Ensemble modeling informs hypoxia management in the northern Gulf of Mexico
Ensemble modeling informs hypoxia management in the northern Gulf of Mexico
复制标题
集成模型为墨西哥湾北部的缺氧管理提供信息
DOI：
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发表时间：
2017
影响因子：
11.1
通讯作者：
A. Katin
中科院分区：
文献类型：
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作者：
D. Scavia;I. Bertani;D. Obenour;R. Turner;D. Forrest;A. Katin
意义 沿海缺氧地区数量正在全球范围内扩散，造成了严重的环境和社会影响。第二大缺氧区位于墨西哥湾北部，与许多沿海水域一样，人为营养负荷是关键驱动因素。我们使用整合多个模型结果的整体方法来解决海湾利益相关者和决策者提出的政策相关问题。通过开发严格的框架将模型内和模型间的不确定性传播到整体中，我们为政策制定者提供了低氧区域对一系列不同氮负荷减少情景的响应，以及相应的概率陈述，允许对替代政策策略进行定量风险评估。由于密西西比河流域的养分输入和水柱分层，墨西哥湾北部几乎每年夏天都会形成大片低溶解氧底层水（缺氧）区域。由于其对生态、经济和商业渔业的影响，政策制定者制定了减少缺氧范围的目标。然而，经过30年的研究和监测以及15年的目标设定和评估，目标仍然难以实现，因为河流氮浓度几乎没有变化。政府间工作组最近将实现 5,000 平方公里 5 年平均缺氧区目标的最后期限延长至 2035 年，并设定了到 2025 年将密西西比河春季氮负荷减少 20% 的临时负荷目标，作为其适应性管理流程的一部分。工作组已要求建模人员重新评估实现 2035 年目标所需的负荷减少量，并确定临时负荷减少 20% 的效果。在这里，我们使用四种截然不同的缺氧模型的概率集合来解决这两个问题。我们的结果表明，在典型的天气条件下，需要将密西西比河的氮负荷减少 59% 才能将缺氧面积减少到 5,000 平方公里。负荷减少 20% 的中期目标预计将导致长期缺氧面积减少 18%。然而，由于显着的年际变化，在连续 5 年评估期之间观察到任何缺氧面积减少的 95% 确定性之前，需要减少 25% 的负荷。
Significance The number of coastal hypoxia areas is spreading worldwide, with severe environmental and societal impacts. The second-largest hypoxic zone occurs in the northern Gulf of Mexico, where anthropogenic nutrient load is a key driving factor, as in many coastal waters. We address policy-relevant questions raised by Gulf stakeholders and decision-makers using an ensemble approach that integrates results from multiple models. Through development of a rigorous framework to propagate intramodel and intermodel uncertainty into the ensemble, we provide policymakers with the response of hypoxic area to a range of different nitrogen load reduction scenarios, with corresponding probabilistic statements that allow for quantitative risk assessment of alternative policy strategies. A large region of low-dissolved-oxygen bottom waters (hypoxia) forms nearly every summer in the northern Gulf of Mexico because of nutrient inputs from the Mississippi River Basin and water column stratification. Policymakers developed goals to reduce the area of hypoxic extent because of its ecological, economic, and commercial fisheries impacts. However, the goals remain elusive after 30 y of research and monitoring and 15 y of goal-setting and assessment because there has been little change in river nitrogen concentrations. An intergovernmental Task Force recently extended to 2035 the deadline for achieving the goal of a 5,000-km2 5-y average hypoxic zone and set an interim load target of a 20% reduction of the spring nitrogen loading from the Mississippi River by 2025 as part of their adaptive management process. The Task Force has asked modelers to reassess the loading reduction required to achieve the 2035 goal and to determine the effect of the 20% interim load reduction. Here, we address both questions using a probabilistic ensemble of four substantially different hypoxia models. Our results indicate that, under typical weather conditions, a 59% reduction in Mississippi River nitrogen load is required to reduce hypoxic area to 5,000 km2. The interim goal of a 20% load reduction is expected to produce an 18% reduction in hypoxic area over the long term. However, due to substantial interannual variability, a 25% load reduction is required before there is 95% certainty of observing any hypoxic area reduction between consecutive 5-y assessment periods.