EGU23-5969
https://doi.org/10.5194/egusphere-egu23-5969
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Winter North Atlantic jet variability under global warming: Past trends and future projections 

Alejandro Hermoso and Sebastian Schemm
Alejandro Hermoso and Sebastian Schemm
  • ETH Zurich, Institute for Atmospheric and Climate Science, Department of Environmental Systems Science, Zürich, Switzerland (alejandro.hermoso@env.ethz.ch)

Regional weather variability and the occurrence of extreme weather events are highly connected to the position of jet streams. Climate models generally project a poleward shift of the jets under the influence of anthropogenic warming. However, ERA5 reanalysis data show that the North Atlantic jet stream in winter has roughly remained in place. We investigate the mechanisms that lead to this behavior.  The analysis reveals that upper-level temperature trends produce a reduction in stability that leads to an increase in baroclinicity. Furthermore, momentum convergence is also intensified across the jet core, producing an acceleration of the jet and not a weakening as suggested by arguments based solely on the Artic amplification. 

 

Numerical simulations from an ensemble of fully coupled climate simulations run with the Community Earth System Model under the SSP3.7 scenario are also analyzed along with idealized warming experiments in an aquaplanet setup with a zonal asymmetry in sea surface temperature. The climate simulations exhibit a large spread during the historical period and only a few ensemble members reproduce the observed trends, suggesting that trends only based on ensemble means could lead to misleading projections. Additionally, the aquaplanet runs display high sensitivity to the location of the asymmetry. This provides a supplementary argument in support of inspecting all individual climate projections as small variations in the original jet position can lead to large disparities in the projected trends. 

How to cite: Hermoso, A. and Schemm, S.: Winter North Atlantic jet variability under global warming: Past trends and future projections , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5969, https://doi.org/10.5194/egusphere-egu23-5969, 2023.

Supplementary materials

Supplementary material file