loading page

Projected changes of the Northern Annular Mode linked to seasonality of the ENSO teleconnection
  • +1
  • Takashi Kawamura,
  • Yu Kosaka,
  • Satoru Okajima,
  • Hisashi Nakamura
Takashi Kawamura
Tokyo Daigaku Sentan Kagaku Gijutsu Kenkyu Center

Corresponding Author:[email protected]

Author Profile
Yu Kosaka
University of Tokyo
Author Profile
Satoru Okajima
Tokyo Daigaku Sentan Kagaku Gijutsu Kenkyu Center
Author Profile
Hisashi Nakamura
University of Tokyo
Author Profile

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.