Unraveling the Origins of Intermodel Discrepancies in Simulating the Aleutian–Icelandic Low Seesaw.
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| Title: | Unraveling the Origins of Intermodel Discrepancies in Simulating the Aleutian–Icelandic Low Seesaw. |
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| Authors: | Hu, Zhehan1,2,3 (AUTHOR), Chen, Shangfeng1,2,3 (AUTHOR) chenshangfeng@mail.iap.ac.cn, Yu, Bin4 (AUTHOR), Chen, Wen5 (AUTHOR), Ju, Xiaoming1,2,3 (AUTHOR) |
| Source: | Journal of Climate. Feb2026, Vol. 39 Issue 3, p941-959. 19p. |
| Subjects: | Jet streams, Atmospheric models, Atmospheric circulation, Theory of wave motion, Teleconnections (Climatology), Climate change |
| Geographic Terms: | North Atlantic Ocean, Pacific Ocean, Atlantic Ocean, Northern Hemisphere, North America, North Pacific Ocean |
| Abstract: | The Aleutian–Icelandic low seesaw (AIS), characterized by an out-of-phase relationship between the Aleutian low (AL) and the Icelandic low (IL), plays a critical role in modulating Northern Hemisphere atmospheric circulation and climate variability. This study evaluates the representation of AIS in 57 models from the Coupled Model Intercomparison Project phase 6 (CMIP6) and investigates the mechanisms underlying intermodel discrepancies. Observations reveal a robust AIS correlation during January–March, linked to a Pacific–North American (PNA)-like wave train that transmits energy from the North Pacific to the North Atlantic. However, CMIP6 models systematically underestimate AIS intensity, with only 11 models simulating correlations stronger than observed. Intermodel differences in AIS intensity are primarily attributed to variations in wave propagation efficiency. Stronger AIS signals are linked to more coherent Plumb wave fluxes over the North Pacific and North America above 300 hPa. These fluxes are influenced by the East Asian subtropical jet through modulation of meridional heat transport and by the Atlantic polar jet via the waveguide effect. Furthermore, the strength of the AIS appears to influence the Pacific center of the Arctic Oscillation (AO), with stronger AIS associated with a more prominent AO Pacific center across models. In addition, the underestimation of the wave flux anomalies at the tropopause, the reduced zonal asymmetry of the background flow in the upper troposphere, and the insufficient representation of the polar-vortex-related wave reflection mechanism may account for the model biases in the AIS representation. Significance Statement: The Aleutian–Icelandic low seesaw (AIS) is a critical atmospheric teleconnection that links climate variability between the North Pacific and North Atlantic, with far-reaching impacts on Northern Hemisphere climate. Although its dynamics have been well studied observationally, its simulation in state-of-the-art climate models remains poorly understood. This study provides a comprehensive evaluation of AIS representation in 57 Coupled Model Intercomparison Model phase 6 (CMIP6) models. We find that most models systematically underestimate AIS intensity compared to reanalysis, primarily due to insufficient wave energy propagation connecting the North Pacific and North Atlantic. These biases are linked to weak zonal asymmetries, unrealistic stratospheric feedbacks, and deficiencies in simulating jet streams. Our findings reveal fundamental limitations in current climate models' ability to capture transbasin teleconnections and stratosphere–troposphere interactions. This work underscores the importance of improving wave dynamics and jet representation in next-generation models to enhance predictive skill for mid–high-latitude climate variability. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | The Aleutian–Icelandic low seesaw (AIS), characterized by an out-of-phase relationship between the Aleutian low (AL) and the Icelandic low (IL), plays a critical role in modulating Northern Hemisphere atmospheric circulation and climate variability. This study evaluates the representation of AIS in 57 models from the Coupled Model Intercomparison Project phase 6 (CMIP6) and investigates the mechanisms underlying intermodel discrepancies. Observations reveal a robust AIS correlation during January–March, linked to a Pacific–North American (PNA)-like wave train that transmits energy from the North Pacific to the North Atlantic. However, CMIP6 models systematically underestimate AIS intensity, with only 11 models simulating correlations stronger than observed. Intermodel differences in AIS intensity are primarily attributed to variations in wave propagation efficiency. Stronger AIS signals are linked to more coherent Plumb wave fluxes over the North Pacific and North America above 300 hPa. These fluxes are influenced by the East Asian subtropical jet through modulation of meridional heat transport and by the Atlantic polar jet via the waveguide effect. Furthermore, the strength of the AIS appears to influence the Pacific center of the Arctic Oscillation (AO), with stronger AIS associated with a more prominent AO Pacific center across models. In addition, the underestimation of the wave flux anomalies at the tropopause, the reduced zonal asymmetry of the background flow in the upper troposphere, and the insufficient representation of the polar-vortex-related wave reflection mechanism may account for the model biases in the AIS representation. Significance Statement: The Aleutian–Icelandic low seesaw (AIS) is a critical atmospheric teleconnection that links climate variability between the North Pacific and North Atlantic, with far-reaching impacts on Northern Hemisphere climate. Although its dynamics have been well studied observationally, its simulation in state-of-the-art climate models remains poorly understood. This study provides a comprehensive evaluation of AIS representation in 57 Coupled Model Intercomparison Model phase 6 (CMIP6) models. We find that most models systematically underestimate AIS intensity compared to reanalysis, primarily due to insufficient wave energy propagation connecting the North Pacific and North Atlantic. These biases are linked to weak zonal asymmetries, unrealistic stratospheric feedbacks, and deficiencies in simulating jet streams. Our findings reveal fundamental limitations in current climate models' ability to capture transbasin teleconnections and stratosphere–troposphere interactions. This work underscores the importance of improving wave dynamics and jet representation in next-generation models to enhance predictive skill for mid–high-latitude climate variability. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 08948755 |
| DOI: | 10.1175/JCLI-D-25-0322.1 |
