical factor enhancing subduction/Obduction.
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subduction Obduction rate in the north pacific diagnosed by an eddy resolving model
Chinese Journal of Oceanology and Limnology, 2016Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Ventilation in the North Pacific is examined using data from the eddy-resolving 1/12° global HYbrid Coordinate Ocean Model (HYCOM) and QuikSCAT wind stress data. For the period January 2004 to December 2006 and area 20°–40°N, the total annual subduction rate is estimated at 79 Sv, and the Obduction rate 41 Sv. Resolving the small-scale and high-frequency components of the eddy field can increase the subduction rate by 42 Sv, and Obduction by 31 Sv. Lateral induction is the dominant contributor to enhancement of subduction/Obduction, and temporal change of mixed layer depth has a secondary role. Further analysis indicates that the high-frequency components of the eddy field, especially those with timescale shorter than 10 days, are the most critical factor enhancing subduction/Obduction.
Thibault Duretz - One of the best experts on this subject based on the ideXlab platform.
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Obduction of old oceanic lithosphere due to reheating and plate reorganization insights from numerical modelling and the ne anatolia lesser caucasus case example
Journal of Geodynamics, 2016Co-Authors: Marc Hassig, Yann Rolland, Thibault Duretz, Marc SossonAbstract:Abstract The ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an Obduction over ∼200 km of oceanic lithosphere of Middle Jurassic age (c. 175–165 Ma) along an entire tectonic boundary (>1000 km) at around 90 Ma. The Obduction process is characterized by four first order geological constraints: (1) Ophiolites represent remnants of a single ophiolite nappe currently of only a few kilometres thick and 200 km long. The oceanic crust was old (∼80 Ma) at the time of its Obduction. (2) The presence of OIB-type magmatism emplaced up to 10 Ma prior to Obduction preserved on top of the ophiolites is indicative of mantle upwelling processes (hotspot). (3) The leading edge of the Taurides-Anatolides, represented by the South Armenian Block, did not experience pressures exceeding 0.8 GPa nor temperatures greater than ∼300 °C during underthrusting below the obducting oceanic lithosphere. (4) An oceanic domain of a maximum 1000 km (from north to south) remained between Taurides-Anatolides and Pontides-Southern Eurasian Margin after the Obduction. We employ two-dimensional thermo-mechanical numerical modelling in order to investigate Obduction dynamics of a re-heated oceanic lithosphere. Our results suggest that thermal rejuvenation (i.e. reheating) of the oceanic domain, tectonic compression, and the structure of the passive margin are essential ingredients for enabling Obduction. Afterwards, extension induced by far-field plate kinematics (subduction below Southern Eurasian Margin), facilitates the thinning of the ophiolite, the transport of the ophiolite on the continental domain, and the exhumation of continental basement through the ophiolite. The combined action of thermal rejuvenation and compression are ascribed to a major change in tectonic motions occurring at 110–90 Ma, which led to simultaneous Obductions in the Oman (Arabia) and NALC regions.
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What are the required conditions to trigger the Obduction/subduction initiation?
2016Co-Authors: Philippe Yamato, Thibault Duretz, Philippe Agard, Mathieu SoretAbstract:The initial stages allowing for the birth of Obduction and/or subduction zones still remain enigmatic and highly debated. Although there is no doubt that initiation occurs on a preexisting lithospheric-scale thermal or mechanical discontinuity (e.g., ridge, supra-subduction zone or transform fault), no consensus has yet been reached on this subject. However, more and more data allowing to address this issue are available (coming from field analyses, metamorphic petrology and geochronology). In particular, metamorphic soles located at the base of ophiolitic nappes, which formed during the very first stages of initiation, yield increasingly precise P-T-t constraints. By confronting such data to thermo-mechanical models, it should be possible to identify which initial configuration allows for metamorphic sole formation and for the emplacement (or not) of an ophiolitic nappe of realistic dimensions. In this study we designed thermo-mechanical models encompassing three initial model configurations, for which P-T-t data from the Semail ophiolite of Oman are then used for the validation of model outputs. The first configuration encompasses an oceanic ridge type initial thermal perturbation (error function). The second configuration mimics the thermal perturbation caused by the arrival of a mantle plume at the base of the lithosphere (gaussian function). The third initial condition corresponds to a case where the Obduction/subduction initiates along a transform fault delimitating lithospheres of contrasting thermal ages (step function). Our results show that Obduction never initiates in ridge type models, excepted for particular conditions that are not compatible with the Oman case. They also indicate that the initial thermal anomaly has to be sharp but not necessary of large amplitude and that the strength of the lithosphere has to be high enough to ensure the establishment of thin and long ophiolitic nappe without buckling. Our results also highlight the key role of shear heating in enabling Obduction/subduction initiation.
