RAPID: Galapagos lake chemistry and plankton assemblage during the 2015-16 El Nino

热带太平洋气候的强有力的重建对于了解过去的气候变化至关重要，因为该地区具有影响全球气候的独特能力。厄尔尼诺-南方涛动（ENSO）每3-7年影响一次地球仪一半以上地区的降水和温度模式。与厄尔尼诺/南方涛动有关的影响包括干旱、洪水、作物歉收、疾病和海洋生产力的变化。重要的是，关于厄尔尼诺/南方涛动在过去如何变化以及在二氧化碳含量较高的世界中可能如何变化，存在很大的不确定性。改进从采样严重不足的东赤道太平洋进行的ENSO重建将有助于阐明ENSO对气候系统大尺度变化的响应，从而为社会带来巨大利益。加拉帕戈斯群岛的淡水和沿海盐湖沉积物提供了对赤道东太平洋降雨量的宝贵的长期连续重建，那里的年降雨量与厄尔尼诺海洋表面温度密切相关。然而，由于缺乏对加拉帕戈斯湖对厄尔尼诺条件的反应的直接测量，迄今为止，这种重建受到了很大的不确定性的阻碍。本项目试图利用目前正在进行的2015-2016年强厄尔尼诺事件，以改善对这些和未来热带太平洋降雨重建的限制。为此目的，将与厄瓜多尔科学家和查尔斯达尔文研究站合作，在厄尔尼诺现象的开始、高峰和衰减阶段，在埃尔琼科湖（圣克里斯托瓦尔岛）和波萨德尔迪亚布洛和波萨弗德（伊萨贝拉岛）进行一整套气象和湖泊测量。测量将包括水文通量（降水、蒸发）及其同位素组成（d2 Hrain），以及湖泊的物理、化学和生物特性（d2 Hlake、温度、盐度、营养物、pH值、浮游植物组合、深度以及植物和藻类生物标志物的d2 H）。这些数据将使现代气候和古气候代用指标之间的关系能够通过罕见的强烈厄尔尼诺事件（最近一次发生在18年前）的过程得到明确的评估。这一数据集将是迄今为止关于厄尔尼诺事件对这些湖泊系统影响的最全面的特征，并将大大推动目前为建立该区域的定量古厄尔尼诺/南方涛动记录所作的努力。这项工作得到了海洋地质学和地球物理学、地球科学全球变化和国际科学与工程办公室的支持。

Robust reconstructions of tropical Pacific climate are critically important for understanding past climate change due to the unique ability of this region to influence climate on a global scale. The El Niño-Southern Oscillation (ENSO) affects precipitation and temperature patterns across more than half of the globe every 3-7 years. Impacts associated with ENSO include drought, flooding, crop failure, disease, and changes in ocean productivity. Importantly, large uncertainties exist regarding how ENSO has changed in the past and how it is likely to change in a higher CO2 world. Improving ENSO reconstructions from the vastly under-sampled eastern equatorial Pacific will help elucidate the response of ENSO to large-scale changes in the climate system and thus poses tremendous benefit to society. Freshwater and coastal saline lake sediments in the Galápagos Islands provide invaluable long continuous reconstructions of rainfall from the eastern equatorial Pacific, where annual rainfall is strongly correlated to El Niño sea surface temperatures. To date, however, such reconstructions have been hampered by large uncertainties owing to the lack of direct measurements of the response of Galápagos lakes to El Niño conditions.This project seeks to leverage the 2015-2016 strong El Niño event that is currently underway to improve constraints on these and future rainfall reconstructions from the tropical Pacific. Towards this end, a comprehensive set of meteorological and lake measurements will be taken at El Junco Lake (San Cristobal Island) and Poza del Diablo and Poza Verde (Isabela Island) during the onset, peak, and decay phase of the El Niño event in collaboration with Equadorian scientists and the Charles Darwin Research Station. Measurements will include hydrologic fluxes (precipitation, evaporation) and their isotopic composition (d2Hrain), as well as physical, chemical, and biological properties of the lakes (d2Hlake, temperature, salinity, nutrients, pH, phytoplankton assemblage, depth, and d2H of plant and algal biomarkers). These data will enable the relationship between modern climate and the paleoclimate proxies to be explicitly evaluated through the course of a rare strong El Niño event (the last of which occurred 18 years ago). This dataset would be the most comprehensive characterization of the influence of El Niño events on these lake systems to date and would greatly advance ongoing efforts to construct quantitative paleo-ENSO records from this region. The work is supported by Marine Geology and Geophysics, Earth Sciences Global Change, and the Office of International Science and Engineering.