Study of the geomagnetic variation and its relation to climate change

地磁变化及其与气候变化关系的研究

• 批准号: 12440118
• 负责人: HAMANO Yozo
• 金额: $ 7.17万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440118/
• 关键词: geomagnetic variation; Archean period; paleointensity; dipole-field; Earth's core; spherical harmonic analysis; 気候変動; 古地球磁場強度; 磁場西方移動; ダイナモ作用; 電磁気構造; マントル; D"層

We studied the variation of the intensity of the Earth's magnetic field for a wide range of time scale, and examined its relation to climate change. For the paleointensities of the Archean to Proterozoic period, we collected samples from the stable cratons in Canada, Australia, and Africa and the paleointensity measurements were made by the Thellier's method. The results indicate that the average value of paleointensity during the last 2 billion years are rather similar to the geomagnetic intensity of the present field, whereas the variation of the intensity around 2.5 billion years ago was found to be very large. During the last 200,000 years, several transient increases or decreases of the intensity were observed. The variations are attributed to the change of the dipole moment. The decreases of the intensity to about 1/10 of the present field corresponds to the excursion time of the magnetic field, and are known to relate to climate change. On the other hand, the relation between the transient increases of the intensity and the climate change is not evident. For the last 2000 years, we obtained a standard curve of the field intensity variation in Japan. The variation of the field intensity for this time scale is mainly controlled by the change of the non- dipole component of the geomagnetic field, although an abrupt increase of the field intensity at about 500 AC is probably due to the change of the dipole moment. As for the recent variation of the field intensity, we developed a new method for decomposing the observed magnetic field into the external, induced, and internal component of core origin by using spherical harmonic analysis, and short period variations of core field with a time scale of several years are identified.

我们研究了大范围时间尺度内地球磁场强度的变化，并研究了其与气候变化的关系。对于太古代至元古代的古强度，我们在加拿大、澳大利亚和非洲的稳定克拉通中采集了样品，并采用泰利尔法进行了古强度测量。结果表明，近20亿年的古强度平均值与现今场的地磁强度相当相似，而25亿年前后的强度变化却非常大。在过去的 20 万年里，观察到了几次强度的短暂增加或减少。这些变化归因于偶极矩的变化。强度降低至当前磁场的约 1/10 对应于磁场的偏移时间，并且已知与气候变化有关。另一方面，强度的短暂增加与气候变化之间的关系并不明显。我们获得了近2000年来日本场强变化的标准曲线。该时间尺度的场强变化主要受地磁场非偶极子分量变化的控制，尽管在 500 AC 左右场强的突然增加可能是由于偶极矩的变化所致。针对最近的场强变化，我们开发了一种新方法，通过使用球谐分析和随时间尺度的核心磁场的短周期变化，将观测到的磁场分解为核心原点的外部、感应和内部分量。已确定数年。

项目成果

Ikeda, T., Tajika, E.: "Carbon cycling and climate change during the last glacial cycle inferred from the isotope records using an ocean biogeochemical carbon cycle model"Global and Planetary Change. (in press). (2002)

Ikeda, T., Tajika, E.：“使用海洋生物地球化学碳循环模型从同位素记录推断出末次冰河周期期间的碳循环和气候变化”全球和行星变化。

Yoshihara, A.: "Intensity of the earth's magnaetic field in late Archean obtained from diabase dikes of the Slave Province"Phys. Earth Planaet. Interiors. 117. 295-307 (2000)

Yoshihara, A.：“从奴隶省的辉绿岩岩脉获得的晚太古代地球磁场强度”Phys。

Yoshihara, A.,, Kondo, M., Hamano, Y.: "Secular variation of the geomagnetic field intensity during the last 2000 years in Japan"Earth Planet. Sci. Letters. (in press). (2003)

Yoshihara, A.,, Kondo, M., Hamano, Y.：“过去 2000 年日本地磁场强度的长期变化”地球。

Yoshihara, A.: "Secular variation of the geomagnetic field intensity during the last 2000 years in Japan"Earth Planet. Sci. Letters. in press. (2003)

Yoshihara, A.：“过去 2000 年日本地磁场强度的长期变化”地球。

Hamano, Y.: "A new time-domain approach for the electromagnetic induction problem in a 3-D heterogeneous earth"Geophys. J. Int. 150. 753-769 (2002)

Hamano, Y.：“一种解决 3D 异质地球电磁感应问题的新时域方法”Geophys。