GLOBAL ATMOSPHERIC IMPACTS INDUCED BY YEAR-ROUND OPEN WATER ADJACENT TO ANTARCTICA

A sensitivity study to evaluate the greatest impact that sea-ice anoma lies around Antarctica could have on the global atmospheric circulatio n is conducted with the National Center for Atmospheric Research Commu nity Climate Model, Version 2. A 15-year seasonal cycle simulation is performed in which all sea ice around Antarctica is removed and replac ed by year-round open water at -1.9 degrees C. The results are compare d to a standard 15-year seasonal cycle run with boundary conditions se t for the present climate. The comparison shows that substantial chang es in pressure, vertical circulation, and precipitation are found in b oth hemispheres as a result of Antarctic sea-ice removal. These anomal ies are more significant in the southern hemisphere during May-Septemb er, 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-sc ale precipitation decreases as the circumpolar trough moves closer to Antarctica in response to the sea-ice removal. Positive and negative a nomalies form a wave-like train in the troposphere. The anomalies incl ude the delayed onset of the winter monsoon over northern China during September. This result is in basic agreement with an observational st udy that found monsoon parameters are correlated with Antarctic sea-ic e characteristics. In addition, the mean meridional circulation and co nvective precipitation have a monthly modulation of roughly 5% in the tropics. Mechanisms for the global atmospheric propagation of the impa ct of the Southern Ocean surface heating anomalies are examined.