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.

Raw (calibrated as per Demer et al., 2015) Simrad EK60 echosounder data (18, 38 and 120 kHz; Kongsberg Maritime, Norway) collected annually in August and September between 2011 and 2016 as part of the Barents Sea Ecosystem Survey (Eriksen et al., 2018) were obtained from the Norwegian Marine Data Centre (Institute of Marine Research, Norway). The data were used to evaluate the StrathE2EPolar (an end-to-end food web model incorporating ice-dependencies to simulate climate-fisheries interactions in the Barents Sea) model. Echosounder data were calibrated and processed (noise removed). Nautical-area-scattering coefficient (NASC, m2 nmi-2: average received echo energy over a given depth range scaled up to a square nautical mile) values were computed between 15 m (maximum vessel draft plus echosounder near-field for all surveys, vessels and frequencies) and 400 m (lower extent of StrathE2EPolar model domain). NASC values at 18 kHz were used as a proxy for fish biomass. NASC values at 120 kHz and where NASC 120 kHz > 38 kHz > 18 kHz were used as a proxy for macro-zooplankton biomass. NASC values were binned into a 0.5 by 0.5-degree grid and averaged to map the spatial distribution of fish and macro-zooplankton. Funded by NERC project Microbes to Megafauna Modelling of Arctic Seas (MiMeMo), NE/R012571/1 (lead), and NE/R012679/1.