Decadal phase shift of summertime Arctic dipole pattern and its nonlinear effect on sea ice extent

The rapid decline in Arctic sea ice during recent decades has been attributed to the combined influence of global warming and internal climate variability. Herein, we elucidate the process by which the decrease in sea ice is accelerated in association with the decadal phase shift of the Arctic dipol...

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Bibliographic Details
Published in:International journal of climatology 2021-07, Vol.41 (9), p.4732-4742
Main Authors: Heo, Eun‐Sook, Sung, Mi‐Kyung, An, Soon‐Il, Yang, Young‐Min
Format: Article
Language:English
Subjects:
Arctic dipole pattern
Arctic observations
Arctic sea ice
Arctic sea ice extent
Arctic zone
Atmospheric circulation
Atmospheric circulation patterns
Climate change
Climate variability
decadal variability
Dipoles
Global warming
Ice environments
Ice melting
Phase shift
Polar environments
Sea ice
State of sea
Summer
Summer circulation
Variability
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Summary:The rapid decline in Arctic sea ice during recent decades has been attributed to the combined influence of global warming and internal climate variability. Herein, we elucidate the process by which the decrease in sea ice is accelerated in association with the decadal phase shift of the Arctic dipole (AD), using observational data and Community Earth System Model (CESM1) simulations. The influence of the AD on Arctic sea ice varied according to its phase; in the negative‐AD decades (1979–1998), atmospheric circulation during summers of positive phase AD acts to reduce the sea ice extent (SIE) in the Pacific sector but increases it in the Atlantic sector. In contrast, in the positive‐AD decades (after 1999), the same atmospheric circulation pattern reduces the SIE in both sectors, resulting in enhanced sea ice melting across the entire Arctic region. A similar nonlinear relationship between the AD phase and SIE change is also observed in CESM1 Pre‐Industrial simulations, which stem from altered background temperature conditions between periods, implying the significant role of internal variability, particularly over the Atlantic sector. However, contrary to the recently observed AD trend, CESM1 Large Ensemble experiments predicted a negative AD trend as global warming proceeded. This suggests that the recent positive AD phase may be naturally driven, but the current state of sea ice decline associated with AD could be altered in the near future because of enhanced global warming. Regression maps of sea ice concentration (SIC) anomalies during October–November (ON) against AD index (shading) from observational data for (a) 1979–1998 (P1) and (b) 1999–2017 (P2). Equivalent regression maps obtained through Pre‐industrial experiments of CESM1 for (c) AD negative decades and (d) AD positive decades. The red box indicates the Barents–Kara Sea region (70–85°N, 20–80°E). The units of the regression maps are percentile, and the hatched region indicates significance at the 90% confidence level (observation) and 95% confidence level (model).
ISSN:0899-8418
1097-0088
DOI:10.1002/joc.7097