Upwelling Dynamics from Days to Years Using Underwater Gliders

本项目是分析利用自主水下航行器滑翔机获得的独特的大陆架水性质时空数据集。自2006年春天以来，滑翔机已经在海上航行了1000多天，采样了400多个跨大陆架部分，在俄勒冈州中部的26000公里处，经历了广泛的风和浮力强迫。滑翔机的数据主要来自纽波特水文（NH）线，这是一个代表区域上升流过程的位置，并且有一个50年的数据库。由于滑翔机在短短几天内对上升流锋面和射流区域进行采样，但几乎连续多年进行采样，因此该分析寻求超过2-3周的沿海上升流过程的船舶快照和空间有限的系泊时间序列。pi将调查观测到的复杂水柱结构，特别是与沿海上升流锋相关的地下温度和叶绿素逆温，以及大陆架中部到内层的低氧近底层。分析将强调风驱动流和沿海上升流急流/锋面附近的大量相对涡度的相互作用，以确定地表水及其所含物质向下注入水柱。该项目还将在现有的滑翔机上增加声学多普勒电流分析器，以估计重要的地转二次环流。该团队将量化物理过程（上升流、水平平流、滞留、水源水变化）对近底层低氧层结构和寿命的相对贡献。2008年期间，NH线以南的第二条东西向滑翔线和连接两条东西向滑翔线的一条南北向滑翔线被占用。这些同步线将用于估计沿海上升流射流与海底滩相互作用时海水及其所含物质的跨陆架通量。所有这些分析都将把滑翔机数据与风测量和遥感地面数据结合起来，以扩展我们对上述大陆架过程的动力学理解。在NH线上的定期滑翔机采样将继续两年（2010-2011），以进一步了解北加利福尼亚海流的实质性年际变化（El Niño，太平洋年代际振荡）。滑翔机数据将与气象和卫星数据以及风力驱动的陆架流的数值模型一起使用，以了解年际变化调制的上升流的动力学和季节变化。知识价值：长，不间断，高分辨率的四年时间序列加上额外的两年，将提供前所未有的能力，可以精细地表征和分析沿海过程的动态，范围从多日风驱动到年际时间尺度。了解与上升流急流相关的流动地形相互作用和地转锋环流是很重要的，因为它们代表了物质跨越大陆架和从表层向海洋内部运输的机制。此外，复杂的锋面环流为生物学上重要的“薄层”的形成提供了一种潜在的新机制。最后，多年的大陆架-斜坡滑翔机数据将确定上升流源-水变化的年际变化对当地大陆架生态系统动力学的重要性。更广泛的影响：实时滑翔机观测提供了大陆架和斜坡上必要的原位数据，以补充遥感地面观测。将新的滑翔机技术应用于沿海海洋的研究引起了公众的兴趣，该团队的教育和推广工作将继续吸引一系列海洋使用者。地下滑翔机观测对数据同化建模工作至关重要。其他科学家和当地渔民通过俄勒冈海洋拨款项目对地下锋面结构、叶绿素和溶解氧浓度特别感兴趣。最后，这个项目支持研究生的研究以及本科生的暑期实习。

This project is to analyze a unique space-time data set of continental shelf water properties obtained using autonomous underwater vehicle gliders. Since spring 2006, gliders have been at sea for over 1000 days, sampled over 400 cross-shelf sections, and covered 26,000 km off central Oregon, during a wide range of wind and buoyancy forcing. Glider data are primarily from along the Newport Hydrographic (NH) line, a location representative of regional upwelling processes and for which there is a 50-year data base. Since the gliders sample the upwelling front and jet region in just days, but do so nearly continuously and for multiple years, this analysis seeks to go beyond 2-3 week, ship-based snapshots of coastal upwelling processes and spatially limited moored time series. The PIs will investigate the observed complex water-column structure, in particular subsurface temperature and chlorophyll inversions associated with the coastal upwelling front, and a low-oxygen, near-bottom layer over the mid to inner shelf. Analyses will emphasize the interaction of wind-driven flow and the substantial relative vorticity near the coastal upwelling jet/front in determining the injection of surface water and the material it contains down into the water column. The project will also add Acoustic Doppler Current Profilers to the existing gliders in order to estimate the important ageostrophic secondary circulations. The team will quantify the relative contribution of physical processes (upwelling, horizontal advection, retention, source-water variability) to the structure and longevity of the near-bottom, low-oxygen layer. During 2008, a second E-W glider line south of the NH line and a N-S glider line connecting the two E-W lines were occupied. These concurrent lines will be used to estimate the cross-shelf flux of water and the material it contains as the coastal upwelling jet interacts with a submarine bank. All these analyses will combine glider data with wind measurements and remotely sensed surface data to extend our dynamical understanding of the above shelf processes. The regular glider sampling on the NH line will be continued for two more years (2010-2011) to further understand the substantial interannual variability (El Niño, Pacific Decadal Oscillation) in the northern California Current. Glider data, will be used together with meteorological and satellite data, and numerical models of wind-driven shelf flows, to understand the dynamics and seasonal variability of upwelling as modulated by interannual variability. Intellectual Merit: The long, uninterrupted, high-resolution time series of four years plus two additional years will offer an unprecedented ability to finely characterize and analyze the dynamics of coastal processes, ranging from multi-day wind-driven to interannual time scales. Understanding flow topography interactions and the ageostrophic cross- frontal circulation associated with the upwelling jet are important, because they represent the mechanisms for transporting material across the shelf and from the surface layer to the interior of the ocean. Furthermore, the complex frontal circulation offers a potentially new formation mechanism for the formation of biologically important "thin-layers." Lastly, the multi-year, shelf-to-slope glider data will pinpoint the importance of interannual variations in upwelling source-water variability to local shelf ecosystem dynamics. Broader Impact: Real-time glider observations provide essential in situ data over the shelf and slope to complement remotely sensed surface observations. Application of new glider technology to the study of the coastal ocean has captured the public's imagination and the education and outreach efforts of this team will continue to engage a range of ocean users. The subsurface glider observations are vital for data-assimilative modeling efforts. The subsurface frontal structure, chlorophyll and dissolved oxygen concentrations are of particular interest to other scientists and local fishermen, who are reached via the Oregon Sea Grant program. Finally, this project supports graduate research as well as summer undergraduate internships.