Quantifying the Effect of the Lunar Nodal Tide on North Pacific Climate Variability

量化月交点潮汐对北太平洋气候变化的影响

• 批准号: 1260680
• 负责人: Andreas Schmittner
• 金额: $ 23.48万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-03-15 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1260680&HistoricalAwards=false
• 关键词: Quantifying; Effect; Lunar; Nodal; Tide

Can variations of the moon's orbit around the earth affect climate? Numerous studies have associated bidecadal variability in observations of physical climate and biogeochemical variables with the LNC. Particularly in and around the North Pacific, where diurnal tide constituents are strong, these observations point towards a significant influence of the LNC on temperatures, oceanic and atmospheric circulation and biogeochemical cycles. Model simulations without LNC forcing show strong internal modes of decadal variability in the North Pacific such as the Pacific Decadal Oscillation. LNC forcing could modulate these internal modes by (1) shifting variability into the bidecadal frequency range, (2) generate resonance, or (3) synchronize their phases. This project will test hypotheses relating LNC oscillations in tides to bidecadal variability in climate via modulations of ocean mixing and attendant effects on temperatures and modes of decadal climate variability.A globally consistent parameterization of tidal mixing, that has already been tested in a climate model of intermediate complexity and shown to lead to climatically significant sea surface temperature anomalies, will be implemented in a comprehensive global climate model. This parameterization includes a new scheme of sub-grid scale bathymetry and separately considers four tidal constituents (M2, S2, K1 and O1) and their temporal variations due to the LNC. The model will be used to simulate the effects of LNC oscillations of tidal mixing on diapycnal diffusivities, temperatures, oceanic and atmospheric circulation, and modes of decadal variability in the North Pacific. Model results will be analyzed and compared to existing observations. Satellite altimeter data, now available over one full LNC, will be analyzed with the goal to improve tidal energy dissipation estimates, tidal mixing parameterizations, and the understanding of mechanisms of barotropic energy loss.Broader Impacts:
Understanding forcing mechanisms of climate change is critically important for decadal climate predictability. In recent decades much progress has been made in identifying and incorporating effects of aerosols, solar and volcanic variability in climate models. However, despite a considerable literature describing observations of the 18.6-year lunar nodal cycle in various climate variables its effect is not included in climate models. This project has the potential to improve climate predictions on decadal time scales particularly in the North Pacific region. Implementing the effect of the lunar nodal cycle on ocean mixing in CCSM4, which is one of the models used by the IPCC assessment reports, will contribute to these international reports of significant policy relevance. The model code will be made available to the large user community. Decadal variability in the North Pacific affects ecosystems and societies. Improved predictability of hypoxic events on the continental shelf of the west coast of North America, for example, may benefit society as these events affect living systems in the California Current Large Marine Ecosystem and many commercially important fisheries in the region. Collaboration between a team of three PIs with different expertise, background (global climate modeling, tides, coupled physical- biological regional ocean modeling) and gender diversity will be fostered. A postdoctoral researcher will be trained in climate modeling and data analysis and given teaching opportunities. An undergraduate student will participate through a summer internship. A session on decadal variability in the North Pacific will be organized at the 2014 Fall Meeting of the American Geophysical Union.

月球绕地球轨道的变化会影响气候吗？许多研究将物理气候和地球化学变量观测中的双尺度变率与LNC联系起来。特别是在北太平洋及其周围地区，昼夜潮汐成分很强，这些观测结果表明LNC对温度，海洋和大气环流以及地球化学循环有重大影响。没有LNC强迫的模式模拟显示了北太平洋年代际变化的强烈内部模式，如太平洋年代际振荡。LNC强迫可以通过（1）将变率转移到双十阶频率范围，（2）产生共振，或（3）同步它们的相位来调制这些内部模式。该项目将检验潮汐LNC振荡与气候双十年变率之间的关系，这一关系是通过海洋混合的调制以及随之而来的对温度和十年气候变率模态的影响来实现的。将在一个全面的全球气候模型中实施。这种参数化包括一个新的方案，亚网格尺度测深，并分别考虑四个潮汐分潮（M2，S2，K1和O 1）和它们的时间变化，由于LNC。该模式将被用来模拟潮汐混合的LNC振荡的影响，对diapycnal扩散，温度，海洋和大气环流，以及在北太平洋的十年变化模式。将对模型结果进行分析，并与现有观测结果进行比较。卫星高度计数据，现在可以在一个完整的LNC，将进行分析，以提高潮汐能耗散估计的目标，潮汐混合参数化，和正压能量loss.Broader影响的机制的理解：#8232;了解气候变化的强迫机制是十分重要的十年气候可预测性。近几十年来，在确定气溶胶、太阳和火山变化的影响并将其纳入气候模型方面取得了很大进展。然而，尽管有相当多的文献描述了18.6年的月球交点周期在各种气候变量中的观测结果，但其影响并未包括在气候模型中。该项目有可能改善十年时间尺度的气候预测，特别是在北太平洋区域。在CCSM 4（IPCC评估报告使用的模型之一）中实施月球交点周期对海洋混合的影响，将有助于这些具有重要政策相关性的国际报告。模型代码将提供给广大用户社区。北太平洋的十年变化影响着生态系统和社会。例如，提高对北美西海岸大陆架缺氧事件的可预测性可能会使社会受益，因为这些事件影响到加州当前大型海洋生态系统的生物系统和该地区许多具有重要商业意义的渔业。将促进具有不同专业知识、背景（全球气候建模、潮汐、物理-生物耦合区域海洋建模）和性别多样性的三名PI之间的合作。一名博士后研究员将接受气候建模和数据分析方面的培训，并获得教学机会。一名本科生将通过暑期实习参加。将在美国地球物理学联合会2014年秋季会议上组织一次关于北太平洋十年期变化的会议。