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Obduction triggered by regional heating during plate reorganization,
Terra Nova, 2016Co-Authors: Y. Rolland, Marc Hassig, Thibault Duretz, Marc SossonAbstract:The reason for Obduction, or tectonic transport of oceanic lithosphere onto continents, is investigated by two-dimensional thermo-mechanical numerical modelling based on the geology of the Anatolia–Lesser Caucasus ophiolites. Heating of the oceanic domain and extension induced by far-field plate kinematics appear to be essential for the Obduction of ~80-Ma-old oceanic crust over distances exceeding 200 km. Heating of the oceanic lithosphere by mantle upwelling is evidenced by a thick alkaline volcanic series emplaced on top of the oceanic crust 10–20 Ma before Obduction, at the onset of Africa–Eurasia convergence. Regional heating reduced the negative buoyancy and strength of the magmatically old lithosphere. Extension facilitated the propagation of Obduction by reducing the mantle lithosphere thickness, which led to the exhumation of eclogite-free continental crust previously underthrusted beneath the ophiolites. This extensional event is ascribed to far-field plate kinematics resulting from renewed Neotethys oceanic subduction beneath Eurasia.
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Obduction triggered by regional heating during plate reorganization
Terra Nova, 2016Co-Authors: Marc Hassig, Yann Rolland, Thibault Duretz, Marc SossonAbstract:International audienceThe reason for Obduction, or tectonic transport of oceanic lithosphere onto continents, is investigated by two-dimensional thermo-mechanical numerical modelling based on the geology of the Anatolia–Lesser Caucasus ophiolites. Heating of the oceanic domain and extension induced by far-field plate kinematics appear to be essential for the Obduction of ~80-Ma-old oceanic crust over distances exceeding 200 km. Heating of the oceanic lithosphere by mantle upwelling is evidenced by a thick alkaline volcanic series emplaced on top of the oceanic crust 10–20 Ma before Obduction, at the onset of Africa–Eurasia convergence. Regional heating reduced the negative buoyancy and strength of the magmatically old lithosphere. Extension facilitated the propagation of Obduction by reducing the mantle lithosphere thickness, which led to the exhumation of eclogite-free continental crust previously underthrusted beneath the ophiolites. This extensional event is ascribed to far-field plate kinematics resulting from renewed Neotethys oceanic subduction beneath Eurasia
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Obduction of old oceanic lithosphere due to reheating and plate reorganization: Insights from numerical modelling and the NE Anatolia – Lesser Caucasus case example
Journal of Geodynamics, 2016Co-Authors: Marc Hassig, Yann Rolland, Thibault Duretz, Marc SossonAbstract:International audienceThe ophiolites of NE Anatolia and of the Lesser Caucasus (NALC) evidence an Obduction over ∼200 km of oceanic lithosphere of Middle Jurassic age (c. 175–165 Ma) along an entire tectonic boundary (>1000 km) at around 90 Ma. The Obduction process is characterized by four first order geological constraints:(1) Ophiolites represent remnants of a single ophiolite nappe currently of only a few kilometres thick and 200 km long. The oceanic crust was old (∼80 Ma) at the time of its Obduction.(2) The presence of OIB-type magmatism emplaced up to 10 Ma prior to Obduction preserved on top of the ophiolites is indicative of mantle upwelling processes (hotspot).(3) The leading edge of the Taurides-Anatolides, represented by the South Armenian Block, did not experience pressures exceeding 0.8 GPa nor temperatures greater than ∼300 °C during underthrusting below the obducting oceanic lithosphere.(4) An oceanic domain of a maximum 1000 km (from north to south) remained between Taurides-Anatolides and Pontides-Southern Eurasian Margin after the Obduction.We employ two-dimensional thermo-mechanical numerical modelling in order to investigate Obduction dynamics of a re-heated oceanic lithosphere. Our results suggest that thermal rejuvenation (i.e. reheating) of the oceanic domain, tectonic compression, and the structure of the passive margin are essential ingredients for enabling Obduction. Afterwards, extension induced by far-field plate kinematics (subduction below Southern Eurasian Margin), facilitates the thinning of the ophiolite, the transport of the ophiolite on the continental domain, and the exhumation of continental basement through the ophiolite. The combined action of thermal rejuvenation and compression are ascribed to a major change in tectonic motions occurring at 110–90 Ma, which led to simultaneous Obductions in the Oman (Arabia) and NALC regions
Fan Wang - One of the best experts on this subject based on the ideXlab platform.
