Collaborative Research: Dynamics of Ocean Climate Changes in the Gulf of Alaska

合作研究：阿拉斯加湾海洋气候变化动态

• 批准号: 0452654
• 负责人: Emanuele Di Lorenzo
• 金额: $ 5.63万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0452654&HistoricalAwards=false
• 关键词: Collaborative; Research; Dynamics; Ocean; Climate

OCE-0452692/0452743/0452654The Gulf of Alaska is a complicated physical oceanographic system that supports economically important fisheries and ecologically important wildlife areas. The Alaska Current, which runs northwestward along the eastern shelf-slope boundary, and the Alaskan Stream, which runs southwestward along the western shelf-slope boundary, both support an energetic open-ocean mesoscale circulation. These mean flows are thought to be driven mainly by wind-stress curl forcing, while the eddies develop as a consequence of baroclinic instability of the mean flows, fluctuating wind stress forcing, and the arrival of remotely driven coastal waves. The Alaska Coastal Current, which winds and meanders along the shelf through numerous straights and islands, is thought to be driven by both coastal fresh-water discharge and wind stresses. An interesting aspect of the large-scale circulation of the Gulf of Alaska is that the open ocean interior is generally an upwelling region, while the coastal regions are generally downwelling. Even so, primary productivity is highest in the coastal regions, which sustain a rich and diverse ecosystem. The mechanisms by which the physical environment affects the productivity of this biological system are complicated and poorly understood. Some of these mechanisms involve cross-shelf mixing processes in which mesoscale eddy variability mix open-ocean nutrient rich waters with shelf waters that contain iron.Intellectual Merit: The ocean circulation of the Gulf of Alaska will be studied using a combination of eddy resolving ocean models, observational analyses and ocean data assimilation products to elucidate the dynamics that control the mean, mesoscale variability and interannual to interdecadal climate variations of the Alaska Current, the Alaskan Stream, as well as the broader-scale interior gyre flows. The eddy-resolving model runs (using the Regional Ocean Modeling System) will incorporate the effects of wind stresses, surface heat fluxes, surface/coastal fresh-water fluxes, and open-ocean boundary fluxes in various combinations to establish the sensitivity of the model mean and mesoscale fields to changes in these forcings as part of the seasonal cycle and as components of climate variations. The study of the ocean analysis products will provide a baseline of model-data compatibility to help link the very limited hydrographic dataset to the dynamically consistent eddy-resolving simulations. The results of the physical oceanographic analysis will be applied in several ways to understand the complicated biological oceanography of the region. This will include analyzing mixed-layer depth variations, computing cross-shelf particle transports, allowing passive tracers to advect and diffuse laterally and vertically, and incorporating simple ecosystem models in the physical model runs. The results will help us to understand the mechanisms that control the seasonal variability of the productivity of the Gulf, the processes that maintain high productivity on the shelf, and the reasons for interannual to interdecadal variations in productivity that affect higher trophic levels, like pelagic fish populations and Steller sea lions.Broader Impact: This research has broader impacts in that it is relevant to commercially important fisheries management (which must deal with decadal variations in fish populations), it may help to untangle the mysteries behind the decline of Steller sea lion populations (a protected marine mammal), which in the 1990's were reduced to 20% of their numbers of the 1970's, and it may contribute to a better understanding of climate variability and predictability (which may influence socially important industries like agriculture and energy production). A graduate student and post-doc will receive training is sophisticated numerical modeling and data assimilation techniques.

OCE-0452692/0452743/0452654阿拉斯加湾是一个复杂的物理海洋系统，支持具有重要经济意义的渔业和具有重要生态意义的野生动物区。沿着东部陆架斜坡边界向西北流动的阿拉斯加洋流和沿着西部陆架斜坡边界向西南流动的阿拉斯加流都支持活跃的公海中尺度环流。这些平均流被认为主要是由风应力旋度强迫驱动的，而涡流则是由于平均流的斜压不稳定性、脉动风应力强迫以及远程驱动的沿海波浪的到来而产生的。 阿拉斯加沿岸流沿着大陆架蜿蜒穿过众多的海峡和岛屿，被认为是由沿海淡水排放和风应力驱动的。 阿拉斯加湾大规模环流的一个有趣的方面是，公海内部通常是上升流区域，而沿海区域通常是下降流。 即便如此，沿海地区的初级生产力最高，维持着丰富多样的生态系统。物理环境影响该生物系统生产力的机制非常复杂且人们知之甚少。其中一些机制涉及跨陆架混合过程，其中中尺度涡流变化将公海营养丰富的水域与含铁的陆架水域混合。智力成果：将利用涡流解析海洋的组合来研究阿拉斯加湾的海洋环流模型、观测分析和海洋数据同化产品，以阐明控制阿拉斯加海流的平均、中尺度变化和年际至年代际气候变化的动力学，阿拉斯加溪流，以及更广泛的内陆环流流。涡流解析模型运行（使用区域海洋建模系统）将结合风应力、表面热通量、表面/沿海淡水通量和公海边界通量的各种组合的影响，以建立模型的敏感性平均和中尺度场对这些强迫变化的影响，作为季节周期的一部分和气候变化的组成部分。海洋分析产品的研究将提供模型数据兼容性的基线，以帮助将非常有限的水文数据集与动态一致的涡旋解析模拟联系起来。物理海洋学分析的结果将通过多种方式应用，以了解该地区复杂的生物海洋学。这将包括分析混合层深度变化、计算跨架粒子传输、允许被动示踪剂横向和垂直平流和扩散，以及在物理模型运行中纳入简单的生态系统模型。研究结果将帮助我们了解控制海湾生产力季节性变化的机制、维持陆架高生产力的过程，以及影响较高营养水平（如中上层鱼类）的生产力年际至年代际变化的原因更广泛的影响：这项研究具有更广泛的影响，因为它与商业上重要的渔业管理相关（必须处理鱼类种群的十年变化），它可能有助于解开背后的谜团北海狮（一种受保护的海洋哺乳动物）数量的减少，在 1990 年代减少到 1970 年代数量的 20%，这可能有助于更好地了解气候变化和可预测性（这可能会影响对社会重要的产业）如农业和能源生产）。研究生和博士后将接受复杂的数值建模和数据同化技术的培训。