This data set was acquired with a SeaBeam Instruments model 2112 multibeam sonar system during Nathaniel B. Palmer expedition NBP9801 conducted in 1998 (Chief Scientist: Dr. John Anderson). These data files include Acoustic Backscatter, Sidescan, Swath Bathymetry 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): Timing of Retreat of the West Antarctic Ice Sheet, and funding was provided the U.S. National Science Foundation.