U.S. Geological Survey calculated percentage of time sediment is mobile for May 2010 to May 2011 at select points in the South Atlantic Bight (SAB_mobile_perc, point shapefile, Geographic, WGS84)

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）长期以来通过统计描述指标，表征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，以期为大陆架生境划分或人类开发利用大陆架的决策提供参考。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时间序列，并利用近底输出的稳态、振荡流速数据及底床粗糙度估算值，以1小时间隔计算海底剪切应力的时间序列。本数据库包含的输出指标为中位数与95百分位数这类统计描述量，借此可生成剪切应力区域分布模式的二维可视化图景。此外，研究人员还将选定点位的剪切应力时间序列与基于实测表层沉积物质地数据计算得到的临界应力值进行对比，以此估算海底沉积物的活动性。