Response of Pacific Subtropical-Tropical Thermocline Water Pathways and Transports to Global Warming and its Implications for ENSO

太平洋副热带-热带温跃层水通道和输送对全球变暖的响应及其对 ENSO 的影响

• 批准号: 0752194
• 负责人: Yiyong Luo
• 金额: $ 16.84万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2012-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0752194&HistoricalAwards=false
• 关键词: Response; Pacific; Subtropical; Tropical; Thermocline

Intellectual Merit:The subtropical-tropical thermocline water pathways are the subsurface branches of the Subtropical Cells (STCs). The STCs are shallow meridional circulation cells in which water flows out of the tropics within the surface layer, subducts in the subtropics, flows equatorward within the thermocline, and upwells in the eastern equatorial ocean. The changes in the Pacific STC transports have profound implications on global climate through its impact on tropical thermocline variability and sea surface temperature (SST) anomalies associated with the El Nio-Southern Oscillation (ENSO). The ENSO is a climate phenomenon that affects weather, ecosystems, and societies across much of the globe. Observations and understanding of ENSO have rapidly progressed over the last few decades; however its considerably temporal irregularity is not well understood. Recent studies have demonstrated that thermocline variability along the equator can be a leading candidate responsible for this irregularity. Observations show that the thermocline water transport from the subtropics to the tropics in the Pacific has considerably been reduced from the 1970s to the 1990s, causing an appreciable SST increase in the tropics. Coupled climate models attribute the observed warming to the anthropogenic forcing. Under the future anthropogenic forcing, global warming may also have significant influence on the Pacific subtropical-tropical thermocline water pathways and transports, and thereby on ENSO. The objectives of this project are to investigate the changes in the large-scale circulation around the subtropics and the tropics in the Pacific under future anthropogenic forcing or global warming, and to explore the role of these changes in the subtropical-tropical thermocline water pathways and transports for modulating ENSO. The hypotheses are that (1) buoyancy forcing plays as important a role as wind forcing in the changes in the large-scale ocean circulation associated with the STCs, and (2) changes in the water pathways and transports from the subtropics to the tropics modulate ENSO properties through shifting the thermocline structure along the equator. Broader Impacts:Understanding ENSO temporal irregularity remains an outstanding issue in the climate variability and predictability with broad societal implications across many scientific disciplines. This research will identify a way of connecting the Pacific STCs with ENSO irregularity and provide a basis for understanding how does global warming affect subtropical-tropical inter-gyre ocean circulation in the Pacific. The results will be applied to future model improvements and be shared with the IPCC climate model community. The results will be disseminated through presentations at scientific meetings/workshops and publications in scientific journals.

知识价值：亚热带-热带温跃层水通道是亚热带气旋(STC)的次表层分支。STC是浅的经向环流单元，在该环流单元中，水在表层内从热带流出，在副热带潜流，在温跃层内向赤道流动，在赤道东部海洋中向上流动。太平洋STC输送的变化通过对热带温跃层变率和与厄尔尼诺-南方涛动(ENSO)有关的海面温度异常的影响，对全球气候产生深远影响。ENSO是一种气候现象，会影响全球大部分地区的天气、生态系统和社会。对ENSO的观测和了解在过去几十年中取得了迅速的进展；然而，人们对其相当大的时间不规则性还没有很好的了解。最近的研究表明，沿赤道的温跃层变化可能是造成这种不规则性的主要原因。观测结果表明，从20世纪70年代到90年代，太平洋副热带到热带的温跃层水输送显著减少，导致热带海温显著升高。耦合气候模型将观测到的气候变暖归因于人为强迫。在未来的人为强迫下，全球变暖还可能对太平洋副热带温跃层的水通道和输送产生重大影响，从而对ENSO产生重大影响。本项目的目标是研究未来人为强迫或全球变暖下太平洋副热带和热带大尺度环流的变化，并探讨这些变化在副热带温跃层水路径和输送中对ENSO的调制作用。假设：(1)浮力强迫在与STCS相关的大尺度海洋环流变化中起着与风强迫同样重要的作用；(2)从亚热带到热带的水路径和输送的变化通过沿赤道移动温跃层结构来调制ENSO特性。更广泛的影响：理解ENSO的时间不规则性仍然是气候可变性和可预测性方面的一个突出问题，具有广泛的社会影响，涉及许多科学学科。这项研究将确定一种将太平洋STCS与ENSO不规律性联系起来的方法，并为理解全球变暖如何影响太平洋副热带-热带环流提供基础。结果将应用于未来的模型改进，并与气专委气候模型社区共享。结果将通过在科学会议/讲习班上的发言和在科学期刊上发表文章来传播。