P2C2: Hydroclimatic response of the tropical Pacific to past changes in mean state: Observations and synthesis

P2C2：热带太平洋对过去平均状态变化的水文气候响应：观测与综合

• 批准号: 1606764
• 负责人: Michael Evans
• 金额: $ 14.1万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1606764&HistoricalAwards=false
• 关键词: P2C2; Hydroclimatic; response; tropical; Pacific

How will El Niño events change as the climate changes? There is currently no consensus on the answer to this question from climate change projections for the 21st century. Yet even small changes in El Niño event strength, duration or frequency have significant effects, both in the US and internationally, on water resources, wildfires, agriculture and ecosystems. This project will contribute new observations and analysis of El Niño/Southern Oscillation (ENSO) activity during two past time intervals for which there are very few data from the tropical Pacific, yet for which the global climate is thought to have been relatively warm and relatively cold, respectively. Results will be compared to climate simulations for the same periods, so that we can better understand if, how and why global climate change can cause changes in El Niño activity. The project will also provide mentored, international, collaborative, and multidisciplinary training for a PhD student and an undergraduate researcher, including educational, outreach and dissemination activities. It will contribute inputs for modeling the interactions between people, fisheries and climate in a location and region with a rich archaeological history of pre-modern settlement, voyaging and exploration. These studies, which are beyond the scope of this project, may ultimately help us understand how societies have and may adapt to past and future climate change.Specifically, paired oxygen isotope and Sr/Ca data series will be developed from existing and diagenetically screened coral samples dating to the Little Ice Age (LIA) and Medieval Climate Anomaly (MCA) time windows from Aitutaki, southern Cook Islands (18.85S, 159.79W). Preliminary analysis suggests interannual variations in present day (PD) coral oxygen isotopic composition from the region primarily reflect sea surface salinity (SSS) variability resulting from changes in the position and strength of the South Pacific Convergence Zone associated with ENSO activity. In conjunction with other hydroclimatic and oceanographic paleoclimate data available for these time windows and the PD, the research team will test whether there were differences in interannual event amplitude and recurrence interval in the LIA and MCA relative to the PD. The team will compare the results to those obtained from similarly sampled, PMIP3-compliant physical climate simulations with both complete and single external radiative forcings. Comparison of observations and simulations, within the context of their uncertainties, will be used to assess if and the extent to which the observed hydroclimatic response is forced or unforced, and by what mechanisms.

厄尔尼诺现象将如何随着气候变化而变化？目前，对21世纪气候变化的预测并没有就这个问题的答案达成共识。然而，即使厄尔尼诺事件的强度、持续时间或频率的微小变化，在美国和国际上都会对水资源、野火、农业和生态系统产生重大影响。该项目将有助于对过去两个时段的厄尔尼诺/南方涛动(ENSO)活动进行新的观测和分析，这两个时段来自热带太平洋的数据很少，而热带太平洋的全球气候被认为分别相对温暖和相对寒冷。结果将与相同时期的气候模拟进行比较，这样我们就可以更好地了解全球气候变化是否、如何以及为什么会导致厄尔尼诺活动的变化。该项目还将为一名博士生和一名本科生提供辅导、国际、协作和多学科培训，包括教育、外联和传播活动。它将为在具有丰富的前现代聚落、航海和探索考古历史的地点和地区建立人、渔业和气候之间的互动模型提供投入。这些研究超出了这个项目的范围，最终可能帮助我们理解社会如何已经以及可能适应过去和未来的气候变化。具体地说，配对的氧同位素和锶/钙数据系列将从现有的和经过成岩筛选的珊瑚样本中开发出来，这些珊瑚样本可以追溯到库克群岛南部艾图塔基(18.85S，159.79W)的小冰期(LIA)和中世纪气候异常(MCA)时间窗。初步分析表明，该区域现今珊瑚氧同位素组成的年际变化主要反映了与ENSO活动有关的南太平洋辐合带位置和强度变化导致的海表面盐度变化。研究小组将结合这些时间窗口和PD的其他水文气候和海洋古气候数据，测试LIA和MCA相对于PD在年际事件幅度和重复间隔方面是否存在差异。该团队将把这些结果与类似采样的、符合PMIP3的物理气候模拟的结果进行比较，这些模拟既有完整的外部辐射强迫，也有单一的外部辐射强迫。在观测和模拟不确定的情况下，将利用观测和模拟的比较来评估观测到的水文气候反应是强迫的还是非强迫的，以及通过什么机制，以及在何种程度上。