RV Investigator Voyage IN2018_V05 EM122 Multibeam Echosounder Data

This record describes multibeam echosounder data collected on RV Investigator voyage IN2018_V05, 'How does a standing meander southeast of Tasmania brake the Antarctic Circumpolar Current?' which departed Hobart on the 16th October 2018 and returned to Hobart on the 16th November 2018. The objectives of the voyage included: (1) Deployment of a fleet of EM-APEX profiling floats, (2) Deployment of a tall mooring at the crest of a meander in the Polar Front of the Antarctic Circumpolar Current, (3) Full-depth hydrographic survey of the physics and biogeochemistry of the targeted ACC meander, conducting transects across the front and (4) Triaxus transects across and along the front. The Kongsberg EM122 multibeam echosounder was used to acquire seafloor bathymetry, backscatter information and watercolumn backscatter from Hobart to Hobart with particular emphasis on the scientific study area bounded between the following approximate coordinates: 54.156° to 57.344° (South) and 148.577° to 156.344° (East). The sonar was set to passive mode during sensitive VMP deployment periods of the voyage in the ACC, when acoustic silent periods were requested by the science party. The EM122 provides a 1 degree by 1 degree angular resolution. The echosounder's nominal frequency is 12 kHz.Data are stored in *.all raw format for bathymetry and backscatter and *.wcd format for watercolumn backscatter at CSIRO. There are 597 files totalling 18.6 GB of raw data in the dataset.Sound velocity profiles were applied to this data during data acquisition. Bathymetry data contained in *.all format are corrected for motion and position.Tide corrections were not applied to the processed data. Processed data had outliers removed. Processed line data are available in *.gsf and ascii format, and processed bathymetry and backscatter grids in geotiff format.Additional information regarding this dataset, including information on processing streams, is contained in the GSM data acquisition and processing report. Additional data products may be available on request.

本记录描述了“调查者”号（RV Investigator）科考船IN2018_V05航次采集的多波束测深声呐（multibeam echosounder）数据，该航次主题为“塔斯马尼亚东南部稳态河曲如何减缓南极绕极流（Antarctic Circumpolar Current, ACC）流速”，航次于2018年10月16日从霍巴特起航，2018年11月16日返回霍巴特。本航次的科学目标包括：(1) 布设EM-APEX剖面浮标阵列；(2) 在南极绕极流极锋（Polar Front）的一处河曲峰顶部署高型系泊潜标；(3) 针对目标南极绕极流河曲的物理与生物地球化学特征开展全水深水文调查，沿锋面布设横穿断面；(4) 沿锋面及横穿锋面开展Triaxus走航剖面观测。本航次使用康斯伯格（Kongsberg）EM122多波束测深声呐采集了霍巴特往返航程的海底地形、反向散射信息及水体反向散射数据，重点研究区域的大致坐标范围为：南纬54.156°至57.344°，东经148.577°至156.344°。在南极绕极流航段的敏感VMP（Velocity Microstructure Profiler，速度微结构剖面仪）部署阶段，科考团队要求声学静默时段，此时声呐切换至被动模式。该EM122声呐的角分辨率为1°×1°，标称工作频率为12 kHz。数据以*.all原始格式存储海底地形与反向散射数据，以*.wcd格式存储水体反向散射数据，均存放于澳大利亚联邦科学与工业研究组织（CSIRO）。本数据集共包含597个文件，总原始数据量达18.6 GB。数据采集阶段已应用声速剖面进行校正。*.all格式存储的地形数据已完成运动与位置校正，但未施加潮汐校正。已处理数据已剔除异常值。处理后的航线数据以*.gsf及ASCII格式提供，处理后的地形与反向散射网格数据以GeoTIFF格式提供。本数据集的更多信息（包括数据处理流程）详见《GSM数据采集与处理报告》。其他数据产品可根据申请提供。