Description: Sub-ice shelf circulation and freezing/melting rates in ocean general circulation models depend critically on an accurate and consistent representation of cavity geometry. Existing global or pan-Antarctic data sets have turned out to contain various inconsistencies and inaccuracies. The goal of this work is to compile independent regional fields into a global data set. We use the S-2004 global 1-minute bathymetry as the backbone and add an improved version of the BEDMAP topography for an area that roughly coincides with the Antarctic continental shelf. Locations of the merging line have been carefully adjusted in order to get the best out of each data set. High-resolution gridded data for upper and lower ice surface topography and cavity geometry of the Amery, Fimbul, Filchner-Ronne, Larsen C and George VI Ice Shelves, and for Pine Island Glacier have been carefully merged into the ambient ice and ocean topographies. Multibeam survey data for bathymetry in the former Larsen B cavity and the southeastern Bellingshausen Sea have been obtained from the data centers of Alfred Wegener Institute (AWI), British Antarctic Survey (BAS) and Lamont-Doherty Earth Observatory (LDEO), gridded, and again carefully merged into the existing bathymetry map. The global 1-minute dataset (RTopo-1 Version 1.0.5) has been split into two NetCDF files. The first contains digital maps for global bedrock topography, ice bottom topography, and surface elevation. The second contains the auxiliary maps for data sources and the surface type mask. A regional subset that covers all variables for the region south of 50 deg S is also available in NetCDF format. Datasets for the locations of grounding and coast lines are provided in ASCII format.

Description: This dataset was created via processing of raw position data acquired by the GPS sensor for scientific equipment on Polar 6/Polar 5 to receive a validated master track which is used as reference of further expedition data.

Description: The increasing catalogue of high-quality ice-penetrating radar data provides a unique insight in the internal layering architecture of the Greenland ice sheet. The stratigraphy, an indicator of past deformation, highlights irregularities in ice flow and reveals large perturbations without obvious links to bedrock shape. In this work, to establish a new conceptual model for the formation process, we analysed the radar data at the onset of the Petermann Glacier, North Greenland, and created a three-dimensional model of several distinct stratigraphic layers. We demonstrate that the dominant structures are cylindrical folds sub-parallel to the ice flow. By numerical modelling, we show that these folds can be formed by lateral compression of mechanically anisotropic ice, while a general viscosity contrast between layers would not lead to folding for the same boundary conditions. We conclude that the folds primarily form by converging flow as the mechanically anisotropic ice is channelled towards the glacier.

Description: In times of warming in polar regions, the prediction of ice sheet discharge is of utmost importance to society, because of its impact on sea level rise. In simulations the flow rate of ice is usually implemented as proportional to the differential stress to the power of the exponent n=3. This exponent influences the softness of the modeled ice, as higher values would produce faster flow under equal stress. We show that the stress exponent, which best fits the observed state of the Greenland Ice Sheet, equals n=4, Our results, which are not dependent on a possible basal sliding component of flow, indicate that most of the interior northern ice sheet is currently frozen to bedrock, except for the large ice streams and marginal ice.

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: Ice Thickness from Jutulstraumen Glacier recorded with the AWI UWB radar system - Focus of this project was to map the disturbances of the radar stratigraphy at the shear margins of the Jutulstraumen, a large outlet glacier in Dronning Maud Land (DML), Antarctica, as well as within its main trunk. This project will help to improve our understanding of the formation processes of such disturbances around shear margins in active ice streams. A better understanding of the process itself will enable to analyse the observed structures in other parts of the ice sheets in terms of their deformation history. For JuRaS the profiles consist of parallel lines directed perpendicular to the flow direction of the main trunk of the Jutulstraumen, as well as profiles across an eastern tributary. Due to our fueling stop in Kohnen Station we were also able to collect a connecting radar line between the location of the EDML ice core to our main survey area, which is useful for referencing and dating reflections in our data and making connections to survey flights conducted in the 1990s, 2000s and later. - AWI Flight Campaign: P6-215_UWB_2018 Project: JuRaS-2018 Region: Antarctica, Dronning Maud Land, Jutulstraumen Ice Stream - Owner / PI: Daniela Jansen (AWI) Email address of the provider: steven.franke@awi.de daniela.jansen@awi.de - Instrument used: AWI UWB (MCoRDS 5) Firn correction: none applied Velocity profile: dielectric constant of 3.15 ( c = 1.68914e8 m/s ) - Ice Thickness uncertainty: is the RMS of the the sum of the crossover mean of 62 intersections (= 24.7 m) and the error of the dielectric (1%). sqrt( (crossover_mean)^2 + ( (-ice_thickness/2) * 0.01 )^2 ) - GPS data was acquired by four NovAtel DL-V3 GPS receivers operating at 20Hz - Level of focusing: focused SAR