Horizontal Temperature Fluxes in the Arctic in CMIP5 Model Results Analyzed with Self-Organizing Maps

Daniel Mewes,Christoph Jacobi

doi:10.3390/atmos11030251

Abstract

The meridional temperature gradient between mid and high latitudes decreases by Arctic amplification. Following this decrease, the circulation in the mid latitudes may change and, therefore, the meridional flux of heat and moisture increases. This might increase the Arctic temperatures even further. A proxy for the vertically integrated atmospheric horizontal energy flux was analyzed using the self-organizing-map (SOM) method. Climate Model Intercomparison Project Phase 5 (CMIP5) model data of the historical and Representative Concentration Pathway 8.5 (RCP8.5) experiments were analyzed to extract horizontal flux patterns. These patterns were analyzed for changes between and within the respective experiments. It was found that the general horizontal flux patterns are reproduced by all models and in all experiments in comparison with reanalyses. By comparing the reanalysis time frame with the respective historical experiments, we found that the general occurrence frequencies of the patterns differ substantially. The results show that the general structure of the flux patterns is not changed when comparing the historical and RCP8.5 results. However, the amplitudes of the fluxes are decreasing. It is suggested that the amplitudes are smaller in the RCP8.5 results compared to the historical results, following a greater meandering of the jet stream, which yields smaller flux amplitudes of the cluster mean.

Highlights

Arctic amplification describes enhanced warming of the Arctic relative to the rest of the world due to climate change [1,2,3]
The results show that the general structure of the flux patterns is not changed when comparing the historical and RCP8.5 results
The general structures of temperature flux pathways at 500 hPa are comparable to the general structure found in the ERA Interim reanalysis by Mewes and Jacobi [20]

Summary

Introduction

Arctic amplification describes enhanced warming of the Arctic relative to the rest of the world due to climate change [1,2,3]. Arctic amplification is characterized by the increase of atmospheric temperatures, as well as the decrease in sea-ice extent in the Arctic region. Due to these changes, during winter, the sea-level pressure decreases over the Arctic [4,5], which influences horizontal transports and fluxes. As Barnes and Polvani [6] have shown, Arctic amplification is not the sole reason for the change of circulation. Due to the direct influence of Arctic warming on circulation changes and vice versa, investigation of horizontal energy fluxes is necessary for an understanding of climate change at high latitudes. Analyzing the results from the Climate Model Intercomparison Project Phase 5 (CMIP5), Taylor et al [7] have already shown that the low-latitude circulation will change in a warming climate

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Conclusion