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During the second half of the twentieth century, the Antarctic Surface Air Temperature (SAT) trends are characterized by fast warming over West Antarctica but mild cooling over East Antarctica. However, after 2000, the warming over several stations in the Antarctic Peninsula slowed down, whereas the South Pole experienced fast warming. These reversed SAT trends show strong regionality and seasonality, together with large uncertainty and disagreement among different observational and reanalysis datasets, which makes it difficult to achieve a comprehensive understanding of the multi-decadal Antarctic SAT trend and its reversal. In this study, we use the Combined Maximum Covariance Analysis (CMCA) method to extract the most coherent modes of the Antarctic SAT trends among six reanalysis datasets and 26 station-based observations. Further analysis shows that the reversals of the SAT trends before and after 2000, especially for austral spring and summer, are mainly attributed to the reversed trends of the leading CMCA modes and their related atmospheric circulation and thermal advection patterns over Antarctica. For austral spring, the reversal of the west-warming-east-cooling pattern over Antarctica is closely related to the changes of thermal advection induced by the anomalous circulation center over the Antarctic Peninsula–Weddell Sea region. For summer, the post-2000 reversal of the Antarctic Peninsula-warming-East Antarctic-cooling is attributed to the stratospheric ozone recovery over the Antarctic, and the associated adjustment of the southern annular mode. The CMCA decomposition better combines the information from different measurements, clarifying the long-term SAT trend and its reversal for different seasons. [ABSTRACT FROM AUTHOR]

Using empirical orthogonal function (EOF) analysis and atmospheric reanalyses, the principal patterns of seasonal West Antarctic surface air temperature (SAT) and their connection to sea ice and the Amundsen Sea low (ASL) are examined. During austral summer, the leading EOF (EOF1) explains 35% of West Antarctic SAT variability and consists of a widespread SAT anomaly over the continent linked to persistent sea ice concentration anomalies over the Ross and Amundsen Seas from the previous spring. Outside of summer, EOF1 (explaining ~40%-50% of the variability) consists of an east-west dipole over the continent with SAT anomalies over the Antarctic Peninsula opposite those over western West Antarctica. The dipole is tied to variability in the southern annular mode (SAM) and in-phase El Niño-Southern Oscillation (ENSO)/SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105°W). The second EOF (EOF2) during autumn, winter, and spring (explaining ~15%-20% of the variability) consists of a dipole shifted approximately 30° west of EOF1 with a widespread SAT anomaly over the continent. During winter and spring, EOF2 is closely tied to variability in ENSO and a tropically forced wave train that influences the ASL in the western Amundsen/eastern Ross Seas (near 135°W) with an opposite-sign circulation anomaly over the Weddell Sea; the ENSO-related circulation brings anomalous thermal advection deep onto the continent. The authors conclude that the ENSO-only circulation pattern is associated with SAT variability across interior West Antarctica, especially during winter and spring, whereas the SAM circulation pattern is associated with an SAT dipole over the continent. [ABSTRACT FROM AUTHOR]