The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Jeanclaude Duplessy - One of the best experts on this subject based on the ideXlab platform.
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changes in north atlantic Deep Water Formation associated with the dansgaard oeschger temperature oscillations 60 10 ka
Quaternary Science Reviews, 2002Co-Authors: Mary Elliot, Laurent Labeyrie, Jeanclaude DuplessyAbstract:We closely comparedhigh-resolution d 13 C records of benthic foraminifera Cibicides wuellerstorfi, a proxy for Deep-Water ventilation, with the Dansgaard–Oeschger temperature oscillations. Our results reveal different perturbations of Deep-Water Formation in the North Atlantic Ocean associated with the millennial-scale climate oscillations during the last glacial period. The cooling episodes associated with the drastic Heinrich events are related to large reductions of Deep-Water Formation and a northward migration of 13 C depleted southern source Deep Waters to 621N in the North Atlantic Ocean. The inter-Heinrich events which are correlatedto the other coldstad ials, are markedby significant changes of sea surface temperature aroundthe Rockall Plateau, variations in the flux of icebergs to the North Atlantic Ocean but are not associated with such important reduction of Deep-Water Formation. If changes in the thermohaline circulation (THC) are associatedwith these millennial-scale climatic oscillation they affect only the Deeper Water masses, below 2000 m, of the North Atlantic Ocean. We thus show that equivalent degree of cooling over Greenland is obtained with different perturbations of Deep-Water Formation. Our results either question the role of the THC as the unique explanation for these millennial-scale climate oscillations, or call upon an amplifying mechanism not yet taken into account. r 2002 Elsevier Science Ltd. All rights reserved.
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Changes in North Atlantic Deep-Water Formation associated with the Dansgaard–Oeschger temperature oscillations (60–10 ka)
Quaternary Science Reviews, 2002Co-Authors: Mary Elliot, Laurent Labeyrie, Jeanclaude DuplessyAbstract:We closely comparedhigh-resolution d 13 C records of benthic foraminifera Cibicides wuellerstorfi, a proxy for Deep-Water ventilation, with the Dansgaard–Oeschger temperature oscillations. Our results reveal different perturbations of Deep-Water Formation in the North Atlantic Ocean associated with the millennial-scale climate oscillations during the last glacial period. The cooling episodes associated with the drastic Heinrich events are related to large reductions of Deep-Water Formation and a northward migration of 13 C depleted southern source Deep Waters to 621N in the North Atlantic Ocean. The inter-Heinrich events which are correlatedto the other coldstad ials, are markedby significant changes of sea surface temperature aroundthe Rockall Plateau, variations in the flux of icebergs to the North Atlantic Ocean but are not associated with such important reduction of Deep-Water Formation. If changes in the thermohaline circulation (THC) are associatedwith these millennial-scale climatic oscillation they affect only the Deeper Water masses, below 2000 m, of the North Atlantic Ocean. We thus show that equivalent degree of cooling over Greenland is obtained with different perturbations of Deep-Water Formation. Our results either question the role of the THC as the unique explanation for these millennial-scale climate oscillations, or call upon an amplifying mechanism not yet taken into account. r 2002 Elsevier Science Ltd. All rights reserved.
A Lascaratos - One of the best experts on this subject based on the ideXlab platform.
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Deep Water Formation in the adriatic sea interannual simulations for the years 1979 1999
Deep Sea Research Part I: Oceanographic Research Papers, 2008Co-Authors: A. Mantziafou, A LascaratosAbstract:Abstract Simulations of the interannual variability of the Deep-Water Formation processes in the Adriatic basin for the years 1979–1999 are performed using the Princeton Ocean Model (POM) with a ∼10 km grid and 6-h atmospheric forcing provided by the European Center for Medium Weather Forecast (ECMWF). Focus is given to the pattern and amplitude of the interannual variability of the Water mass Formation processes in terms of Deep-Water Formation sites, rates and characteristics. The connection of this variability with the interannual variability of (a) the atmospheric forcing and (b) the open boundary characteristics is investigated. The model performance is tested against the few available observations of Deep-Water Formation processes inside the basin and generally shows a good agreement with the main characteristics of the mixed layer and the Deep-Water Formation rates. A strong interannual variability is found in the calculated Deep-Water Formation rate of the basin, which is highly dependent on the interannual variability of the atmospheric forcing. This rate becomes three times larger than climatology during the biennium 1992–1993, and during all years it is associated mostly with the events of enhanced buoyancy loss and not with the mean winter buoyancy fields. Advection through the open boundary plays an important role in determining the characteristics and volume of Deep Water formed inside the Adriatic basin, but it is the high frequency atmospheric forcing that determines the amplitude of the interannual variability of Deep-Water Formation rates.
