A new bed elevation dataset for Greenland

Abstract

We present a new bed elevation dataset for Greenland derived from a combination of multiple airborne ice thickness surveys undertaken between the 1970s and 2012. Around 420 000 line kilometres of airborne data were used, with roughly 70% of this having been collected since the year 2000, when the last comprehensive compilation was undertaken. The airborne data were combined with satellite-derived elevations for non-glaciated terrain to produce a consistent bed digital elevation model (DEM) over the entire island including across the glaciated–ice free boundary. The DEM was extended to the continental margin with the aid of bathymetric data, primarily from a compilation for the Arctic. Ice thickness was determined where an ice shelf exists from a combination of surface elevation and radar soundings. The across-track spacing between flight lines warranted interpolation at 1 km postings for significant sectors of the ice sheet. Grids of ice surface elevation, error estimates for the DEM, ice thickness and data sampling density were also produced alongside a mask of land/ocean/grounded ice/floating ice. Errors in bed elevation range from a minimum of ±10 m to about ±300 m, as a function of distance from an observation and local topographic variability. A comparison with the compilation published in 2001 highlights the improvement in resolution afforded by the new datasets, particularly along the ice sheet margin, where ice velocity is highest and changes in ice dynamics most marked. We estimate that the volume of ice included in our land-ice mask would raise mean sea level by 7.36 m, excluding any solid earth effects that would take place during ice sheet decay

Simulation of the Greenland Ice Sheet over two glacial–interglacial cycles: investigating a sub-ice- shelf melt parameterization and relative sea level forcing in an ice-sheet–ice-shelf model

“…In this method, the SSM increases with water depth (W D ) by a power law relation with a constant a and exponent m. Table 3 for colours). The solid orange line marks the present-day ice volume (Bamber et al, 2013).…”

“…As the roughness at the base of ice sheet is a relatively unknown quantity, a range of sliding coefficients (A s ) were investigated between 0.04 × 10 −10 and 1.8 × 10 −10 m 8 N −3 yr −1 . Present-day input fields of the ice thickness, the surface elevation, and the bed topography are taken from Bamber et al (2013) with input climate fields (surface mass balance (SMB), refreezing, surface air temperature (SAT)) adapted from the RACMO2 dataset (van Angelen et al, 2014). All these external datasets are interpolated and projected onto the 20 × 20 km ice model grid using the mapping software OBLIMAP2.0 (Reerink et al, 2010(Reerink et al, , 2016.…”

“…First, IMAU-ICE was run for 100 kyr, under a constant PD climate (using the input climate fields taken from the RACMO2 dataset) to reach an equilibrium state with the aim of replicating the observed PD configuration (Bamber et al, 2013). The sensitivity to the flow enhancement factor (m enh , varied between 1 and 5) was investigated for the range of sliding coefficients (A s ).…”

Force Balance along Isunnguata Sermia, West Greenland

“…InSAR-derived surface velocities from Joughin et al (2010) define motion over the study reach during the winter period between Dec 1, 2008 andFeb 28, 2009, and are provided at 500 m spatial resolution. The digital elevation model (DEM) of bedrock topography by Bamber et al (2013) is used. This DEM is informed by airborne radar flightlines that were collected at dense spacing (∼500 m) through much of our study area as part of the IceBridge mission (Allen et al, 2010), and is posted at 1 km resolution.…”

“…This has motivated the collection of new high resolution datasets over the last decade of GrIS surface topography (e.g., Helm et al, 2014;Howat et al, 2014), bed geometry (e.g., Bamber et al, 2013), and surface velocity (e.g., Joughin et al, 2010;Rignot and Mouginot, 2012). While gravity drives the flow of ice, numerous other factors (e.g., basal topography and substrate, ice temperature, and rheology) also influence the basal sliding and deformational motion of the ice sheet in response to gravitational forcing.…”