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

以前的研究表明，北太平洋含有世界海洋中最高的溶解二氧化硅深水浓度，卡斯卡迪亚盆地似乎是这种全球尺度异常的源区。 数据汇编表明，一个. plume。溶解二氧化硅的主要来源是这个小的边缘盆地，可以追溯到几千英里，从东北太平洋的起源到南部的夏威夷海脊，几乎到西部的西伯利亚。 根据该地区汇编的数据进行的箱形模型计算表明，北太平洋深水二氧化硅异常需要卡斯卡迪亚盆地近2 Tmols/年的通量才能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是流入海洋的河流二氧化硅总量的40%，但这种解释需要大量的验证。 虽然海盆内有几个已查明的溶解二氧化硅来源，包括脊轴喷口区、脊翼热液循环、增生楔处沉积物的压缩和沉积物孔隙沃茨的向上扩散通量，但这些过程无论是单独的还是总体的，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进行一项实地计划，以提供所需的CTD和Niskin/营养测量的空间分布，以构建一个合理的二氧化硅库存和地转底层水通量。他们计划（a）汇编卡斯卡迪亚盆地的所有现有CTD/养分数据，该盆地数量很多，但位置有限，（B）在2004年增加机会巡航的新数据，（c）绘制深水二氧化硅的地理分布和存量图，其中包括现有数据未取样地区的40个新的水力铸造剖面图，（d）利用新数据确定盆地尺度的底层水循环模式;（e）确定底层水的Ge/Si比率，以区分生物源区和地质源区。该计划的主要目标是量化进入盆地的溶解二氧化硅通量，并确定负责的源区。华盛顿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，允许来自华盛顿大学和其他机构的其他非海洋学学生参加游轮，为学生论文获取数据，并为公众提供关于科学研究的大量宣传。此外，虽然世界海洋环流实验对卡斯卡迪亚盆地的取样很少，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性质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.