Projected Changes of the Northern Annular Mode Linked to Seasonality of the ENSO Teleconnection

Abstract The Northern Annular Mode (NAM) induces anomalous wintertime weather over the extratropical Northern Hemisphere as the leading mode of atmospheric circulation variability. Yet, modulations of its statistical properties in a changing climate need elucidating. This study investigates the seasonality of NAM variability and its modulations under global warming with a large‐ensemble atmospheric simulation data set. We find that the Aleutian Low anomaly associated with the NAM strengthens in a warmer climate, which is linked to a seasonally earlier emergence of the Aleutian‐Icelandic Low seesaw (AIS). The El Niño‐Southern Oscillation (ENSO) teleconnection extends more eastward under global warming, which increases the ENSO‐NAM correlation through the earlier AIS development. Our findings suggest increased predictability of the NAM under global warming, with uncertainties due to potential ENSO changes.