Investigation of a Dynamical Response of the Tropical Pacific to Orbital and Solar Forcing during the Holocene

在过去的几个世纪里，太阳亮度的微小变化可能影响了地球海洋-大气循环的某些模式，例如厄尔尼诺-南方涛动(ENSO)。一些气候模型模拟表明，持续较亮的太阳会导致热带太平洋出现更冷或更像拉尼娜现象的状态。这种反应被称为“海洋动力恒温器”，因为ENSO反应往往会抵消太阳加热的直接变暖效应。然而，到目前为止，支持恒温器对太阳强迫做出反应的古气候证据是模棱两可的，而且仅限于过去1000年。从下加利福尼亚州附近采集的海洋沉积物岩心的初步结果似乎支持过去14,000年来ENSO系统百年至千年尺度的太阳强迫，以及与地球绕太阳轨道变化有关的较慢反应。这项新的研究由科罗拉多大学博尔德分校的一名研究人员领导，将使用相同位置的额外核心来进一步阐明ENSO对过去12000年来太阳和轨道变化的响应。这项工作将检验这样一个假设，即气候系统的一个主要模式比目前大多数气候模型模拟的更敏感。如果这里生成的数据支持这一断言，它们将为政府间气候变化专门委员会级别的模型提供关键目标。这种类型的数据模型相互比较最终可能导致对未来气候变化的更强有力的预测，特别是对于一个对农业、渔业和自然灾害产生重要经济和社会影响的系统。该项目还将为一名博士生和一名地质学本科生提供研究和培训经验。

Small variations in the Sun's brightness over past centuries may have impacted certain modes of the Earth's ocean-atmosphere circulation, such as the El Niño - Southern Oscillation (ENSO). Some climate model simulations suggest that a persistently brighter sun leads to a colder or more "La Niña-like" state in the tropical Pacific. This response is dubbed the "ocean dynamical thermostat" because the ENSO response tends to counteract the direct warming effect of solar heating. However, paleoclimatic evidence in support of a thermostat response to solar forcing is thus far equivocal and limited to the past 1000 years. Initial results from an ocean sediment core collected off of Baja California appear to support centennial-to-millennial-scale solar forcing of the ENSO system over the past 14,000 years, as well as a slower response related to changes in the Earth's orbit around the Sun. This new study, led by a researcher at the University of Colorado, Boulder, will use additional cores from the same location to further elucidate the response of ENSO to both solar and orbital changes over the past 12,000 years.This work will test the hypothesis that a major mode of the climate system is more sensitive to solar forcing than is currently simulated by most climate models. If the data generated here support that assertion, they will provide a crucial target for IPCC-class models. This type of data-model intercomparison could ultimately lead to more robust predictions of future climate change, particularly for a system that results in economically and societally important impacts on agriculture, fisheries, and natural disasters. This project will also provide research and training experiences for a PhD student and an undergraduate geology student.