The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform

Madeline Farber - One of the best experts on this subject based on the ideXlab platform.

Axel Timmermann - One of the best experts on this subject based on the ideXlab platform.

  • Tropical Air-Sea Interactions Accelerate the Recovery of the Atlantic Meridional Overturning Circulation after a Major Shutdown
    Journal of Climate, 2007
    Co-Authors: Uta Krebs, Axel Timmermann
    Abstract:

    Abstract Using a coupled ocean–sea ice–atmosphere model of intermediate complexity, the authors study the influence of air–sea interactions on the stability of the Atlantic Meridional Overturning Circulation (AMOC). Mimicking glacial Heinrich events, a Complete Shutdown of the AMOC is triggered by the delivery of anomalous freshwater forcing to the northern North Atlantic. Analysis of fully and partially coupled freshwater perturbation experiments under glacial conditions shows that associated changes of the heat transport in the North Atlantic lead to a cooling north of the thermal equator and an associated strengthening of the northeasterly trade winds. Because of advection of cold air and an intensification of the trade winds, the intertropical convergence zone (ITCZ) is shifted southward. Changes of the accumulated precipitation lead to the generation of a positive salinity anomaly in the northern tropical Atlantic and a negative anomaly in the southern tropical Atlantic. During the Shutdown phase of ...

  • Is the wind-stress forcing essential for the meridional overturning circulation?
    Geophysical Research Letters, 2004
    Co-Authors: Axel Timmermann, Hugues Goosse
    Abstract:

    [ 1 ] We use a global couple d atm osphere-ocean sea-ice model of interm ediate complexity to demonstrate that wind- forcing i s a crucial element to sustain meridional overturning flow i n t he Atlantic. Neglecting wind-stress in our multi- century-lon g simulations leads to a Complete Shutdown of the conveyor belt ci r culation. This r esult may have tremendous impacts f or an assessment of the sensitivity of 2-d clima t e models which typicall y do not capture wind-driven gyres. It is argued that wind effects may be a key element in determining the f ate and length of a collapsed THC state. Possible paleo implications will be discussed

Brigitte Vollmar - One of the best experts on this subject based on the ideXlab platform.

  • Complete Shutdown of microvascular perfusion upon hepatic cryothermia is critically dependent on local tissue temperature
    British journal of cancer, 2000
    Co-Authors: G. Schüder, Georg Pistorius, M Fehringer, Gernot Feifel, Michael D. Menger, Brigitte Vollmar
    Abstract:

    Since microvascular dysfunction with Complete circulatory arrest and, thus, prolongation of tissue ischaemia is considered a potential mechanism for cell necrosis following hepatic cryosurgery, we determined the temperature necessary for induction of Complete nutritive perfusion failure in cryothermia-treated rat livers. After localization of the cryoprobe with seven thermocouples and application of a single or double freeze-thaw cycle, in vivo fluorescence microscopy of the cryoinjured left lobe was performed over a 2-h period using a computer-controlled stepping motor, which guaranteed analysis of the identical liver tissue segments with exact allocation of the thermocouples and thus determination of tissue temperature. Cryothermia resulted in a central non-perfused part of injury, surrounded by a heterogeneously perfused peripheral zone. The non-perfused area after single and double freezing continuously increased over the first 90-min period due to a successive Shutdown of perfusion within the peripheral border zone. Analysis of the thermocouples' temperature at the end of freezing revealed the 0 degrees C-front at 11.7 mm (single freeze-thaw cycle) and 12.1 mm (double freeze-thaw cycle) distant from the centre of the cryoprobe, which exactly corresponds with the initial (30 min) expansion of the area with nutritive perfusion failure. The increased non-perfused tissue area at 2 h conformed a critical border temperature between 8.29 +/- 1.63 degrees C and 9.07 +/- 0.24 degrees C. From these findings, we conclude that freezing of liver tissue to temperatures of at least < 0 degrees C causes Complete/irreversible perfusion failure, which consequently will result in cell death and tissue necrosis, and may thus be supposed as a prerequisite for the safe and successful application of cryosurgery in hepatic tumour ablation.

Claire Waelbroeck - One of the best experts on this subject based on the ideXlab platform.

  • lgm hosing approach to heinrich event 1 results and perspectives from data model integration using water isotopes
    Quaternary Science Reviews, 2014
    Co-Authors: Didier M. Roche, Didier Paillard, Thibaut Caley, Claire Waelbroeck
    Abstract:

    Abstract Freshwater hosing has long been used in climate models to represent the perturbation associated with the release of icebergs during Heinrich Events. However, freshwater hosing ignores some of the icebergs-induced feedbacks on climate. It therefore bears the question whether the perturbed climate obtained through classical freshwater hosing experiments is realistic enough to be used as a proxy for a Heinrich Event. Using the fully coupled, water isotope enabled, climate model i LOVECLIM, we conducted a series of freshwater hosing experiments, accounting for the depleted signature of ice-sheet sourced water, under LGM conditions. Using paleoceanographic data, we integrated simulated and measured δ 18 O calcite at the surface and within the ocean column to evaluate whether (i) LGM freshwater hosing is a good proxy for Heinrich Event 1 and whether (ii) different sources for the freshwater in the North Atlantic result in different spatial anomalies that could be used to fingerprint the source of melt water. Results obtained with two sets of experiments indicate that first order simulated δ 18 O calcite anomalies are broadly consistent with the measured anomalies and that a Complete Shutdown of the thermohaline circulation is not consistent with the reconstructed patterns from foraminiferal calcite. A more detailed statistical analysis of the planktic and benthic δ 18 O calcite anomalies shows that the best experiment is obtained for a severely disturbed thermohaline circulation but not a Complete Shutdown. With our model sensitivity, this corresponds to a freshwater flux between 0.18 Sv and 0.3 Sv. Our results also indicate a better agreement when the freshwater flux is applied in the Labrador Sea than when directly applied to the Ruddiman Belt.

