The Evolving Role of the Ocean and the Atmosphere in Decadal to Multidecadal Modes of Climate Variability

海洋和大气在十年至多年气候变化模式中的演变作用

• 批准号: 2241752
• 负责人: Amy Clement
• 金额: $ 118.56万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2026-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2241752&HistoricalAwards=false
• 关键词: Evolving; Role; Ocean; Atmosphere; Decadal

Efforts to address climate change impacts are complicated by the difficulty of distinguishing between the effects of external forcing, predominantly caused by human activities, and the natural internal variability of the climate system. Decade-to-decade variations are typically characterized by a set of climate modes such as the Atlantic Multidecadal Oscillation (AMO), in which the Atlantic north of the equator has alternating episodes of warming and cooling that last 20 to 40 years. The climate modes are generally regarded as natural variability because they can be found in observations from the 1800s and earlier, before the rise of industrial emissions. For this reason regional climate change is often viewed as the superposition of natural variability in the form of climate modes and externally forced change which is distinct from the modes, with a different spatial pattern and involving different physical mechanisms.Here the Principal Investigators (PIs) question this assumption and pose a more challenging hypothesis: prior to 1950 climate modes are largely natural variability arising from atmosphere-ocean coupling, but after 1950 the modes are largely externally forced, and the relationship between the ocean and atmosphere is altered by the external forcing. The hypothesis is motivated by the PIs' recent work with simulations of 20th century climate which include forcing by the radiative effects of aerosol pollution. The dominant sources of aerosol emissions have shifted from western Europe and the eastern US to China and southern Asia, thus the response to shifting aerosol radiative forcing could cause regional climate change on the decadal timescale. The hypothesis is also predicated on the idea that the climate system responds to external forcing through the dynamics that generate the internal variability modes, so that the response to external forcing amounts to an excitation of the natural internal modes.The research is conducted with a variety of climate model simulations including large ensembles (LEs) of simulations performed with the Community Earth System Model (CESM). These include LEs of simulations with no external forcing and single-forcing simulations which isolate the response to aerosol forcing. The work also takes advantage of the hierarchy of simpler configurations developed for CESM, including the "pencil ocean" configuration developed under AGS-2040073, which represents turbulent vertical heat transfer in the ocean but does not simulate the lateral movement of water in ocean currents.The work has societal relevance given the need to address climate change impacts at the regional level. If the PIs' hypothesis is correct it will require some revision of uncertainty estimates for regional climate projections, which do not currently take into account uncertainty in the future evolution of aerosol emissions. The work also has implications for climate prediction efforts, in which it is commonly assumed that climate modes can be predicted from the current state of the atmosphere and oceans and a sufficiently accurate representation of the coupling between the two (see for example AGS-2231237). The work is also directly relevant to climate impacts on coastal communities, particularly given that the AMO has a substantial effect on Atlantic hurricane activity. The researchers work with the Miami Climate Resilience Committee and the Resilient305 Research Collaborative provides a direct application of research results to community-based decision making. The project also provides support and training to a postdoctoral associate, a graduate student and an undergraduate, and the PIs perform a number of outreach activities including the University of Miami Women in Science day, an annual event for girls in the 6th and 7th grade.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.

解决气候变化影响的努力很难区分外部强迫的影响，主要是由人类活动引起的以及气候系统的自然内部变异性。 十年到十年的变化通常以一组气候模式（例如大西洋多年代振荡（AMO））为特征，在该气候模式下，赤道北部的大西洋北部具有交替的变暖和冷却发作，过去20到40年。气候模式通常被视为自然变异性，因为它们可以在1800年代和更早的工业排放兴起之前的观察结果中找到。 因此，由于这个原因，区域气候变化通常被视为自然变异性在气候模式和外部强迫变化的形式中的叠加，这与模式不同，其空间模式不同，并涉及不同的物理机制。在这里，首席研究人员（PIS）提出了这个假设，并提出了更具挑战性的假设：在1950年的气候下，自然的氛围是在1950年的自然范围内，但在1950年的自然风险范围内，该氛围是氛围的。模式在很大程度上是强迫的，外部强迫会改变海洋和大气之间的关系。该假设是由PI的最新作品进行的，其中包括20世纪气候的模拟，其中包括通过气溶胶污染的辐射作用强迫。 气溶胶排放的主要来源已从西欧和美国东部转变为中国和南亚，因此对变化气溶胶辐射强迫的反应可能会导致衰老时间范围的区域气候变化。 该假设还基于这样的想法，即气候系统通过产生内部变异性模式的动力学做出了反应，因此对外部强迫的响应量对自然内部模式的激发量进行了量。研究是通过各种气候模型模拟（包括大型合奏）（包括大型合成）（LES）与社区泥土系统模型（CESM）进行的。 其中包括没有外部强迫和单构模拟的模拟，这些模拟分离了对气溶胶强迫的响应。 这项工作还利用了为CESM开发的更简单配置的层次结构，包括根据AGS-2040073开发的“铅笔海洋”配置，该配置代表了海洋中湍流的垂直传热，但没有模拟洋流中水的横向流动。鉴于需要解决区域层面的气候变化，该工作具有社会意义。 如果PIS的假设是正确的，则需要对区域气候预测的不确定性估计进行一些修改，目前尚未考虑到未来气溶胶排放的不确定性。 这项工作还对气候预测工作有影响，在这种情况下，通常假定可以从大气和海洋的当前状态来预测气候模式，并且可以充分准确地表示两者之间的耦合（例如，参见AGS-2231237）。 这项工作也与气候对沿海社区的影响直接相关，尤其是考虑到AMO对大西洋飓风活动具有重大影响。 研究人员与迈阿密气候弹性委员会合作，而Resilient 305 Research Collaboration为基于社区的决策提供了直接应用研究结果。 该项目还为博士后同事，研究生和本科生提供支持和培训，PIS进行了许多外展活动，包括迈阿密大学妇女在科学日，每年为6年级和7年级的女孩举办的年度活动。这项奖项反映了NSF的法定任务，并通过评估智能委员会的评估，并通过评估了基金会的范围和广阔的范围。

项目成果

Tropical Atlantic multidecadal variability is dominated by external forcing

• DOI: 10.1038/s41586-023-06489-4
• 发表时间: 2023-09
• 期刊: Nature
• 影响因子: 64.8
• 作者: C. He;A. Clement;Sydney M Kramer;M. Cane;J. Klavans;Tyler M. Fenske;L. Murphy