Collaborative Research: Testing Mechanisms of Tropical Climate Change and Variability Using New Cores from the Line Islands

热带太平洋的海洋-大气耦合相互作用是现代全球年际气候变率的主要来源。这种变率表现为厄尔Niño-Southern涛动（ENSO），其范围远远超出了热带太平洋，影响着全球的气候和人口。因此，了解气候变化如何改变这些相互作用对于人类社会减缓和适应未来的变化至关重要。发现是外部强迫还是内部变率决定了ENSO行为，将极大地加深我们对ENSO的理论认识，并提高我们准确预测气候变化下ENSO行为的能力。除了这些广泛的科学和社会效益外，该项目还将为研究生和本科生提供研究机会。该项目还为K-12教学模块的开发提供了一个平台，这些模块将与公立学校教师以及加州大学圣克鲁斯分校正在培训的本科科学教师合作设计。该项目正在开发过去25万年赤道太平洋海面温度变化的记录，以测试改变热带气候和厄尔尼诺Niño-Southern涛动（ENSO）行为的因素。ENSO是全球年际气候变率的主要原因，但目前尚不清楚其行为如何随未来气候变化而变化。当全球温度不同时，了解ENSO过去的行为变化将是这方面的重大进展。ENSO行为是由太平洋中部莱恩群岛附近深海沉积物中化石有孔虫壳的化学成分决定的海洋表面温度的变化来重建的。每个浮游有孔虫壳的Mg/Ca比值和氧同位素组成记录了一个月的海面温度快照。对来自单一沉积层的许多单个贝壳的测量记录了沉积期间海洋表面温度的变化。由于ENSO是莱恩群岛附近海面温度变化的主要原因，过去温度变化的变化表明ENSO行为在过去是如何变化的。这些数据将测试赤道太平洋对来自地球轨道的太阳日照变化的动态响应，以及对全球温度和温室气体（pCO2）强迫的冰期-间冰期变化的动态响应，从而提高我们对ENSO现象及其未来可能变化的理解。

Coupled ocean-atmosphere interactions in the tropical Pacific are the leading source of modern global interannual climate variability. This variability, expressed as the El Niño-Southern Oscillation (ENSO), extends far beyond the tropical Pacific, affecting climate and human populations globally. Understanding how climate change alters these interactions is therefore critical for human societies to mitigate and adapt to future change. Discovering whether external forcing or internal variability determines ENSO behavior will greatly deepen our theoretical understanding of ENSO and improve our ability to accurately forecast ENSO behavior under altered climates. In addition to these broad scientific and societal benefits, this project will provide research opportunities for graduate and undergraduate students. The project also provides a platform for the development of K-12 teaching modules, which will be designed in collaboration with public school teachers as well as an undergraduate science teacher in training at the University of California, Santa Cruz.This project is developing records of equatorial Pacific Ocean sea-surface temperature variability during the past 250,000 years to test factors that alter tropical climate and the behavior of the El Niño-Southern Oscillation (ENSO). ENSO is the dominant cause of interannual climate variability globally, yet it is not known how its behavior could change with future climate change. Understanding past changes in the behavior of ENSO, when global temperatures were different, will be a significant advance in this regard. ENSO behavior is reconstructed from the variability of sea-surface temperatures determined by the chemistry of fossil foraminifera shells in deep-sea sediments near the Line Islands, in the central Pacific. The Mg/Ca ratio and oxygen isotope composition of each individual planktonic foraminifera shell records a one-month snapshot of sea-surface temperature. Measurement of many individual shells from a single sediment layer documents the variability of sea surface temperatures over the time of deposition. Because ENSO is the primary cause of sea-surface temperature variability near the Line Islands, past changes in temperature variability show how ENSO behavior changed in the past. These data will test the dynamic response of the equatorial Pacific to changes in solar insolation from Earth's orbit, and to glacial-interglacial changes in global temperature and greenhouse gas (pCO2) forcing, improving our understanding of the ENSO phenomenon and how it might change in the future.