Ice-shelf melting around Antarctica

We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.

, 1. Ice shelf thickness
Ice thickness is from BEDMAP-2 (1) and NASA Operation IceBridge (OIB) (18-19), which are available, respectively, at www.antarctica.ac.uk › Projects AZ › Bedmap2 and at the National Snow and Ice Data Center nsidc.org/data/icebridge/ data_summaries.html. BEDMAP-2 merges measurements of ice thickness from airborne radio echo sounding with estimates derived from radar-altimetry observations of surface elevation from 1994 (20). The altimetry product uses the most inland grounding line positions from InSAR (21), MOA (36), or ASAID (37) to minimize the omission of floating sectors. Ice thickness may be erroneously high where ice is not in hydrostatic equilibrium, e.g., in a transition region. Along most glaciers, MOA and ASAID grounding lines (GL) have lateral errors up to 50 km (21), which impact the calculation of ice thickness, volume flux, and basal melt rate. Here, we only rely on a systematic, precise mapping of GL with InSAR (available at nsidc.org/data/docs/meas..., , # Ice-shelf melting around Antarctica

[https://doi.org/10.5061/dryad.5hqbzkhg2](https://doi.org/10.5061/dryad.5hqbzkhg2)

## Description of the data and file structure

#### File: Ant\_MeltingRate.v2.nc

**Ice-Shelf Melting Around Antarctica**

The file is a netcdf file in Polar Stereographic format, with a coordinate reference system (CRS) EPSG:3031, 5,000 meters posting, 5601 columns x 5601 rows, origin at -2,800,000 meters, +2,800,000 meters.

1. lat: Latitude of grid points in degrees, 2d array, floating point, from -90 to -54.7 deg. 

2. lon: Longitude of grid points in degrees, 2d array, floating point, from 0 to 360 degrees. 

3. melt_actual: Actual melt rate B in meters per year, 2d array, floating point, from -10.44724 to +158.4632 m/yr

4. melt_steadystate: Steady state (no thickening) melt rate B in meters per year, 2d array, floating point, from -9.025163 to +152.8616 m/yr

5. xaxis: x values of grid in meters, 1d array, floating point, from -2,800,000 meters, +2,800,000 me...,