Testing of the tropically excited arctic warming mechanism (TEAM) with traditional el Niño and la Niña

Abstract

By analyzing El Niño and La Ninña composites with 40-yr European Centre for Medium-Range Weather Forecasts(ECMWF) Re-Analysis (ERA-40) data, evidence is presented here that the surface air temperature of the Arctic winter (December-February) is anomalously warm during La Niña and cold during El Niño. Surface and top-of-the-atmosphere energy fluxes were used to calculate the composite zonal-mean poleward moist static energy transport. The result shows that the La Niña warming in the Arctic is associated with an increased poleward energy transport in the extratropics. The opposite characteristics are found for El Niño. Because the total tropical convective heating is more localized during La Niña than El Niño, these findings suggest that the Arctic surface air temperature anomalies associated with ENSO may be attributed to the tropically excited Arctic warming mechanism (TEAM). In the tropics, consistent with previous studies, the anomalous poleward energy transport is positive during El Niño and negative during La Niña. Given the debate over whether a warmer world would take on more El Niño-like or La Niña-like characteristics, the findings of this study underscore the need for further investigation of tropical influence on polar climate. © 2012 American Meteorological Society.