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Deep-Water Formation in the Adriatic Sea: Interannual simulations for the years 1979–1999
Deep Sea Research Part I: Oceanographic Research Papers, 2008Co-Authors: A. Mantziafou, A LascaratosAbstract:Abstract Simulations of the interannual variability of the Deep-Water Formation processes in the Adriatic basin for the years 1979–1999 are performed using the Princeton Ocean Model (POM) with a ∼10 km grid and 6-h atmospheric forcing provided by the European Center for Medium Weather Forecast (ECMWF). Focus is given to the pattern and amplitude of the interannual variability of the Water mass Formation processes in terms of Deep-Water Formation sites, rates and characteristics. The connection of this variability with the interannual variability of (a) the atmospheric forcing and (b) the open boundary characteristics is investigated. The model performance is tested against the few available observations of Deep-Water Formation processes inside the basin and generally shows a good agreement with the main characteristics of the mixed layer and the Deep-Water Formation rates. A strong interannual variability is found in the calculated Deep-Water Formation rate of the basin, which is highly dependent on the interannual variability of the atmospheric forcing. This rate becomes three times larger than climatology during the biennium 1992–1993, and during all years it is associated mostly with the events of enhanced buoyancy loss and not with the mean winter buoyancy fields. Advection through the open boundary plays an important role in determining the characteristics and volume of Deep Water formed inside the Adriatic basin, but it is the high frequency atmospheric forcing that determines the amplitude of the interannual variability of Deep-Water Formation rates.
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an eddy resolving numerical study of the general circulation and Deep Water Formation in the adriatic sea
Deep Sea Research Part I: Oceanographic Research Papers, 2004Co-Authors: A. Mantziafou, A LascaratosAbstract:Abstract General circulation and Deep-Water Formation (DWF) processes in the Adriatic basin in a climatological year were numerically simulated in a high-resolution (1/20th of a degree) implementation of the Princeton Ocean Model (POM). The “perpetual” year atmospheric data were computed from the ECMWF Reanalysis data (1°×1°) covering the period 1979–1994. The model reproduces the main basin features of the general circulation, Water mass distribution and their seasonal variability. The Adriatic Deep Water exiting through the Otranto Strait is produced with two different mechanisms inside the basin: (a) by open ocean Deep convection over the Southern Adriatic Pit and Middle Adriatic Pit (b) on the continental shelf of the Northern and Middle Adriatic. The estimated contributions of both mechanisms suggest that 82% of the Adriatic Deep Water is formed inside the Southern Adriatic Pit, while all the higher density Water in this Water mass comes from the northern regions. The role of mesoscale eddies at the periphery of the dense-Water chimney in the Southern Adriatic Pit was examined and their contribution to the lateral buoyancy flux, during the convection process, found to be small. The DWF rate at Otranto Strait is 0.28 Sv with σ θ over 29.15. The sensitivity of the DWF processes to interannual variability of the buoyancy forcing and river runoff was assessed with a number of process-study numerical experiments. In these experiments the effect of an imposed “extreme” buoyancy forcing during 1 year, on the DWF rates, was to modify them during the specific year, but the effects were still present in the following normal climatological year. This shows that the DWF rates and their mass characteristics at a specific year depend not only on the atmospheric conditions prevailing that specific year but on the previous year's as well, thus leading to the concept of a “memory” of the basin.
Edward A Boyle - One of the best experts on this subject based on the ideXlab platform.
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Rapid Communication Relation of subtropical Atlantic temperature, high-latitude ice rafting, Deep Water Formation, and European climate 130,000-60,000 years ago
2020Co-Authors: Scott J Lehman, Julian P Sachs, Andrew M Crotwell, Edward A BoyleAbstract:A new, high-resolution record of sea surface temperature from the subtropical western North Atlantic documents a series of abrupt coolings within marine isotope stage 5 which can be objectively correlated with marine-core evidence for increased ice-sheet discharge at subpolar latitudes and reduced North Atlantic Deep Water Formation. These results indicate that ice-sheet forcing of Deep ocean circulation influenced surface temperatures over much of the North Atlantic. A proposed correlation to the pollen record of Grande Pile, France, indicates that each cold event seen in the pollen sequence has a unique counterpart in the record of subtropical ocean temperature. If this correlation is correct, it suggests that the warmest part of the European Eemian ended suddenly in response to oceanographic changes, and that the subsequent post-temperate phase of the Eemian extended well into the interval of ice sheet growth corresponding to marine isotope substage 5d. r 2002 Elsevier Science Ltd. All rights reserved.
