Investigating Periodicities in Abyssal Hill Morphology of the Atlantic Ocean: Possible Evidence of Mantle Dynamics

研究大西洋深海山形态的周期性：地幔动力学的可能证据

• 批准号: 2341367
• 负责人: John Goff
• 金额: $ 17.05万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2341367&HistoricalAwards=false
• 关键词: Investigating; Periodicities; Abyssal; Hill; Morphology

Non-Technical DescriptionThough covered by the oceans, abyssal hills are the most common landform on earth. They form at the world’s mid-ocean ridge spreading centers and are important records of the plate spreading process. Past studies of abyssal hills have treated them as purely random processes. The statistical parameters of such processes, such as mean, variance, characteristic scale, etc., can be correlated to plate spreading conditions, such as spreading rate, magma supply and crustal thickness. In this way, abyssal hills across the oceans can be used to probe plate dynamics through space and time. Recently, however, some studies have reported the detection of periodic signals embedded within otherwise random abyssal hill profiles. Such a signal could be evidence of previously-unrecognized influence on mid-ocean ridge magma processes, such as climate-driven changes in sea level, or deep-seated modulations of magma delivery. This study will use a new, robust algorithm developed by the lead PI. It detects and quantifies (amplitude, wavelength) periodic signals embedded within a random field. The algorithm will be applied to bathymetric data in the North and South Atlantic Oceans. There, decades-worth of surveys and transits provide abundant data for analysis. Periodic values will first be correlated to past spreading parameters to establish basic relationships. Regional variations in periodic values will then be investigated. This will permit investigating possible deep-earth controls on the formation of periodic signals. The result should establish key constraints in the future modeling of mid-ocean ridges. In addition, the code will be made available to the general public with a user-friendly interface. This will enable non-expert researchers and students in a variety of fields to make use of the algorithm. Technical DescriptionThe existence, or not, of periodicities in abyssal hill morphology has been vigorously debated in recent publications, and some have hypothesized that such periodicities are evidence of external forcing, such as by the impact of Milankovitch cycle-caused sea level fluctuations on the volcanic construction process at mid-ocean ridges (MORs), or internally forced, such as by modulations of mantle upwelling. This project will employ a newly-developed empirically pre-whitening algorithm for detecting and quantifying periodic signals that are embedded in a random field. It will be applied to the abundant archival trackline bathymetry data in the North and South Atlantic Oceans, which samples large and diverse regions of abyssal hills formed at slow-spreading MORs. This will enable testing of a first hypothesis: that temporal periodicities are present in slow-spreading MOR-generated abyssal hills. Preliminary analysis provides initial support, but confidently doing so requires much more than a few anecdotal examples. The existence of periodicities in the seafloor fabric could have significant implications for understanding and modeling MOR dynamics. If periodicities in abyssal hill morphology do exist, what factors of MOR spreading are they responsive to? This question leads us to a second hypothesis: that variations in temporal periodicities exist that are related to spreading properties and mantle conditions at the MOR at the time of formation. It can be tested directly by correlating periodic parameters to paleo-spreading rates, and indirectly by comparing periodic parameters to aperiodic statistical parameters, such as RMS height and characteristic scale, which are themselves correlated with various MOR parameters as noted above. This project will also investigate whether or not there are regional patterns to the periodicities measured, which could be indicative of responsiveness to mantle heterogeneities. For example, recent modeling indicates that periods and amplitudes of crustal thickness-derived seafloor periodicities will be dependent on mantle permeability, a poorly-constrained parameter that is critical for modeling melt transport in the mantle. By modernizing the original code for operation in a Python coding environment, the technique will be accessible to a wider audience, and has the potential to be used in interpreting a wide variety of Earth science and other time series (e.g., climate and weather, oceanographic, etc…). The team will promote the code through social media and develop materials to train interested users. Support of an early career scientist and building capacity in computational geoscience is a further broader impact.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

尽管被海洋覆盖，深海丘陵是地球上最常见的地貌。它们形成于世界洋中脊扩张中心，是板块扩张过程的重要记录。过去对深海山的研究将其视为纯粹的随机过程。这些过程的统计参数，如平均值、方差、特征尺度等，可以与板块扩张条件相关联，如扩张速度、岩浆供应和地壳厚度。通过这种方式，横跨海洋的深海山丘可以用来探测穿越空间和时间的板块动力学。然而，最近一些研究报道了嵌入在随机深海山剖面中的周期性信号的检测。这样的信号可能是以前未被认识到的对洋中脊岩浆过程的影响的证据，例如气候驱动的海平面变化，或岩浆输送的深层调节。这项研究将使用由首席PI开发的一种新的鲁棒算法。它检测和量化（振幅，波长）周期信号嵌入在一个随机场。该算法将应用于北大西洋和南大西洋的水深数据。在那里，数十年的调查和凌日为分析提供了丰富的数据。周期值将首先与过去的扩散参数相关联，以建立基本关系。然后将研究周期值的区域变化。这将允许研究可能的深地控制周期信号的形成。这一结果将为未来海洋中脊的模拟建立关键的约束条件。此外，该代码将以用户友好的界面向公众提供。这将使各种领域的非专业研究人员和学生能够使用该算法。技术描述深海山形态是否存在周期性在最近的出版物中引起了激烈的争论，一些人假设这种周期性是外部强迫的证据，例如由米兰科维奇旋回引起的海平面波动对海洋中脊（MORs）火山构造过程的影响，或内部强迫的证据，例如由地幔上升流的调节。该项目将采用一种新开发的经验预白化算法来检测和量化嵌入随机场的周期信号。它将应用于北大西洋和南大西洋丰富的档案轨道测深数据，这些数据采样了在缓慢扩散的MORs形成的大型和不同区域的深海山丘。这将使第一个假设得到验证：即在缓慢扩散的莫尔形成的深海山丘中存在时间周期性。初步分析提供了初步的支持，但自信地这样做需要的远不止一些轶事例子。海底结构中周期性的存在可能对理解和模拟MOR动力学具有重要意义。如果深海山的形态确实存在周期性，那么它们对MOR传播的响应因素是什么？这个问题将我们引向第二个假设：时间周期的变化存在，这与形成时MOR的扩展特性和地幔条件有关。可以通过将周期参数与古扩展速率进行直接关联，也可以通过将周期参数与非周期统计参数（如均方根高度和特征比例尺）进行比较来间接检验，这些参数本身与上述各种MOR参数相关。该项目还将研究测量到的周期性是否存在区域模式，这可能表明对地幔非均质性的响应。例如，最近的模拟表明，由地壳厚度引起的海底周期性的周期和振幅将取决于地幔渗透率，这是一个约束较差的参数，对于模拟地幔中的熔体运输至关重要。通过将原始代码现代化以在Python编码环境中运行，该技术将为更广泛的受众所访问，并有可能用于解释各种各样的地球科学和其他时间序列（例如，气候和天气，海洋学等）。该团队将通过社交媒体推广代码，并开发材料来培训感兴趣的用户。支持早期职业科学家和建立计算地球科学的能力是进一步的更广泛的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。