Evaluating the Accuracy of Biogeochemical Cycling Rates from Transient Tracers

评估瞬态示踪剂生物地球化学循环速率的准确性

• 批准号: 1634256
• 负责人: Sabine Mecking
• 金额: $ 41.3万
• 依托单位: University of Washington
• 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 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634256&HistoricalAwards=false
• 关键词: Evaluating; Accuracy; Biogeochemical; Cycling; Rates

The ability to predict future oceanic uptake of carbon dioxide and, consequently, the response of the coupled ocean/land/atmosphere system to climate forcing, requires an understanding of both how the physical, chemical, and biological systems presently function and how they are likely to respond to predicted environmental changes. Oxygen consumption/utilization (OUR) and nutrient regeneration (NRR) rates in the ocean interior provide an attractive bottom-up approach to infer marine productivity in the sunlit surface waters. Oxygen utilization rates are often estimated using the distributions of "transient tracers,' compounds such as chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) that are introduced in to the atmosphere and oceans by human activity. Tracer-based estimates are subject to uncertainties based on several factors including the time history of the tracers and ocean mixing. Investigators at the University of Washington plan to use ocean models to examine the sources of these uncertainties and determine where in the oceans the tracer-based estimates agree best (and worst) with the actual rates. The investigation of biogeochemical cycling rates and surface ocean productivity based on tracer techniques will be put into context with those from other measurement systems such as satellite or Argo floats and will provide an improved view of biogeochemical cycling in the ocean. Recommendations on where the technique works will be important for the interpretation of results from future hydrographic cruises and can guide strategies for future tracer measurements. The investigators will include undergraduate summer students in the research, and participate in outreach programs in local schools.The investigators will address the biases and uncertainties in the tracer-based OURs and NRRs using a multi-model approach. Analysis of existing tracer model output, including oxygen, phosphate, CFCs, SF6, ideal ages and transit time distributions (TTDs), will reveal in which regions and during which times transient tracer ages (combined with oxygen fields) give the best estimation of the known oxygen consumption terms in the model. They will expand this work using the National Center for Atmospheric Research's Parallel Ocean Program model output (ocean-only configuration) which contains a much larger variety of biogeochemical parameters and more complex biogeochemistry (though no SF6, TTDs or ideal age spun up to steady state). In addition to OURs, this allows investigation of the accuracy of tracer-inferred NRRs, including denitrification rates, silicate production rates, and calcium carbonate dissolution, as well as regeneration rates of dissolved organic nutrients. Finally, a planned, near-future addition of multi-biogeochemical tracer algorithms to the current offline will enable the investigators to look at complex biogeochemistry and the full spectrum of transient tracer, ideal, and TTD ages simultaneously. Finally they will address the robustness of apparent changes in OURs/NRRs observed during recent and upcoming Climate Variability and Prediction/Global Ocean Ship-based Hydrographic Investigations Program (CLIVAR/GO-SHIP) Repeat Hydrography (RH) sections.

预测未来海洋吸收二氧化碳的能力，以及因此耦合的海洋/陆地/大气系统对气候强迫的响应，需要了解物理，化学和生物系统目前如何运作，以及它们可能如何响应预测的环境变化。海洋内部的氧消耗/利用率（OUR）和营养再生率（NRR）提供了一个有吸引力的自下而上的方法来推断阳光照射的表面沃茨的海洋生产力。氧气利用率通常使用“瞬态示踪剂”的分布来估计，这些化合物如氯氟烃（CFC）和六氟化硫（SF6），是由人类活动引入大气和海洋的。基于示踪剂的估计受到若干因素的不确定性的影响，包括示踪剂的时间历史和海洋混合。华盛顿大学的研究人员计划使用海洋模型来检查这些不确定性的来源，并确定海洋中基于示踪剂的估计与实际速率最吻合（和最差）的地方。利用示踪技术对海洋地球化学循环速率和表层海洋生产力进行的调查将与卫星或阿尔戈浮标等其他测量系统的调查相结合，并将提供更好的海洋地球化学循环情况。关于该技术在何处起作用的建议对于解释未来水文航行的结果很重要，并可指导未来示踪剂测量的战略。研究人员将包括本科暑期学生的研究，并参加在当地学校的推广计划。研究人员将解决的偏见和不确定性，在基于示踪剂的OUR和NRR使用多模型的方法。现有示踪剂模型输出的分析，包括氧气，磷酸盐，CFCs，SF6，理想年龄和渡越时间分布（TTD），将揭示在哪些区域和在此期间瞬态示踪剂年龄（结合氧气场）给出最佳估计的已知氧气消耗量的模型。他们将使用国家大气研究中心的并行海洋计划模型输出（仅海洋配置）来扩展这项工作，该模型输出包含更多种类的地球化学参数和更复杂的地球化学（尽管没有SF6，TTD或理想年龄旋转到稳定状态）。除了OURs，这允许调查示踪剂推断的NRR的准确性，包括反硝化速率，硅酸盐生产率，碳酸钙溶解，以及溶解的有机营养素的再生率。最后，一个有计划的，不久的将来增加多地球化学示踪剂算法，目前离线将使研究人员能够同时查看复杂的地球化学和全谱的瞬态示踪剂，理想的，和TTD年龄。最后，他们将讨论在最近和即将到来的气候变率和预测/全球海洋船舶水文调查计划（CLIVAR/GO-SHIP）重复水文（RH）部分中观察到的OURs/NRR明显变化的鲁棒性。