Data and derived products from airborne radar sounding survey over Devon Ice Cap, Canadian Arctic

Data and derived products used in Rutishauser et al., “Radar sounding survey over Devon Ice Cap indicates the potential for a diverse hypersaline subglacial hydrological environment”, accepted for publication, The Cryosphere, https://doi.org/10.5194/tc-2021-220 Corresponding author: [e-mail] Description of datasets: ------------------------------------------ 2018_DIC_UTIG.IR2HI1B.kml Geolocation of the SRH1 profile lines. Coordinates in EPSG: 4326 - WGS 84 (latitude, longitude) ------------------------------------------ 2018_DIC_UTIG.IR2HI1B.tgz HiCARS 2 L1B echo strength profiles (radargrams) in NetCDF format. The naming of the files has the structure IR2HI1B_YYYYDOY_PST_x (e.g. IR2HI1B_2018153_DEV_JKB2t_Y87b_000.nc), where YYYY is the survey year (e.g. 2018), DOY is the survey day of the year (e.g. 153), PST is the profile name (e.g. DEV_JKB2t_Y87b), and x is the segment number if the profile was split in two (e.g. 000). For each profile, a PDF file showing the profile location and the radargram is included. ------------------------------------------ 2018_DIC_UTIG.Level2.tgz Level 2 datasets for each profile, organized in the following folders: 2018_DIC_UTIG.ILUTP2: Laser altimeter geolocated surface elevation 2018_DIC_UTIG.IR2HI2: HiCARS 2 unfocused (pik1) geolocated ice thickness, ice surface elevation, bed elevation, surface- and bed reflection coefficients, and aircraft roll 2018_DIC_UTIG.IRHFOC2: HiCARS 2 focused (foc1) geolocated ice thickness, ice surface elevation, bed elevation, surface- and bed reflection coefficients, and aircraft roll 2018_DIC_UTIG.IRSPC2: HiCARS 2 derived basal interface specularity content ------------------------------------------ Devon_basal_ice_temperature.tif: Modeled basal ice temperature [ºC] using a 1D advection diffusion model. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_bedrockDEM.tif: Digital elevation model (DEM) of the bedrock topography beneath Devon Ice Cap [m asl.]. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_gridded_RMSD_bedrock.tif: Root mean square deviation (RMDS) of the bedrock topography [m]. The RMSD was computed along each profile line, then interpolated on a 500x500m grid using the QGIS GDAL moving average grid interpolation. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_gridded_specularity.tif: Specularity content from along the profile lines interpolated on a 500x500m grid using the QGIS GDAL moving average grid interpolation. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_ice_thickness.tif: Gridded ice thickness [m] generated by subtracting the bedrock DEM from ice surface elevations derived from the ArcticDEM, Polar Geospatial Center from DigitalGlobe Inc. imagery. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_modeled_Geology.zip Devon_modeled_subglacial_geology.tif: Map of the projected geological units beneath Devon Ice Cap. The assigned numbers correspond to the following geological units: 1: pPe, 2: Cm-cf, 3: Oe, 4: Ocb, 5: Oct. Details on the geological units can be found in (Harrison et al., 2016; Mayr, 1980; Thorsteinsson & Mayr, 1987). 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. {pPe, Oe, Oct, Ocb,Cm_rb}_Model.stl: 3D geometry of the modeled geological units beneath Devon Ice Cap, originally published in (Rutishauser et al., 2018). Coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. Devon_load_geology_stl_files.py: Python script to load and plot the 3D geology layers in the .stl files. ------------------------------------------ Devon_subgl_hydraulic_head.tif: Subglacial hydraulic head [m] beneath Devon Ice Cap. