Does Global Warming Drive Changes in Arctic Sea Ice?

Abstract

Satellite radiometry and visual imagery of Arctic sea ice since 1979 have allowed us to track its dramatic seasonal cycle in which 70% of the March maximum sea ice area is gone by September. This extreme seasonal cycle is taken to imply that Arctic sea ice area is sensitive to ambient temperature. The satellite data also show a long term year to year decline in Arctic sea ice in every season concurrent with global warming. This concurrence has led to the assumption that the observed long term decline in sea ice is a response to global warming. This study is a test of that hypothesis. Arctic sea ice data for each calendar month are tested for the responsiveness of sea ice area to global warming at annual and five-year time scales using detrended correlation analysis. Satellite measurements of lower troposphere temperature over the north polar region are used as the relevant measure of global warming. It is found that of the twelve calendar months only two contain both statistically significant sea ice loss and statistically significant correlation of the rate of sea ice loss with global warming. These results do not constitute convincing evidence of correlation required to support the assumption that sea ice decline is driven by global warming. It is likely that the observed loss in sea ice area is a more complex phenomenon possibly with roles for winds, ocean currents, geothermal heat, and natural multidecadal variability of ocean characteristics not measured and not fully understood. Global warming may play a role in what may be a complex multivariate phenomenon but the data do not show that global warming drives year to year changes in Arctic sea ice area or that the decline can be halted or moderated by taking climate action.