Projected changes of the Northern Annular Mode linked to seasonality of
the ENSO teleconnection
Abstract
The Northern Annular Mode (NAM) is the dominant pattern of atmospheric
circulation variability in the wintertime Northern Hemisphere
extratropics. This study utilizes a large ensemble atmospheric
simulation dataset to examine the seasonality of the NAM variability and
its modulations under global warming. We show an enhancement of the
Aleutian Low anomaly associated with the NAM in a warmer climate. This
enhancement is related to the emergence of the Aleutian-Icelandic Low
seesaw (AIS) from early winter, which is in contrast prominent only in
late winter in the historical climate. The large ensemble reveals a
significant increase in the fraction of the NAM variance explained by
sea surface temperature and sea ice variability, suggesting a higher
potential predictability. In particular, the eastward extension of the
El Niño-Southern Oscillation (ENSO) teleconnection under global warming
contributes to the AIS formation even in early winter and a higher
NAM-ENSO correlation.