Sensitivity of the current Antarctic surface mass balance to sea surface conditions using MAR

• Published in: The cryosphere 2018-12, Vol.12 (12), p.3827-3839
• Main Authors: Kittel, Christoph, Amory, Charles, Agosta, Cécile, Delhasse, Alison, Doutreloup, Sébastien, Huot, Pierre-Vincent, Wyard, Coraline, Fichefet, Thierry, Fettweis, Xavier
• Format: Article
• Language: English
• Subjects: Annual variations; Anomalies; Antarctic; Atmospheric models; Boundary conditions; Climate; Climate models; Coastal zone; Cyclones; Earth sciences & physical geography; General circulation models; Ice sheet; Interannual variability; Intercomparison; Mass balance; Natural history; Ocean temperature; Oceans; Perturbations; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Precipitation; Precipitation (Meteorology); Regional climate models; Regional climates; Sciences de la terre & géographie physique; Sciences of the Universe; Sea ice; Sea ice concentrations; Sea surface; Sea Surface Conditions; Sea surface temperature; Sensitivity; SMB; Surface temperature; Variability
• ISSN: 1994-0424; 1994-0416; 1994-0424; 1994-0416
• DOI: 10.5194/tc-12-3827-2018

Estimates for the recent period and projections of the Antarctic surface mass balance (SMB) often rely on high-resolution polar-oriented regional climate models (RCMs). However, RCMs require large-scale boundary forcing fields prescribed by reanalyses or general circulation models (GCMs). Since the recent variability of sea surface conditions (SSCs, namely sea ice concentration, SIC, and sea surface temperature, SST) over the Southern Ocean is not reproduced by most GCMs from the 5th phase of the Coupled Model Intercomparison Project (CMIP5), RCMs are then subject to potential biases. We investigate here the direct sensitivity of the Antarctic SMB to SSC perturbations around the Antarctic. With the RCM “Modèle Atmosphérique Régional” (MAR), different sensitivity experiments are performed over 1979–2015 by modifying the ERA-Interim SSCs with (i) homogeneous perturbations and (ii) mean anomalies estimated from all CMIP5 models and two extreme ones, while atmospheric lateral boundary conditions remained unchanged. Results show increased (decreased) precipitation due to perturbations inducing warmer, i.e. higher SST and lower SIC (colder, i.e. lower SST and higher SIC), SSCs than ERA-Interim, significantly affecting the SMB of coastal areas, as precipitation is mainly related to cyclones that do not penetrate far into the continent. At the continental scale, significant SMB anomalies (i.e greater than the interannual variability) are found for the largest combined SST/SIC perturbations. This is notably due to moisture anomalies above the ocean, reaching sufficiently high atmospheric levels to influence accumulation rates further inland. Sensitivity experiments with warmer SSCs based on the CMIP5 biases reveal integrated SMB anomalies (+5 % to +13 %) over the present climate (1979–2015) in the lower range of the SMB increase projected for the end of the 21st century.