4a.2
The Antarctic Dipole and its predictability
Xiaojun Yuan, Lamont-Doherty Earth Observatory, Columbia Univ., Palisades, NY; and D. Martinson
Antarctic sea ice field has demonstrated strong interannual variability. Some of the variability existed in forms of propagating wave and others are associated with the atmospheric standing waves. Sea ice extent in many areas of the Antarctic has been suggested to be associated with the tropical climate variation such as ENSO events. This study clarifies the wave type of the strongest variability existed in the sea ice extent field and explores the possibility of forecasting this variability using easily observed surface temperature. The sea ice edge in the central/eastern Pacific and Atlantic sectors of the Antarctic shows larger variability than other regions. The ice edge in these two regions usually has an out-phase relationship, which we call the "Antarctic Dipole". The dipole consists of a strong standing mode and small propagating motion with each basin. It makes up dominant part of the Antarctic Circumpolar Wave in the area. The dipole is clearly associated with the ENSO events in the tropics. Using a simple linear regression model and surface air temperature two months ahead, we can predict an Antarctic Dipole Index with a relatively good skill (explains 42% of total Dipole variance). The prediction performs better in the extreme warm and cold years. The Antarctic Dipole is most predictable in La Niņa years.
Session 4a, Upper-Ocean/Sea Ice Exchanges (Parallel with Session 4B)
Thursday, 17 May 2001, 1:30 PM-3:00 PM
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