Abstract
The last few decades have seen a significant decline in Arctic sea ice, generating concerns about both its causes and its longer-term implications. In this paper, we introduce an empirical technique to examine the dynamics of Arctic sea ice extent. Using quantile autoregression, we find that the negative effect of atmospheric CO2 is stronger in the upper tail of the ice distribution. We also document that Arctic sea ice dynamics have become more unstable over the last three decades, especially during the summer. The rising summer instability occurs across quantiles, indicating that it is due to the joint effects of rising atmospheric CO2 and nonlinear feedbacks (and not due to outside shocks). While we do not find evidence of “critical slowing”, we see the increasing instability as a cause for concern. We also use the model to predict the evolution of Arctic sea ice extent under alternative CO2 concentration scenarios.
Highlights
This paper investigates the recent evolution of Arctic sea ice extent and the factors affecting its dynamics using a novel empirical technique
This is important as it makes covariance analyses unfit to the study of ice dynamics. This paper addresses these challenges by studying how nonlinear dynamics and anthropogenic CO2 emissions affect the instability of Arctic sea ice extent
Our analysis focuses on three issues: 1/ what are the implications of our analysis for dynamic instability of Arctic sea ice? 2/ what are the longer-term effects of CO2? And 3/ what do they imply for the evolution and potential disappearance of Arctic sea ice over the few
Summary
This paper investigates the recent evolution of Arctic sea ice extent and the factors affecting its dynamics using a novel empirical technique. The generation and melting of sea ice are affected by energy flux involving seasonal variations in solar radiation and thermodynamic exchange and heat transport in the atmosphere and ocean.[1,2,3,4,5,6,7] Heat exchanges are associated with feedback effects arising in albedo and in atmospheric and ocean circulations that fluctuate over space and time. These feedback effects generate complex nonlinear dynamics that can generate instability in climate.[8]. Many previous studies focus on thresholds and bifurcations in Arctic sea ice extent using climate models (e.g.,1,3) but statistically identifying critical thresholds remains a challenge.[7,10] assessing the linkages between climate change and Arctic sea ice loss remains difficult.[11,12] This is due in large part to the complexity of feedback effects: while ice-albedo is important,[13] there are spatial and temporal feedback effects related to atmospheric and ocean circulation.[3,7,14,15] Incomplete knowledge about these feedback effects makes it difficult to evaluate Arctic sea ice dynamics and its longer-term implications
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