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G. Ramstein - One of the best experts on this subject based on the ideXlab platform.
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the role of eastern tethys seaway closure in the middle miocene climatic transition ca 14 ma
Climate of The Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
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The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)
Climate of the Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoal-ing and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reor-ganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO 2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
Noémie Hamon - One of the best experts on this subject based on the ideXlab platform.
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the role of eastern tethys seaway closure in the middle miocene climatic transition ca 14 ma
Climate of The Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
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The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)
Climate of the Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoal-ing and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reor-ganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO 2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
V. Lefebvre - One of the best experts on this subject based on the ideXlab platform.
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the role of eastern tethys seaway closure in the middle miocene climatic transition ca 14 ma
Climate of The Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
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The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)
Climate of the Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoal-ing and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reor-ganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO 2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
Yannick Donnadieu - One of the best experts on this subject based on the ideXlab platform.
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An Earth System modeling study of the recent geological history of the global Oceanic Circulation over the Cenozoic
2019Co-Authors: Yannick Donnadieu, Jean-baptiste Ladant, Guillaume Dupont-nivet, Agathe Toumoulin, Fernando PobleteAbstract:The impact of the Drake Passage (DP) opening on climate is being debated for dozens of years. Indeed, being one of the major geographical changes occurring during the Eocene and at the beginning of a global climate cooling, it has often generated a lot of interest. To date, even though the overall signal remains unclear, it is considered as one of the main potential cause of the contemporaneous climate change. Several model studies have been aiming to assess the importance of this gateway opening through different more or less complex models. However, according to our knowledge on palaeoenvironments, most of them considered unrealistic boundary conditions (notably a low pCO2 or a today-like geography) that might corrupt the transposition of their results to the original deep-time context. In order to better understand if and how climate might have been affected by this gateway opening, the DP question is here evaluated using an up2date IPCC like model, the IPSL-CM5A2. Several simulations have been done using boundary conditions encountered over the Cenozoic from the Early Eocene to the Middle Miocene. For each time period, the role of the atmospheric CO2 level and of the depth and geometry of major marine gateways have been tested. We aim here to better understanding the history of the deep Oceanic Circulation and its link to the strength of the Antarctic Circumpolar Current. A particular focus will be done on the Eocene-Oligocene transition and on the Early Miocene, a time period during which it has been suggested a narrowing of the Drake Passage. Finally, the impact of the East Tethysian gateway will also be studied both on the global Oceanic Circulation and on its impact on atmospheric dynamics, specifically over the continents surrounding the Mediterranean region.
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Evolution of the neodymium isotopic signature of neritic seawater on a northwestern Pacific margin: new constrains on possible end-members for the composition of deep-water masses in the Late Cretaceous ocean.
Chemical Geology, 2013Co-Authors: Mathieu Moiroud, Yannick Donnadieu, Emmanuelle Pucéat, Germain Bayon, Kazuyoshi Moriya, Jean-françois Deconinck, Maud BoyetAbstract:The Neodymium(Nd) isotope composition of fish remains has beenwidely used to track past changes in Oceanic Circulation. Although the number of published Nd isotope data for the Cretaceous has markedly increased in the last years, no consensus has been reached on the structure of the Oceanic Circulation and its evolution during the Late Cretaceous. Yet this period is characterised bymajor geodynamical and climatic changes andmarked by the disappearance of global Oceanic anoxic events inwhich changes in Oceanic Circulation modesmay have played a significant role. In this study we present the first record of Nd isotopic composition of fish remains from continental margin environments on the northwestern Pacific margin (Yezo Group in the Hokkaidō area, Northern Japan) for the Late Cretaceous period. This record, interpreted in terms of Nd isotopic composition of local neritic seafloor seawater, is characterised by relatively radiogenic Nd isotope compositions and presents variations of several ε-units from the Turonian to the Campanian ranging from ~−5.5 to ~0.5 ε-units, although most values remain in the ~−1 to ~−3 range. Conversely, the local detrital fraction remains more constant and around −4 ε-units on the studied interval. This new set of seawater Nd data contains some of the most radiogenic values for the Cretaceous published yet. The more radiogenic seawater Nd isotope values compared to that of the sediments points to an input of radiogenic seawater in the studied area by surface currents during the Late Cretaceous. Similarly to the modern configuration, these radiogenic waters could have been conveyed in the studied area by a southward current comparable to the modern Oyashio current bathing the Hokkaidō area. Our data are then consistent with the presence in the northern Pacific of highly radiogenic seawater, and support the northern and northwestern Pacific as a possible radiogenic source for the deep parts of the basin. As such this work represents a first step toward a better characterisation of the various end-members that could have contributed to the Nd isotopic signature of the deep-water masses filling the Cretaceous oceans.
