Title: February 2015 in situ proglacial river ice thickness, ground penetrating radar (GPR) data, and bright reflector mappings from southwest Greenland Authors: Lincoln H Pitcher1,*, Laurence C. Smith2,3,1, Colin J. Gleason4, Clément Miège5, Jonathan C. Ryan2, Birgit Hagedorn6, Dirk van As7, Winnie Chu8, and Richard R. Forster9 1Department of Geography, University of California - Los Angeles, Los Angeles, California, 90095, USA 2Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island, 02912, USA 3Department of Earth, Environmental, and Planetary Sciences and Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island, 02912, USA 4Department of Civil and Environmental Engineering, University of Massachusetts – Amherst, Amherst, Massachusetts, 01003, USA 5Department of Geography, Rutgers University, Piscataway, New Jersey, 08901, USA 6Sustainable Earth Research LLC, Anchorage, Alaska, 99508, USA 7Geological Survey of Denmark and Greenland, 1350 Copenhagen, DK 8Department of Geophysics, Stanford University, Stanford, California, 94305 9Department of Geography, University of Utah, Salt Lake City, Utah, 84112 *Corresponding author: Lincoln Pitcher (lincolnpitcher@ucla.edu) Dataset accompanies submitted manuscript: Pitcher, L.H, Smith, L.C., Gleason, C.J., Miège, C., Ryan, J.C., Hagedorn, B., van As, D., Chu, W., Forster, R.R. (submitted). Direct observation of wintertime meltwater drainage from the Greenland Ice Sheet. Submitted to Geophysical Research Letters, December 2019. Abstract This data set contains in situ surveys of proglacial river ice collected in southwest Greenland during February 2015. Including: (1) point locations of river ice thickness measured in mechanically drilled boreholes. (2) Ground penetrating radar (GPR) data for surveys across frozen proglacial rivers, both raw GPR data and processed echograms are provided. (3) Approximate point locations of bright reflectors mapped beneath the Isortoq River ice. This data accompanies the manuscript: Pitcher et. al. (submitted). - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - DATA TABLE FOR IN SITU PROGLACIAL RIVER BOREHOLE AND GROUND PENETRATING RADAR (GPR) SURVEYS File Name: greenland_2015_feb_proglacial_river_surveys.csv File Type: tabular data, saved as .csv Description: the file contains latitude and longitude coordinate locations and river ice thickness measurements of validation boreholes mechanically drilled through proglacial river ice in southwest Greenland during February 2015. Also included are approximate start and stop coordinates for accompanying ground penetrating radar (GPR) surveys, as well as file names of for raw GPR data files and processed GPR echograms. Description of column headings: site_name name of field site yyyy year of data collection, 4 digits mm month of data collection, 2 digits dd day of data collection, 2 digits date date of data collection, formatted as day/month/year id site identifier TN: end of transect on north bank of river TS: end of transect on south bank of river H1–H*: borehole numeric identifier depth_m thickness of proglacial river ice. Units: meters latitude location, degrees north, units: decimal degrees longitude location, degrees west, units: decimal degrees info description of site echo file name of accompanying processed GPR echogram, with site id map file name of accompanying processed GPR transect, with site id GPR_file_1 file name of accompanying GPR data GPR_file_2 file name of accompanying GPR data - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - GROUND PENETRATING RADAR (GPR) DATA Description of data files: *.txt header information for GPR data *.dzt original GPR data collected in field *_R.dzt GPR data restored by removing gain applied in situ *_G5.dzt GPR data with linear gain applied multiplying each relative-amplitude sample by 5 to enhance features Description: Ground penetrating radar (GPR) data collected in situ during February 2015. Surveys were conducted using a SIR-3000 Geophysical Survey Systems, Inc. (GSSI©) GPR controller and a 400-MHz antenna installed on a 0.6 cm thick plastic Siglin© sled. Surveys were conducted on foot by establishing cross sections orthogonal to flow direction spanning frozen proglacial rivers. At most field sites, two GPR profiles were collected, with start and stop points on opposite banks. Accompanying GPR surveys, field validation boreholes were drilled through proglacial river ice. Refer to greenland_2015_feb_proglacial_river_surveys.csv for GPR survey locations, file names, and field validation borehole information. Also, refer to manuscript and supplementary material in Pitcher et. al. (submitted) for further information about field data collection. GPR data are provided in native .dzt format with .txt file header. If needed, open-source tools to open this data type are available at: https://github.com/dlilien/ImpDAR. GPR data are organized by survey location. