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.

预测未来海洋对二氧化碳的吸收以及海洋/陆地/大气耦合系统对气候强迫的响应的能力，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运作以应对预测的环境变化。海洋内部的耗氧/利用（OUR）和养分再生（NRR）率提供了一种有吸引力的自下而上的方法来推断阳光照射的表层水域的海洋生产力。氧气利用率通常使用“瞬态示踪剂”的分布进行估算，这些物质是由人类活动引入大气和海洋的含氯氟烃 (CFC) 和六氟化硫 (SF6) 等化合物。基于示踪剂的估算受到基于示踪剂的不确定性的影响。华盛顿大学的研究人员计划使用海洋模型来研究这些不确定性的来源并确定海洋中的位置。基于示踪剂的估计与实际速率最吻合（和最差）。基于示踪剂技术的生物地球化学循环速率和表面海洋生产力的调查将与卫星或 Argo 浮标等其他测量系统的调查结合起来。关于该技术在何处发挥作用的改进视图对于解释未来水文巡航的结果非常重要，并且可以指导未来示踪剂测量的策略。研究人员将让暑期本科生参与研究，并参与当地学校的外展项目。研究人员将使用多模型方法解决基于示踪剂的 OUR 和 NRR 中的偏差和不确定性。对现有示踪剂模型输出（包括氧气、磷酸盐、CFC、SF6、理想年龄和渡越时间分布 (TTD)）的分析将揭示瞬态示踪剂年龄（与氧场相结合）在哪些区域和时间段内给出了对模型中已知的耗氧量项。他们将利用国家大气研究中心的平行海洋计划模型输出（仅海洋配置）来扩展这项工作，该模型包含更多种类的生物地球化学参数和更复杂的生物地球化学（尽管没有 SF6、TTD 或理想年龄旋转到稳定状态） ）。除了 OUR 之外，还可以研究示踪剂推断的 NRR 的准确性，包括反硝化率、硅酸盐生产率和碳酸钙溶解度，以及溶解有机营养物的再生率。最后，计划在不久的将来在当前离线状态下添加多种生物地球化学示踪算法，将使研究人员能够同时查看复杂的生物地球化学和瞬态示踪剂、理想年龄和 TTD 年龄的全谱。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) 重复水文测量 (RH) 部分中观察到的 OUR/NRR 明显变化的稳健性。