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evolution of the neodymium isotopic signature of neritic seawater on a northwestern pacific margin new constrains on possible end members for the composition of deep water masses in the late cretaceous ocean
Chemical Geology, 2013Co-Authors: Mathieu Moiroud, Yannick Donnadieu, Emmanuelle Pucéat, Germain Bayon, Kazuyoshi Moriya, Jean-françois Deconinck, Maud BoyetAbstract:The Neodymium(Nd) isotope composition of fish remains has beenwidely used to track past changes in Oceanic Circulation. Although the number of published Nd isotope data for the Cretaceous has markedly increased in the last years, no consensus has been reached on the structure of the Oceanic Circulation and its evolution during the Late Cretaceous. Yet this period is characterised bymajor geodynamical and climatic changes andmarked by the disappearance of global Oceanic anoxic events inwhich changes in Oceanic Circulation modesmay have played a significant role. In this study we present the first record of Nd isotopic composition of fish remains from continental margin environments on the northwestern Pacific margin (Yezo Group in the Hokkaidō area, Northern Japan) for the Late Cretaceous period. This record, interpreted in terms of Nd isotopic composition of local neritic seafloor seawater, is characterised by relatively radiogenic Nd isotope compositions and presents variations of several e-units from the Turonian to the Campanian ranging from ~−5.5 to ~0.5 e-units, although most values remain in the ~−1 to ~−3 range. Conversely, the local detrital fraction remains more constant and around −4 e-units on the studied interval. This new set of seawater Nd data contains some of the most radiogenic values for the Cretaceous published yet. The more radiogenic seawater Nd isotope values compared to that of the sediments points to an input of radiogenic seawater in the studied area by surface currents during the Late Cretaceous. Similarly to the modern configuration, these radiogenic waters could have been conveyed in the studied area by a southward current comparable to the modern Oyashio current bathing the Hokkaidō area. Our data are then consistent with the presence in the northern Pacific of highly radiogenic seawater, and support the northern and northwestern Pacific as a possible radiogenic source for the deep parts of the basin. As such this work represents a first step toward a better characterisation of the various end-members that could have contributed to the Nd isotopic signature of the deep-water masses filling the Cretaceous oceans.
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modeling evidences for global warming arctic seawater freshening and sluggish Oceanic Circulation during the early toarcian anoxic event
Paleoceanography, 2012Co-Authors: Guillaume Dera, Yannick DonnadieuAbstract:[1] The paleoecological disturbances recorded during the Early Toarcian warming event (183 Myr ago), including marine anoxia, sea level rise, seawater acidification, carbonate production crisis, and species extinctions, are often regarded as past examples of Earth's possible responses to the rapid emergence of super greenhouse conditions. However, physical mechanisms explaining both the global and local expressions of paleoenvironmental events are still highly debated. Here we analyze the paleoclimatic and paleoceanographic consequences of increases in atmospheric pCO2 levels at a multiscale resolution using a fully coupled ocean–atmosphere model (FOAM). We show that, in association with stronger high-latitude precipitation rates and enhanced continental runoff, the demise of polar sea ice due to the global warming event involved a regional freshening of Arctic surface seawaters. These disturbances lead to progressive slowdowns of the global Oceanic Circulation accountable for widespread ocean stratification and bottom anoxia processes in deep Oceanic settings and epicontinental basins. In agreement with very negative oxygen isotope values measured on fossil shells from the NW Tethys, our simulations also show that recurrent discharges of brackish and nutrient-rich Arctic surface waters through the Viking Corridor could have led to both vertical and geographical gradients in salinity and seawater δ18O in the NW Tethyan seas. Locally contrasted conditions in water mass density and rises in productivity rates due to strong nutrient supplies could partly explain the regional severity of the anoxic event in the restricted Euro-boreal domains, as it has been previously suggested and modeled regionally.