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MJO-induced Intraseasonal Mixed Layer Depth Variability in the Equatorial Indian Ocean and Impacts on Subsurface Water Obduction
Journal of Physical Oceanography, 2021Co-Authors: Ling Ling Liu, Fan WangAbstract:AbstractChange of ocean surface mixed layer depth (MLD) is critical for vertical exchanges between the surface and subsurface oceans and modulates surface temperature variabilities on various timescales. In-situ observations have documented prominent intraseasonal variability (ISV) of MLD with 30-105-day periods in the equatorial Indian Ocean (EIO) where the Madden-Julian oscillation (MJO) initiates. Simulation of Hybrid Coordinate Ocean Model (HYCOM) reveals a regional maximum of intraseasonal MLD variability in the EIO (70°E-95°E, 3°S-3°N) with a standard deviation of ~14 m. Sensitivity experiments of HYCOM demonstrate that among all the MJO-related forcing effects, the wind-driven downwelling and mixing are primary causes for intraseasonal MLD deepening and explain 83.7% of the total ISV. The ISV of MLD gives rise to high-frequency entrainments of subsurface water, leading to an enhancement of annual entrainment rate by 34%. However, only a small fraction of these entrainment events (< 20%) can effectively contribute to the annual Obduction rate of 1.36 Sv, a quantification for the amount of resurfacing thermocline water throughout a year that mainly (84.6%) occurs in the summer monsoon season (May-October). The ISV of MLD achieves the maximal intensity in April-May and greatly affects the subsequent Obduction. Estimation based on our HYCOM simulations suggests that MJOs overall reduce the Obduction rate in the summer monsoon season by as much as 53%. A conceptual schematic is proposed to demonstrate how springtime intraseasonal MLD deepening events caused by MJO winds narrow down the time window for effective entrainment and thereby suppress the Obduction of thermocline water.
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ventilation in the south china sea subduction versus Obduction
Deep Sea Research Part I: Oceanographic Research Papers, 2020Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Abstract We investigate ventilation in the South China Sea (SCS) based on a recently developed framework for annual subduction/Obduction in monsoon-dominated oceans. It is found that subduction occur in winter, and it was greatly weakened by ~58% due to the summer monsoon. Furthermore, there is a second Obduction window opened up during the summer monsoon period, besides the winter Obduction window. The winter subduction is concentrated in two narrow regions: one is located in the northern SCS and the other in the eastern SCS from 10°N to 15°N. The winter Obduction distributes widely in two areas: the northeastern SCS and the area south of 10°N, while the summer Obduction occurs primarily near the Vietnam. The key factors regulating subduction/Obduction and their variability at different areas are different: the lateral induction term is the key contributor for subduction in the northern SCS; however, for the subduction in the eastern SCS and the Obduction process, the vertical pumping term is dominant. Furthermore, the subducted (obducted) water in the SCS would penetrate into (come from) the subsurface ocean at the depth ~ 100m after (before) one year.
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Ventilation of a Monsoon‐Dominated Ocean: Subduction and Obduction in the North Indian Ocean
Journal of Geophysical Research: Oceans, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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ventilation of a monsoon dominated ocean subduction and Obduction in the north indian ocean
Journal of Geophysical Research, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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Subduction/Obduction rate in the North Pacific diagnosed by an eddy-resolving model
Chinese Journal of Oceanology and Limnology, 2016Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Ventilation in the North Pacific is examined using data from the eddy-resolving 1/12° global HYbrid Coordinate Ocean Model (HYCOM) and QuikSCAT wind stress data. For the period January 2004 to December 2006 and area 20°–40°N, the total annual subduction rate is estimated at 79 Sv, and the Obduction rate 41 Sv. Resolving the small-scale and high-frequency components of the eddy field can increase the subduction rate by 42 Sv, and Obduction by 31 Sv. Lateral induction is the dominant contributor to enhancement of subduction/Obduction, and temporal change of mixed layer depth has a secondary role. Further analysis indicates that the high-frequency components of the eddy field, especially those with timescale shorter than 10 days, are the most critical factor enhancing subduction/Obduction.
Ling Ling Liu - One of the best experts on this subject based on the ideXlab platform.
