Investigating the Influence of Anomalous Heating Related to Arctic Amplification on Wintertime Stationary Wave Activity: An Idealized Approach

Abstract:

Recently there has been a raft of manuscripts which claim to show that arctic amplification (AA, largely due to increased thermal forcing around the time of the late-summer sea-ice minimum) is responsible for broad changes in the large-scale wintertime mid-latitude atmospheric circulation patterns and could even lead to an increase in extreme weather events. A number of responses to these studies have shown that the results are likely artefacts of the chosen methodology, but do not discount the potential influence of AA on the mid-latitude circulation. Relatively few studies have demonstrated physical mechanisms or physical pathways by which AA may drive a lagged atmospheric response. In this investigation we employ a linear stationary wave model to investigate the hypothesis that AA, in the form of a low-level anomalous heating of the atmosphere, may drive a lagged mid-latitude circulation response. A change in the quasi-stationary wave pattern may be regarded as a necessary though not sufficient condition for any subsequent changes in the frequency, timing or magnitude of extreme events. The low-order model is well suited to the question due to its ability to reproduce the observed atmospheric circulation, and its simplicity – as it requires only four forcing components plus the zonal mean state from reanalysis or a GCM, interpreting the model results is relatively straightforward. An ensemble of simulations are performed with idealized low-level diabatic heatings imposed in regions matching the observed thermal anomaly maxima during the record sea-ice minimum event of 2012. The preliminary results are presented here and we evaluate the atmospheric response of the mid-latitude stationary waves, if any, to the heating and identify the driving mechanisms.