Research Centre for Palaeoclimatology, Ritsumeikan University, Kusatsu 525-8577, Japan.
Research Center for Inland Seas, Kobe University, Kobe 657-8501, Japan.
Sci Rep. 2017 Jan 16;7:40682. doi: 10.1038/srep40682.
The weakening of the geomagnetic field causes an increase in galactic cosmic ray (GCR) flux. Some researchers argue that enhanced GCR flux might lead to a climatic cooling by increasing low cloud formation, which enhances albedo (umbrella effect). Recent studies have reported geological evidence for a link between weakened geomagnetic field and climatic cooling. However, more work is needed on the mechanism of this link, including whether the umbrella effect is playing a central role. In this research, we present new geological evidence that GCR flux change had a greater impact on continental climate than on oceanic climate. According to pollen data from Osaka Bay, Japan, the decrease in temperature of the Siberian air mass was greater than that of the Pacific air mass during geomagnetic reversals in marine isotope stages (MIS) 19 and 31. Consequently, the summer land-ocean temperature gradient was smaller, and the summer monsoon was weaker. Greater terrestrial cooling indicates that a reduction of insolation is playing a key role in the link between the weakening of the geomagnetic field and climatic cooling. The most likely candidate for the mechanism seems to be the increased albedo of the umbrella effect.
地磁场的减弱会导致银河宇宙射线（GCR）通量增加。一些研究人员认为，增强的 GCR 通量可能通过增加低云形成来导致气候冷却，从而增强反照率（伞效应）。最近的研究报告了地质证据，证明地磁场减弱与气候冷却之间存在联系。然而，对于这种联系的机制，还需要更多的研究，包括伞效应是否在其中发挥了核心作用。在这项研究中，我们提出了新的地质证据，表明 GCR 通量变化对大陆气候的影响大于对海洋气候的影响。根据来自日本大阪湾的花粉数据，在地磁场反转期间，海洋同位素阶段（MIS）19 和 31 的西伯利亚气团的温度下降大于太平洋气团的温度下降。因此，夏季陆海温度梯度变小，夏季季风较弱。大陆地区的降温幅度更大，表明太阳辐射的减少在地磁场减弱与气候冷却之间的联系中起着关键作用。该机制最有可能的候选者似乎是伞效应的反照率增加。
