Data set: "A 21st Century Warming Threshold for Sustained Greenland Ice Sheet Mass Loss"

<p>This data set includes&nbsp;the materials required to reproduce the figures and tables presented in the study: &quot;A 21^st Century Warming Threshold for Sustained Greenland Ice Sheet Mass Loss&quot;. The data consist of:</p> <ul> <li>Maps of annual historical and projected surface mass balance (SMB)&nbsp;of the Greenland ice sheet (GrIS) from RACMO2.3p2 at 1 km spatial resolution in NetCDF format.</li> </ul> <ol> <li><strong>smb_rec.1950-2014.BN_RACMO2.3p2-CESM2-Historical.1km.YY.nc</strong>: annual cumulative GrIS SMB (kg m^-2 or mm w.e. per year) from RACMO2.3p2 forced by CESM2&nbsp;for the historical period 1950-2014, further statistically downscaled to 1 km spatial resolution.</li> <li><strong>smb_rec.2015-2099.BN_RACMO2.3p2-CESM2-SSP5-85.1km.YY.nc</strong>:&nbsp;annual cumulative GrIS SMB (kg m^-2 or mm w.e. per year) from RACMO2.3p2 forced by CESM2 under a high-end warming scenario SSP5-8.5&nbsp;for the period 2015-2099, further statistically downscaled to 1 km spatial resolution.</li> <li><strong>Icemask_Topography_lon_lat_average_1km_GrIS.nc</strong>: mask file including an ice mask (Promicemask)&nbsp;separating Greenland&#39;s peripheral glaciers and ice caps (values 1 and 2) from the main ice sheet (value 3), surface topography derived from the GIMP DEM, and longitude/latitude coordinates on the 1 km grid.&nbsp;</li> </ol> <p>NB: the&nbsp;NetCDF files above use a&nbsp;Polar Stereographic North (EPSG:3413) projection with&nbsp;a horizontal&nbsp;resolution of&nbsp;1 km x 1 km. The reference point is located at 45&ordm;W longitude and 70&ordm;N latitude.</p> <ul> <li>Time series of historical and projected annual GrIS-integrated SMB (Gigatons or Gt per year) and annual mean GrIS temperature (TGrIS; K) from RACMO2.3p2 at 1 km spatial resolution in ASCII format.</li> </ul> <ol> <li><strong>SMB_TGrIS_RACMO2.3p2-CESM2_Historical_1950-2014.dat</strong>: time series of annual GrIS-integrated SMB (Gt yr^-1) and mean TGrIS (K) from the CESM2-forced RACMO2.3p2 simulation for the historical period 1950-2014.</li> <li><strong>SMB_TGrIS_RACMO2.3p2-CESM2_SSP5-8.5_2015-2099.dat</strong>:&nbsp;time series of annual GrIS-integrated SMB (Gt yr^-1) and mean TGrIS (K) from the CESM2-forced RACMO2.3p2 projection under a high-end warming scenario SSP5-8.5 (2015-2099).</li> </ol> <ul> <li>Time series of historical and projected reconstruction of annual&nbsp;GrIS-integrated SMB&nbsp;(Gt yr^-1) and&nbsp;mean TGrIS (K) from 12 CESM2 historical members and 10 CESM2 projections under various warming scenarios, namely&nbsp;SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5.</li> </ul> <ol> <li><strong>Reconstructed_SMB_CESM2_Historical_1950-2014.dat</strong>: time series of reconstructed&nbsp;annual GrIS-integrated SMB (Gt yr^-1) from the parent historical CESM2 simulation (HIST-parent) used to force RACMO2.3p2 and 11&nbsp;additional historical CESM2 members (HIST-X) for 1950-2014.&nbsp;&nbsp;</li> <li><strong>Reconstructed_SMB_CESM2_Projections_2015-2099.dat</strong>:&nbsp; time series of reconstructed&nbsp;annual GrIS-integrated SMB (Gt yr^-1) from the parent&nbsp;CESM2 projection (SSP5-8.5-parent) used to force RACMO2.3p2 and 9&nbsp;additional&nbsp;CESM2 projection members (SSP1-2.6-X to SSP5-8.5-X ) for 2015-2099.&nbsp;</li> <li><strong>TGrIS_CESM2_Historical_1950-2014.dat</strong>:&nbsp;time series of&nbsp;annual mean TGrIS (K) from the parent historical CESM2 simulation (HIST-parent) used to force RACMO2.3p2 and 11&nbsp;additional historical CESM2 members (HIST-X) for 1950-2014.</li> <li><strong>TGrIS_CESM2_Projections_2015-2099.dat</strong>:&nbsp;time series of annual mean TGrIS (K)&nbsp;from the parent&nbsp;CESM2 projection (SSP5-8.5-parent) used to force RACMO2.3p2 and 9&nbsp;additional&nbsp;CESM2 projection members (SSP1-2.6-X to SSP5-8.5-X ) for 2015-2099.&nbsp;</li> </ol> <p>NB: the file&nbsp;<strong>Crossref_sim_names.txt&nbsp;</strong>cross-references the simulation abbreviations in the above .dat files&nbsp;to&nbsp;official simulation names from the National Center for Atmospheric Research (NCAR).</p> <p>The daily&nbsp;downscaled SMB&nbsp;data set&nbsp;from the CESM2-forced RACMO2.3p2&nbsp;historical simulation and&nbsp;SSP5-8.5 projection&nbsp;are freely available from the authors upon request and without conditions (contact:&nbsp;<strong>b.p.y.noel@uu.nl</strong>). Besides SMB, the data set includes daily total precipitation (snow and rain), snowfall, total melt (snow and ice), meltwater runoff, retention and refreezing, total sublimation (surface and drifting snow),&nbsp;snow drift erosion, as well as 2 m air temperature&nbsp;at 1 km horizontal resolution.&nbsp;</p> <p>Abstract: &quot;Under anticipated future warming, the Greenland ice sheet (GrIS) will pass a threshold when meltwater runoff exceeds the accumulation of snow, resulting in a negative surface mass balance (SMB &lt; 0) and sustained mass loss. In spite of several recent warm summers with high melt rates, SMB &lt; 0 has not been reached since at least the year 1958. Here we dynamically and statistically downscale the outputs of an Earth system model to 1 km resolution to infer that a Greenland near-surface atmospheric warming of 4.5 &plusmn; 0.3 &deg;C&mdash;relative to pre-industrial&mdash;is required for GrIS SMB to become persistently negative. Climate models from CMIP5 and CMIP6 translate this regional temperature change to a global warming threshold of 2.7 &plusmn; 0.2 &deg;C. Under a high-end warming scenario, this threshold may be reached around 2055, while for a strong mitigation scenario it will likely not be passed.&quot;</p>