• European Marine Science
• National Science Foundation close
• Collaborative Research: Ice sheet s... close

Abstract. The Greenland ice sheet is one of the largest contributors to global meansea-level rise today and is expected to continue to lose mass as the Arcticcontinues to warm. The two predominant mass loss mechanisms are increasedsurface meltwater run-off and mass loss associated with the retreat ofmarine-terminating outlet glaciers. In this paper we use a large ensemble ofGreenland ice sheet models forced by output from a representative subset ofthe Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level risecontributions over the 21st century. The simulations are part of theIce Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate thesea-level contribution together with uncertainties due to future climateforcing, ice sheet model formulations and ocean forcing for the twogreenhouse gas concentration scenarios RCP8.5 and RCP2.6. The resultsindicate that the Greenland ice sheet will continue to lose mass in bothscenarios until 2100, with contributions of 90±50 and 32±17 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largestmass loss is expected from the south-west of Greenland, which is governed bysurface mass balance changes, continuing what is already observed today.Because the contributions are calculated against an unforced controlexperiment, these numbers do not include any committed mass loss, i.e. massloss that would occur over the coming century if the climate forcingremained constant. Under RCP8.5 forcing, ice sheet model uncertaintyexplains an ensemble spread of 40 mm, while climate model uncertainty andocean forcing uncertainty account for a spread of 36 and 19 mm,respectively. Apart from those formally derived uncertainty ranges, thelargest gap in our knowledge is about the physical understanding andimplementation of the calving process, i.e. the interaction of the ice sheetwith the ocean. info:eu-repo/semantics/published

