Yuko M. Okumura
National Center for Atmospheric Research
|When:||Friday, April 08, 2011, 10:30 p.m. to 11:30 p.m.|
|Where:||Seminar Conference Room, 10100 Burnet Road, Bldg 196-ROC, Austin, Texas 78758|
|Host:||Charles Jackson, UTIG|
The Antarctic continent holds about 90% of the global ice and plays an important role in a changing climate. Antarctic climate variability is, however, poorly understood beyond interannual time scales mainly due to the paucity of long, reliable meteorological observations. The present study explores the nature and cause of low-frequency climate variability over Antarctica through analysis of various instrumental data and annually-resolved ice core and coral records for the past 100-200 years. During the 20th century, Antarctic ice core records indicate strong linkages to sea surface temperature (SST) variations in the tropical Pacific and Atlantic on decadal-multidecadal time scales. Antarctic surface temperature anomalies inferred from the ice cores are consistent with the associated changes in atmospheric circulation and thermal advection. A set of atmospheric general circulation model experiments supports the idea that the decadal SST variations in the tropics force atmospheric teleconnections that affect Antarctic surface temperatures. When coral records are used as proxies of tropical SSTs, similar Antarctic-tropical linkages are identified for the past two centuries. Over the past 50 years, a change in the phase of Pacific and Atlantic interdecadal variations may have contributed to the rapid warming of the Antarctic Peninsula and West Antarctica.