Description: There is widespread, but often indirect, evidence that a significant fraction of the bed beneath the Greenland Ice Sheet is thawed (at or above the pressure melting point for ice). This includes the beds of major outlet glaciers and their tributaries and a large area around the NorthGRIP borehole in the ice-sheet interior. The ice-sheet scale distribution of basal water is, however, poorly constrained by existing observations. In principle, airborne radio-echo sounding (RES) enables the detection of basal water from bed-echo reflectivity, but unambiguous mapping is limited by uncertainty in signal attenuation within the ice. Here we introduce a new, RES diagnostic for basal water that is associated with wet-dry transitions in bed material: bed-echo reflectivity variability. This technique acts as a form of edge detector and is a sufficient, but not necessary, criteria for basal water. However, the technique has the advantage of being attenuation-insensitive and suited to data combination enabling combined analysis of over a decade of Operation IceBridge survey data. The basal water predictions are compared with existing analyses of the basal thermal state (frozen and thawed beds) and geothermal heat flux. In addition to the outlet glaciers, we demonstrate widespread water storage in the northern and eastern interior. Notably, we observe a quasi-linear 'corridor' of basal water extending from NorthGRIP to Petermann glacier that spatially correlates with elevated heat flux predicted by a recent magnetic model. Finally, with a general aim to stimulate regional- and process-specific investigations, the basal water predictions are compared with bed topography, subglacial flow paths, and ice-sheet motion. The basal water distribution, and its relationship with the thermal state, provides a new constraint for numerical models.

Description: Radar-detected internal layering contains information on past accumulation rates and patterns. In this study, we assume that the radar layers are isochrones, and use the layer stratigraphy in combination with ice-core measurements and numerical methods to retrieve accumulation information for the northern part of central Greenland. Measurements of the dielectric properties of an ice core from the NEEM (North Greenland Eemian Ice Drilling) site, allow for correlation of the radar layers with volcanic horizons to obtain an accurate age of the layers. We obtain 100 a averaged accumulation patterns for the period 1311-2011 for a 300 by 350 km area encompassing the two ice-core sites: NEEM and NGRIP (North Greenland Ice Core Project). Our results show a clear trend of high accumulation rates west of the ice divide and low accumulation rates east of the ice divide. At the NEEM site, this accumulation pattern persists throughout our study period with only minor temporal variations in the accumulation rate. In contrast, the accumulation rate shows more pronounced temporal variations (based on our centennial averages) from 170 km south of the NEEM site to the NGRIP site. We attribute this variation to shifts in the location of the high?low accumulation boundary away from the ice divide.

Description: This project aims to acquire airborne data with AWI's UWB (ultrawideband) ice-penetrating radar to extend the knowledge of detailed subglacial topography downstream of the EastGRIP ice core site, following on from a previous UWB radar survey in 2018. The ice thickness data also opportunistically includes profiles that were flown in different survey modes, both upstream and surrounding EastGRIP. The majority of profiles are oriented parallel or perpendicular to ice flow direction.

Description: We assess the basal conditions of the onset region of the Northeast Greenland Ice Stream (NEGIS) in a systematic analysis of airborne ultra-wideband radar data. We evaluate basal roughness and basal return echoes as well as hydraulic pathways in the context of the current ice stream geometry and ice surface velocity. The data comprises three individual datasets: 1) Spectral subglacial bed roughness data 2) Bed return power (BRP) and waveform abruptness data 3) Hydropotential and subglacial water routing data (geotiff and nc files) Email address of the provider: steven.franke@awi.de, daniela.jansen@awi.de, olaf.eisen@awi.de

Description: Here, we present a record of more than 8000 km of radar survey lines of radio echo sounding data covering an area of 24 000 km2 centred on the drill site for the East Greenland Ice-core Project (EGRIP) in the central part of the North East Greenland Ice Stream (NEGIS). The acquisition system was a multichannel ultra-wideband radar mounted on AWI's Polar6 aircraft. Our data yield a new detailed model of ice-thickness distribution and basal topography in the region.

Description: Here, we present a record of more than 8000 km of radar survey lines of radio echo sounding data covering an area of 24 000 km2 centred on the drill site for the East Greenland Ice-core Project (EGRIP) in the central part of the North East Greenland Ice Stream (NEGIS). The acquisition system was a multichannel ultra-wideband radar mounted on AWI's Polar6 aircraft. Our data yield a new detailed model of ice-thickness distribution and basal topography in the region.

Description: Here, we present a record of more than 8000 km of radar survey lines of radio echo sounding data covering an area of 24 000 km2 centred on the drill site for the East Greenland Ice-core Project (EGRIP) in the central part of the North East Greenland Ice Stream (NEGIS). The acquisition system was a multichannel ultra-wideband radar mounted on AWI's Polar6 aircraft. Our data yield a new detailed model of ice-thickness distribution and basal topography in the region.