Coastal SEES: developing new modeling tools to predict ocean acidification impacts on coastal ecosystems

二氧化碳在海水中溶解的直接后果是水的酸度增加，这对依赖碳酸盐化学物质进行生命功能的生物体产生了影响。随着美国西海岸沿着低pH值和低氧事件的发生，在未来几十年内，频率可能会增加，幅度可能会恶化，因此，仔细记录与沿海涌升流的季节性和年际变化相关的水柱pH值和氧气的现今变化至关重要，并在空间（公里）和时间（天）尺度上产生参考pH值和氧气场，以评估其对生态系统过程的影响。为了满足这一需求，拟议的研究使用了最先进的，数据同化，耦合物理-地球化学建模框架，以量化的时间变化的低pH值和低氧入侵沿着加州中部在空间尺度上相关的沿海生态系统。此外，建模工作依赖于一种整体方法，以确定可以在每日至季节时间尺度上预测低pH值和低氧事件发生频率和持续时间的确定程度，这是改善旨在减轻海洋酸化对海洋生物影响的未来管理战略的一个关键组成部分。预计研究结果还将适用于其他东部边界流上升流系统，并提高对沿海上升流对海洋地球化学过程影响的更广泛认识（例如，近岸海-气CO2通量的长期符号和量级）。这项研究将有助于培养新一代精通多学科海洋科学和管理概念的科学家。具体而言，它将为两名博士后研究人员和一名研究生提供以下方面的培训：（1）耦合物理-地球化学数据同化，（2）模型模拟的区域到地方降尺度，（3）复杂数值模型解决方案的解释，以及（4）针对海洋酸化问题创建旨在改善资源管理的产品。此外，首席首席研究员将为普通观众举办讲座，介绍如何使用模型和观测来研究加州海岸沿着海洋酸化。（几天到几周）尺度对沿海海洋观测系统和监测方案提出了挑战，数据同化物理-地球化学模型的常规使用将极大地提高当前预测加州中部近海低pH和低氧事件发生的能力。在这方面，这项研究具有以下短期和长期效益：（1）确定沿岸上升流变化与大陆架上低pH值和低氧条件的频率、幅度和持续时间之间的联系，（2）检查长期超过某些pH值和氧阈值的可能性，低于这些阈值的条件对关键海洋生物有害，（3）通过识别pH和氧气变化性预计最大的特定区域来指导有效监测系统网络的实施，以及（4）实施能够预测加州中部外极端低pH和低氧事件发生的建模框架，并评估其用于决策目的的有用性。这些发展有助于实现沿海SEES的总体目标，即在各种空间和时间尺度上促进对沿海系统基本的相互关联过程的理解，提高预测未来沿海系统状态和影响的能力，并确定将研究成果转化为政策和管理领域并用于增强沿海可持续性的途径。

An immediate consequence of the dissolution of CO2 in seawater is an increase in the acidity of the water, which has implications for organisms that rely on carbonate chemistry for vital functions. As the occurrence of lower pH and lower oxygen events along the U.S. west coast is likely to increase in frequency and worsen in magnitude over the next decades, it is paramount to carefully document present-day variability in water column pH and oxygen associated with seasonal and interannual changes in coastal upwelling, and produce reference pH and oxygen fields at the spatial (kilometers) and temporal (days) scales needed to assess their impact on ecosystem processes. To address this need, the proposed research uses a state-of-the art, data-assimilative, coupled physical-biogeochemical modeling framework to quantify the temporal variability of low pH and low oxygen intrusions along central California at the spatial scales relevant to coastal ecosystems. In addition, the modelling effort relies on an ensemble approach to identify the degree of certainty with which the frequency of occurrence and duration of low pH and low oxygen events can be predicted on daily to seasonal timescales, a critical component for improving future management strategies designed to mitigate the effects of ocean acidification on marine organisms. It is also anticipated that the results will apply to other eastern boundary current upwelling systems and improve broader knowledge of coastal upwelling impacts on biogeochemical processes (e.g., the long-term sign and magnitude of nearshore air-sea CO2 fluxes). The study will contribute to training a new generation of scientists versed in multidisciplinary ocean science and management concepts. Specifically, it will provide training for two post-doctoral researchers and one graduate student in (1) coupled physical-biogeochemical data assimilation, (2) regional-to-local downscaling of model simulations, (3) interpretation of complex numerical model solutions, and (4) creation of products targeted at improving resource management in the face of ocean acidification. In addition, the lead PI will give general audience lectures on the use of models and observations to study ocean acidification along the California coast.Because the significant amount of variability occurring over relatively short spatial ( 100 km) and temporal (days to weeks) scales presents a challenge for coastal ocean observing systems and monitoring programs, the routine use of data-assimilative physical-biogeochemical models would greatly enhance current capabilities for predicting the occurrence of low pH and low oxygen events off central California. In this regard, this research has the following short- and long-term benefits: (1) establish the connections between alongshore upwelling variability and the frequency, magnitude and duration of low pH and low oxygen conditions on the shelf, (2) examine the probability that certain pH and oxygen thresholds below which conditions become detrimental to key marine organisms are exceeded for extended periods, (3) guide the implementation of an efficient monitoring system network by identifying specific regions where pH and oxygen variability is expected to be largest, and (4) implement a modeling framework capable of predicting the occurrence of extreme low pH and low oxygen events off central California, and assess its usefulness for decision-making purposes. These developments contribute to Coastal SEES overarching objectives of advancing understanding of fundamental, interconnected processes in coastal systems on a variety of spatial and temporal scales, improving capabilities for predicting future coastal system states and impacts, and identifying pathways by which research results will be translated to policy and management domains and used to enhance coastal sustainability.