Persistent high paleosecular variation activity in southern hemisphere for at least 10 000 years
Persistent high paleosecular variation activity in southern hemisphere for at least 10 000 years
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DOI：
10.1016/j.epsl.2016.08.015
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发表时间：
2016-11-01
影响因子：
5.3
通讯作者：
Panovska, Sanja
中科院分区：
文献类型：
--
作者：
Constable, Catherine;Korte, Monika;Panovska, Sanja
对地磁场的直接观测表明，长期变化在大西洋半球较强，而在太平洋地区相对较小。至少自公元1840年以来，由于南半球反向通量斑块的增长和迁移，偶极子一直在衰变。我们调查了这种地磁长期变化的现代模式是否持续存在，并可以在全球古地磁场模型中检测到。两个新的时变球谐模型的结果综合表明，地理上不同的地磁长期变化至少延伸到10000 BP。这些模型使用相同的数据库，但方法不同，导致结果存在一些地区差异。一致的大尺度地表特征包括北半球的强平均场和南半球总体变异性较大的较弱场。存在纵向结构，西太平洋的平均场弱于东太平洋，显著的负倾角异常延伸到印度尼西亚、非洲和巴西，但中太平洋的异常较弱。略微积极的倾斜度异常发生在美洲以西。古分子变化活动在南部高纬度达到峰值，在赤道和中纬度太平洋以下活动减少。虽然偶极子在0-10000BP的范围内既有增长，也有衰退，但我们的结果表明，地磁古分子变化优先集中在与现代磁场中看到的长期变化相似的地理区域。(C)2016年提交人。爱思唯尔出版公司(Elsevier B.V.)
Direct observations of the geomagnetic field show that secular variation is strong in the Atlantic hemisphere, and comparatively reduced in the Pacific region. The dipole has been decaying since at least 1840 AD, driven by growth and migration of reverse flux patches in the southern hemisphere. We investigate whether anything like this modern pattern of geomagnetic secular variation persists and can be detected in global paleomagnetic field models. Synthesis of results from two new time-varying spherical harmonic models shows that geographically distinct geomagnetic secular variation extends to at least 10000 BP. The models use the same database but differ in methodology, leading to some regional differences in results. Consistent large-scale surface features include strong average fields in the northern hemisphere and weaker fields with greater overall variability in the south. Longitudinal structure is present, with weaker average fields in the western Pacific than in the east, and prominent negative inclination anomalies extending beneath Indonesia, across Africa and to Brazil, but weaker anomalies in the central Pacific. Marginally positive inclination anomalies occur west of the Americas. Paleosecular variation activity peaks at high southern latitudes, and there is a pattern of reduced activity at equatorial and mid-latitudes beneath the Pacific. Although the dipole has exhibited both growth and decay over the interval 0-10 000 BP, our results show that geomagnetic paleosecular variation is preferentially focused in similar geographic regions to secular variation seen in the modern field. (C) 2016 The Authors. Published by Elsevier B.V.