Abstract
The response of the Greenland Ice Sheet (GrIS) to a warmer climate is uncertain on long time scales. Climate models, such as those participating in the Coupled Model Intercomparison Project phase 6 (CMIP6), are used to assess this uncertainty. The Community Earth System Model version 2.1 (CESM2) is a CMIP6 model capable of running climate simulations with either one-way coupling (fixed ice sheet geometry) or two-way coupling (dynamic geometry) to the GrIS. The model features prognostic snow albedo, online downscaling using elevation classes, and a firn pack to refreeze percolating melt water. Here we evaluate the representation of the GrIS surface energy balance and surface mass balance in CESM2 at 1° resolution with fixed GrIS geometry. CESM2 agrees closely with ERA-Interim reanalysis data for key controls on GrIS SMB: surface pressure, sea ice extent, 500 hPa geopotential height, wind speed, and 700 hPa air temperature. Cloudsat-CALIPSO data show that supercooled liquid-containing clouds are adequately represented, whereas comparisons to Moderate Resolution Imaging Spectroradiometer and CM SAF Cloud, Albedo, and Surface Radiation data set from Advanced Very High Resolution Radiometer data second edition data suggest that CESM2 underestimates surface albedo. The seasonal cycle and spatial patterns of surface energy balance and surface mass balance components in CESM2 agree well with regional climate model RACMO2.3p2, with GrIS-integrated melt, refreezing, and runoff bracketed by RACMO2 counterparts at 11 and 1 km. Time series of melt, runoff, and SMB show a break point around 1990, similar to RACMO2. These results suggest that GrIS SMB is realistic in CESM2, which adds confidence to coupled ice sheet-climate experiments that aim to assess the GrIS contribution to future sea level rise.
| Original language | English |
|---|---|
| Article number | e2019JF005318 |
| Number of pages | 25 |
| Journal | Journal of Geophysical Research: Earth Surface |
| Volume | 125 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Feb 2020 |
Funding
This work was carried out under the program of the Netherlands Earth System Science Centre (NESSC), financially supported by the Ministry of Education, Culture and Science (OCW, Grant 024.002.001). The CESM project is supported primarily by the National Science Foundation (NSF). This material is based upon work supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement 1852977. Computing and data storage resources, including the Cheyenne supercomputer (doi:10.5065/D6RX99HX), were provided by the Computational and Information Systems Laboratory (CISL) at NCAR. We thank all the scientists, software engineers, and administrators who contributed to the development of CESM2. The HIST-EC climate simulation was performed on SURFsara HPC systems with support from NWO Exacte Wetenschappen. Climate data for simulations HIST-01 (historical.r1i1p1f1) to HIST-06 (historical.r6i1p1f1) are publicly available from Earth System Grid Federation (https://esgf.llnl.gov/nodes.html). Climate data for simulation HIST-EC are publicly available from Zenodo; native resolution https://doi.org/10.5281/zenodo.3369633, 11?km offline downscaled https://doi.org/10.5281/zenodo.3369635, and 1?km offline downscaled https://doi.org/10.5281/zenodo.3368630. RACMO climate data used in this paper are publicly available from Zenodo as well; 11?km native https://doi.org/10.5281/zenodo.3368404, and 1?km downscaled https://doi.org/10.5281/zenodo.3367210.
Keywords
- CESM2
- ESM
- GCM
- Greenland
- ice sheets
- surface mass balance
