These files contain ground penetrating radar (GPR) data collected from the glacier margins and forelands of Falljökull and of Kvíárjökull, south-east Iceland, between 2012 and 2014. The data were collected using a Sensors and Software PulseEKKO Pro GPR system. For each glacier the data are stored in folders that indicate the month and year in which the surveys were conducted. Each GPR profile has a Sensors and Software GPR (.DT1) file, and associated header (.HD) and GPS (.GPS) files. The .HD files (which can be opened as text files) give the parameters and equipment used for each profile. GPS files are not available for some of the profiles collected on Falljökull in April 2013 (due to damage that occurred to the GPS linked with the PulseEKKO Pro system). For these profiles start, finish, and mid profile positions were recorded using differential GPS, and locations of these profiles are instead given by GIS shapefiles in the relevant folders. These datasets have been used in the publications listed below. Further information relating to the data collection methodology can be found therein. Phillips, Emrys; Everest, Jez; Evans, David J.A.; Finlayson, Andrew; Ewertowski, Marek; Guild, Ailsa; Jones, Lee. 2017 Concentrated, ‘pulsed’ axial glacier flow: structural glaciological evidence from Kvíárjökull in SE Iceland. Earth Surface Processes and Landforms, 42 (13). 1901-1922. https://doi.org/10.1002/esp.4145 Phillips, Emrys; Finlayson, Andrew; Bradwell, Tom; Everest, Jez; Jones, Lee. 2014 Structural evolution triggers a dynamic reduction in active glacier length during rapid retreat: evidence from Falljökull, SE Iceland. Journal of Geophysical Research: Earth Surface, 119 (10). 2194-2208. https://doi.org/10.1002/2014JF003165 Phillips, Emrys; Finlayson, Andrew; Jones, Lee. 2013 Fracturing, block-faulting and moulin development associated with progressive collapse and retreat of a polar maritime glacier: Virkisjokul-Falljokull, SE Iceland. Journal of Geophysical Research: Earth Surface, 118 (3). 1545-1561. https://doi.org/10.1002/jgrf.20116 Flett, Verity; Maurice, Louise; Finlayson, Andrew; Black, Andrew; MacDonald, Alan; Everest, Jez; Kirkbride, Martin. 2017. Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland. Hydrology Research, 48 (6). 1666-1681. https://doi.org/10.2166/nh.2017.205

Three datasets, ground-penetrating radar, side-scan sonar and sub-bottom profile data (CHIRP), were collected in April and June 2022 from the proximal Skeiðarársandur area (~63.9 N, 17.2 E) and Skeiðarársandur coastline (63.7 N, 17.5 E) that lie at the mouth of Gígjukvísl. Ground-penetrating radar (GPR) data acquired for this project on 15th and 18th April 2022 provide new insights into the sediment architecture of differing depositional environments at Skeiðarársandur, southeast Iceland, including: (i) a recently emplaced jökulhlaup deposit in a large ice-proximal depression, and (ii) the coastal environment of a vast glaciofluvial braidplain. Radar data collected in the ice-proximal depression utilised a 250 MHz Utsi GroundVue (GV) 3, a shielded single-channel bistatic radar system suited to near surface (0-10 m depth). Approximately 30 km of 250 MHz GPR data were collected parallel and perpendicular to the jökulhlaup flow direction. The GPR data from the coastal regions of Skeiðarársandur were collected using a 100 MHz Utsi GV7. The 100 MHz Utsi GV7 is a ruggedised and unshielded radar system with a centre-frequency of 100 MHz and an emitted bandwidth of ~1-160 MHz. The radar system has a maximum time-window of 800 ns and each stacked radar trace is comprised of 256 samples (i.e. one sample every 3.125 ns). Approximately 12 km of 100 MHz radar data were collected at the Skeiðarársandur coastline. File format for the raw data includes .dat, .gps, .gpt and .hdr. Positional (Lat, Lon) data were acquired using a handheld GPS connected via USB to the ruggedised laptop (100 MHz Utsi GV7) or connected directly to GPR control unit (250 MHz Utsi GV3). All GPS data were recorded directly in the Utsi GroundVue software by logging an NMEA string concurrent with radar trace samples (i.e. an XY position for each individual sampled radar trace). Side scan sonar, CHIRP and single-beam echosounding data were collected within a large proglacial lake fronting Skeiðarárjökull (63.5 N, 16.3 W) between 11th to 24th June. Side scan data was acquired using an AquaScan Precision Side Scan Sonar System. During surveys the tow fish was lowered to a constant relative position and depth below the boat hull. This data provides an imaging of the lakebed which is used for qualitative description of lakebed features (filed are .xtf). A hull mounted Sonarmite BTX single-beam echosounder was used to provide depth control which was linked via Bluetooth a hull mounted Leica GS14 (.txt files). Sub bottom data was acquired using Bathy 2010PC CHIRP Sub Bottom Profiler operating at dual frequency (3.5KHz and 10.0KHz). This was towed alongside the boat and used to constrain lakebed depth as well as buried sediment architecture. Ping rate varied based on depth of returns. Raw data was collected at .seg files. All lake survey data is georeferenced using GNSS data from boat mounted Leica GS14 receiving real-time corrections from a base station over a known location.