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| Menviel, L.; Mouchet, A.; Meissner, K. J.; Joos, F.; England, M. H.. |
| δ13CO2 measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale changes in atmospheric CO2. However, the interpretation of δ13CO2 is not straightforward. Using carbon isotope-enabled versions of the LOVECLIM and Bern3D models, we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ13CO2 as well as on the oceanic δ13C distribution. In general, we find that the formation rates of AABW, NADW, NPDW and AAIW are negatively correlated with changes in δ13CO2:... |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00293/40406/38965.pdf |
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| Menviel, L.; Timmermann, A.; Friedrich, T.; England, M. H.. |
| Millennial-scale variability associated with Dansgaard-Oeschger events is arguably one of the most puzzling climate phenomena ever discovered in paleoclimate archives. Here, we set out to elucidate the underlying dynamics by conducting a transient global hindcast simulation with a 3-D intermediate complexity earth system model covering the period 50 to 30 ka BP. The model is forced by time-varying external boundary conditions (greenhouse gases, orbital forcing, and ice-sheet orography and albedo) and anomalous North Atlantic freshwater fluxes, which mimic the effects of changing northern hemispheric ice volume on millennial timescales. Together these forcings generate a realistic global climate trajectory, as demonstrated by an extensive model/paleo data... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00274/38487/36951.pdf |
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| Golledge, N. R.; Menviel, L.; Carter, L.; Fogwill, C. J.; England, M. H.; Cortese, G.; Levy, R. H.. |
| During the last glacial termination, the upwelling strength of the southern polar limb of the Atlantic Meridional Overturning Circulation varied, changing the ventilation and stratification of the high-latitude Southern Ocean. During the same period, at least two phases of abrupt global sea-level rise-meltwater pulses-took place. Although the timing and magnitude of these events have become better constrained, a causal link between ocean stratification, the meltwater pulses and accelerated ice loss from Antarctica has not been proven. Here we simulate Antarctic ice sheet evolution over the last 25 kyr using a data-constrained ice-sheet model forced by changes in Southern Ocean temperature from an Earth system model. Results reveal several episodes of... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00497/60847/64264.pdf |
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| Menviel, L.; England, M. H.; Meissner, K. J.; Mouchet, A.; Yu, J.. |
| Paleoproxy records indicate that a marked weakening of the Atlantic Meridional Overturning Circulation (AMOC) during Heinrich events was often accompanied by a notable atmospheric CO2 increase. However, previous modeling studies display conflicting atmospheric CO2 responses to an AMOC shutdown. Here we use model simulations combined with paleoproxy records to show that depending on the deep and bottom water transport in the Northern and Southern Pacific Ocean during an AMOC weakening, the ocean can act either as a sink or a source of carbon. Results from idealized meltwater experiments as well as from a transient experiment covering Heinrich stadial 4 suggest that a shutdown of the AMOC during Heinrich stadials 4 (HS4) and 1 (HS1) led to an enhancement of... |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00291/40227/38679.pdf |
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