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<p>Antarctic climate has experienced dramatic changes in recent decades. However, a systematic investigation into externally forced Antarctic amplification (AnA) remains limited. This study examines forced AnA from 1959 to 2014, utilizing over 300 ensemble members from six large ensemble simulations: ACCESS-ESM1.5, CESM2, FGOALS-g3, GFDL-SPEAR-MED, MIROC6, and MPI-ESM1-2-LR. Antarctic surface air temperature (SAT) trends exhibit considerable inter-member spread, with external forcing explaining between 72% (GFDL-SPEAR-MED) and 86% (FGOALS-g3) of the annual trends. On both annual and seasonal scales, the warming magnitude derived from the multi-member mean (MME) is weaker than that of ERA5. After estimating and removing the effects of Antarctic mode (AM), Interdecadal Pacific Oscillation (IPO), and El Niño-Southern Oscillation (ENSO) on SAT changes, the externally forced AnA index (AnAI) ranges from 1.48 (MIROC6) to 1.69 (CESM2) annually. Surface downward longwave radiation (FLDS), along with downward latent and sensible heat fluxes, plays an important role in mediating the impacts of IPO and ENSO on Antarctic SAT variability. Both IPO and ENSO contribute to Antarctic warming by intensifying 500 hPa geopotential height, which promotes the poleward advection of warm, moist air. This process increases specific humidity and subsequently enhances FLDS. Notably, the effect of IPO on FLDS is more pronounced over East Antarctica, whereas ENSO exerts a stronger influence over West Antarctica. In the surface energy balance, thermal forcing plays a more critical role than humidity advection. The inter-member spread in SAT trends is partly associated with IPO. Externally forced AnA presents seasonal differences, with the most pronounced amplification occurring during austral winter. Since 2000, IPO contributed to a slowdown in Southern Hemisphere warming, coupled with AM amplified Antarctic warming; both processes acted in concert to enhance recent AnA. In summary, over the historical period, externally forced AnAI remained consistently close to 1.50 on an annual scale.</p>

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Antarctic amplification in external forcing: Insights from large ensemble simulations

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Jiangping Zhu,
  • Aihong Xie,
  • Shimeng Wang,
  • Xiang Qin,
  • Bowei Li

摘要

Antarctic climate has experienced dramatic changes in recent decades. However, a systematic investigation into externally forced Antarctic amplification (AnA) remains limited. This study examines forced AnA from 1959 to 2014, utilizing over 300 ensemble members from six large ensemble simulations: ACCESS-ESM1.5, CESM2, FGOALS-g3, GFDL-SPEAR-MED, MIROC6, and MPI-ESM1-2-LR. Antarctic surface air temperature (SAT) trends exhibit considerable inter-member spread, with external forcing explaining between 72% (GFDL-SPEAR-MED) and 86% (FGOALS-g3) of the annual trends. On both annual and seasonal scales, the warming magnitude derived from the multi-member mean (MME) is weaker than that of ERA5. After estimating and removing the effects of Antarctic mode (AM), Interdecadal Pacific Oscillation (IPO), and El Niño-Southern Oscillation (ENSO) on SAT changes, the externally forced AnA index (AnAI) ranges from 1.48 (MIROC6) to 1.69 (CESM2) annually. Surface downward longwave radiation (FLDS), along with downward latent and sensible heat fluxes, plays an important role in mediating the impacts of IPO and ENSO on Antarctic SAT variability. Both IPO and ENSO contribute to Antarctic warming by intensifying 500 hPa geopotential height, which promotes the poleward advection of warm, moist air. This process increases specific humidity and subsequently enhances FLDS. Notably, the effect of IPO on FLDS is more pronounced over East Antarctica, whereas ENSO exerts a stronger influence over West Antarctica. In the surface energy balance, thermal forcing plays a more critical role than humidity advection. The inter-member spread in SAT trends is partly associated with IPO. Externally forced AnA presents seasonal differences, with the most pronounced amplification occurring during austral winter. Since 2000, IPO contributed to a slowdown in Southern Hemisphere warming, coupled with AM amplified Antarctic warming; both processes acted in concert to enhance recent AnA. In summary, over the historical period, externally forced AnAI remained consistently close to 1.50 on an annual scale.