PAST CLIMATE AND THE ROLE OF OCEAN HEAT-TRANSPORT - MODEL SIMULATIONSFOR THE CRETACEOUS

A series of general circulation model experiments using Global Environ mental and Ecological Simulation of Interactive Systems (GENESIS) were executed to evaluate the sensitivity of simulated mid-Cretaceous clim ate to smalt perturbations in ocean heat transport. Three experiments were performed: (1) mixed layer ocean with no ocean heat transport, ZE ROQ, (2) ocean heat transport specified as required for GENESIS to bes t match modern observations, ONEQ, and (3) doubled ocean heat transpor t, TWOQ. The ONEQ experiment represents an ocean heat transport which is actually about 15% of the values given by Carissimo et al. (1985) f rom modern observations. As a sensitivity experiment these model simul ations represent a doubling of the role of the ocean. However, relativ e to the observations, they represent small perturbations to the total poleward heat transport in the model. With the exception of the tropi cs, no major changes in the structure of the general circulation of th e atmosphere resulted from the modification of the ocean heat transpor t. However, relatively small increases in ocean heat transport resulte d in a number of significant differences between simulations, includin g tropical. cooling, polar warming, weakened equator-to-pole surface t emperature gradients, weakened midlatitude jets, decreased land-sea pr essure contrast, and decreased midlatitude storminess. The experiments indicate that changes in ocean heat transport which are well within t he realm of possibility for Earth history can have significant climati c impact. Although ocean heat transport may be a significant factor in explaining Cretaceous polar warmth, the changes specified in these ex periments alone are not sufficient to explain the polar warmth of the Cretaceous.