In situ proglacial river ice thickness, ground penetrating radar (GPR) data, and bright reflector mappings from southwest Greenland, February 2015

Meltwater export from the Greenland Ice Sheet (GrIS) is a significant contributor to sea level rise. Despite this, relatively little is known about the temporal and spatial dynamics of meltwater routing through and retention in/under the GrIS. Thus to investigate if GrIS hydrologic processes stay active year-round, we deployed to southwest Greenland during winter, approximately 4 months after summertime surface melt. We surveyed the frozen Isortoq, Sandflugtdalen, Ørkendalen, and Watson proglacial rivers, which drain all meltwater runoff from tributary Isunguata Sermia, Russell, Leverett, Ørkendalen, and Isorlersuup outlet glaciers. At each river site, we established transects across the river ice perpendicular to summertime flow direction. We then executed ground penetrating radar (GPR) surveys along each transect and also mechanically drilled boreholes through the river ice. We discovered evidence of minimal meltwater export beneath proglacial river ice in the Isortoq River. Geochemical analysis of this water suggests that it was sourced from the GrIS. Surveys in neighboring proglacial rivers revealed no evidence of meltwater runoff. We suggest that the discovered runoff only in the Isortoq River is the result of residual meltwater storage and release enabled by a deep, spatially pervasive, subglacial trough beneath Isunguata Sermia outlet glacier. This suggests that GrIS hydrological processes can stay active year-round. The enclosed data supports these results, and includes: point locations of river ice thickness measured in mechanically drilled boreholes; GPR data and processed echograms; approximate point locations of bright reflectors mapped beneath the Isortoq River ice. This data supports the methods, results and conclusions in Pitcher et al. (2020).

格陵兰冰盖（Greenland Ice Sheet, GrIS）的融水输出是海平面上升的重要贡献因素。尽管如此，学界对融水在格陵兰冰盖内部及冰下的运移路径与滞留状态的时空动态认知仍相对有限。为探究格陵兰冰盖水文过程是否全年持续活跃，我们于夏季地表融水结束约4个月后的冬季，在格陵兰西南部开展研究部署。我们对冰封的伊索托克河（Isortoq）、桑夫勒河谷河（Sandflugtdalen）、奥尔肯河谷河（Ørkendalen）与沃森冰前河流进行了踏勘，这些河道承接了支流伊松瓜塔塞尔米亚冰川（Isunguata Sermia）、拉塞尔冰川（Russell）、莱弗雷特冰川（Leverett）、奥尔肯河谷冰川与伊索勒苏普冰川（Isorlersuup）的全部融水径流。在每个河道测点，我们沿垂直于夏季径流流向的方向在河冰上布设测线，随后沿每条测线开展探地雷达（ground penetrating radar, GPR）勘测，并通过机械钻探在河冰上钻孔。我们在伊索托克河的冰下观测到了少量融水输出的证据，对该水体的地球化学分析表明其来源为格陵兰冰盖。对邻近冰前河流的勘测未发现融水径流的迹象。我们提出，仅在伊索托克河观测到径流，是伊松瓜塔塞尔米亚冰川下方存在一条深厚且空间分布广泛的冰下槽谷，使得残留融水得以储存并释放所致。这一发现表明格陵兰冰盖的水文过程可全年保持活跃。本配套数据支持上述研究结果，包含以下内容：机械钻探测得的河冰厚度测点坐标；探地雷达数据与处理后的回声图；伊索托克河冰下明亮反射体的近似测点坐标。本数据集可佐证Pitcher等人（2020年）研究中的方法、结果与结论。