Every winter, the high-latitude oceans are struck by severe storms that are considerably smaller than the weather-dominating synoptic depressions1. Accompanied by strong winds and heavy precipitation, these often explosively developing mesoscale cyclones—termed polar lows1—constitute a threat to offshore activities such as shipping or oil and gas exploitation. Yet owing to their small scale, polar lows are poorly represented in the observational and global reanalysis data2 often used for climatological investigations of atmospheric features and cannot be assessed in coarse-resolution global simulations of possible future climates. Here we show that in a future anthropogenically warmed climate, the frequency of polar lows is projected to decline. We used a series of regional climate model simulations to downscale a set of global climate change scenarios3 from the Intergovernmental Panel of Climate Change. In this process, we first simulated the formation of polar low systems in the North Atlantic and then counted the individual cases. A previous study4 using NCEP/NCAR re-analysis data5 revealed that polar low frequency from 1948 to 2005 did not systematically change. Now, in projections for the end of the twenty-first century, we found a significantly lower number of polar lows and a northward shift of their mean genesis region in response to elevated atmospheric greenhouse gas concentration. This change can be related to changes in the North Atlantic sea surface temperature and mid-troposphere temperature; the latter is found to rise faster than the former so that the resulting stability is increased, hindering the formation or intensification of polar lows. Our results provide a rare example of a climate change effect in which a type of extreme weather is likely to decrease, rather than increase.
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We thank the Max Planck Institute for Meteorology in Germany for providing access to their ECHAM5/MPI-OM climate change simulations. We acknowledge the modelling groups for making their model output available for analysis, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) for collecting and archiving this data, and the WCRP’s Working Group on Coupled Modelling (WGCM) for organizing the model data analysis activity. The WCRP CMIP3 multi-model data set is supported by the Office of Science, US Department of Energy. M.Z. was funded by the DFG within the special research project 512 and thanks B. Rockel, E. Zorita and K. Hodges for their help. H.v.S. was partially supported by the International Detection and Attribution Group (IDAG), funded by the DoE, and thanks H. Hinzpeter for directing his attention to the phenomenon of polar lows in the early 1980s.
This file contains Supplementary Methods, Supplementary Table 1, Supplementary Analysis, Supplementary Figures 1- 4 with legends and additional references.
About this article
Cyclones and their possible changes in the Arctic by the end of the twenty first century from regional climate model simulations
Theoretical and Applied Climatology (2015)