Response of Global Atmospheric Circulation to Antarctic Meltwater.

In response to rising levels of atmospheric greenhouse gas concentrations, significant mass loss from the Antarctic Ice Sheet (AIS) has been observed in recent decades. Many modeling studies have focused on understanding and constraining the response of the ocean and global surface temperatures to the addition of meltwater in the Southern Ocean. Significant cooling of surface air and sea surface temperatures and expansion of Southern Hemisphere sea ice, have been documented as robust responses to the addition of AIS meltwater in coupled model simulations. Less attention has been paid to constraining the impact of AIS meltwater on global atmospheric circulation patterns. We address this knowledge gap by analyzing the results from meltwater perturbation experiments performed using two fully coupled climate models developed at NOAA’s Geophysical Fluid Dynamics Laboratory (GFDL), GFDL-CM4 and GFDL-ESM4. Identical experiments are performed where a 0.1 Sv freshwater perturbation is applied to the ocean’s surface under a pre-industrial control background state. We find strong tropospheric cooling and localized stratospheric warming extending throughout the atmosphere as a result of the strong surface response. The altered thermal structure of the atmosphere results in changes in wind patterns and jet structure in both hemispheres. We also present a multi-model analysis from similar experiments submitted as the Tier 1 Antwater experiment from the Southern Ocean Freshwater release model experiments Initiative (SOFIA). Such results highlight the global influence of AIS mass loss and motivate the need for additional work using coupled models to improve our understanding of the full climate response.