Arctic Amplification & Sea-Ice Loss

Arctic amplification—defined as the accelerated near-surface warming of the Arctic relative to the global mean—is closely connected to sea-ice loss. These changes have important implications not only for high-latitude climate but also for large-scale atmospheric and oceanic circulation.

Atmospheric circulation responses to polar sea-ice loss typically have a low signal-to-noise ratio, making them challenging to detect from the short observational record alone. Targeted climate-model experiments offer a powerful way to quantify the sea-ice influence. In atmosphere-only experiments, we perturb sea-ice conditions while holding other boundary conditions fixed. In fully coupled models, sea-ice changes can also be imposed through albedo perturbations or nudging approaches.

My research leverages these targeted experiments to isolate the forced response to Arctic sea-ice loss and to understand how internal variability, background state, and model resolution shape the resulting circulation changes.

Scientific Questions

  • How does Arctic sea-ice loss influence large-scale atmospheric circulation, and how do these responses depend on the background state?

  • What roles do internal variability and signal-to-noise ratio play in shaping the detectability of sea-ice-induced circulation changes?

  • How do different modeling strategies, including atmosphere-only and fully coupled approaches, affect attribution of forced responses to sea-ice loss?

  • To what extent does model resolution influence the simulated dynamical response to Arctic sea-ice change?

Recent Findings

Using CESM sea-ice experiments designed following the PAMIP protocol, we assess the relative importance of stratospheric response versus internal variability. We find that the stratospheric polar vortex response to sea-ice loss is small compared with intrinsic variability, and that this variability strongly influences the detectability (signal-to-noise ratio) of the wintertime tropospheric response.

Boreal winter (DJF) zonal-mean zonal wind response (shading; m/s) to future Arctic sea-ice loss as a function of pressure (hPa; y-axis) and latitude (x-axis) based on targeted CESM2 simulations: (a) all 200 members; (b) members 1–100; and (c) members 101–200. Black contours (interval of 10 m/s; zero contour thickened) indicate the climatology. Stippling indicates 90% significance based on a two-sided Student’s t-test with false discovery rate adjustment. Adopted from Sun et al. (2022).

Boreal winter (DJF) zonal-mean zonal wind response (shading; m/s) to future Arctic sea-ice loss as a function of pressure (hPa; y-axis) and latitude (x-axis) based on targeted CESM2 simulations: (a) all 200 members; (b) members 1–100; and (c) members 101–200. Black contours (interval of 10 m/s; zero contour thickened) indicate the climatology. Stippling indicates 90% significance based on a two-sided Student’s t-test with false discovery rate adjustment. Adopted from Sun et al. (2022).

  • Sensitivity of sea-ice-loss-induced atmospheric response to stratospheric basic state, and how it can be used to constrain the PAMIP multi-model ensemble. (Sigmond and Sun 2024; 2025)

  • Influence of future Arctic sea-ice loss on North American daily weather patterns. (Gervais et al. 2024)

  • Arctic sea-ice-loss impacts on Northern Hemisphere summertime storminess and heat extremes. (Kang et al. 2023; Wu et al. 2025)

On-going Work

  • Arctic sea-ice-loss effects in the Arctic-refined CESM (Sun et al. 2025, in review)

  • Co-leading the development of the PAMIP Phase-2 modeling protocol.

References

  • Gervais, M., L. Sun, C. Deser, 2024: Impacts of Projected Arctic Sea Ice Loss on Daily Weather Patterns over North America, J. Climate, 37, 1065–1085. [Link].

  • Kang, J., T. Shaw and L. Sun, 2023: Arctic Sea Ice Loss Weakens Northern Hemisphere Summertime Storminess but Not Until the Late 21st Century, Geophys. Res. Lett., 50, e2022GL102301. [Link].

  • Sigmond, M. and L. Sun, 2024: The role of the basic state in the climate response to future sea ice loss, Environ. Res. Climate, 3, 031002. [Link].

  • Sigmond, M. and L. Sun, 2025: Atmospheric jet stream response to future Arctic sea ice loss not underestimated by climate models, NPJ Clim. Atmos. Sci., Accepted.

  • Sun, L., C. Deser, I. Simpson and M. Sigmond, 2022: Uncertainty in the winter atmospheric response to Arctic sea ice loss: the role of stratospheric polar vortex internal variability, J. Climate, 35, 3109–3130. [Link].

  • Sun, L., R. Wills, C. Deser, A. Herrington, I. Simpson, M. Gervais, 2025: Increased Model Resolution Amplifies Arctic Precipitation and Atmospheric Circulation Response to Sea-Ice Loss, J. Climate, in review. [Preprint].

  • Wu, Y., L. Sun and O. Terry, 2025: Can Arctic Sea Ice Melting Lead to More Summertime Heat Extremes? Geophys. Res. Lett., 52, e2025GL116668. [Link].

Learn More

See additional details in the Publications section.

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