RAPID: El Nino Event Impacts on Organic Matter Export and Composition in the Amazon River

亚马逊河是海洋最大的淡水和碳来源之一。因此，了解影响亚马逊河淡水输送的因素对于了解亚马逊河和接收大西洋的碳循环非常重要。厄尔尼诺Niño-Southern涛动（ENSO）是引起热带东太平洋风和海面温度变化并影响热带和亚热带气候的周期性事件。美国国家气象局预测，2023年夏季，厄尔尼诺Niño可能会在太平洋上空形成。这些情况预计将持续到2024年2月。这一事件预计将影响亚马逊流域的降水和气温，以及亚马逊河的淡水输送。该项目旨在研究2023-2024年El Niño事件期间从亚马逊河输送到大西洋的溶解有机碳的数量和化学成分。参与该项目的科学家计划从2023年夏末到2024年夏末收集样本。该研究将确定事件发生之前、期间和之后的情况。这组独特的样本将使科学家团队能够研究ENSO如何影响有机碳向沿海海洋的输送。该项目为早期职业研究人员提供支持，并促进美国研究人员与受亚马逊河变化直接影响的巴西研究人员之间的国际合作和包容性。本项目研究El Niño南方涛动（ENSO）异常如何影响从亚马逊河到大西洋的溶解有机碳（DOC）出口和溶解有机物质（DOM）组成。根据最近的研究，假设与非enso年和La Niña年相比，即将到来的2023年El Niño事件将减少亚马逊河的年DOC通量和陆地DOM输出比例。这一假设将通过将已建立的最先进的光学和分子水平表征技术（例如，傅里叶变换离子回旋共振质谱；FT-ICR质谱）与El Niño年过程中的DOC通量计算联系起来进行检验。通过对总体DOC通量和分子水平组成的分析，将揭示亚马孙流域和上游降水减少和气温升高对DOM出口数量和质量的月度变化。从下游最远的亚马逊河测量站Óbidos（巴西）采集的DOM通量和详细表征（FT-ICR MS、光学、荧光分析）将直接与2011-2012年Niña年和随后的2012-2013水文正常年获得的结果进行比较，以确定全球气候异常如何影响DOC向海洋系统的输出，并为未来的预测创建一个框架。从这项拟议的研究中获得的数据将为更大规模的研究奠定基础，这些研究将调查ENSO循环如何影响其他主要热带-亚热带河流的排放和碳输出，以及最终ENSO循环如何影响全球陆地-海洋碳输出。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Amazon River is one of the largest sources of freshwater and carbon to the ocean. Thus, understanding the factors that influence freshwater delivery from the Amazon River is important for understanding the carbon cycle of the Amazon River and the receiving Atlantic Ocean. El Niño–Southern Oscillation (ENSO) is a periodic event that causes changes in winds and sea surface temperature over the tropical eastern Pacific Ocean and affects climate in the tropics and subtropics. The National Weather Service predicts that El Niño conditions are likely to form across the Pacific during Summer 2023. These conditions are expected to last through February 2024. This event is expected to impact precipitation and air temperatures in the Amazon Basin and freshwater delivery from the Amazon River. This project aims to study the amount and chemical composition of dissolved organic carbon delivered from the Amazon River to the Atlantic Ocean during the 2023-2024 El Niño event. Scientists involved in this project plan to collect samples from late Summer 2023 through late Summer 2024. The study will identify conditions before, during and after this event. This unique set of samples will enable the team of scientists to study how ENSO influences the delivery of organic carbon to the coastal ocean. This project provides support for an early career researcher and promotes international cooperation and inclusivity between researchers from the United States of America and researchers in Brazil who are directly impacted by the changing Amazon River. This project examines how El Niño Southern Oscillation (ENSO) anomalies impact the export of dissolved organic carbon (DOC) and composition of dissolved organic matter (DOM) from the Amazon River to the Atlantic Ocean. Based on recent studies, it has been hypothesized that the upcoming 2023 El Niño event will reduce the annual DOC flux and proportion of exported terrestrial DOM from the Amazon River compared to non-ENSO and La Niña years. This hypothesis will be examined by linking established state-of-the-art optical and molecular-level characterization techniques (e.g., Fourier-transform ion cyclotron resonance mass spectrometry; FT-ICR MS) with DOC flux calculations over the course of an El Niño year. Analyzing both bulk DOC fluxes and the molecular-level composition will reveal how the quantity and quality of DOM export will change monthly in response to reduced precipitation and higher temperature across the Amazon Basin and headwaters. DOC fluxes as well as detailed characterizations (FT-ICR MS, optical, fluorescence analysis) of DOM sampled from the furthest downstream Amazon River gauging station at Óbidos (Brazil) will be directly compared to results obtained from the 2011-2012 La Niña year and the following 2012-2013 hydrologically normal year to determine how global climate anomalies impact the DOC export to marine systems and to create a framework for future predictions. Data obtained from this proposed study will lay the foundations for larger studies investigating how ENSO cycles impact discharge and carbon export from other major tropical-subtropical rivers and ultimately, how ENSO cycles impact global land-ocean carbon export.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.