scholarly journals Stable isotopes of fossil teeth corroborate key general circulation model predictions for the Last Glacial Maximum in North America

2010 ◽  
Vol 37 (22) ◽  
pp. n/a-n/a ◽  
Author(s):  
Matthew J. Kohn ◽  
Moriah McKay
2012 ◽  
Vol 8 (5) ◽  
pp. 4885-4922
Author(s):  
X. Xu ◽  
G. Lohmann ◽  
M. Werner ◽  
X. Zhang

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.


2010 ◽  
Vol 6 (5) ◽  
pp. 2005-2054
Author(s):  
U. Mikolajewicz

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.


2011 ◽  
Vol 7 (1) ◽  
pp. 161-180 ◽  
Author(s):  
U. Mikolajewicz

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 complicated. 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 salinity in the Mediterranean in spite of reduced net evaporation.


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