米兰科维奇旋回理论不是轨道尺度古气候分析和解释的一把潜在万能钥匙

Milankovitch theory is not a potential versatile key for orbital-scale paleoclimate analysis and interpretation

关键词:  米兰科维奇旋回理论  古气候  轨道参数  周期  轨道尺度

Key words:  Milankovitch theory  paleoclimate  orbital parameters  cycle  orbital scale

摘要:

米兰科维奇旋回理论认为地球轨道参数（偏心率、地轴倾斜度、岁差）三要素的变化引起到达北半球中高纬度夏季日射量的变化是导致冰期-间冰期旋回的根本原因，北纬65°附近的夏季入射太阳辐射变化是驱动冰期-间冰期旋回的关键。米兰科维奇旋回理论已被古气候学家奉为经典。最近几年，有一种趋势逐渐显现出来：高分辨率的气候代用指标展现出相关周期性（如100 ka、41 ka和20 ka），则自主用米兰科维奇旋回理论去解释。鉴于此，基于两组不受轨道参数影响的数据，意在说明轨道参数的周期变化可以被地质载体所记录，但地质载体表现出的周期性（如100 ka）却不一定由轨道参数变化所致。确定一个气候代用指标具有某种周期性（如100 ka）仅仅只是一个开始，但还不能直接与米兰科维奇旋回理论相联系。在轨道尺度古气候研究中，可能需要注意这一点，或者至少得证明代用指标变化的物理、化学等机制与古气候变化是相关的。另外，需要注重地层年代学的可靠性。

Abstract:

The Milankovitch theory posits that variations in Earth’s orbital parameters (eccentricity, obliquity, and precession) cause changes in summer insolation at mid-to-high latitudes in the Northern Hemisphere. These variations are considered the fundamental driver of glacial-interglacial cycles. In particular, changes in summer solar radiation around 65°N are regarded as pivotal in triggering these cycles. This theory has been widely accepted as a classic in the field of paleoclimatology. In recent years, a trend has emerged whereby high-resolution climate proxies exhibiting periodicities such as 100 ka, 41 ka, and 20 ka are automatically attributed to Milankovitch theory. In light of this, the present study employs two datasets uninfluenced by orbital parameters to demonstrate that while periodic variations in orbital parameters can be recorded in geological archives, the periodicities displayed by these archives (e.g. 100 ka) are not necessarily caused by orbital changes. The identification of a particular periodicity in a climate proxy (e.g. 100 ka) is merely a preliminary finding and should not be directly associated with Milankovitch theory without additional corroborating evidence. In the context of orbital-scale paleoclimate studies, a cautious approach is imperative. At the very least, it must be demonstrated that the physical, chemical, or other mechanisms underpinning proxy variations are correlated with paleoclimate changes. Furthermore, greater emphasis should be placed on the reliability of stratigraphic chronology.