Characteristics of 3D structures of ADCP echo intensity anomaly observed over hydrothermal vent fields of the Snail, Archean and Pika in the South Mariana Trough

We conducted 4 dives of the AUV `Urashima´, owned by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), over three hydrothermal vent fields (called as the Snail, Archean and Pika Sites; Fig.1) within the South Mariana Trough in the R/V Yokosuka cruise of July 2009 (YK09-8; JAMSTEC, 2009). The AUV mounted upward a 600-kHz acoustic Doppler current profiler (ADCP) and observed both of current velocity and echo intensity measured by reflected sound pulses from multiple layers over the AUV. The present study shows 3D images of the echo intensity maxima obtained with the ADCP, which indicates expansion and advection of hydrothermal plumes from the vent sites, and is the first study to examine the characteristics of hydrothermal plumes with current velocity and echo intensity measured with an ADCP mounted on an AUV.