Ensemble Estimation of Central Tropical Pacific Climate over the last 6,000 Years

过去 6000 年中部热带太平洋气候的集合估计

• 批准号: 1502832
• 负责人: Kim Cobb
• 金额: $ 51.6万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1502832&HistoricalAwards=false
• 关键词: Ensemble; Estimation; Central; Tropical; Pacific

Significant uncertainty surrounds future climate change impacts in many regions of the world, particularly regarding potential changes in tropical rainfall levels, and their extremes. Much of the uncertainty stems from poor constraints on future trends in the El Nino-Southern Oscillation (ENSO), a natural climate cycle that affects temperature and rainfall patterns around the globe, with its largest effects in the tropics. The instrumental record of ENSO is too short to isolate statistically robust trends, so this study seeks to provide hundreds of years worth of additional observations of past ENSO variability in an effort to: 1) quantify the natural baseline for this globally-relevant climate cycle, and 2) assess whether recent changes fall outside the range of natural variability. Using a suite of well-dated and high-resolution coral records from the central tropical Pacific, the study will extend the record of ENSO and longer-term climate patterns in the heart of the ENSO region. As such, it will inform future projections of tropical Pacific climate and constrain regional rainfall trends throughout the tropics and beyond. Tropical Pacific climate trends are difficult to isolate from the short instrumental record of climate, owing to significant tropical climate variability on interannual to decadal timescales. Recent paleoclimate records hint that the El Nino-Southern Oscillation (ENSO) may be intensifying in response to anthropogenic climate forcing, implying that tropical rainfall extremes may increase in coming decades. Such records also show that natural ENSO variability is much larger than previously thought, requiring a larger number of paleo-reconstruction to define natural ENSO variability and distinguish it from possible anthropogenic signals. The last 6,000 years is an particularly important baseline for probing past ENSO variability, as global climate models show that ENSO may be sensitive to a range of natural climate forcings over this period. This project involves generation of a highly-replicated reconstruction of both mean climate and climate variability in the tropical Pacific over the last 6,000 years using hundreds of fossil coral records from Christmas Island (2ºN, 157ºW), which lies in the heart of the El Niño-Southern Oscillation (ENSO) region. The research team, which includes a graduate student, will compare the new reconstructions to numerical climate model simulations of tropical Pacific paleoclimate variability, probing the relationships between climate forcing, mean climate state, and ENSO variability.

未来气候变化对世界许多地区的影响存在巨大的不确定性，特别是热带降雨水平及其极端情况的潜在变化。大部分不确定性源于对厄尔尼诺-南方涛动（ENSO）未来趋势的约束不力，这是一种影响全球温度和降雨模式的自然气候周期，对热带地区的影响最大。 ENSO 的仪器记录太短，无法隔离统计上强劲的趋势，因此本研究旨在提供数百年来对过去 ENSO 变化的额外观测，以期：1）量化这一全球相关气候周期的自然基线，2）评估最近的变化是否超出自然变化范围。该研究将利用来自热带太平洋中部的一套日期明确的高分辨率珊瑚记录，扩展 ENSO 的记录以及 ENSO 区域中心的长期气候模式。因此，它将为热带太平洋气候的未来预测提供信息，并限制整个热带地区及其他地区的区域降雨趋势。由于热带气候在年际到年代际时间尺度上的显着变化，热带太平洋气候趋势很难从短期仪器气候记录中分离出来。最近的古气候记录暗示，厄尔尼诺-南方涛动（ENSO）可能会因人为气候强迫而加剧，这意味着未来几十年热带极端降雨量可能会增加。这些记录还表明，ENSO 的自然变化比之前认为的要大得多，需要大量的古重建来定义 ENSO 的自然变化并将其与可能的人为信号区分开来。过去 6000 年是探索过去 ENSO 变化的一个特别重要的基线，因为全球气候模型显示 ENSO 可能对这一时期的一系列自然气候强迫敏感。该项目涉及利用位于厄尔尼诺南方涛动 (ENSO) 区域中心的圣诞岛（北纬 2°，西经 157°）的数百个珊瑚化石记录，对热带太平洋过去 6,000 年的平均气候和气候变率进行高度复制的重建。该研究小组包括一名研究生，他们将把新的重建结果与热带太平洋古气候变率的数值气候模型模拟进行比较，探讨气候强迫、平均气候状态和 ENSO 变率之间的关系。