Reconstructing Holocene geomagnetic field variation: new methods, models and implications
Reconstructing Holocene geomagnetic field variation: new methods, models and implications
复制标题
DOI：
10.1093/gji/ggu120
复制
发表时间：
2014-07
影响因子：
2.8
通讯作者：
A. Nilsson;R. Holme;M. Korte;N. Suttie;M. Hill
中科院分区：
文献类型：
--
作者：
A. Nilsson;R. Holme;M. Korte;N. Suttie;M. Hill
全新世地磁场的重建及其在千年时间尺度上的变化对于理解地核的过程很重要，但也可用于研究长期的日地关系，并作为地质和考古档案的相对年代测定工具。在这里，我们基于考古文物、火成岩和沉积物记录中存储的磁场方向和强度，提出了跨越过去 9000 年的一系列新的球谐地磁场模型。新的建模策略引入了替代数据处理方法，重点是从沉积数据中提取更多信息。为了减少一些单独记录的影响，所有沉积数据都在 50 年的桶中重新采样，这也意味着在反演过程中对古地磁数据给予更多的权重。沉积磁偏角数据被视为相对值，并根据先验信息进行迭代调整。最后，处理沉积物数据年表的另一种方法使我们能够评估年龄不确定性的可能范围（通常高达或可能超过 500 年），并根据与初步模型预测的比较来调整每个记录的时间尺度。由于数据调整，与之前的全新世地磁场模型相比，功率已从四极和八极转移到更高的程度。我们发现了过去 4000 年北部高纬度高强度通量斑块在核心地幔边界主要向西漂移的证据。新模型还显示，在内核相切圆柱体的边缘或内部间歇性地出现反向通量，可能源自赤道。 （较少的）
Reconstructions of the Holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long-term solar-terrestrial relationships and as relative dating tools for geological and archaeological archives. Here, we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts, igneous rocks and sediment records. A new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data. To reduce the influence of a few individual records all sedimentary data are resampled in 50-yr bins, which also means that more weight is given to archaeomagnetic data during the inversion. The sedimentary declination data are treated as relative values and adjusted iteratively based on prior information. Finally, an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties, often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model. As a result of the data adjustments, power has been shifted from quadrupole and octupole to higher degrees compared with previous Holocene geomagnetic field models. We find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr. The new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder, possibly originating from the equator. (Less)