Extracted Level 2 data include three data types: 1) Position data are included in .GPX files organized by campaign where “ICP8” refers to the 2016-2017 ICECAP2 field season and “ICP9” refers to the 2017-2018 field season. We recommend opening these files in QGIS or on similar platform. Metadata for each sonobuoy deployment include the unique identifier for each profile as well as the date, time, and aircraft longitude, latitude, elevation, and speed (in East, North, Up coordinates) at the time of deployment. Season identifier, flight number, and unique profile identifier are also displayed. In QGIS, for example, clicking on the drop locations using the “Identify Features” tool is a convenient way of investigating the metadata. 2) Profile data are released as Exportable Data Files (EDF), an ASCII format with a metadata header followed by the profile data. 3) Profile data are also released as Hierarchical Data Format (HDF) files using a .h5 extension. This format is provided so users can take advantage of numerous and freely available Python and MATLAB resources simplifying importing and investigating the profiles. Project 4346 demonstrated the use of Airborne eXpendable Bathy-Thermograph (AXBT) and Airborne eXpendable Conductivity, Temperature, Depth (AXCTD) sensors from a BT-67 Basler aircraft in East Antarctica. The primary objective was to use AXBT and AXCTD sensors to infer seafloor depth where no previous measurements had been made by ship, often by deploying sensors into narrow gaps in sea ice. Inferring a snapshot of the ocean state by detecting major thermoclines was a secondary objective. Although several sensors were purchased with external funds, the efforts to develop operational and subsequent data analysis approaches were unfunded as this was an add-on, target of opportunity. The effort is best described as a prototype demonstration project to test whether the seafloor depth could be inferred beneath narrow sea ice leads from a rapidly flying aircraft. All but eight AXBT sensors were donated to the University of Texas Institute for Geophysics (UTIG); AXCTDs were purchased by the Antarctic Gateway Partnership. Receiver and data processing equipment were loaned to UTIG.

Extracted Level 0 data are provided as audio files recorded in flight with a Sony PX470 voice recorder. These files were processed to generate the associated Level 2 products. Project 4346 demonstrated the use of Airborne eXpendable Bathy-Thermograph (AXBT) and Airborne eXpendable Conductivity, Temperature, Depth (AXCTD) sensors from a BT-67 Basler aircraft in East Antarctica. The primary objective was to use AXBT and AXCTD sensors to infer seafloor depth where no previous measurements had been made by ship, often by deploying sensors into narrow gaps in sea ice. Inferring a snapshot of the ocean state by detecting major thermoclines was a secondary objective. Although several sensors were purchased with external funds, the efforts to develop operational and subsequent data analysis approaches were unfunded as this was an add-on, target of opportunity. The effort is best described as a prototype demonstration project to test whether the seafloor depth could be inferred beneath narrow sea ice leads from a rapidly flying aircraft. All but eight AXBT sensors were donated to the University of Texas Institute for Geophysics (UTIG); AXCTDs were purchased by the Antarctic Gateway Partnership. Receiver and data processing equipment were loaned to UTIG.