This archive provides the forcing data and ice sheet model output produced as part of the publication "Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison", published in The Cryosphere, https://www.the-cryosphere.net/12/1433/2018/ Goelzer, H., Nowicki, S., Edwards, T., Beckley, M., Abe-Ouchi, A., Aschwanden, A., Calov, R., Gagliardini, O., Gillet-Chaulet, F., Golledge, N. R., Gregory, J., Greve, R., Humbert, A., Huybrechts, P., Kennedy, J. H., Larour, E., Lipscomb, W. H., Le clec´h, S., Lee, V., Morlighem, M., Pattyn, F., Payne, A. J., Rodehacke, C., Rückamp, M., Saito, F., Schlegel, N., Seroussi, H., Shepherd, A., Sun, S., van de Wal, R., and Ziemen, F. A.: Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison, The Cryosphere, 12, 1433-1460, 2018, doi:10.5194/tc-12-1433-2018. Contact: Heiko Goelzer, h.goelzer@uu.nl Further information on ISMIP6 and initMIP-Greenland can be found here: http://www.climate-cryosphere.org/activities/targeted/ismip6 http://www.climate-cryosphere.org/wiki/index.php?title=InitMIP-Greenland Users should cite the original publication when using all or part of the data. In order to document CMIP6’s scientific impact and enable ongoing support of CMIP, users are also obligated to acknowledge CMIP6, ISMIP6 and the participating modelling groups. *** Important note *** For consistency with future ISMIP6 intercomparison exercises and some observational data sets, we have re-gridded all output to a diagnostic grid following the EPSG:3413 specifications, which differs from the grid originally used to distribute the forcing data. We also provide the forcing data conservatively interpolated to the new grid. Archive overview ---------------- README.txt - this information dSMB.zip - The original surface mass balance anomaly forcing data and description dSMB/ dsmb_01B13_ISMIP6_v2.nc dsmb_05B13_ISMIP6_v2.nc dsmb_10B13_ISMIP6_v2.nc dsmb_20B13_ISMIP6_v2.nc README_dSMB_v2.txt dSMB_epsg3413.zip - The surface mass balance anomaly forcing data and description, interpolated to the new grid on EPSG:3413 dSMB_epsg3413/ dsmb_01e3413_ISMIP6_v2.nc dsmb_05e3413_ISMIP6_v2.nc dsmb_10e3413_ISMIP6_v2.nc dsmb_20e3413_ISMIP6_v2.nc README_dSMB_v2_epsg3413.txt <group>_<model>_<experiment>.zip - The model output per group, model and experiment (init, ctrl, asmb) <group1>_<model1>_init/ acabf_GIS_<group1>_<model1>_init.nc ... <group1>_<model1>_ctrl/ acabf_GIS_<group1>_<model1>_ctrl.nc ... <group1>_<model1>_asmb/ acabf_GIS_<group1>_<model1>_asmb.nc ... <group1>_<model2>_init/ ... <group1>_<model2>_ctrl/ ... <group1>_<model2>_asmb/ ... <group2>_<model1>_init/ ... <group2>_<model1>_ctrl/ ... <group2>_<model1>_asmb/ ... The following script may be used to download the content of the archive. #!/bin/bash wget https://zenodo.org/record/1173088/files/README.txt wget https://zenodo.org/record/1173088/files/dSMB_epsg3413.zip wget https://zenodo.org/record/1173088/files/dSMB.zip for amodel in ARC_PISM AWI_ISSM1 AWI_ISSM2 BGC_BISICLES1 BGC_BISICLES2 BGC_BISICLES3 DMI_PISM1 DMI_PISM2 DMI_PISM3 DMI_PISM4 DMI_PISM5 IGE_ELMER1 IGE_ELMER2 ILTS_SICOPOLIS ILTSPIK_SICOPOLIS IMAU_IMAUICE1 IMAU_IMAUICE2 IMAU_IMAUICE3 JPL_ISSM LANL_CISM LSCE_GRISLI MIROC_ICIES1 MIROC_ICIES2 MPIM_PISM UAF_PISM1 UAF_PISM2 UAF_PISM3 UAF_PISM4 UAF_PISM5 UAF_PISM6 UCIJPL_ISSM ULB_FETISH1 ULB_FETISH2 VUB_GISM1 VUB_GISM2; do wget https://zenodo.org/record/1173088/files/${amodel}_init.zip wget https://zenodo.org/record/1173088/files/${amodel}_ctrl.zip wget https://zenodo.org/record/1173088/files/${amodel}_asmb.zip done {"references": ["Goelzer, H., Nowicki, S., Edwards, T., Beckley, M., Abe-Ouchi, A., Aschwanden, A., Calov, R., Gagliardini, O., Gillet-Chaulet, F., Golledge, N. R., Gregory, J., Greve, R., Humbert, A., Huybrechts, P., Kennedy, J. H., Larour, E., Lipscomb, W. H., Le clec\u00b4h, S., Lee, V., Morlighem, M., Pattyn, F., Payne, A. J., Rodehacke, C., R\u00fcckamp, M., Saito, F., Schlegel, N., Seroussi, H., Shepherd, A., Sun, S., van de Wal, R., and Ziemen, F. A.: Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison, The Cryosphere, 12, 1433-1460, https://doi.org/10.5194/tc-12-1433-2018, 2018.", "Nowicki, S. M. J., Payne, A., Larour, E., Seroussi, H., Goelzer, H., Lipscomb, W., Gregory, J., Abe-Ouchi, A., and Shepherd, A.: Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6, Geosci. Model Dev., 9, 4521-4545, https://doi.org/10.5194/gmd-9-4521-2016, 2016."]}

The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) brings together a consortium of international ice-sheet and climate modellers to simulate the contribution from the Greenland and Antarctic ice sheets to future sea-level rise. In this document, we describe the set-up and main results of the ISMIP6 Greenland Tier-1 and Tier-2 experiments carried out with the ice-sheet model SICOPOLIS. The companion document for the Antarctic ice sheet is available at https://doi.org/10.5281/zenodo.3971232. V1.0.1: References updated; some minor corrections. V1: Full report. V0.1: Abstract only. Funding acknowledgements: Japan Society for the Promotion of Science (JSPS) KAKENHI grant Nos. JP16H02224 and JP17H06104. Leadership Research Grant of Hokkaido University's Institute of Low Temperature Science (ILTS). Arctic Challenge for Sustainability (ArCS) project of the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) (program grant number JPMXD1300000000). PalMod project (PalMod 1.1 and 1.3 with grants 01LP1502C and 01LP1504D) of the German Federal Ministry of Education and Research (BMBF).

Abstract Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous data sets, particularly in the marine‐terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine‐based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing. Key Points We present a comprehensive, seamless bed topography across the ice‐ocean margin around GreenlandTwo to 4 times more glaciers have calving fronts grounded below 200 m compared to previous mappingsTotal ice volume of Greenland is 2.99 ± 0.02 times 106 km3, yielding a potential sea level rise of 7.42 m, 7 cm greater than previous estimates

Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercom-parison exercise is to compare, evaluate, and improve the ini-tialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercom-parison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises. International audience