Global atmospheric impacts induced by year-round open water adjacent to Antarctica

A sensitivity study to evaluate the greatest impact that sea-ice anomalies around Antarctica could have on the global atmospheric circulation is conducted with the National Center for Atmospheric Research Community Climate Model, Version 2. A 15-year seasonal cycle simulation is performed in which all sea ice around Antarctica is removed and replaced by year-round open water at -1.9 degrees C. The results are compared to a standard 15-year seasonal cycle run with boundary conditions set for the present climate. The comparison shows that substantial changes in pressure, vertical circulation, and precipitation are found in both hemispheres as a result of Antarctic sea-ice removal. These anomalies are more significant in the southern hemisphere during May-September, whereas the anomalies are more notable in the northern hemisphere during September-November, a result which was not present in previous perpetual simulations. Convective precipitation increases and large-scale precipitation decreases as the circumpolar trough moves closer to Antarctica in response to the sea-ice removal. Positive and negative anomalies form a wave-like train in the troposphere. The anomalies include the delayed onset of the winter monsoon over northern China during September. This result is in basic agreement with an observational study that found monsoon parameters are correlated with Antarctic sea-ice characteristics. In addition, the mean meridional circulation and convective precipitation have a monthly modulation of roughly 5% in the tropics. Mechanisms for the global atmospheric propagation of the impact of the Southern Ocean surface heating anomalies are examined.