The role and response of the tropical Pacific thermocline in Plio-Pleistocene climate trends and obliquity cycles

热带太平洋温跃层在上更新世气候趋势和倾角循环中的作用和响应

• 批准号: 0623204
• 负责人: Steven Hovan
• 金额: --
• 依托单位: Indiana University of Pennsylvania Research Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623204&HistoricalAwards=false
• 关键词: role; response; tropical; Pacific; thermocline

THE ROLE AND RESPONSE OF THE TROPICAL PACIFIC THERMOCLINE IN PLIO-PLEISTOCENE CLIMATE TRENDS AND OBLIQUITY CYCLESToday, the 'normal' mean state of the tropical Pacific is temporarily perturbed by short-lived El Nino events, which have global climate effects. However, there is growing evidence that the mean state has not been stable over long (geologic) timescales due to changes in sub-surface oceanic (thermocline) conditions, and that changes in the mean state have profound global climate effects that could explain the onset of the ice ages. The proposed study will focus on the last 5 Ma of earth history, which includes the early Pliocene warm period, the most recent period of sustained global warmth relative to today, and the global cooling that led to the ice ages. This project will test the hypotheses that 1) the early Pliocene warm period included El Nino-like mean conditions and the transition to cooler ice age climate was accompanied by a gradual shoaling of the thermocline and a switch from permanent 'El Nino-like' to modern 'normal' conditions and 2) higher frequency (41 kyr, glacial-interglacial) sea surface temperature (SST) variability in the tropical Pacific is related to changes in thermocline conditions. To address these hypotheses, we will analyze the elemental (Mg/Ca) and stable isotope composition of fossil foraminifera as well as organic biomarkers and sediment composition from deep sea sediments to reconstruct SST, precipitation, wind strength, and thermocline depth. This study will contribute to a fundamental understanding of the role of tropical Pacific processes in global climate change and will provide a data set for modelers to improve our interpretations and test their hierarchy of models. A graduate student and undergraduates will conduct research on this project. Research-based learning is encouraged for undergraduates. The PI's are involved with initiatives and/or established programs to increase student diversity and to expose high school students to cutting-edge science.

热带太平洋温跃层在上更新世气候趋势和倾斜度中的作用和响应今天，热带太平洋的“正常”平均状态暂时受到短暂的厄尔尼诺事件的干扰，这些事件对全球气候产生影响。然而，越来越多的证据表明，由于次表层海洋(温跃层)条件的变化，平均状态在长时间(地质)尺度上并不稳定，平均状态的变化具有深远的全球气候影响，可以解释冰期的开始。这项拟议的研究将集中在地球历史的最后5 Ma，包括上新世早期暖期，相对于今天来说最近的全球持续变暖时期，以及导致冰期的全球降温。该项目将检验以下假设：1)上新世早期暖期包括类似厄尔尼诺的平均条件，向较凉爽的冰期气候的过渡伴随着温跃层的逐渐变浅和从永久的“类似厄尔尼诺”条件向现代“正常”条件的转变；2)热带太平洋较高的频率(41KYR，冰期-间冰期)海表面温度(SST)变化与温跃层条件的变化有关。为了解决这些假设，我们将分析有孔虫化石的元素(镁/钙)和稳定同位素组成，以及深海沉积物中的有机生物标志物和沉积物成分，以重建SST、降水、风强和温跃层深度。这项研究将有助于从根本上理解热带太平洋过程在全球气候变化中的作用，并将为模型师提供一个数据集，以改进我们的解释并检验他们的模型层次。一名研究生和本科生将对这一项目进行研究。鼓励本科生进行研究性学习。PI参与了增加学生多样性和让高中生接触尖端科学的倡议和/或既定计划。