冰期与Milankovitch理论

Ice Ages and Milankovitch Theory

本文综述了20年来冰期及其形成理论研究的突破性进展。随着新技术的应用,从深海沉积、大陆冰盖及湖相沉积中获得大量新的地质气候证据。地质气候时间序列的频谱分析,地球轨道变化和日照变化的精密计算以及气候模拟,终于导致了第四纪冰期研究上的重大突破和Milankovitch理论的复兴。在解释第四纪冰期的各种理论与假设中,唯有天文学理论得到了大量科学证据的有力支持。无论在时域和谱域方面,轨道变化在气候系统中都留下了清晰的足迹。

This paper reviews the significant advances, principal progress, and breakthrough from studies of the Ice Ages and Milankovitch theory in the past two decades. With the improvements in dating and in interpretation of geological data and with advantage in consideing monthly insolation as well as with the development of climate models, it seems to have laid to Milankovitch renaissance. Observations on deep-sea cores and polar ice core demostrate that late Pleistocene climate is dominated by three broad-band cycles centered near periods of 23 kyr, 41 kyr, and 100 kyr. The periods' of climate cycles match orbital cycles of precession, obliquity, and eccentricity. Each orbit-climate pair is significantly correlated. This evidence shows that both in the frequency and in the time domains orbital influences are felt by climate system. It is concluded that changes in the earths orbital geometry are the fundamental caure of the succession of Quaternary ice ages. And at least near the obliquty and precession frequecies, a considerable fraction of the climate variance is driven in some way by insolation changes forced by changes in the earths orbit. Modeling experiments show that the link betweeen orbital variations and climate not only was tied to ice volume but also to atmosphere circulations, deep water formation, and greenhouse gases. Among the competing theories and hypotheses to explain the coming and going of the Quaternary ice ages only the astronomical theory has been supported so far by substantial physical evidences. Except for the daily and annual cycles, there is no other place in the climatic spectrum for which this exactitude is possible. Consequently, the astronomical theory is the only one that can be used to predict precisely the duration of natural quasiperiodic changes in climate. Assuming no human interference at the astronomical scale, orbital forcing predicts that the general cooling that began 6 kyr B.P. will continue with a first moderate cold peak around 5 kyr A.P., a major cooling about 23 kyr A.P., and full ice age conditions 60 kyr A.P..