Troposphere‐stratosphere dynamical coupling in the southern high latitudes and its linkage to the Amundsen Sea

Extremes in the distribution of Southern Hemisphere stratospheric heat flux are connected simultaneously to anomalous high‐latitude tropospheric weather patterns in reanalysis, consistent with results from the Northern Hemisphere. The dynamical links are revealed using a metric based on extreme stratospheric planetary‐scale wave heat flux events, defined as the 10th and 90th percentiles of the daily high‐latitude wave 1 heat flux distribution at 50 hPa. We show extreme negative (positive) heat flux events are linked to a westward (eastward) shift in the Amundsen Sea Low and anomalous warming (cooling) over the Amundsen Bellingshausen Seas in reanalysis data. Since coupling to the stratosphere via planetary waves has significant impacts on the tropospheric circulation of both hemispheres, it is important to understand which coupled climate models can reproduce this phenomenon. The heat flux metric is used to evaluate troposphere‐stratosphere coupling in models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and compare their performance across hemispheres. The results show that models with a degraded representation of stratospheric extremes exhibit robust biases in tropospheric sea level pressure variability over the Antarctic Peninsula. Models which fail to capture the extremes in stratospheric heat flux, significantly underestimate the variance of the distribution of mean sea level pressure anomalies over Western Antarctica.