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Effect of changes in delta18O content of the surface ocean on estimated sea surface temperatures in past warm climate.
Paleoceanography, 2006Co-Authors: D. M. Roche, Yannick Donnadieu, Emmanuelle Pucéat, D. PaillardAbstract:Using a coupled climate model of intermediate complexity including oxygen 18, CLIMBER-2, we investigate the evolution of the distribution of surface water 18O composition under warm climate conditions. We then determine the impact of changes of the surface water 18O distribution on ocean surface temperatures inferred from calcite oxygen 18. Our results show that published temperature reconstructions based on oxygen 18 from calcite are systematically biased by 2 to 4C in the absence of major Oceanic Circulation changes and up to 7C in the presence of major Oceanic Circulation changes. As the bias introduced is shown to vary with latitude, our work has major implications on past latitudinal temperature gradient reconstructions based on oxygen 18 measurements.
P. Sépulchre - One of the best experts on this subject based on the ideXlab platform.
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the role of eastern tethys seaway closure in the middle miocene climatic transition ca 14 ma
Climate of The Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:Abstract. The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoaling and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reorganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
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The role of East-Tethys seaway closure in the middle Miocene climatic transition (ca. 14 Ma)
Climate of the Past, 2013Co-Authors: Noémie Hamon, P. Sépulchre, V. Lefebvre, G. RamsteinAbstract:The Middle Miocene Climatic Transition (MMCT, approximately 14 Ma) is a key period in Cenozoic cooling and cryospheric expansion. Despite being well documented in isotopic record, the causes of the MMCT are still a matter of debate. Among various hypotheses, some authors suggested that it was due the final closure of the eastern Tethys seaway and subsequent Oceanic Circulation reorganisation. The aim of the present study is to quantify the impact of varying Tethys seaway depths on middle Miocene ocean and climate, in order to better understand its role in the MMCT. We present four sensitivity experiments with a fully coupled ocean-atmosphere general Circulation model. Our results indicate the presence of a warm and salty water source in the northern Indian Ocean when the eastern Tethys is deep open (4000 or 1000 m), which corresponds to the Tethyan Indian Saline Water (TISW) described on the basis of isotopic studies. This water source is absent in the experiments with shallow (250 m) and closed Tethys seaway, inducing strong changes in the latitudinal density gradient and ultimately the reinforcement of the Antarctic Circumpolar Current (ACC). Moreover, when the Tethys seaway is shallow or closed, there is a westward water flow in the Gibraltar Strait that strengthens the Atlantic Meridional Overturning Circulation (AMOC) compared to the experiments with deep-open Tethys seaway. Our results therefore suggest that the shoal-ing and final closure of the eastern Tethys seaway played a major role in the Oceanic Circulation reorganisation during the middle Miocene. The results presented here provide new constraints on the timing of the Tethys seaway closure and particularly indicate that, prior to 14 Ma, a deep-open Tethys seaway should have allowed the formation of TISW. Moreover, whereas the final closure of this seaway likely played a major role in the reor-ganisation of Oceanic Circulation, we suggest that it was not the main driver of the global cooling and Antarctica ice-sheet expansion during the MMCT. Here we propose that the initiation of the MMCT was caused by an atmospheric pCO 2 drawdown and that the Oceanic changes due to the Tethys seaway closure amplified the response of global climate and East Antarctic Ice Sheet.
