Recorded presentation1.5
South Pacific ENSO teleconnection variations linked to the SAM
Ryan L. Fogt, NOAA Earth System Research Laboratory, Boulder, CO; and D. H. Bromwich and K. M. Hines
High latitude South Pacific El Niño – Southern Oscillation (ENSO) teleconnection variability associated with phases of the Southern Hemisphere Annular Mode (SAM) events is examined. The primary focus is on multi-month, multi-event variations during the last 50 years, thereby highlighting the mean impacts of the joint ENSO-SAM distribution. Extending the study period to 50 years has allowed confirmation of findings that were indicated by analysis of the modern satellite era (1979-present). The main results indicate that when ENSO is in phase with the SAM, the teleconnection is amplified and remains statistically different than climatology. In contrast, when ENSO is out of phase with the SAM, the teleconnection is significantly weakened, especially during La Niña events. Through examining the zonal asymmetries of the Southern Hemisphere atmospheric circulation, it is clear when the two modes are out of phase that the influence of strong SAM events alters the mean flow and subsequently blocks the propagation of the tropical ENSO teleconnection to the high southern latitudes. As both ENSO and SAM have been linked to Antarctic climate variations, especially in West Antarctica, unlocking their combined impacts is necessary to both better understand the historical variations from ice cores and the reliability of future climate projections. The latter is of paramount interest, as currently the most marked changes across Antarctica in terms of ice loss and warming are in the regions most strongly influenced by ENSO and SAM, namely West Antarctica and the Antarctic Peninsula. We demonstrate this fact by concluding with a discussion of the 2007-2008 austral summer, a year marked with both a strong La Niña event and a positive phase SAM event (i.e., ENSO and SAM were in phase). The combined impact of these modes aided in generating the maximum December Antarctic sea ice extent on record in 2007.
Session 1, Polar Weather and Climate Variations (Present)
Monday, 18 May 2009, 8:30 AM-10:00 AM, Capitol Ballroom AB
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