Journal Article

What is the surface mass balance of Antarctica? An intercomparison of regional climate model estimates

Agosta, Cécile, Simonsen, Sebastian B., Fettweis, Xavier, Phillips, Tony, van Lipzig, Nicole P. M., Mottram, Ruth, van Meijgaard, Erik, Gossart, Alexandra, Boberg, Fredrik, Kittel, Christoph, van Wessem, J. Melchior, van de Berg, Willem Jan, Orr, Andrew, Hansen, Nicolaj, Webster, Stuart, Amory, Charles, Souverijns, Niels

2021

Overview

We compare the performance of five different regional climate models (RCMs) (COSMO-CLM2, HIRHAM5, MAR3.10, MetUM, and RACMO2.3p2), forced by ERA-Interim reanalysis, in simulating the near-surface climate and surface mass balance (SMB) of Antarctica. All models simulate Antarctic climate well when compared with daily observed temperature and pressure, with nudged models matching daily observations slightly better than free-running models. The ensemble mean annual SMB over the Antarctic ice sheet (AIS) including ice shelves is 2329±94 Gt yr−1 over the common 1987–2015 period covered by all models. There is large interannual variability, consistent between models due to variability in the driving ERA-Interim reanalysis. Mean annual SMB is sensitive to the chosen period; over our 30-year climatological mean period (1980 to 2010), the ensemble mean is 2483 Gt yr−1. However, individual model estimates vary from 1961±70 to 2519±118 Gt yr−1. The largest spatial differences between model SMB estimates are in West Antarctica, the Antarctic Peninsula, and around the Transantarctic Mountains. We find no significant trend in Antarctic SMB over either period. Antarctic ice sheet (AIS) mass loss is currently equivalent to around 0.5 mm yr−1 of global mean sea level rise (Shepherd et al., 2020), but our results indicate some uncertainty in the SMB contribution based on RCMs. We compare modelled SMB with a large dataset of observations, which, though biased by undersampling, indicates that many of the biases in SMB are common between models. A drifting-snow scheme improves modelled SMB on ice sheet surface slopes with an elevation between 1000 and 2000 m, where strong katabatic winds form. Different ice masks have a substantial impact on the integrated total SMB and along with model resolution are factored into our analysis. Targeting undersampled regions with high precipitation for observational campaigns will be key to improving future estimates of SMB in Antarctica.

• Publisher: Copernicus GmbH,European Geosciences Union,Copernicus,Copernicus Publications
• Subject: Ablation / Antarctic climate / Antarctic ice sheet / Climate / Climate change / Climate models / Climatological means / Climatology / Comparative analysis / Earth Sciences / Earth sciences & physical geography / Elevation / Estimates / Glaciation / Glaciology / Ice / Ice formation / Ice sheets / Ice shelves / Interannual variability / Intercomparison / Katabatic winds / Land ice / Mass / Mass balance / Mean sea level / Model matching / Mountains / Net losses / Physical, chemical, mathematical & earth Sciences / Physique, chimie, mathématiques & sciences de la terre / Precipitation / Regional climate models / Regional climates / Sciences de la terre & géographie physique / Sciences of the Universe / Sea level / Sea level changes / Sea level rise / Simulation / Snow / Spatial variations / Target marketing / Water surface slope / Winds