  • LGM hosing approach to Heinrich Event 1: results and perspectives from data–model integration using water isotopes
    Quaternary Science Reviews, 2014
    Co-Authors: Didier M. Roche, Didier Paillard, Thibaut Caley, Claire Waelbroeck
    Abstract:

    Abstract Freshwater hosing has long been used in climate models to represent the perturbation associated with the release of icebergs during Heinrich Events. However, freshwater hosing ignores some of the icebergs-induced feedbacks on climate. It therefore bears the question whether the perturbed climate obtained through classical freshwater hosing experiments is realistic enough to be used as a proxy for a Heinrich Event. Using the fully coupled, water isotope enabled, climate model i LOVECLIM, we conducted a series of freshwater hosing experiments, accounting for the depleted signature of ice-sheet sourced water, under LGM conditions. Using paleoceanographic data, we integrated simulated and measured δ 18 O calcite at the surface and within the ocean column to evaluate whether (i) LGM freshwater hosing is a good proxy for Heinrich Event 1 and whether (ii) different sources for the freshwater in the North Atlantic result in different spatial anomalies that could be used to fingerprint the source of melt water. Results obtained with two sets of experiments indicate that first order simulated δ 18 O calcite anomalies are broadly consistent with the measured anomalies and that a Complete Shutdown of the thermohaline circulation is not consistent with the reconstructed patterns from foraminiferal calcite. A more detailed statistical analysis of the planktic and benthic δ 18 O calcite anomalies shows that the best experiment is obtained for a severely disturbed thermohaline circulation but not a Complete Shutdown. With our model sensitivity, this corresponds to a freshwater flux between 0.18 Sv and 0.3 Sv. Our results also indicate a better agreement when the freshwater flux is applied in the Labrador Sea than when directly applied to the Ruddiman Belt.

Didier M. Roche - One of the best experts on this subject based on the ideXlab platform.

  • lgm hosing approach to heinrich event 1 results and perspectives from data model integration using water isotopes
    Quaternary Science Reviews, 2014
    Co-Authors: Didier M. Roche, Didier Paillard, Thibaut Caley, Claire Waelbroeck
    Abstract:

    Abstract Freshwater hosing has long been used in climate models to represent the perturbation associated with the release of icebergs during Heinrich Events. However, freshwater hosing ignores some of the icebergs-induced feedbacks on climate. It therefore bears the question whether the perturbed climate obtained through classical freshwater hosing experiments is realistic enough to be used as a proxy for a Heinrich Event. Using the fully coupled, water isotope enabled, climate model i LOVECLIM, we conducted a series of freshwater hosing experiments, accounting for the depleted signature of ice-sheet sourced water, under LGM conditions. Using paleoceanographic data, we integrated simulated and measured δ 18 O calcite at the surface and within the ocean column to evaluate whether (i) LGM freshwater hosing is a good proxy for Heinrich Event 1 and whether (ii) different sources for the freshwater in the North Atlantic result in different spatial anomalies that could be used to fingerprint the source of melt water. Results obtained with two sets of experiments indicate that first order simulated δ 18 O calcite anomalies are broadly consistent with the measured anomalies and that a Complete Shutdown of the thermohaline circulation is not consistent with the reconstructed patterns from foraminiferal calcite. A more detailed statistical analysis of the planktic and benthic δ 18 O calcite anomalies shows that the best experiment is obtained for a severely disturbed thermohaline circulation but not a Complete Shutdown. With our model sensitivity, this corresponds to a freshwater flux between 0.18 Sv and 0.3 Sv. Our results also indicate a better agreement when the freshwater flux is applied in the Labrador Sea than when directly applied to the Ruddiman Belt.

  • LGM hosing approach to Heinrich Event 1: results and perspectives from data–model integration using water isotopes
    Quaternary Science Reviews, 2014
    Co-Authors: Didier M. Roche, Didier Paillard, Thibaut Caley, Claire Waelbroeck
    Abstract:

    Abstract Freshwater hosing has long been used in climate models to represent the perturbation associated with the release of icebergs during Heinrich Events. However, freshwater hosing ignores some of the icebergs-induced feedbacks on climate. It therefore bears the question whether the perturbed climate obtained through classical freshwater hosing experiments is realistic enough to be used as a proxy for a Heinrich Event. Using the fully coupled, water isotope enabled, climate model i LOVECLIM, we conducted a series of freshwater hosing experiments, accounting for the depleted signature of ice-sheet sourced water, under LGM conditions. Using paleoceanographic data, we integrated simulated and measured δ 18 O calcite at the surface and within the ocean column to evaluate whether (i) LGM freshwater hosing is a good proxy for Heinrich Event 1 and whether (ii) different sources for the freshwater in the North Atlantic result in different spatial anomalies that could be used to fingerprint the source of melt water. Results obtained with two sets of experiments indicate that first order simulated δ 18 O calcite anomalies are broadly consistent with the measured anomalies and that a Complete Shutdown of the thermohaline circulation is not consistent with the reconstructed patterns from foraminiferal calcite. A more detailed statistical analysis of the planktic and benthic δ 18 O calcite anomalies shows that the best experiment is obtained for a severely disturbed thermohaline circulation but not a Complete Shutdown. With our model sensitivity, this corresponds to a freshwater flux between 0.18 Sv and 0.3 Sv. Our results also indicate a better agreement when the freshwater flux is applied in the Labrador Sea than when directly applied to the Ruddiman Belt.