Recurrence interval of sediment mobility at select points in the Middle Atlantic Bight for May, 2010 - May, 2011 (MAB_mobile_freq_v1_1.SHP, Geographic, WGS 84)

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来刻画海底剪切应力的区域差异与沉积物活动性。本项目旨在识别剪切应力的分布模式，以期为栖息地划定或大陆架的人类开发决策提供参考。本次统计刻画覆盖从海岸至约120米水深的大陆架区域，分辨率约为5千米。研究通过数值模型生成波浪与环流的时间序列数据，并利用近底稳态流速、振荡流速输出值以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。随后计算该数据库所包含的中位数、95百分位数等统计量，以此生成海底剪切应力区域分布模式的二维图景。此外，研究还将选定点位的应力时间序列与基于观测表层沉积物质地数据计算得到的临界应力值进行对比，以估算海底沉积物的活动性。