This data set was acquired with a SeaBeam Instruments model 2112 multibeam sonar system during Nathaniel B. Palmer expedition NBP9909 conducted in 1999 (Chief Scientist: Dr. John Bengtson). These data files include Swath Bathymetry, Acoustic Backscatter data and were processed at sea using the open source MB-System multibeam sonar processing software. These data are included in the GMRT Synthesis, beginning with version 1. Data were acquired as part of the project(s): Antarctic Pack Ice Seals, and funding was provided by the U.S. National Science Foundation.