OCEAN RESPONSE TO THE LAST DEGLACIATION:CONVENTIONAL PALEOCLIMATE MODELS AND CONTROVERSY
大洋环流型式转换在冰期旋回中的作用及经典第四纪冰期理论质疑(续)

Geological evidence, obtained from oxygen-isotopic analysis of deep sea sediments, continental ice sheets, mountain glaciers and polar ice cores in the both hemispheres shows that the last glaciation terminated at about 14000 aB. P. It occurred prior to the insolation maximum as expected by the Milankovitch astronomical theory. The evidence also shows that the glacial-interglacial cycles are dominated by the 100 000a periodicity with asymmetrical shape. Long-term ice build-up ends abruptly with rapid wasting. The insolation perturbations induced by the earth's orbital parameters have greater powers only at 41000a, and 23000a/19000a cycles. Thus the characteristics of geological records deny direct simple response of the climatic changes to the solar radiation forcing. While summarizing the leading hypothesis for explanation of the ice ages and the ice sheet-size-climate linkage, this paper centres on the ocean-operation-climate model. This model stresses the impact of the Atlantic conveyor belt of the oceanic circulation on the northern hemispheric climate with the analyses of energy, water mass and salinity balance. Based on geological evidence from deep sea sediments, the model suggests that the ocean circulation pattern was different during glacial time than today. The Younger Dryas cold event probably exemplifies the influence of the ocean reorganization on climate. Here we also discuss some basic problems regarding climate theories of the ice ages.