VHF Radio Echo Sounding from Dome C to Little Dome C

These are ice-penetrating radar data connecting the newly chosen Beyond EPICA Little Dome C core site to the EPICA Dome C core site, collected in late 2019. These data are presented in a paper in The Cryosphere (https://doi.org/10.5194/tc-2020-345), where full processing and collection methods are described. Data collection and processing Data were collected using a new very high frequency (VHF) radar, built by the Remote Sensing Center at the University of Alabama (Yan et al., 2020). The system transmitted 8 us chirps, with peak transmit power of 125--250 W per channel, at 200 MHz center frequency and 60 MHz bandwidth. There were 5--8 operational channels at various points. The antennas were pulled behind a tracked vehicle, with controlling electronics in the rear of the vehicle. Data were collected at travel speeds of 2--3.5 m/s. Data processing consisted of coherent integration (i.e. unfocused SAR), pulse compression, motion compensation (by tracking internal horizons), coherent channel combination, and de-speckling using a median filter. Two-way travel time was converted to depth assuming a correction of 10 m of firn-air and a constant radar wave speed of 168.5 m/us (e.g., Winter et al., 2017). After other processing was complete, different radargrams were spliced together to create a continuous profile extending from EPICA Dome C to the Beyond EPICA Little Dome C core site, and then the data were interpolated to have constant, 10-m horizontal spacing. The re-interpolated data were used for horizon tracing, which was done semi-automatically to follow amplitude peaks between user-defined clicks. For the bed reflection, we always picked the first notable return in the region of the bed. File description The file format is hdf5, which can be read with many programming languages. There are three groups in the file: processed_data, picks, and geographic_information. The processed_data gives the return power matrix (dB), and the depth (m) and two-way travel time (us) for the fast-time dimension. The picks give the depths (m) of different reflecting horizons traced in the corresponding paper. Ages and age uncertainties (kyr), interpolated from the AICC2012 timescale, are included as attributes on each pick. Bed and basal unit picks are included (ageless). The geographic_information gives latitude and longitude (decimal degrees), and the distance along-profile (km). References Bazin, L., Landais, A., Lemieux-Dudon, B., Toyé Mahamadou Kele, H., Veres, D., Parrenin, F., Martinerie, P., Ritz, C., Capron, E., Lipenkov, V., Loutre, M. F., Raynaud, D., Vinther, B., Svensson, A., Rasmussen, S. O., Severi, M., Blunier, T., Leuenberger, M., Fischer, H., Masson-Delmotte, V., Chappellaz, J., and Wolff, E.: An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120-800 ka, 9, 1715–1731, https://doi.org/10.5194/cp-9-1715-2013, 2013. Winter, A., Steinhage, D., Arnold, E. J., Blankenship, D. D., Cavitte, M. G. P., Corr, H. F. J., Paden, J. D., Urbini, S., Young, D. A., and Eisen, O.: Comparison of measurements from different radio-echo sounding systems and synchronization with the ice core at Dome C, Antarctica, 11, 653–668, https://doi.org/10.5194/tc-11-653-2017, 2017. Yan, J.-B., Li, L., Nunn, J. A., Dahl-Jensen, D., O’Neill, C., Taylor, R. A., Simpson, C. D., Wattal, S., Steinhage, D., Gogineni, P., Miller, H., and Eisen, O.: Multiangle, Frequency, and Polarization Radar Measurement of Ice Sheets, 13, 2070–2080, https://doi.org/10.1109/JSTARS.2020.2991682, 2020.