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relation of subtropical atlantic temperature high latitude ice rafting Deep Water Formation and european climate 130 000 60 000 years ago
Quaternary Science Reviews, 2002Co-Authors: Scott J Lehman, Julian P Sachs, Andrew M Crotwell, Lloyd D Keigwin, Edward A BoyleAbstract:Abstract A new, high-resolution record of sea surface temperature from the subtropical western North Atlantic documents a series of abrupt coolings within marine isotope stage 5 which can be objectively correlated with marine-core evidence for increased ice-sheet discharge at subpolar latitudes and reduced North Atlantic Deep Water Formation. These results indicate that ice-sheet forcing of Deep ocean circulation influenced surface temperatures over much of the North Atlantic. A proposed correlation to the pollen record of Grande Pile, France, indicates that each cold event seen in the pollen sequence has a unique counterpart in the record of subtropical ocean temperature. If this correlation is correct, it suggests that the warmest part of the European Eemian ended suddenly in response to oceanographic changes, and that the subsequent post-temperate phase of the Eemian extended well into the interval of ice sheet growth corresponding to marine isotope substage 5d.
Mary Elliot - One of the best experts on this subject based on the ideXlab platform.
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changes in north atlantic Deep Water Formation associated with the dansgaard oeschger temperature oscillations 60 10 ka
Quaternary Science Reviews, 2002Co-Authors: Mary Elliot, Laurent Labeyrie, Jeanclaude DuplessyAbstract:We closely comparedhigh-resolution d 13 C records of benthic foraminifera Cibicides wuellerstorfi, a proxy for Deep-Water ventilation, with the Dansgaard–Oeschger temperature oscillations. Our results reveal different perturbations of Deep-Water Formation in the North Atlantic Ocean associated with the millennial-scale climate oscillations during the last glacial period. The cooling episodes associated with the drastic Heinrich events are related to large reductions of Deep-Water Formation and a northward migration of 13 C depleted southern source Deep Waters to 621N in the North Atlantic Ocean. The inter-Heinrich events which are correlatedto the other coldstad ials, are markedby significant changes of sea surface temperature aroundthe Rockall Plateau, variations in the flux of icebergs to the North Atlantic Ocean but are not associated with such important reduction of Deep-Water Formation. If changes in the thermohaline circulation (THC) are associatedwith these millennial-scale climatic oscillation they affect only the Deeper Water masses, below 2000 m, of the North Atlantic Ocean. We thus show that equivalent degree of cooling over Greenland is obtained with different perturbations of Deep-Water Formation. Our results either question the role of the THC as the unique explanation for these millennial-scale climate oscillations, or call upon an amplifying mechanism not yet taken into account. r 2002 Elsevier Science Ltd. All rights reserved.
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Changes in North Atlantic Deep-Water Formation associated with the Dansgaard–Oeschger temperature oscillations (60–10 ka)
Quaternary Science Reviews, 2002Co-Authors: Mary Elliot, Laurent Labeyrie, Jeanclaude DuplessyAbstract:We closely comparedhigh-resolution d 13 C records of benthic foraminifera Cibicides wuellerstorfi, a proxy for Deep-Water ventilation, with the Dansgaard–Oeschger temperature oscillations. Our results reveal different perturbations of Deep-Water Formation in the North Atlantic Ocean associated with the millennial-scale climate oscillations during the last glacial period. The cooling episodes associated with the drastic Heinrich events are related to large reductions of Deep-Water Formation and a northward migration of 13 C depleted southern source Deep Waters to 621N in the North Atlantic Ocean. The inter-Heinrich events which are correlatedto the other coldstad ials, are markedby significant changes of sea surface temperature aroundthe Rockall Plateau, variations in the flux of icebergs to the North Atlantic Ocean but are not associated with such important reduction of Deep-Water Formation. If changes in the thermohaline circulation (THC) are associatedwith these millennial-scale climatic oscillation they affect only the Deeper Water masses, below 2000 m, of the North Atlantic Ocean. We thus show that equivalent degree of cooling over Greenland is obtained with different perturbations of Deep-Water Formation. Our results either question the role of the THC as the unique explanation for these millennial-scale climate oscillations, or call upon an amplifying mechanism not yet taken into account. r 2002 Elsevier Science Ltd. All rights reserved.