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MJO-induced Intraseasonal Mixed Layer Depth Variability in the Equatorial Indian Ocean and Impacts on Subsurface Water Obduction
Journal of Physical Oceanography, 2021Co-Authors: Ling Ling Liu, Fan WangAbstract:AbstractChange of ocean surface mixed layer depth (MLD) is critical for vertical exchanges between the surface and subsurface oceans and modulates surface temperature variabilities on various timescales. In-situ observations have documented prominent intraseasonal variability (ISV) of MLD with 30-105-day periods in the equatorial Indian Ocean (EIO) where the Madden-Julian oscillation (MJO) initiates. Simulation of Hybrid Coordinate Ocean Model (HYCOM) reveals a regional maximum of intraseasonal MLD variability in the EIO (70°E-95°E, 3°S-3°N) with a standard deviation of ~14 m. Sensitivity experiments of HYCOM demonstrate that among all the MJO-related forcing effects, the wind-driven downwelling and mixing are primary causes for intraseasonal MLD deepening and explain 83.7% of the total ISV. The ISV of MLD gives rise to high-frequency entrainments of subsurface water, leading to an enhancement of annual entrainment rate by 34%. However, only a small fraction of these entrainment events (< 20%) can effectively contribute to the annual Obduction rate of 1.36 Sv, a quantification for the amount of resurfacing thermocline water throughout a year that mainly (84.6%) occurs in the summer monsoon season (May-October). The ISV of MLD achieves the maximal intensity in April-May and greatly affects the subsequent Obduction. Estimation based on our HYCOM simulations suggests that MJOs overall reduce the Obduction rate in the summer monsoon season by as much as 53%. A conceptual schematic is proposed to demonstrate how springtime intraseasonal MLD deepening events caused by MJO winds narrow down the time window for effective entrainment and thereby suppress the Obduction of thermocline water.
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ventilation in the south china sea subduction versus Obduction
Deep Sea Research Part I: Oceanographic Research Papers, 2020Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Abstract We investigate ventilation in the South China Sea (SCS) based on a recently developed framework for annual subduction/Obduction in monsoon-dominated oceans. It is found that subduction occur in winter, and it was greatly weakened by ~58% due to the summer monsoon. Furthermore, there is a second Obduction window opened up during the summer monsoon period, besides the winter Obduction window. The winter subduction is concentrated in two narrow regions: one is located in the northern SCS and the other in the eastern SCS from 10°N to 15°N. The winter Obduction distributes widely in two areas: the northeastern SCS and the area south of 10°N, while the summer Obduction occurs primarily near the Vietnam. The key factors regulating subduction/Obduction and their variability at different areas are different: the lateral induction term is the key contributor for subduction in the northern SCS; however, for the subduction in the eastern SCS and the Obduction process, the vertical pumping term is dominant. Furthermore, the subducted (obducted) water in the SCS would penetrate into (come from) the subsurface ocean at the depth ~ 100m after (before) one year.
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Ventilation of a Monsoon‐Dominated Ocean: Subduction and Obduction in the North Indian Ocean
Journal of Geophysical Research: Oceans, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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ventilation of a monsoon dominated ocean subduction and Obduction in the north indian ocean
Journal of Geophysical Research, 2018Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Based on the characteristics of oceanic circulation in a monsoon-dominated ocean, a new framework of annual ventilation, including subduction and Obduction, is postulated and applied to the North Indian Ocean based on both SODA and GODAS. It is revealed that besides the winter season, ventilation can also occur in summer. Considering the horizontal resolution, SODA results are mainly discussed, with GODAS results given for validity of key conclusions. The annual subduction/Obduction rate in the North Indian Ocean based on SODA is estimated at 10.2 Sv/11 Sv averaged from 1960 to 2009, with 4.2 Sv/6.2 Sv occurring during winter monsoon period and 6 Sv/4.8 Sv during summer monsoon period, respectively. Both subduction and Obduction feature great interannual variability, with the vertical pumping term of decisive importance. Furthermore, the concepts of the penetration depth through subduction and the origin depth through Obduction are postulated. The penetration depth in the Arabian Sea is on the order of 50 to 200 m; the origin depth through Obduction in the Arabian Sea is deeper than that in the Bay of Bengal, with the deepest on the order of 200 to 250 m along the western boundary.
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Subduction/Obduction rate in the North Pacific diagnosed by an eddy-resolving model
Chinese Journal of Oceanology and Limnology, 2016Co-Authors: Ling Ling Liu, Rui Xin Huang, Fan WangAbstract:Ventilation in the North Pacific is examined using data from the eddy-resolving 1/12° global HYbrid Coordinate Ocean Model (HYCOM) and QuikSCAT wind stress data. For the period January 2004 to December 2006 and area 20°–40°N, the total annual subduction rate is estimated at 79 Sv, and the Obduction rate 41 Sv. Resolving the small-scale and high-frequency components of the eddy field can increase the subduction rate by 42 Sv, and Obduction by 31 Sv. Lateral induction is the dominant contributor to enhancement of subduction/Obduction, and temporal change of mixed layer depth has a secondary role. Further analysis indicates that the high-frequency components of the eddy field, especially those with timescale shorter than 10 days, are the most critical factor enhancing subduction/Obduction.
