The linkage between Arctic sea ice changes and mid-latitude atmospheric circulation in reanalysis data and model simulations - The role of tropo-stratospheric coupling

摘要

Observed global warming trends have their maximum in Arctic regions, a phenomenon referred to as Arctic Amplification. Consequently, Arctic sea ice shows a strong decreasing trend. These changes imprint modifications on atmospheric flow patterns not only in Arctic regions themselves. Changes of teleconnections and planetary scale motions like Rossby waves affect mid-latitude climate as well.ududWe identified mechanisms that link recent Arctic changes through vertically propagating planetary waves to weakening events of the stratospheric polar vortex. Related anomalies then propagate downward and lead to negative AO-like situations in the troposphere. These results based on ERA-Interim reanalysis data do not allow to entirely dismiss other potential forcing factors leading to observed mid-latitude climate changes. More importantly, properly designed Atmospheric General Circulation Model (AGCM) experiments with AFES and ECHAM6 are able to reproduce observed atmospheric circulation changes if only observed sea ice changes in the Arctic are prescribed. This includes the potential mechanism explaining how Arctic Amplification can lead to a negative AO response via a stratospheric pathway. A further examination of barotropic-baroclinic interactions based on nonlinear kinetic energy and enstrophy interaction will be given by Handorf et al. (abstract submitted).