Assessing the Viability of Pristine Fossil Corals from the Dominican Republic as Indicators of ENSO at the Miocene/Pliocene Boundary

厄尔尼诺-南方涛动 (ENSO) 是地球年际气候变率的最大单一来源，并且由于大量研究表明 ENSO 对大气和表层海洋的温室变暖很敏感，因此我们更好地了解 ENSO 在未来几十年和几个世纪中可能如何反应至关重要。对海洋沉积物的研究已经检验了热带太平洋平均状态的百年到千年尺度的动态，但这些结果大多缺乏识别 ENSO 波段（2-7 年）内变化所需的时间分辨率。珊瑚在其每年带状的文石骨架中保存了海面温度和上升流的记录，因此可用于与 ENSO 一致的光谱频率。这项研究的结果将广泛有助于我们了解ENSO在一个被认为是人类造成变暖的世界的最新模拟时期的性质。该研究项目将从多米尼加共和国古拉博组的原始珊瑚化石中产生大约半个世纪之久的每月解析的氧和碳同位素比记录，作为对最新中新世ENSO变化的测试。该记录将使研究人员能够测试中新世期间太平洋的三种拟议状态：根深蒂固的厄尔尼诺状况、根深蒂固的拉尼娜状况或现代ENSO模式。研究结果还可能对中美洲海道 (CAS) 最终关闭之前的流量建模产生影响。中美洲地峡的完全形成（以及 CAS 的闭合）在 3.5 Ma 左右导致了东太平洋和加勒比地区的灭绝和物种形成，并可能通过海洋环流的变化促进了北半球的冰川作用。然而，对这些效应的建模受到 CAS 流动性质仍然存在相当大的不确定性的限制，这主要是由于开口宽度和窗台深度的模糊性。康奈尔学院（一所小型四年制文理学院，没有研究生课程）的一名本科生将通过积极参与该项目的各个方面（包括在全国会议上展示结果）来接受古气候学研究方法的高级培训。

The El Nino-Southern Oscillation (ENSO) represents the single largest source of interannual climate variability on Earth, and because numerous studies have suggested that ENSO is sensitive to greenhouse warming of the atmosphere and surface ocean, it is critical that we better understand how ENSO may respond over coming decades and centuries. Studies of marine sediments have examined centennial- to millennial-scale dynamics of the mean state of the tropical Pacific, but these results have mostly lacked the temporal resolution necessary to identify variability within the ENSO band (2-7 yr). Corals preserve records of sea surface temperature and upwelling in their annually-banded aragonite skeletons, and thus can be used for spectral frequencies consistent with ENSO. The results of this study will contribute broadly to our understanding of the nature of ENSO during a time period considered the most recent analog for an anthropogenically-warmed world.The research project will generate a roughly half-century-long record of monthly-resolved oxygen and carbon isotopic ratios from a pristine fossil coral from the Gurabo Formation of the Dominican Republic as a test of ENSO variability in the latest Miocene. The record will allow the researchers to test three proposed states of the Pacific during the Miocene: entrenched El Nino conditions, entrenched La Nina conditions, or a modern ENSO pattern. The results may also have implications for modeling of flow through the Central American Seaway (CAS) prior to its final closure. Complete formation of the Central American Isthmus (and closure of the CAS) around 3.5 ma led to pulses of extinction and speciation in both the eastern Pacific and the Caribbean, and may have contributed to Northern Hemisphere glaciation through changes to ocean circulation. However, modeling these effects are limited by the still considerable uncertainties in the nature of flow through the CAS, largely owing to ambiguities surrounding the width of the opening(s) and depth of the sill. An undergraduate student from Cornell College (a small, four-year liberal arts school with no graduate programs) will receive advanced training in paleoclimatology research methods by actively participate in all aspects of this project, including presentation of results at a national meeting.