资源环境科技发展态势分析平台

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 similar to 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 Nino-Southern Oscillation (ENSO)/SAM combinations that influence the depth of the ASL over the central Amundsen Sea (near 105 degrees W). The second EOF (EOF2) during autumn, winter, and spring (explaining similar to 15%-20% of the variability) consists of a dipole shifted approximately 30 degrees 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 degrees 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.