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_subgl_hydraulic_slope.tif Slope [º] of the subglacial hydraulic head beneath Devon Ice Cap. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_subgl_lakes_brine_network.zip Devon_subgl_lake_outline.shp: Shoreline of the subglacial lakes beneath Devon Ice Cap (identified in this study). Coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. Devon_brine_network_outline.shp: Outlines of the mapped subglacial brine network beneath Devon Ice Cap. Coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ Devon_subgl_water_routes.zip Devon_modeled_subgl_water_routes_{1, 2, 3}std.tif: Modeled subglacial water routes derived via application of a flow accumulation algorithm to the hydraulic head. The model is run 1000 times with normally distributed random errors of 1, 2 and 3 standard deviations of the hydraulic head uncertainty added to the hydraulic head (represented in the file name). Pixel values represent the model counts for which the cell has a minimum of 10 upstream cells draining into it. 500 m grid cell size, coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. Devon_extracted_subgl_water_routes.shp: Modeled subglacial water routes derived via the application of a flow accumulation algorithm to the hydraulic head. Coordinates in EPSG: 32617 - WGS 84 / UTM zone 17N. ------------------------------------------ SpecularityJustification.zip Jupyter notebook and example datafile to show the justification for the chosen specularity threshold of 0.4 for declaring a detection of possible subglacial water. ------------------------------------------ Acknowledgments The aerogeophysical survey and subsequent standard data processing were funded by the Weston Family Foundation. We also thank the G. Unger Vetlesen Foundation and the UTIG Postdoctoral Fellowship program who provided further funding for data analysis. M.L.S. was partially supported by NASA NNX16AJ64G and NASA 80NSSC20K1134. We thank PCSP and Kenn Borek Air Ltd. for logistical support, and the Nunavut Research Institute and the peoples of Grise Fjord and Resolute Bay for permission to conduct airborne surveys over Devon Ice Cap. Finally, we thank Scott Kempf for assistance with data processing, and Sam Christian and Miguel Liu-Schiaffini for help with radar reflection picking. References Harrison, J. C., Lynds, T., Ford, A., & Rainbird, R. H. (2016). Geology, simplified tectonic assemblage map of the Canadian Arctic Islands, Northwest Territories - Nunavut. Geological Survey of Canada, Canadian Geoscience, Map 80. https://doi.org/10.4095/297416 Mayr, U. (1980). Stratigraphy and correlation of lower Paleozoic formations, subsurface of Bathurst Island and adjacent smaller islands, Canadian Arctic Archipelago. Geological Survey of Canada, Bulletin, 306. https://doi.org/10.4095/102157 Rutishauser, A., Blankenship, D. D., Sharp, M., Skidmore, M. L., Greenbaum, J. S., Grima, C., Schroeder, D. M., Dowdeswell, J. A., & Young, D. A. (2018). Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic. Science Advances, 4(4), eaar4353. https://doi.org/10.1126/sciadv.aar4353 Thorsteinsson, R., & Mayr, U. (1987). The sedimentary rocks of Devon island, canadian arctic archipelago. https://doi.org/10.4095/122451

本数据集及衍生产物来自Rutishauser等人发表于《The Cryosphere》（已接收）的论文《雷达测深调查揭示德文冰盖下存在多样高盐次表层水文环境的潜力》，论文DOI：https://doi.org/10.5194/tc-2021-220。通讯作者：[e-mail]。
数据集说明：
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2018_DIC_UTIG.IR2HI1B.kml：SRH1测线的地理定位文件，坐标采用EPSG:4326——WGS 84坐标系（格式为纬度、经度）。
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2018_DIC_UTIG.IR2HI1B.tgz：NetCDF格式的HiCARS 2 L1B回波强度剖面（雷达图）文件包。文件命名规则为`IR2HI1B_YYYYDOY_PST_x`（示例：`IR2HI1B_2018153_DEV_JKB2t_Y87b_000.nc`），其中YYYY为调查年份（如2018），DOY为调查日序数（如153），PST为剖面名称（如DEV_JKB2t_Y87b），x为剖面分段编号（若剖面被拆分，如000）。每个剖面均附带展示其测线位置与雷达图的PDF文件。
