Collaborative Research: Examination of the Potential Sources for the Mid-Water Silica Anomaly in the NE Pacific

以往的研究表明，北太平洋是世界海洋中深海溶解二氧化硅浓度最高的地区，卡斯卡迪亚盆地可能是这一全球尺度异常的源区。数据汇编表明，.plume。大量溶解的二氧化硅起源于这个小的边缘盆地，它可以追溯到几千英里，从东太平洋的起源到南部的夏威夷山脊，几乎到西部的西伯利亚。基于该地区汇编数据的箱型模型计算表明，北太平洋深水二氧化硅异常需要来自Cascadia盆地近2 Tmols/年的通量来维持观测到的浓度水平。如果正确的话，这种溶解的二氧化硅通量占到流入海洋的河流二氧化硅总量的惊人40%，但这种解释需要大量的验证。虽然已经确定了盆地内溶解二氧化硅的几个来源，包括脊-轴喷口场、脊-侧翼热液环流、增生楔的沉积物压缩和沉积物孔隙水向上扩散通量，但这些过程（无论是单独的还是集体的）似乎都不足以产生所观察到的深水二氧化硅异常。在这项研究中，华盛顿大学和南加州大学的研究人员将开展一个实地项目，提供所需的CTD空间分布和Niskin/营养物测量，以构建合理的二氧化硅库存和地转地底水通量。他们计划(a)汇编来自Cascadia盆地的所有现有CTD/营养数据，这些数据数量庞大，但位置有限，(b)增加2004年巡航机会的新数据，(c)绘制深水二氧化硅的地理分布和库存图，使用40个新的水文剖面，这些剖面来自没有现有数据采样的地区，(d)使用新数据确定盆地尺度的底部水循环模式，(e)确定底部水的Ge/Si比率。区分生物和地质源区。该计划的主要目标是量化进入盆地的溶解二氧化硅的通量，并确定负责的来源区域。更广泛的影响：西澳大学的大型远洋实地项目支持研究生和本科生的学术研究，允许西澳大学和其他机构的非海洋学学生参加游轮活动，为学生论文获取数据，并为公众对科学研究的认识提供实质性的宣传。此外，尽管WOCE对Cascadia盆地的采样很差，但收集到的少量数据表明，这个小盆地在决定整个太平洋深水的特性方面发挥了不成比例的作用。

ABSTRACTOCE-0452565 / OCE-0452088Previous studies have shown that the North Pacific contains the highest deep-water concentrations of dissolved silica in the world ocean, and Cascadia Basin appears to be the source region for this global-scale anomaly. Data compilations indicate that a .plume. of dissolved silica originates from within this small marginal Basin, which can be traced for several thousand miles, from an origin in the NE Pacific to the Hawaiian Ridge in the south and almost to Siberia in the west. Box model calculations based on compiled data in the area indicate that the North Pacific deep-water silica anomaly requires a flux from Cascadia Basin of nearly 2 Tmols/year to sustain the observed concentration levels. If correct, this dissolved silica flux is an astonishing 40% of the total riverine silica input to the oceans, but this interpretation requires substantial verification. Although there are several identified sources for dissolved silica within the Basin, including ridge-axis vent fields, ridge-flank hydrothermal circulation, compression of sediments at the accretionary wedge and the upward diffusive flux from sediment pore waters, none of these processes, either individually or in aggregate, appear to be adequate to produce the observed deep-water silica anomaly. In this study, researchers at the University of Washington and the University of Southern California will conduct a field program to provide the required spatial distribution of CTD and Niskin/nutrient measurements needed to construct a reasonable silica inventory and geostrophic bottom water flux. They plan to (a) compile all existing CTD/nutrient data from Cascadia Basin, which is substantial in number, but limited in location, (b) add new data from cruises-of-opportunity in 2004, (c) map the geographic distribution and inventory of deep-water silica with 40 new hydrocast profiles from areas not sampled by existing data, (d) use the new data to determine the basin-scale pattern of bottom water circulation and (e) determine the Ge/Si ratios of the bottom water, to distinguish biological from geological source regions. The primary goals of the program are to quantify the flux of dissolved silica into the Basin and identify the source regions that are responsible.Broader Impacts: Large ocean-going field programs at UW support graduate and undergraduate students in their academic research, allow participation of additional non- Oceanography students from UW and from other institutions on the cruises, acquire data for student theses, and provide substantial out-reach in public awareness about scientific research. Further, although Cascadia Basin was poorly sampled by WOCE, the few data collected suggest a disproportionate role for this small basin in determining properties of the entire Pacific Deep Water.