The El Niño-Southern Oscillation modulation of West Antarctic precipitation

ino periods.Atmospheric numerical analyses from the European Centre for Medium-Range Weather Forecasts(ECMWF) are used to compute the moisture flux convergence, and thus the net flux of water to the Earth's surface, or P-E, for a sector of West Antarctica (120 degrees W - 180 degrees, 75 degrees S - 90 degrees S) for 1980-1998. P-E closely approximates snow accumulation for most parts of the ice sheet. A close relation between P-E and the Southern Oscillation Index (SOI) is present for the entire period. The variations are in phase for the early 1980s to 1990, and then abruptly switch to antiphase for 1990-1998. Ground-based accumulation and deuterium isotope concentrations provided by annually and sub-annually dated ice cores from the sector provide strong qualitative support for the derived accumulation variations. The atmospheric circulation is examined for the strong El Nino events in 1982/83 and 1997/98. These respectively occur before and after the switch in association between the SOI and P-E, and are characterized by low and high precipitation amounts. In the former case the local circulation is organized to deliver limited amounts of moisture to the sector while during the 1997/98 event moisture flows into the sector directly from the ocean in a deep atmospheric layer. On the broadscale, the circulation characteristics are quite similar for both El N