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2018_DIC_UTIG.Level2.tgz：各剖面的二级数据集，按以下文件夹组织：
- 2018_DIC_UTIG.ILUTP2：激光高度计地理定位的冰面高程数据
- 2018_DIC_UTIG.IR2HI2：HiCARS 2未聚焦（pik1）处理的地理定位数据，包含冰厚、冰面高程、床底高程、冰面与床底反射系数以及飞行器滚转参数
- 2018_DIC_UTIG.IRHFOC2：HiCARS 2聚焦（foc1）处理的地理定位数据，包含冰厚、冰面高程、床底高程、冰面与床底反射系数以及飞行器滚转参数
- 2018_DIC_UTIG.IRSPC2：HiCARS 2衍生的基底界面镜面反射率数据
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Devon_basal_ice_temperature.tif：基于一维平流扩散模型模拟得到的德文冰盖基底冰温（单位：摄氏度），网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_bedrockDEM.tif：德文冰盖下伏基岩地形的数字高程模型（DEM，单位：米，海拔基准面），网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_gridded_RMSD_bedrock.tif：基岩地形的均方根偏差（RMDS），单位：米。均方根偏差沿各测线计算，随后通过QGIS GDAL移动平均网格插值法插值至500×500米的网格中。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_gridded_specularity.tif：沿测线获取的镜面反射率数据，通过QGIS GDAL移动平均网格插值法插值至500×500米的网格中。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_ice_thickness.tif：网格化冰厚数据（单位：米），通过从基于DigitalGlobe公司影像由极地地理空间中心发布的ArcticDEM提取的冰面高程中减去基岩DEM得到。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_modeled_Geology.zip、Devon_modeled_subglacial_geology.tif：德文冰盖下伏投影地质单元分布图。各编号对应的地质单元如下：1: pPe，2: Cm-cf，3: Oe，4: Ocb，5: Oct。地质单元的详细信息可参考（Harrison等人，2016；Mayr，1980；Thorsteinsson & Mayr，1987）。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
{pPe, Oe, Oct, Ocb, Cm_rb}_Model.stl：德文冰盖下伏模拟地质单元的三维几何模型文件，最初发表于（Rutishauser等人，2018）。坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
Devon_load_geology_stl_files.py：用于加载并绘制.stl文件中三维地质图层的Python脚本。
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Devon_subgl_hydraulic_head.tif：德文冰盖下的次表层水头数据（单位：米）。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_subgl_hydraulic_slope.tif：德文冰盖下次表层水头的坡度数据（单位：度）。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_subgl_lakes_brine_network.zip、Devon_subgl_lake_outline.shp：本研究识别出的德文冰盖下次表层湖泊岸线文件。坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。Devon_brine_network_outline.shp：德文冰盖下已测绘的次表层卤水网络轮廓文件。坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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Devon_subgl_water_routes.zip、Devon_modeled_subgl_water_routes_{1, 2, 3}std.tif：通过对次表层水头应用流量累积算法得到的模拟次表层水流路径文件。该模型共运行1000次，分别向水头数据中添加服从正态分布的、对应1、2、3倍水头不确定性标准差的随机误差（文件名中已标注误差倍数）。栅格像素值代表该单元格至少有10个上游汇水单元格汇入的模型运行次数。网格分辨率为500米，坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。Devon_extracted_subgl_water_routes.shp：通过对次表层水头应用流量累积算法得到的模拟次表层水流路径矢量文件。坐标采用EPSG:32617——WGS 84 / UTM 17N坐标系。
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SpecularityJustification.zip：用于验证本次研究中选取0.4作为次表层水体探测镜面反射率阈值合理性的Jupyter Notebook文件与示例数据集。
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致谢
航空地球物理调查及后续标准数据处理工作由威斯顿家族基金会（Weston Family Foundation）资助。本研究的数据分析工作得到了G. Unger Vetlesen基金会与UTIG博士后奖学金项目的进一步支持。M.L.S.部分受NASA项目NNX16AJ64G与NASA项目80NSSC20K1134资助。感谢PCSP与Kenn Borek航空有限公司提供的后勤支持，感谢努纳武特研究院、格赖斯峡湾与Resolute Bay原住民为在德文冰盖开展航空测量提供的许可。最后，感谢Scott Kempf在数据处理方面提供的协助，以及Sam Christian与Miguel Liu-Schiaffini在雷达反射波拾取工作中提供的帮助。
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参考文献
1. Harrison, J. C., Lynds, T., Ford, A., & Rainbird, R. H. (2016). 《加拿大北极群岛、西北地区-努纳武特地区地质简化构造组合图》，加拿大地质调查局，加拿大地球科学图集80。https://doi.org/10.4095/297416
2. Mayr, U. (1980). 《加拿大北极群岛巴瑟斯特岛及周边小岛屿下伏下古生界地层地层学与对比》，加拿大地质调查局公报306。https://doi.org/10.4095/102157
3. Rutishauser, A., Blankenship, D. D., Sharp, M., Skidmore, M. L., Greenbaum, J. S., Grima, C., Schroeder, D. M., Dowdeswell, J. A., & Young, D. A. (2018). 《加拿大北极德文冰盖下发现高盐次表层湖泊群》，《Science Advances》，4(4), eaar4353。https://doi.org/10.1126/sciadv.aar4353
4. Thorsteinsson, R., & Mayr, U. (1987). 《加拿大北极群岛德文岛沉积岩》，https://doi.org/10.4095/122451