Half interpercentile range (half of the difference between the 16th and 84th percentiles) of wave-current bottom shear stress in the Middle Atlantic Bight for May, 2010 - May, 2011 (MAB_hIPR.SHP)

The U.S. Geological Survey has been characterizing the regional variation in shear stress on the sea floor and sediment mobility through statistical descriptors. The purpose of this project is to identify patterns in stress in order to inform habitat delineation or decisions for anthropogenic use of the continental shelf. The statistical characterization spans the continental shelf from the coast to approximately 120 m water depth, at approximately 5 km resolution. Time-series of wave and circulation are created using numerical models, and near-bottom output of steady and oscillatory velocities and an estimate of bottom roughness are used to calculate a time-series of bottom shear stress at 1-hour intervals. Statistical descriptions such as the median and 95th percentile, which are the output included with this database, are then calculated to create a two-dimensional picture of the regional patterns in shear stress. In addition, time-series of stress are compared to critical stress values at select points calculated from observed surface sediment texture data to determine estimates of sea floor mobility.美国地质调查局（U.S. Geological Survey）一直通过统计描述指标，刻画海底剪切应力与沉积物活动性的区域差异。本项目旨在识别剪切应力的分布模式，为栖息地划定或大陆架人类开发利用决策提供参考支撑。本次统计表征覆盖了从海岸至约120米水深的大陆架区域，空间分辨率约为5千米。研究团队通过数值模型生成波浪与环流的时间序列数据，并利用近底稳态与振荡流速输出结果，以及底床粗糙度估算值，以每小时的时间步长计算海底剪切应力的时间序列。随后，计算中位数、95%百分位数（本数据库包含此类输出指标）这类统计描述量，从而构建出剪切应力区域分布模式的二维图景。此外，研究团队还将剪切应力时间序列与通过实测表层沉积物粒度数据计算得到的选定点位临界应力值进行对比，以估算海底沉积物的活动性。