Michel Crepon - One of the best experts on this subject based on the ideXlab platform.
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large scale preconditioning of Deep Water Formation in the northwestern mediterranean sea
Journal of Physical Oceanography, 1996Co-Authors: Gurvan Madec, Pascale Delecluse, Michel Crepon, Francois LottAbstract:Abstract The large-scale processes preconditioning the winter Deep-Water Formation in the northwestern Mediterranean Sea are investigated with a primitive equation numerical model where convection is parameterized by a non-penetrative convective adjustment algorithm. The ocean is forced by momentum and buoyancy fluxes that have the gross features of mean winter forcing found in the MEDOC area. The wind-driven barotropic circulation appears to be a major ingredient of the preconditioning phase of Deep-Water Formation. After three months, the ocean response is dominated by a strong barotropic cyclonic vortex located under the forcing area, which fits the Sverdrup balance away from the northern coast. In the vortex center, the whole Water column remains trapped under the forcing area all winter. This trapping enables the thermohaline forcing to drive Deep-Water Formation efficiently. Sensitivity studies show that, β effect and bottom topography play a paramount role and confirm that Deep convection occurs on...
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a three dimensional numerical study of Deep Water Formation in the northwestern mediterranean sea
Journal of Physical Oceanography, 1991Co-Authors: Gurvan Madec, Pascale Delecluse, Michel Chartier, Michel CreponAbstract:Abstract Deep-Water Formation (DWF) in the northwestern Mediterranean Sea and the subsequent horizontal circulation are investigated in a rectangular basin with a three-dimensional primitive equation model. The basin is forced by constant climatological heat and salt fluxes. Convective motion is parameterized by a simple nonpenetrative convective adjustment process plus Richardson number–dependent vertical eddy viscosity and diffusivity. A homogeneous column of dense Water is progressively formed in the forcing area. Meanders of 40-km wavelength develop at the periphery of the column. These features agree with observations. Energy studies show that the meanders are generated mainly through a baroclinic instability process. These meanders, and the associated cells of vertical motion, contribute to the process of DWF. They generate vertical advection, while the associated horizontal advection tends to restratify the surface Water of the column, and thus to inhibit very Deep convection. Just before the end o...
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Thermohaline-Driven Deep Water Formation in the Northwestern Mediterranean Sea
Elsevier oceanography series, 1991Co-Authors: Gurvan Madec, Michel CreponAbstract:Abstract Deep Water Formation (DWF) occuring in the Northwestern Mediterranean Sea in winter is investigated using an analytical model and a 3D primitive equation numberical model forced by a simplified thermohaline forcing. It is found that the longshore forcing variations excite Kelvin wave fronts which contribute to detachment off the coast of the Deep convective area. Dealing with a realistic values of surface cooling and evaporation, the numerical model reproduces the main features of DWF observed in nature, and the convection penetrates down to the ocean bottom after 3 months. The importance of the convective process versus the baroclinic adjustment process is discussed. The thermohaline forcing is found to be a major component of the horizontal circulation of the Northwestern Mediterranean Sea.
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The effect of thermohaline forcing variability on Deep Water Formation in the western Mediterranean Sea: a high-resolution three-dimensional numerical study
Dynamics of Atmospheres and Oceans, 1991Co-Authors: Gurvan Madec, Michel Chartier, Michel CreponAbstract:Abstract Deep Water Formation in the northwestern Mediterranean Sea is investigated with a high-resolution three-dimensional primitive equation numerical model. A rectangular basin is forced by various heat and salt fluxes. A 1000-m thick patch of dense Water is formed within the forcing area, which is surrounded by a cyclonic vortex. Meanders develop at the periphery of the patch and then tend to occupy the whole patch area. These features agree with observations. Sensitivity studies of the space and time variability of the forcing are presented. It is found that these variabilities are of great importance in Deep Water Formation. Deep Water Formation appears to depend on a convective process parameterized by a simple non-penetrative convective adjustment and on vertical motion induced by baroclinic instability. The two processes are strongly linked. The convective process triggers the depth of the convection while the baroclinic adjustment process is responsible for the volume of dense Water formed.
