Upwelling Dynamics from Days to Years Using Underwater Gliders

该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特性的时空数据集。自2006年春季以来，在大范围的风和浮力的作用下，滑翔机已经在海上航行了1000多天，采样了400多个跨陆架区段，覆盖了俄勒冈州中部26,000公里处。滑翔机的数据主要来自纽波特水文线(NH)沿线，这是一个代表区域上升流过程的位置，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急流区域进行采样，但几乎连续和多年这样做，本分析试图超越2-3周的沿海上升流过程的船基快照和空间有限的停泊时间序列。PIS将调查观测到的复杂水柱结构，特别是与沿海上升流锋有关的次表层温度和叶绿素逆温，以及中至内大陆架上方的低氧近底层。分析将强调在确定地表水及其所含物质向下注入水柱时，风力驱动的流动与沿海上升流/锋面附近相当大的相对涡度之间的相互作用。该项目还将在现有滑翔机上增加声学多普勒海流剖面仪，以估计重要的非地转次级环流。该小组将量化物理过程(上升流、水平平流、滞留、源水变化)对近底部低氧层结构和寿命的相对贡献。2008年，NH线以南的第二条东西向滑翔线和连接这两条东西向线的一条北S滑翔线被占用。这些同时出现的线将被用来估计沿海上升流与海底岸边相互作用时，水及其所含物质的跨陆架通量。所有这些分析都将结合滑翔机数据、风测量和遥感地表数据，以扩展我们对上述陆架过程的动力学理解。NH线上的定期滑翔机采样将再持续两年(2010-2011年)，以进一步了解加州北部洋流的显著年际变化(厄尔尼诺，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驱动的陆架流动的数值模型一起使用，以了解受年际变化调制的上升流的动力学和季节变化。智力优势：四年外加两年的长、不间断、高分辨率的时间序列将提供前所未有的能力，以精细地描述和分析海岸过程的动态，从多天的风力驱动到年际时间尺度。了解水流地形相互作用和与上升流相关的非地转跨锋面环流是很重要的，因为它们代表了跨越大陆架和从表层向海洋内部输送物质的机制。此外，复杂的锋面环流为生物上重要的“薄层”的形成提供了一种潜在的新的形成机制。最后，从陆架到斜坡的多年滑翔机数据将明确上升源水变化的年际变化对当地陆架生态系统动态的重要性。更广泛的影响：实时滑翔机观测提供了大陆架和斜坡上的基本现场数据，以补充遥感表面观测。将新的滑翔机技术应用于沿海海洋研究激发了公众的想象力，该小组的教育和推广工作将继续吸引一系列海洋用户。次表层滑翔机观测对于数据同化建模工作至关重要。其他科学家和当地渔民特别感兴趣的是地下锋面结构、叶绿素和溶解氧浓度，他们是通过俄勒冈州海洋赠款计划获得的。最后，该项目支持研究生研究和本科生暑期实习。

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.