by Patrick Yang
Many global climate models project that anthropogenic global warming will lead to increased snowfall in Antarctica due to increased moisture in the atmosphere. However, the actual trend in Antarctica shows a discrepancy. Surface mass balance (SMB), the difference between the amount of snow accumulated and sublimated, has not shown any significant increase, despite the rise in global temperature. This discrepancy may be caused by natural climate variability, which is characteristic of the chaotic variation in Antarctica’s climate.
A recent study led by Michael Previdi, Ph.D., of Columbia University, evaluated SMB simulations from 35 coupled atmosphere-ocean climate models from the most recent Coupled Model Intercomparison Project (CMIP5), which quantified the SMB increase caused by global warming. His team determined that from 1961 to 2005, forced SMB increase by global warming was 124 billion tons per year, which is smaller than the SMB increase by natural variability of 126 billion tons per year. Since forced SMB increase was smaller than natural SMB increase, it is possible that the forced response was completely or partially masked by natural variability.
Despite the current obscurity of the effects of global warming on SMB, CMIP5 models predict that after 2015, there is a 66% chance that anthropogenic global warming will become evident in Antarctica’s surface mass balance. By 2040, these chances increase to 90%. Since the total amount of water on earth is constant, water stored as snow or ice will decrease water available to increase sea levels. CMIP5 simulations show that increased snowfall in Antarctica may mitigate rises in global sea level by up to 3 inches by 2100. Although three inches may not seem too significant, with recent global sea level rises at 3.2mm per year, any mitigation is welcomed.
- M. Previdi, L.M. Polvani, Anthropogenic impact on Antarctic surface mass balance, currently masked by natural variability, to emerge by mid-century. Environmental Research Letters 11, 1-9 (2016). doi: 10.1088/1748-9326/11/9/094001.
- Image retrieved from: https://www.pexels.com/photo/ice-antarctica-blue-ocean-7495/.