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - GROUND PENETRATING RADAR (GPR) ECHOGRAMS AND TRANSECT MAPS Description: At each field site, ground penetrating radar (GPR) surveys were conducted across frozen proglacial river channels orthogonal to summertime flow directions. At most sites, two GPR surveys were conducted, traveling in opposite directions across the channel. Field site names and coordinate locations are provided in greenland_2015_feb_proglacial_river_surveys.csv. Original GPR data files are provided as *.dzt files. Description of data collections and interpretation of data is provided in manuscript and supplementary information of Pitcher et. al. (submitted). The following files are processed echograms with borehole locations/river ice thickness and GPR profile location plot with best estimated mean travel speeds. Note that only the echogram and location plot best matching boreholes and field notes is given for each site. Description of data files: ØrkendalenRiverDownstream_GPR091corrected_echo.tif Processed echogram for Ørkendalen River, downstream site. Plotted from FILE____091_R_G5.DZT. Borehole location/ice thickness given in: greenland_2015_feb_proglacial_river_surveys.csv. ØrkendalenRiverDownstream_GPR091corrected_map.tif GPR profile location plot for FILE____091_R_G5.DZT. ØrkendalenRiverGlacierTerminus_GPR052_echo.tif Processed echogram for Ørkendalen River, glacier terminus site. Plotted from FILE____052_R_G5.DZT. Borehole location/ice thickness given in: greenland_2015_feb_proglacial_river_surveys.csv. ØrkendalenRiverGlacierTerminus_GPR052_map.tif GPR profile location plot for FILE____052_R_G5.DZT. SandflugtdalenRiver_GPR060_echo.tif Processed echogram for Sandflugtdalen River site. Plotted from FILE____060_R_G5.DZT. Borehole location/ice thickness given in: greenland_2015_feb_proglacial_river_surveys.csv. SandflugtdalenRiver_GPR060_map.tif GPR profile location plot for FILE____060_R_G5.DZT. WatsonRiverDownstream_GPR044corrected_echo.tif Processed echogram for Watson River, downstream site. Plotted from FILE____044_R_G5.DZT. Borehole location/ice thickness given in: greenland_2015_feb_proglacial_river_surveys.csv. WatsonRiverDownstream_GPR044corrected_map.tif GPR profile location plot for FILE____044_R_G5.DZT. WatsonRiverUpstream_GPR055_echo.tif Processed echogram for Watson River, upstream site. Plotted from FILE____055_R_G5.DZT. Borehole location/ice thickness given in: greenland_2015_feb_proglacial_river_surveys.csv. WatsonRiverUpstream_GPR055_map.tif GPR profile location plot for FILE____055_R_G5.DZT. Note: Echogram for Isortoq River GPR data given in Figure 2 of Pitcher et. al. (submitted). GPR .dzt data provided here. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - LOCATION OF BRIGHT REFLECTORS BENEATH ISORTOQ RIVER PROGLACIAL RIVER ICE Data file name: GPR_bright_reflectors_isortoq_river.shp Data file type: .shp point file, Geoographic Coordinate System: GCS_WGS_1984 Description: the file contains approximate point locations of bright reflectors found in ground penetrating radar (GPR) echograms. These bright reflectors are interpreted as likely locations of meltwater beneath proglacial Isortoq River ice. Note that a GPS was not integrated with the GPR during these surveys. Therefore, the spatial location is manually and roughly approximated from field notes, feature tracking within GPR data, and satellite imagery. Despite limitations in geolocation, the spatial pervasiveness of bright reflectors is consistent with a spatially pervasive water filled conduit network beneath proglacial river ice. See Figure 2 in manuscript of Pitcher et. al. (submitted) for further interpretations as well as Pitcher et al (submitted) supporting information for description of GPR processing. Description of attribute table fields: FID unique numeric field identifier lat approximate reflector location, degrees north, units: decimal degrees lon approximate reflector location, degrees west, units: decimal degrees