Exploring a possible connection between U.S. tornado activity and Arctic sea ice

Robert J Trapp,Kimberly A Hoogewind

doi:10.1038/s41612-018-0025-9

Abstract

The significant losses in Arctic sea ice over the past few decades appear to have been accompanied by changes in global-scale and regional-scale atmospheric circulation. Such circulation changes have in turn been used to support arguments that low Arctic sea-ice extent (SIE) has helped to promote extreme weather events within the mid-latitudes. The contemporaneous variability in U.S. tornado incidence over the past decade provides motivation to explore whether the essence of these arguments also applies to tornadoes. Here, robust statistical correlations are found between tornado activity and SIE during boreal summer, specifically in July. The statistical relationship is supported by the presence of anomalous regional circulation and storm track that are unfavorable (favorable) for tornado-bearing thunderstorm formation when SIE is low (high).

Highlights

The significant losses in Arctic sea ice over the past few decades[1] have been accompanied by lower-tropospheric temperature changes[2] that appear to have contributed to changes in globalscale and regional-scale atmospheric circulation
Not the focus of this study, we find that the F/EF1+ tornado reports over this longer time series correlate strongly with seaice extent (SIE) in July (Rp = + 0.57, Rs = +0.55, p = 0.000 using raw data, and Rp = +0.45, Rs = +0.40, p = 0.006 using detrended data; Supplement Fig. S2)
The analyses demonstrate that the atmospheric conditions during years of low panArctic sea ice in July are generally unsupportive of July tornado activity, and perhaps of convective precipitation, within the Great Plains region of the U.S Such unsupportive conditions can be dynamically linked to anomalous circulation and storm track in central North America

Summary

Introduction

The significant losses in Arctic sea ice over the past few decades[1] have been accompanied by lower-tropospheric temperature changes[2] that appear to have contributed to changes in globalscale and regional-scale atmospheric circulation. Such circulation changes— the geographical shifts, enhanced undulations, blocking patterns, and speed reductions in the jet stream3– 7—have been used to support arguments that low Arctic sea ice helps to promote extreme weather events within the midlatitudes.[8,9,10]. Consider that such anomalous circulation would cause a northward shift in the synoptic-scale forcing and

Objectives

Results

Conclusion