Robustness of the stratospheric pathway in linking the Barents-Kara Sea sea ice variability to the mid-latitude circulation in CMIP5 models

摘要

This study investigates the robustness of the stratospheric pathway in linking the sea ice variability over the Barents-Kara Sea in late autumn and early winter to the mid-latitude circulation in the subsequent winter. Two groups of models from the Coupled Model Intercomparison Project phase 5 (CMIP5) archive, one with a well-resolved stratosphere (high-top models) and the other with a poorly-resolved stratosphere (low-top models) are explored to distinguish the role of the stratospheric pathway. The results show that, collectively, high-top models are able to capture the persistent mid-latitude circulation response in the subsequent winter. The response in low-top models is, however, weaker and not as long-lasting most likely due to lack of stratospheric variability. Analysis of eddy heat flux reveals that stronger vertical wave propagation leads to a stronger response in stratospheric polar vortex in high-top models. In particular, it shows that zonal wave-2 eddy heat flux is crucial in leading to a stronger linear constructive interference with the climatological waves in high-top models. The results find that multi-model ensemble of CMIP5 high-top models is able to capture the prolonged impact of sea ice variability on the mid-latitude circulation and out performs the low-top models in this regard. Our study suggests that the representation of the stratosphere in climate models plays an important role in amplifying and extending the mid-latitude circulation response.