Towards detecting and attributing long-term changes in CO2 outgassing in the equatorial Pacific

致力于检测和归因赤道太平洋二氧化碳排放的长期变化

• 批准号: 1635465
• 负责人: Yuko Okumura
• 金额: $ 40.79万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635465&HistoricalAwards=false
• 关键词: Towards; detecting; attributing; long; term; Towards; detecting; attributing; long; term

Changes in carbon dioxide (CO2) sources and sinks in the ocean are highly uncertain, and could therefore have a significant influence on future atmospheric CO2 levels. Outgassing of CO2 in the tropical Pacific is the largest natural source of this powerful greenhouse gas to the atmosphere. This project will use a combination of existing and new Earth System Model (ESM) simulations to study ongoing and future changes in sea-air CO2 exchange over the tropical Pacific. The research approach will focus on robust mechanisms governing changes in equatorial outgassing in 21th Century simulations of climate and ocean biogeochemistry. The research proposed here could provide answers regarding the ability of the tropical oceans to continue to slow their outgassing of CO2, thus contributing to moderating the increase of atmospheric CO2. In addition, the proposed analysis of sampling biases is a first step towards understanding the requirements of future expansions of the ocean carbon observing system in the tropical oceans. Last, this project will support one early career researcher and one post-doctoral scholar, who will receive cross-disciplinary training in climate dynamics and ocean biogeochemistry. A combination of advanced diagnostics and new simulations will be used to identify and understand the dynamics and physics of the robust mechanisms, i.e. those that can be linked to simple dynamical and physical processes and therefore are independent of parameterized processes. New simulations will be performed with the objective of isolating the effects of increasing CO2, ocean circulation, and warmer temperatures on equatorial outgassing. Model dependence of the results will be explored using existing output from a multi-model ensemble. The project will also explore how these mechanisms operate in subsequent centuries as atmospheric CO2 stabilizes and the carbon cycle approaches a new equilibrium. Strategies for evaluating the simulated mechanisms using observed changes during the 1984-2012 period will be considered. Emphasis will be placed on reducing uncertainty due to limited sampling of spatial and temporal variability of pCO2 over the equatorial Pacific. The effect of ongoing multi-decadal changes in Pacific climate will also be studied using new ocean-only simulations designed to isolate the effect of increasing CO2 from changes in circulation. The outcomes of this work are manifold, including 1) study of robust mechanisms in model projections; 2) evaluation of the long-term response of equatorial outgassing beyond year 2100; 3) a systematic evaluation of the existing observing system in the tropical Pacific; and 4) evaluation of the effect of multi-decadal changes in Pacific climate on the observed changes in the tropical carbon cycle.

海洋中二氧化碳（CO2）源和下沉的变化是高度不确定的，因此可能会对未来的大气二氧化碳水平产生重大影响。在热带太平洋中，二氧化碳的气味是这种强大的温室气体对大气的最大自然来源。该项目将结合现有和新的地球系统模型（ESM）模拟，研究热带太平洋地区海上二氧化碳交换的正在进行和未来的变化。研究方法将重点介绍21世纪气候和海洋生物地球化学模拟赤道量化变化的强大机制。这里提出的研究可以提供有关热带海洋继续减慢其二氧化碳量的能力的答案，从而有助于调节大气二氧化碳的增加。此外，提出的对采样偏见的分析是了解热带海洋中海洋碳观察系统未来扩展的要求的第一步。最后，该项目将支持一位早期的职业研究员和一名博士后学者，他们将接受气候动态和海洋生物地球化学的跨学科培训。 高级诊断和新模拟的组合将用于识别和理解可靠机制的动力学和物理，即可以与简单的动力学和物理过程链接的机制，因此与参数化过程无关。将进行新的模拟，目的是隔离增加二氧化碳，海洋循环和较高温度对赤道量大的影响的影响。将使用来自多模型集合的现有输出来探索结果的模型依赖性。该项目还将探讨随着大气二氧化碳的稳定，碳循环接近新的平衡，这些机制如何在随后的几个世纪中运作。将考虑使用1984 - 2012年期间使用观察到的变化评估模拟机制的策略。由于PCO2对赤道太平洋的空间和时间变化的采样有限，将重点放在降低不确定性上。还将使用旨在隔离循环变化的二氧化碳效果的新的纯海洋模拟来研究太平洋气候中持续的多年变化的影响。这项工作的结果是多种多样的，包括1）研究模型预测中鲁棒机制的研究； 2）评估赤道超过2100年以上的赤道供应的长期响应； 3）对热带太平洋现有观察系统的系统评估； 4）评估太平洋气候多年多变化对观察到的热带碳循环变化的影响。