Reconstructing space/time patterns of the Earth's magnetic field in the Holocene from Arctic sedimentary records

缺乏对高纬度地磁场的了解已经成为理解地球动力学过程的根本限制。对北极全新世古地磁记录的了解将填补这一需求，并提供一种有价值的测年工具。北极古地磁资料的缺乏是由于北极物流的困难和古地磁的附加限制。通过与几个专门研究北极高纬度湖泊沉积物的小组一起进行全新世古地磁研究，首席研究员通过复制记录表明，北极沉积物可以准确地记录地磁场。通过对古地磁记录与年代学的相互校正，可以重建北极第一个高分辨率古地磁长期变化（PSV）和相对古强度（RPI）记录（2700年）。这些记录的时间跨度不够久远，无法回答有关北极地磁场与研究更深入的中纬度地区地磁场之间千年尺度变化关系的问题。首席研究员将继续这种背带关系，以解决记录长度、年代曲线的发展以及评估PSV和RPI记录的空间模式等问题。2005年野外季节的取芯考察计划将大大延长沉积物记录（从~ 4.5米到~ 20米）。通过在加拿大北极群岛、阿拉斯加布鲁克斯山脉和斯瓦尔巴群岛进行额外的取心，我们也有了新的机会来扩大我们的观测空间。学术价值：最近的地磁观测涵盖了上个世纪，地球动力学理论和建模表明，极地地磁场是独特的，可能与地球其他地方有本质上的不同，但也是对全球理解的关键部分。结果将在时间上延伸，在空间上扩展，并完善我们对北极高地地磁场的理解。如果极场是唯一的，它应该表现为明显的长期变化行为。最初的数据表明，它在十年到百年的时间尺度上可能是独一无二的，但在百年到千年的时间尺度上可能不是，需要更长的记录来验证这一点。生成的数据将为古球谐模拟倡议提供唯一的高北极贡献。测定北极沉积物的年代是困难的，而且仅限于产生分裂沉积物的湖泊。因此。古研究仅限于可能提供高质量记录的潜在档案的一小部分。首席研究员展示了过去2700年地磁古长期变化与基于变量的年表的相互校准。并打算将其扩展到过去的8000年，以产生一个可以用于海洋和陆地沉积物的北极的主要年代曲线。更广泛的影响：这项研究将把最近对北磁极剧烈迁移的观察放在一个历史背景下，以更好地评估当前的地磁行为，包括地磁场强度的显著崩溃和即将到来的反转的可能性，这在媒体和电视上被广泛推测。这项工作将提供对历史极光观测的地理分布的见解。研究生培训将是这个项目的重点。通过与斯瓦尔巴REU计划的合作，古环境磁学将成为一个重点。古地磁数据集将通过向国家地球物理数据中心和其他目前完全缺乏高北极古地磁数据的数据库和建模计划提供。

ABSTRACTStonerOPP-0520533A lack of understanding of the geomagnetic field at high latitudes has been a fundamentallimitation to understanding of the geodynamo process. An understanding of the Arctic's Holocene paleomagnetic record would fill this need and provide a valuable needed dating tools. The lack of Arctic paleomagnetic data results from the difficulty of Arctic logistics and with the added constraints of paleomagnetism. Through piggybacking Holocene paleomagnetic studies with several groups who specialize in the study of high Arctic lake sediments, the Principal Investigator shows through replicate records that Arctic sediments can accurately record the geomagnetic field. The inter-calibration of the paleomagnetic record with varve-based chronologies allows reconstruction of the first high Arctic high-resolution paleomagnetic secular variation (PSV) and relative paleointensity (RPI) records (2700 yrs.). These records do not extend far enough back in time to answer questions on the relationship of the millennial scale variability between the geomagnetic field of the Arctic to that of the more thoroughly studied mid-latitudes. The Principal Investigator will continue this piggyback relationship to address issues of record length, development of dating curves and to assess spatial patterns of the PSV and RPI records. Coring expeditions schedule for the 2005 field season will significantly lengthen (from ~ 4.5 to ~ 20 m) sediment records. New opportunities are also available to spatial expand our observations with additional coring in the Canadian Arctic Archipelago, Alaskan Brooks Range and Svalbard. Intellectual Merit: Recent geomagnetic observations covering the last century, geodynamo theory, and modeling suggest that the polar geomagnetic field is unique and possibly substantially different from the rest of the Earth, but also a critical to piece to a global understanding. Results will temporally extend, spatially expand, and refine our understanding of the geomagnetic field of the High Arctic. If the polar field is unique, it should manifest as distinct secular variation behavior. Initial data suggest that it may be unique on decadal to centennial timescales, but possibly not at multi-centennial to millennial timescales and longer records are needed to test this. The data generated will provide the only high Arctic contribution to paleo spherical harmonic modeling initiatives. Dating of Arctic sediments is difficult, and limited to lakes producing varved sediments. Thus. paleo-studies are limited to a small subset of the potential archives that could provide high quality records. The Principal Investigator has demonstrated the inter-calibration of geomagnetic paleosecular variation with varve-based chronologies for the last 2700 yrs. and intends to extend this to the last 8000 yrs to produce a primary dating curve for the Arctic that can be used for both marine and terrestrial sediments.Broader Impacts: This research will place recent observations of dramatic migration ofthe North Magnetic Pole into a historical context to better assess the present geomagnetic behavior including the prominent collapse of geomagnetic field intensity and the possibility of an upcoming reversal that has been widely speculated on in press and television. This work will provide insights into the geographical distribution of historical aurora observations. Graduate student training will be a focus of this project. Through collaborations with the Svalbard REU Program, paleo-and-environmental magnetism will be a focus. Paleomagnetic datasets will be made available through contribution to the national geophysical data center and to other database and modeling initiatives that at present are completely devoid of high Arctic paleomagnetic data.