scholarly journals Application of Ocean Models for the Interpretation of Atmospheric General Circulation Model Experiments on the Climate of the Last Glacial Maximum

1992 ◽  
Vol 7 (6) ◽  
pp. 769-782 ◽  
Author(s):  
M. Lautenschlager ◽  
U. Mikolajewicz ◽  
E. Maier-Reimer ◽  
C. Heinze
Keyword(s):  
General Circulation Model ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Circulation Model ◽  
Model Experiments ◽  
Atmospheric General Circulation ◽  
Ocean Models ◽  
The Last Glacial Maximum ◽  
The Last Glacial

scholarly journals Influence of Last Glacial Maximum boundary conditions on the global water isotope distribution in an atmospheric general circulation model

2013 ◽  
Vol 9 (2) ◽  
pp. 789-809 ◽  
Author(s):  
T. Tharammal ◽  
A. Paul ◽  
U. Merkel ◽  
D. Noone
Keyword(s):  
Boundary Conditions ◽  
Surface Temperature ◽  
General Circulation Model ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Atmospheric General Circulation Model ◽  
Ice Sheet ◽  
Circulation Model ◽  
Atmospheric General Circulation ◽  
Water Isotope

Abstract. To understand the validity of δ18O proxy records as indicators of past temperature change, a series of experiments was conducted using an atmospheric general circulation model fitted with water isotope tracers (Community Atmosphere Model version 3.0, IsoCAM). A pre-industrial simulation was performed as the control experiment, as well as a simulation with all the boundary conditions set to Last Glacial Maximum (LGM) values. Results from the pre-industrial and LGM simulations were compared to experiments in which the influence of individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea surface temperature (SST), and orbital parameters) were changed each at a time to assess their individual impact. The experiments were designed in order to analyze the spatial variations of the oxygen isotopic composition of precipitation (δ18Oprecip) in response to individual climate factors. The change in topography (due to the change in land ice cover) played a significant role in reducing the surface temperature and δ18Oprecip over North America. Exposed shelf areas and the ice sheet albedo reduced the Northern Hemisphere surface temperature and δ18Oprecip further. A global mean cooling of 4.1 °C was simulated with combined LGM boundary conditions compared to the control simulation, which was in agreement with previous experiments using the fully coupled Community Climate System Model (CCSM3). Large reductions in δ18Oprecip over the LGM ice sheets were strongly linked to the temperature decrease over them. The SST and ice sheet topography changes were responsible for most of the changes in the climate and hence the δ18Oprecip distribution among the simulations.

scholarly journals Variations of oceanic oxygen isotopes at the present day and the LGM: equilibrium simulations with an oceanic general circulation model

2012 ◽  
Vol 8 (5) ◽  
pp. 4885-4922
Author(s):  
X. Xu ◽  
G. Lohmann ◽  
M. Werner ◽  
X. Zhang
Keyword(s):  
Oxygen Isotope ◽  
General Circulation Model ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Circulation Model ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Oceanic General Circulation Model ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The isotope-enabled oceanic general circulation model, MPI-OM, is used to simulate the oxygen isotope compositions of sea waters in the oceans under preindustrial and last glacial maximum climate conditions. Simulated oceanic isotope distributions at the last glacial maximum (21 000 yr ago) show features similar to the preindustrial in most basins but the Northern North Atlantic. With the exception of the ice sheet impact, the oxygen-18 content variations at sea surface during the last glacial maximum are mainly controlled by the changes in boundary isotopic fluxes in most regions, while the changes from subsurface to bottom waters are mostly due to the differences in the water mass circulations. The changes in topography at the northern high latitudes have a remarkable influence on the isotopic composition in the Arctic Ocean. The pre-industrial and the last glacial maximum calcite oxygen isotope compositions in the surface water and their difference are also calculated. These results are compared with the observed values from different foraminifera species and are in agreement with the observations in most regions.

scholarly journals Modeling Mediterranean ocean climate of the Last Glacial Maximum

2010 ◽  
Vol 6 (5) ◽  
pp. 2005-2054
Author(s):  
U. Mikolajewicz
Keyword(s):  
General Circulation Model ◽  
Last Glacial Maximum ◽  
General Circulation ◽  
Circulation Model ◽  
Glacial Maximum ◽  
Strong Increase ◽  
Last Glacial ◽  
The Mediterranean ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. A regional ocean general circulation model of the Mediterranean is used to study the climate of the last glacial maximum. The atmospheric forcing for these simulations has been derived from simulations with an atmospheric general circulation model, which in turn was forced with surface conditions from a coarse resolution earth system model. The model is successful in reproducing the general patterns of reconstructed sea surface temperature anomalies with the strongest cooling in summer in the northwestern Mediterranean and weak cooling in the Levantine, although the model underestimates the extent of the summer cooling in the western Mediterranean. However, there is a strong vertical gradient associated with this pattern of summer cooling, which makes the comparison with reconstructions nontrivial. The exchange with the Atlantic is decreased to roughly one half of its present value, which can be explained by the shallower Strait of Gibraltar as a consequence of lower global sea level. This reduced exchange causes a strong increase of the salinity in the Mediterranean in spite of reduced net evaporation.

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