Abstract
Precipitation data from the new ERA40 reanalyses and from a 200‐year simulation confirm a robust main mode of precipitation variability in west Antarctica. An intermittently strong ENSO signature is found in this mode. However, high correlation with ENSO indices appears infrequent. Thus, the high correlation found in ERA40, and previously in other chronologically realistic data, in the late 1980s and the 1990s may not be expected to last. Unlike previously suggested by others, the sign of the correlation between ENSO indices and west Antarctic precipitation, when significant, does not appear to change in time: Precipitation variability at the ENSO pace in the Bellingshausen‐Weddell (Ross‐Amunsden) region is consistently in phase (phase opposition, respectively) with the Southern Oscillation Index. This is consistent with a tropospheric wave train connecting the tropical Pacific and west Antarctic regions, which modulates in phase opposition the advection of air and moisture in the 2 regions.
Highlights
[4] To do so, longer and alternative datasets are used, namely the new ERA40 meteorological reanalysis and forecasts database, and a 200-year coupled atmosphereocean general circulation model (AOGCM) simulation, both of which are presented in section 2 along with the analysis methods
[2] Hints of an ENSO signature in Antarctic precipitation have been reported in the past [e.g., Cullather et al, 1996; Bromwich et al, 2000] and challenged [e.g., Genthon and Krinner, 1998]
From meteorological analyses and climate model results, Genthon et al [2003] show that the Antarctic tropospheric circulation variability is dominated by two modes, a 1st one related to the Antarctic Oscillation (AAO), and a 2nd one to the ENSO
Summary
[2] Hints of an ENSO signature in Antarctic precipitation have been reported in the past [e.g., Cullather et al, 1996; Bromwich et al, 2000] and challenged [e.g., Genthon and Krinner, 1998]. Facing the Pacific ocean, west Antarctica is likely the Antarctic region most directly exposed to ENSO. Tropospheric wave trains [Trenberth and Carron, 2000; Kidson and Renwick, 2002] have been identified, which connect the tropical Pacific to the west Antarctic seas and coasts at the ENSO pace. From meteorological analyses and climate model results, Genthon et al [2003] show that the Antarctic tropospheric circulation variability is dominated by two modes, a 1st one related to the Antarctic Oscillation (AAO), and a 2nd one to the ENSO. Both modes have a strong pole of variability in west Antarctica.
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