Relationship between the melting Arctic Sea Ice Extent and North Atlantic Oscillation Index
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Arctic Sea Ice Extent (SIE) maintains the ocean circulation at the equilibrium and provides strong feedback in the earth's climate system. When the Arctic Sea Ice melts in the summer, it results in the oceans absorbing and heating up the Arctic. As Arctic SIE is melting increasing rate, the oceans absorb and heat up further. This contributes to rising sea surface temperature, which has a larger impact on global atmospheric pressure. Thus, the climate scientists are alarmed that global warming will cause the polar ice caps to melt and that may lead to a "critical instability". In our study, we construct a phase-space using the velocity and acceleration of the Arctic Sea Ice Extent (SIE) as two variables. From the data analysis, we show that in recent decades the melting arctic SIE resulted in increasing phase-space volume, i.e., the phase-line distribution function has not been constant along the trajectories. Our aim is to investigate the effect of the melting Arctic SIE on the climate - particularly on the North Atlantic Oscillation (NAO) index, a measure of variability in the atmospheric pressure at sea level. Based on a Granger causal model and a conservative Bootstrap statistical test, we find that the changing phase-plane SIE does have a significant (at 0.01 percent) effect on the NAO index. It indicates melting SIE has a significant effect on the changing weather pattern of the North Atlantic region, especially in Europe and North America. In addition, we see that the yearly median of NAO is greater than the yearly average NAO, which indicates that the distribution of NAO is negatively skewed, even though NAO follows nearly a mean zero stationary process. Our statistical study hints that we will soon see a warmer climate in Eastern USA and Northern Europe. Naturally, a warmer northern Europe would lead to a shrinking SIE, which can be a cause of alarm.
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